// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2013 Boris BREZILLON <b.brezillon.dev@gmail.com>
 *
 * Derived from:
 *      https://github.com/yuq/sunxi-nfc-mtd
 *      Copyright (C) 2013 Qiang Yu <yuq825@gmail.com>
 *
 *      https://github.com/hno/Allwinner-Info
 *      Copyright (C) 2013 Henrik Nordström <Henrik Nordström>
 *
 *      Copyright (C) 2013 Dmitriy B. <rzk333@gmail.com>
 *      Copyright (C) 2013 Sergey Lapin <slapin@ossfans.org>
 */

#include <linux/dma-mapping.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/rawnand.h>
#include <linux/mtd/partitions.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/interrupt.h>
#include <linux/iopoll.h>
#include <linux/reset.h>

#define NFC_REG_CTL             0x0000
#define NFC_REG_ST              0x0004
#define NFC_REG_INT             0x0008
#define NFC_REG_TIMING_CTL      0x000C
#define NFC_REG_TIMING_CFG      0x0010
#define NFC_REG_ADDR_LOW        0x0014
#define NFC_REG_ADDR_HIGH       0x0018
#define NFC_REG_SECTOR_NUM      0x001C
#define NFC_REG_CNT             0x0020
#define NFC_REG_CMD             0x0024
#define NFC_REG_RCMD_SET        0x0028
#define NFC_REG_WCMD_SET        0x002C
#define NFC_REG_A10_IO_DATA     0x0030
#define NFC_REG_A23_IO_DATA     0x0300
#define NFC_REG_ECC_CTL         0x0034
#define NFC_REG_ECC_ST          0x0038
#define NFC_REG_H6_PAT_FOUND    0x003C
#define NFC_REG_A10_ECC_ERR_CNT 0x0040
#define NFC_REG_H6_ECC_ERR_CNT  0x0050
#define NFC_REG_ECC_ERR_CNT(nfc, x)     ((nfc->caps->reg_ecc_err_cnt + (x)) & ~0x3)
#define NFC_REG_H6_RDATA_CTL    0x0044
#define NFC_REG_H6_RDATA_0      0x0048
#define NFC_REG_H6_RDATA_1      0x004C
#define NFC_REG_A10_USER_DATA   0x0050
#define NFC_REG_H6_USER_DATA    0x0080
#define NFC_REG_USER_DATA(nfc, x)       (nfc->caps->reg_user_data + ((x) * 4))
#define NFC_REG_H6_USER_DATA_LEN 0x0070
/* A USER_DATA_LEN register can hold the length of 8 USER_DATA registers */
#define NFC_REG_USER_DATA_LEN_CAPACITY 8
#define NFC_REG_USER_DATA_LEN(nfc, step) \
         (nfc->caps->reg_user_data_len + \
         ((step) / NFC_REG_USER_DATA_LEN_CAPACITY) * 4)
#define NFC_REG_SPARE_AREA(nfc) (nfc->caps->reg_spare_area)
#define NFC_REG_A10_SPARE_AREA  0x00A0
#define NFC_REG_PAT_ID(nfc) (nfc->caps->reg_pat_id)
#define NFC_REG_A10_PAT_ID      0x00A4
#define NFC_REG_MDMA_ADDR       0x00C0
#define NFC_REG_MDMA_CNT        0x00C4
#define NFC_REG_H6_EFNAND_STATUS 0x0110
#define NFC_REG_H6_SPARE_AREA   0x0114
#define NFC_REG_H6_PAT_ID       0x0118
#define NFC_REG_H6_DDR2_SPEC_CTL 0x011C
#define NFC_REG_H6_NDMA_MODE_CTL 0x0120
#define NFC_REG_H6_MDMA_DLBA_REG 0x0200
#define NFC_REG_H6_MDMA_STA     0x0204
#define NFC_REG_H6_MDMA_INT_MAS 0x0208
#define NFC_REG_H6_MDMA_DESC_ADDR 0x020C
#define NFC_REG_H6_MDMA_BUF_ADDR 0x0210
#define NFC_REG_H6_MDMA_CNT     0x0214

#define NFC_RAM0_BASE           0x0400
#define NFC_RAM1_BASE           0x0800

/* define bit use in NFC_CTL */
#define NFC_EN                  BIT(0)
#define NFC_RESET               BIT(1)
#define NFC_BUS_WIDTH_MSK       BIT(2)
#define NFC_BUS_WIDTH_8         (0 << 2)
#define NFC_BUS_WIDTH_16        (1 << 2)
#define NFC_RB_SEL_MSK          BIT(3)
#define NFC_RB_SEL(x)           ((x) << 3)
/* CE_SEL BIT 27 is meant to be used for GPIO chipselect */
#define NFC_CE_SEL_MSK          GENMASK(26, 24)
#define NFC_CE_SEL(x)           ((x) << 24)
#define NFC_CE_CTL              BIT(6)
#define NFC_PAGE_SHIFT_MSK      GENMASK(11, 8)
#define NFC_PAGE_SHIFT(x)       (((x) < 10 ? 0 : (x) - 10) << 8)
#define NFC_SAM                 BIT(12)
#define NFC_RAM_METHOD          BIT(14)
#define NFC_DMA_TYPE_NORMAL     BIT(15)
#define NFC_DEBUG_CTL           BIT(31)

/* define bit use in NFC_ST */
#define NFC_RB_B2R              BIT(0)
#define NFC_CMD_INT_FLAG        BIT(1)
#define NFC_DMA_INT_FLAG        BIT(2)
#define NFC_CMD_FIFO_STATUS     BIT(3)
#define NFC_STA                 BIT(4)
#define NFC_NATCH_INT_FLAG      BIT(5)
#define NFC_RB_STATE(x)         BIT(x + 8)
#define NFC_RB_STATE_MSK        GENMASK(11, 8)
#define NDFC_RDATA_STA_1        BIT(12)
#define NDFC_RDATA_STA_0        BIT(13)

/* define bit use in NFC_INT */
#define NFC_B2R_INT_ENABLE      BIT(0)
#define NFC_CMD_INT_ENABLE      BIT(1)
#define NFC_DMA_INT_ENABLE      BIT(2)
#define NFC_INT_MASK            (NFC_B2R_INT_ENABLE | \
                                 NFC_CMD_INT_ENABLE | \
                                 NFC_DMA_INT_ENABLE)

/* define bit use in NFC_TIMING_CTL */
#define NFC_TIMING_CTL_EDO      BIT(8)
#define NFC_TIMING_CTL_E_EDO    BIT(9)

/* define NFC_TIMING_CFG register layout */
#define NFC_TIMING_CFG(tWB, tADL, tWHR, tRHW, tCAD)             \
        (((tWB) & 0x3) | (((tADL) & 0x3) << 2) |                \
        (((tWHR) & 0x3) << 4) | (((tRHW) & 0x3) << 6) |         \
        (((tCAD) & 0x7) << 8))

#define NFC_TIMING_CFG2(tCDQSS, tSC, tCLHZ, tCSS, tWC)          \
        ((((tCDQSS) & 0x1) << 11) | (((tSC) & 0x3) << 12) |     \
         (((tCLHZ) & 0x3) << 14) | (((tCSS) & 0x3) << 16) |     \
         (((tWC) & 0x3) << 18))

/* define bit use in NFC_CMD */
#define NFC_CMD_LOW_BYTE_MSK    GENMASK(7, 0)
#define NFC_CMD_HIGH_BYTE_MSK   GENMASK(15, 8)  /* 15-10 reserved on H6 */
#define NFC_CMD_ADR_NUM_MSK     GENMASK(9, 8)
#define NFC_CMD(x)              (x)
#define NFC_ADR_NUM_MSK         GENMASK(18, 16)
#define NFC_ADR_NUM(x)          (((x) - 1) << 16)
#define NFC_SEND_ADR            BIT(19)
#define NFC_ACCESS_DIR          BIT(20)
#define NFC_DATA_TRANS          BIT(21)
#define NFC_SEND_CMD1           BIT(22)
#define NFC_WAIT_FLAG           BIT(23)
#define NFC_SEND_CMD2           BIT(24)
#define NFC_SEQ                 BIT(25)
#define NFC_DATA_SWAP_METHOD    BIT(26)
#define NFC_ROW_AUTO_INC        BIT(27)
#define NFC_H6_SEND_RND_CMD2    BIT(27)
#define NFC_SEND_CMD3           BIT(28)
#define NFC_SEND_CMD4           BIT(29)
#define NFC_CMD_TYPE_MSK        GENMASK(31, 30)
#define NFC_NORMAL_OP           (0 << 30)
#define NFC_ECC_OP              (1 << 30)
#define NFC_PAGE_OP             (2U << 30)

/* define bit use in NFC_RCMD_SET */
#define NFC_READ_CMD_MSK        GENMASK(7, 0)
#define NFC_RND_READ_CMD0_MSK   GENMASK(15, 8)
#define NFC_RND_READ_CMD1_MSK   GENMASK(23, 16)
#define NFC_RND_READ_CMD2_MSK   GENMASK(31, 24)

/* define bit use in NFC_WCMD_SET */
#define NFC_PROGRAM_CMD_MSK     GENMASK(7, 0)
#define NFC_RND_WRITE_CMD_MSK   GENMASK(15, 8)
#define NFC_READ_CMD0_MSK       GENMASK(23, 16)
#define NFC_READ_CMD1_MSK       GENMASK(31, 24)

/* define bit use in NFC_ECC_CTL */
#define NFC_ECC_EN              BIT(0)
#define NFC_ECC_PIPELINE        BIT(3)
#define NFC_ECC_EXCEPTION       BIT(4)
#define NFC_ECC_BLOCK_SIZE_MSK  BIT(5)
#define NFC_ECC_BLOCK_512       BIT(5)
#define NFC_RANDOM_EN(nfc)      (nfc->caps->random_en_mask)
#define NFC_RANDOM_DIRECTION(nfc) (nfc->caps->random_dir_mask)
#define NFC_ECC_MODE_MSK(nfc)   (nfc->caps->ecc_mode_mask)
#define NFC_ECC_MODE(nfc, x)    field_prep(NFC_ECC_MODE_MSK(nfc), (x))
/* RANDOM_PAGE_SIZE: 0: ECC block size  1: page size */
#define NFC_A23_RANDOM_PAGE_SIZE        BIT(11)
#define NFC_H6_RANDOM_PAGE_SIZE BIT(7)
#define NFC_RANDOM_SEED_MSK     GENMASK(30, 16)
#define NFC_RANDOM_SEED(x)      ((x) << 16)

/* define bit use in NFC_ECC_ST */
#define NFC_ECC_ERR(x)          BIT(x)
#define NFC_ECC_ERR_MSK(nfc)    (nfc->caps->ecc_err_mask)

/*
 * define bit use in NFC_REG_PAT_FOUND
 * For A10/A23, NFC_REG_PAT_FOUND == NFC_ECC_ST register
 */
#define NFC_ECC_PAT_FOUND_MSK(nfc) (nfc->caps->pat_found_mask)

#define NFC_ECC_ERR_CNT(b, x)   (((x) >> (((b) % 4) * 8)) & 0xff)

#define NFC_USER_DATA_LEN_MSK(step) \
        (0xf << (((step) % NFC_REG_USER_DATA_LEN_CAPACITY) * 4))

#define NFC_DEFAULT_TIMEOUT_MS  1000

#define NFC_MAX_CS              7

/*
 * On A10/A23, this is the size of the NDFC User Data Register, containing the
 * mandatory user data bytes following the ECC for each ECC step.
 * Thus, for each ECC step, we need the ECC bytes + USER_DATA_SZ.
 * Those bits are currently unsused, and kept as default value 0xffffffff.
 *
 * On H6/H616, this size became configurable, from 0 bytes to 32, via the
 * USER_DATA_LEN registers.
 */
#define USER_DATA_SZ 4

/**
 * struct sunxi_nand_chip_sel - stores information related to NAND Chip Select
 *
 * @cs: the NAND CS id used to communicate with a NAND Chip
 * @rb: the Ready/Busy pin ID. -1 means no R/B pin connected to the NFC
 */
struct sunxi_nand_chip_sel {
        u8 cs;
        s8 rb;
};

/**
 * struct sunxi_nand_hw_ecc - stores information related to HW ECC support
 *
 * @ecc_ctl: ECC_CTL register value for this NAND chip
 */
struct sunxi_nand_hw_ecc {
        u32 ecc_ctl;
};

/**
 * struct sunxi_nand_chip - stores NAND chip device related information
 *
 * @node: used to store NAND chips into a list
 * @nand: base NAND chip structure
 * @ecc: ECC controller structure
 * @clk_rate: clk_rate required for this NAND chip
 * @timing_cfg: TIMING_CFG register value for this NAND chip
 * @timing_ctl: TIMING_CTL register value for this NAND chip
 * @nsels: number of CS lines required by the NAND chip
 * @sels: array of CS lines descriptions
 */
struct sunxi_nand_chip {
        struct list_head node;
        struct nand_chip nand;
        struct sunxi_nand_hw_ecc ecc;
        unsigned long clk_rate;
        u32 timing_cfg;
        u32 timing_ctl;
        int nsels;
        struct sunxi_nand_chip_sel sels[] __counted_by(nsels);
};

static inline struct sunxi_nand_chip *to_sunxi_nand(struct nand_chip *nand)
{
        return container_of(nand, struct sunxi_nand_chip, nand);
}

/*
 * NAND Controller capabilities structure: stores NAND controller capabilities
 * for distinction between compatible strings.
 *
 * @has_mdma:           Use mbus dma mode, otherwise general dma
 *                      through MBUS on A23/A33 needs extra configuration.
 * @has_ecc_block_512:  If the ECC can handle 512B or only 1024B chuncks
 * @has_ecc_clk:        If the controller needs an ECC clock.
 * @has_mbus_clk:       If the controller needs a mbus clock.
 * @reg_io_data:        I/O data register
 * @reg_ecc_err_cnt:    ECC error counter register
 * @reg_user_data:      User data register
 * @reg_user_data_len:  User data length register
 * @reg_spare_area:     Spare Area Register
 * @reg_pat_id:         Pattern ID Register
 * @reg_pat_found:      Data Pattern Status Register
 * @random_en_mask:     RANDOM_EN mask in NFC_ECC_CTL register
 * @random_dir_mask:    RANDOM_DIRECTION mask in NFC_ECC_CTL register
 * @ecc_mode_mask:      ECC_MODE mask in NFC_ECC_CTL register
 * @ecc_err_mask:       NFC_ECC_ERR mask in NFC_ECC_ST register
 * @pat_found_mask:     ECC_PAT_FOUND mask in NFC_REG_PAT_FOUND register
 * @dma_maxburst:       DMA maxburst
 * @ecc_strengths:      Available ECC strengths array
 * @nstrengths:         Size of @ecc_strengths
 * @max_ecc_steps:      Maximum supported steps for ECC, this is also the
 *                      number of user data registers
 * @user_data_len_tab:  Table of lenghts supported by USER_DATA_LEN register
 *                      The table index is the value to set in NFC_USER_DATA_LEN
 *                      registers, and the corresponding value is the number of
 *                      bytes to write
 * @nuser_data_tab:     Size of @user_data_len_tab
 * @sram_size:          Size of the NAND controller SRAM
 */
struct sunxi_nfc_caps {
        bool has_mdma;
        bool has_ecc_block_512;
        bool has_ecc_clk;
        bool has_mbus_clk;
        unsigned int reg_io_data;
        unsigned int reg_ecc_err_cnt;
        unsigned int reg_user_data;
        unsigned int reg_user_data_len;
        unsigned int reg_spare_area;
        unsigned int reg_pat_id;
        unsigned int reg_pat_found;
        unsigned int random_en_mask;
        unsigned int random_dir_mask;
        unsigned int ecc_mode_mask;
        unsigned int ecc_err_mask;
        unsigned int pat_found_mask;
        unsigned int dma_maxburst;
        const u8 *ecc_strengths;
        unsigned int nstrengths;
        const u8 *user_data_len_tab;
        unsigned int nuser_data_tab;
        unsigned int max_ecc_steps;
        int sram_size;
};

/**
 * struct sunxi_nfc - stores sunxi NAND controller information
 *
 * @controller: base controller structure
 * @dev: parent device (used to print error messages)
 * @regs: NAND controller registers
 * @ahb_clk: NAND controller AHB clock
 * @mod_clk: NAND controller mod clock
 * @ecc_clk: NAND controller ECC clock
 * @mbus_clk: NAND controller MBUS clock
 * @reset: NAND controller reset line
 * @assigned_cs: bitmask describing already assigned CS lines
 * @clk_rate: NAND controller current clock rate
 * @chips: a list containing all the NAND chips attached to this NAND
 *         controller
 * @complete: a completion object used to wait for NAND controller events
 * @dmac: the DMA channel attached to the NAND controller
 * @caps: NAND Controller capabilities
 */
struct sunxi_nfc {
        struct nand_controller controller;
        struct device *dev;
        void __iomem *regs;
        struct clk *ahb_clk;
        struct clk *mod_clk;
        struct clk *ecc_clk;
        struct clk *mbus_clk;
        struct reset_control *reset;
        unsigned long assigned_cs;
        unsigned long clk_rate;
        struct list_head chips;
        struct completion complete;
        struct dma_chan *dmac;
        const struct sunxi_nfc_caps *caps;
};

static inline struct sunxi_nfc *to_sunxi_nfc(struct nand_controller *ctrl)
{
        return container_of(ctrl, struct sunxi_nfc, controller);
}

static irqreturn_t sunxi_nfc_interrupt(int irq, void *dev_id)
{
        struct sunxi_nfc *nfc = dev_id;
        u32 st = readl(nfc->regs + NFC_REG_ST);
        u32 ien = readl(nfc->regs + NFC_REG_INT);

        if (!(ien & st))
                return IRQ_NONE;

        if ((ien & st) == ien)
                complete(&nfc->complete);

        writel(st & NFC_INT_MASK, nfc->regs + NFC_REG_ST);
        writel(~st & ien & NFC_INT_MASK, nfc->regs + NFC_REG_INT);

        return IRQ_HANDLED;
}

static int sunxi_nfc_wait_events(struct sunxi_nfc *nfc, u32 events,
                                 bool use_polling, unsigned int timeout_ms)
{
        int ret;

        if (events & ~NFC_INT_MASK)
                return -EINVAL;

        if (!timeout_ms)
                timeout_ms = NFC_DEFAULT_TIMEOUT_MS;

        if (!use_polling) {
                init_completion(&nfc->complete);

                writel(events, nfc->regs + NFC_REG_INT);

                ret = wait_for_completion_timeout(&nfc->complete,
                                                msecs_to_jiffies(timeout_ms));
                if (!ret)
                        ret = -ETIMEDOUT;
                else
                        ret = 0;

                writel(0, nfc->regs + NFC_REG_INT);
        } else {
                u32 status;

                ret = readl_poll_timeout(nfc->regs + NFC_REG_ST, status,
                                         (status & events) == events, 1,
                                         timeout_ms * 1000);
        }

        writel(events & NFC_INT_MASK, nfc->regs + NFC_REG_ST);

        if (ret)
                dev_err(nfc->dev, "wait interrupt timedout\n");

        return ret;
}

static int sunxi_nfc_wait_cmd_fifo_empty(struct sunxi_nfc *nfc)
{
        u32 status;
        int ret;

        ret = readl_poll_timeout(nfc->regs + NFC_REG_ST, status,
                                 !(status & NFC_CMD_FIFO_STATUS), 1,
                                 NFC_DEFAULT_TIMEOUT_MS * 1000);
        if (ret)
                dev_err(nfc->dev, "wait for empty cmd FIFO timedout\n");

        return ret;
}

static int sunxi_nfc_rst(struct sunxi_nfc *nfc)
{
        u32 ctl;
        int ret;

        writel(0, nfc->regs + NFC_REG_ECC_CTL);
        writel(NFC_RESET, nfc->regs + NFC_REG_CTL);

        ret = readl_poll_timeout(nfc->regs + NFC_REG_CTL, ctl,
                                 !(ctl & NFC_RESET), 1,
                                 NFC_DEFAULT_TIMEOUT_MS * 1000);
        if (ret)
                dev_err(nfc->dev, "wait for NAND controller reset timedout\n");

        return ret;
}

static int sunxi_nfc_dma_op_prepare(struct sunxi_nfc *nfc, const void *buf,
                                    int chunksize, int nchunks,
                                    enum dma_data_direction ddir,
                                    struct scatterlist *sg)
{
        struct dma_async_tx_descriptor *dmad;
        enum dma_transfer_direction tdir;
        dma_cookie_t dmat;
        int ret;

        if (ddir == DMA_FROM_DEVICE)
                tdir = DMA_DEV_TO_MEM;
        else
                tdir = DMA_MEM_TO_DEV;

        sg_init_one(sg, buf, nchunks * chunksize);
        ret = dma_map_sg(nfc->dev, sg, 1, ddir);
        if (!ret)
                return -ENOMEM;

        if (!nfc->caps->has_mdma) {
                dmad = dmaengine_prep_slave_sg(nfc->dmac, sg, 1, tdir, DMA_CTRL_ACK);
                if (!dmad) {
                        ret = -EINVAL;
                        goto err_unmap_buf;
                }
        }

        writel(readl(nfc->regs + NFC_REG_CTL) | NFC_RAM_METHOD,
               nfc->regs + NFC_REG_CTL);
        writel(nchunks, nfc->regs + NFC_REG_SECTOR_NUM);
        writel(chunksize, nfc->regs + NFC_REG_CNT);

        if (nfc->caps->has_mdma) {
                writel(readl(nfc->regs + NFC_REG_CTL) & ~NFC_DMA_TYPE_NORMAL,
                       nfc->regs + NFC_REG_CTL);
                writel(chunksize * nchunks, nfc->regs + NFC_REG_MDMA_CNT);
                writel(sg_dma_address(sg), nfc->regs + NFC_REG_MDMA_ADDR);
        } else {
                dmat = dmaengine_submit(dmad);

                ret = dma_submit_error(dmat);
                if (ret)
                        goto err_clr_dma_flag;
        }

        return 0;

err_clr_dma_flag:
        writel(readl(nfc->regs + NFC_REG_CTL) & ~NFC_RAM_METHOD,
               nfc->regs + NFC_REG_CTL);

err_unmap_buf:
        dma_unmap_sg(nfc->dev, sg, 1, ddir);
        return ret;
}

static void sunxi_nfc_dma_op_cleanup(struct sunxi_nfc *nfc,
                                     enum dma_data_direction ddir,
                                     struct scatterlist *sg)
{
        dma_unmap_sg(nfc->dev, sg, 1, ddir);
        writel(readl(nfc->regs + NFC_REG_CTL) & ~NFC_RAM_METHOD,
               nfc->regs + NFC_REG_CTL);
}

static void sunxi_nfc_select_chip(struct nand_chip *nand, unsigned int cs)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
        struct sunxi_nfc *nfc = to_sunxi_nfc(sunxi_nand->nand.controller);
        struct sunxi_nand_chip_sel *sel;
        u32 ctl;

        if (cs >= sunxi_nand->nsels)
                return;

        ctl = readl(nfc->regs + NFC_REG_CTL) &
              ~(NFC_PAGE_SHIFT_MSK | NFC_CE_SEL_MSK | NFC_RB_SEL_MSK | NFC_EN);

        sel = &sunxi_nand->sels[cs];
        ctl |= NFC_CE_SEL(sel->cs) | NFC_EN | NFC_PAGE_SHIFT(nand->page_shift);
        if (sel->rb >= 0)
                ctl |= NFC_RB_SEL(sel->rb);

        writel(mtd->writesize, nfc->regs + NFC_REG_SPARE_AREA(nfc));

        if (nfc->clk_rate != sunxi_nand->clk_rate) {
                clk_set_rate(nfc->mod_clk, sunxi_nand->clk_rate);
                nfc->clk_rate = sunxi_nand->clk_rate;
        }

        writel(sunxi_nand->timing_ctl, nfc->regs + NFC_REG_TIMING_CTL);
        writel(sunxi_nand->timing_cfg, nfc->regs + NFC_REG_TIMING_CFG);
        writel(ctl, nfc->regs + NFC_REG_CTL);
}

static void sunxi_nfc_read_buf(struct nand_chip *nand, uint8_t *buf, int len)
{
        struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
        struct sunxi_nfc *nfc = to_sunxi_nfc(sunxi_nand->nand.controller);
        int ret;
        int cnt;
        int offs = 0;
        u32 tmp;

        while (len > offs) {
                bool poll = false;

                cnt = min(len - offs, nfc->caps->sram_size);

                ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
                if (ret)
                        break;

                writel(cnt, nfc->regs + NFC_REG_CNT);
                tmp = NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD;
                writel(tmp, nfc->regs + NFC_REG_CMD);

                /* Arbitrary limit for polling mode */
                if (cnt < 64)
                        poll = true;

                ret = sunxi_nfc_wait_events(nfc, NFC_CMD_INT_FLAG, poll, 0);
                if (ret)
                        break;

                if (buf)
                        memcpy_fromio(buf + offs, nfc->regs + NFC_RAM0_BASE,
                                      cnt);
                offs += cnt;
        }
}

static void sunxi_nfc_write_buf(struct nand_chip *nand, const uint8_t *buf,
                                int len)
{
        struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
        struct sunxi_nfc *nfc = to_sunxi_nfc(sunxi_nand->nand.controller);
        int ret;
        int cnt;
        int offs = 0;
        u32 tmp;

        while (len > offs) {
                bool poll = false;

                cnt = min(len - offs, nfc->caps->sram_size);

                ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
                if (ret)
                        break;

                writel(cnt, nfc->regs + NFC_REG_CNT);
                memcpy_toio(nfc->regs + NFC_RAM0_BASE, buf + offs, cnt);
                tmp = NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD |
                      NFC_ACCESS_DIR;
                writel(tmp, nfc->regs + NFC_REG_CMD);

                /* Arbitrary limit for polling mode */
                if (cnt < 64)
                        poll = true;

                ret = sunxi_nfc_wait_events(nfc, NFC_CMD_INT_FLAG, poll, 0);
                if (ret)
                        break;

                offs += cnt;
        }
}

/* These seed values have been extracted from Allwinner's BSP */
static const u16 sunxi_nfc_randomizer_page_seeds[] = {
        0x2b75, 0x0bd0, 0x5ca3, 0x62d1, 0x1c93, 0x07e9, 0x2162, 0x3a72,
        0x0d67, 0x67f9, 0x1be7, 0x077d, 0x032f, 0x0dac, 0x2716, 0x2436,
        0x7922, 0x1510, 0x3860, 0x5287, 0x480f, 0x4252, 0x1789, 0x5a2d,
        0x2a49, 0x5e10, 0x437f, 0x4b4e, 0x2f45, 0x216e, 0x5cb7, 0x7130,
        0x2a3f, 0x60e4, 0x4dc9, 0x0ef0, 0x0f52, 0x1bb9, 0x6211, 0x7a56,
        0x226d, 0x4ea7, 0x6f36, 0x3692, 0x38bf, 0x0c62, 0x05eb, 0x4c55,
        0x60f4, 0x728c, 0x3b6f, 0x2037, 0x7f69, 0x0936, 0x651a, 0x4ceb,
        0x6218, 0x79f3, 0x383f, 0x18d9, 0x4f05, 0x5c82, 0x2912, 0x6f17,
        0x6856, 0x5938, 0x1007, 0x61ab, 0x3e7f, 0x57c2, 0x542f, 0x4f62,
        0x7454, 0x2eac, 0x7739, 0x42d4, 0x2f90, 0x435a, 0x2e52, 0x2064,
        0x637c, 0x66ad, 0x2c90, 0x0bad, 0x759c, 0x0029, 0x0986, 0x7126,
        0x1ca7, 0x1605, 0x386a, 0x27f5, 0x1380, 0x6d75, 0x24c3, 0x0f8e,
        0x2b7a, 0x1418, 0x1fd1, 0x7dc1, 0x2d8e, 0x43af, 0x2267, 0x7da3,
        0x4e3d, 0x1338, 0x50db, 0x454d, 0x764d, 0x40a3, 0x42e6, 0x262b,
        0x2d2e, 0x1aea, 0x2e17, 0x173d, 0x3a6e, 0x71bf, 0x25f9, 0x0a5d,
        0x7c57, 0x0fbe, 0x46ce, 0x4939, 0x6b17, 0x37bb, 0x3e91, 0x76db,
};

/*
 * sunxi_nfc_randomizer_ecc512_seeds and sunxi_nfc_randomizer_ecc1024_seeds
 * have been generated using
 * sunxi_nfc_randomizer_step(seed, (step_size * 8) + 15), which is what
 * the randomizer engine does internally before de/scrambling OOB data.
 *
 * Those tables are statically defined to avoid calculating randomizer state
 * at runtime.
 */
static const u16 sunxi_nfc_randomizer_ecc512_seeds[] = {
        0x3346, 0x367f, 0x1f18, 0x769a, 0x4f64, 0x068c, 0x2ef1, 0x6b64,
        0x28a9, 0x15d7, 0x30f8, 0x3659, 0x53db, 0x7c5f, 0x71d4, 0x4409,
        0x26eb, 0x03cc, 0x655d, 0x47d4, 0x4daa, 0x0877, 0x712d, 0x3617,
        0x3264, 0x49aa, 0x7f9e, 0x588e, 0x4fbc, 0x7176, 0x7f91, 0x6c6d,
        0x4b95, 0x5fb7, 0x3844, 0x4037, 0x0184, 0x081b, 0x0ee8, 0x5b91,
        0x293d, 0x1f71, 0x0e6f, 0x402b, 0x5122, 0x1e52, 0x22be, 0x3d2d,
        0x75bc, 0x7c60, 0x6291, 0x1a2f, 0x61d4, 0x74aa, 0x4140, 0x29ab,
        0x472d, 0x2852, 0x017e, 0x15e8, 0x5ec2, 0x17cf, 0x7d0f, 0x06b8,
        0x117a, 0x6b94, 0x789b, 0x3126, 0x6ac5, 0x5be7, 0x150f, 0x51f8,
        0x7889, 0x0aa5, 0x663d, 0x77e8, 0x0b87, 0x3dcb, 0x360d, 0x218b,
        0x512f, 0x7dc9, 0x6a4d, 0x630a, 0x3547, 0x1dd2, 0x5aea, 0x69a5,
        0x7bfa, 0x5e4f, 0x1519, 0x6430, 0x3a0e, 0x5eb3, 0x5425, 0x0c7a,
        0x5540, 0x3670, 0x63c1, 0x31e9, 0x5a39, 0x2de7, 0x5979, 0x2891,
        0x1562, 0x014b, 0x5b05, 0x2756, 0x5a34, 0x13aa, 0x6cb5, 0x2c36,
        0x5e72, 0x1306, 0x0861, 0x15ef, 0x1ee8, 0x5a37, 0x7ac4, 0x45dd,
        0x44c4, 0x7266, 0x2f41, 0x3ccc, 0x045e, 0x7d40, 0x7c66, 0x0fa0,
};

static const u16 sunxi_nfc_randomizer_ecc1024_seeds[] = {
        0x2cf5, 0x35f1, 0x63a4, 0x5274, 0x2bd2, 0x778b, 0x7285, 0x32b6,
        0x6a5c, 0x70d6, 0x757d, 0x6769, 0x5375, 0x1e81, 0x0cf3, 0x3982,
        0x6787, 0x042a, 0x6c49, 0x1925, 0x56a8, 0x40a9, 0x063e, 0x7bd9,
        0x4dbf, 0x55ec, 0x672e, 0x7334, 0x5185, 0x4d00, 0x232a, 0x7e07,
        0x445d, 0x6b92, 0x528f, 0x4255, 0x53ba, 0x7d82, 0x2a2e, 0x3a4e,
        0x75eb, 0x450c, 0x6844, 0x1b5d, 0x581a, 0x4cc6, 0x0379, 0x37b2,
        0x419f, 0x0e92, 0x6b27, 0x5624, 0x01e3, 0x07c1, 0x44a5, 0x130c,
        0x13e8, 0x5910, 0x0876, 0x60c5, 0x54e3, 0x5b7f, 0x2269, 0x509f,
        0x7665, 0x36fd, 0x3e9a, 0x0579, 0x6295, 0x14ef, 0x0a81, 0x1bcc,
        0x4b16, 0x64db, 0x0514, 0x4f07, 0x0591, 0x3576, 0x6853, 0x0d9e,
        0x259f, 0x38b7, 0x64fb, 0x3094, 0x4693, 0x6ddd, 0x29bb, 0x0bc8,
        0x3f47, 0x490e, 0x0c0e, 0x7933, 0x3c9e, 0x5840, 0x398d, 0x3e68,
        0x4af1, 0x71f5, 0x57cf, 0x1121, 0x64eb, 0x3579, 0x15ac, 0x584d,
        0x5f2a, 0x47e2, 0x6528, 0x6eac, 0x196e, 0x6b96, 0x0450, 0x0179,
        0x609c, 0x06e1, 0x4626, 0x42c7, 0x273e, 0x486f, 0x0705, 0x1601,
        0x145b, 0x407e, 0x062b, 0x57a5, 0x53f9, 0x5659, 0x4410, 0x3ccd,
};

static u16 sunxi_nfc_randomizer_step(u16 state, int count)
{
        state &= 0x7fff;

        /*
         * This loop is just a simple implementation of a Fibonacci LFSR using
         * the x16 + x15 + 1 polynomial.
         */
        while (count--)
                state = ((state >> 1) |
                         (((state ^ (state >> 1)) & 1) << 14)) & 0x7fff;

        return state;
}

static u16 sunxi_nfc_randomizer_state(struct nand_chip *nand, int page,
                                      bool ecc)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
        int mod = mtd_div_by_ws(mtd->erasesize, mtd);

        if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
                mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);

        if (ecc) {
                if (mtd->ecc_step_size == 512)
                        seeds = sunxi_nfc_randomizer_ecc512_seeds;
                else
                        seeds = sunxi_nfc_randomizer_ecc1024_seeds;
        }

        return seeds[page % mod];
}

static void sunxi_nfc_randomizer_config(struct nand_chip *nand, int page,
                                        bool ecc)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        u32 ecc_ctl;
        u16 state;

        if (!(nand->options & NAND_NEED_SCRAMBLING))
                return;

        state = sunxi_nfc_randomizer_state(nand, page, ecc);
        ecc_ctl = readl(nfc->regs + NFC_REG_ECC_CTL) & ~NFC_RANDOM_SEED_MSK;
        writel(ecc_ctl | NFC_RANDOM_SEED(state), nfc->regs + NFC_REG_ECC_CTL);
}

static void sunxi_nfc_randomizer_enable(struct nand_chip *nand)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);

        if (!(nand->options & NAND_NEED_SCRAMBLING))
                return;

        writel(readl(nfc->regs + NFC_REG_ECC_CTL) | NFC_RANDOM_EN(nfc),
               nfc->regs + NFC_REG_ECC_CTL);
}

static void sunxi_nfc_randomizer_disable(struct nand_chip *nand)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);

        if (!(nand->options & NAND_NEED_SCRAMBLING))
                return;

        writel(readl(nfc->regs + NFC_REG_ECC_CTL) & ~NFC_RANDOM_EN(nfc),
               nfc->regs + NFC_REG_ECC_CTL);
}

static void sunxi_nfc_randomize_bbm(struct nand_chip *nand, int page, u8 *bbm)
{
        u16 state = sunxi_nfc_randomizer_state(nand, page, true);

        bbm[0] ^= state;
        bbm[1] ^= sunxi_nfc_randomizer_step(state, 8);
}

static void sunxi_nfc_randomizer_write_buf(struct nand_chip *nand,
                                           const uint8_t *buf, int len,
                                           bool ecc, int page)
{
        sunxi_nfc_randomizer_config(nand, page, ecc);
        sunxi_nfc_randomizer_enable(nand);
        sunxi_nfc_write_buf(nand, buf, len);
        sunxi_nfc_randomizer_disable(nand);
}

static void sunxi_nfc_randomizer_read_buf(struct nand_chip *nand, uint8_t *buf,
                                          int len, bool ecc, int page)
{
        sunxi_nfc_randomizer_config(nand, page, ecc);
        sunxi_nfc_randomizer_enable(nand);
        sunxi_nfc_read_buf(nand, buf, len);
        sunxi_nfc_randomizer_disable(nand);
}

static void sunxi_nfc_hw_ecc_enable(struct nand_chip *nand)
{
        struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);

        writel(sunxi_nand->ecc.ecc_ctl, nfc->regs + NFC_REG_ECC_CTL);
}

static void sunxi_nfc_hw_ecc_disable(struct nand_chip *nand)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);

        writel(0, nfc->regs + NFC_REG_ECC_CTL);
}

static inline void sunxi_nfc_user_data_to_buf(u32 user_data, u8 *buf)
{
        buf[0] = user_data;
        buf[1] = user_data >> 8;
        buf[2] = user_data >> 16;
        buf[3] = user_data >> 24;
}

static inline u32 sunxi_nfc_buf_to_user_data(const u8 *buf)
{
        return buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
}

static void sunxi_nfc_hw_ecc_get_prot_oob_bytes(struct nand_chip *nand, u8 *oob,
                                                int step, bool bbm, int page)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);

        sunxi_nfc_user_data_to_buf(readl(nfc->regs + NFC_REG_USER_DATA(nfc, step)), oob);

        /* De-randomize the Bad Block Marker. */
        if (bbm && (nand->options & NAND_NEED_SCRAMBLING))
                sunxi_nfc_randomize_bbm(nand, page, oob);
}

/*
 * On H6/H6 the user_data length has to be set in specific registers
 * before writing.
 */
static void sunxi_nfc_reset_user_data_len(struct sunxi_nfc *nfc)
{
        int loop_step = NFC_REG_USER_DATA_LEN_CAPACITY;

        /* not all SoCs have this register */
        if (!nfc->caps->reg_user_data_len)
                return;

        for (int i = 0; i < nfc->caps->max_ecc_steps; i += loop_step)
                writel(0, nfc->regs + NFC_REG_USER_DATA_LEN(nfc, i));
}

static void sunxi_nfc_set_user_data_len(struct sunxi_nfc *nfc,
                                        int len, int step)
{
        bool found = false;
        u32 val;
        int i;

        /* not all SoCs have this register */
        if (!nfc->caps->reg_user_data_len)
                return;

        for (i = 0; i < nfc->caps->nuser_data_tab; i++) {
                if (len == nfc->caps->user_data_len_tab[i]) {
                        found = true;
                        break;
                }
        }

        if (!found) {
                dev_warn(nfc->dev,
                         "Unsupported length for user data reg: %d\n", len);
                return;
        }

        val = readl(nfc->regs + NFC_REG_USER_DATA_LEN(nfc, step));

        val &= ~NFC_USER_DATA_LEN_MSK(step);
        val |= field_prep(NFC_USER_DATA_LEN_MSK(step), i);
        writel(val, nfc->regs + NFC_REG_USER_DATA_LEN(nfc, step));
}

static void sunxi_nfc_hw_ecc_set_prot_oob_bytes(struct nand_chip *nand,
                                                const u8 *oob, int step,
                                                bool bbm, int page)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        u8 user_data[USER_DATA_SZ];

        /* Randomize the Bad Block Marker. */
        if (bbm && (nand->options & NAND_NEED_SCRAMBLING)) {
                memcpy(user_data, oob, sizeof(user_data));
                sunxi_nfc_randomize_bbm(nand, page, user_data);
                oob = user_data;
        }

        writel(sunxi_nfc_buf_to_user_data(oob),
               nfc->regs + NFC_REG_USER_DATA(nfc, step));
}

static void sunxi_nfc_hw_ecc_update_stats(struct nand_chip *nand,
                                          unsigned int *max_bitflips, int ret)
{
        struct mtd_info *mtd = nand_to_mtd(nand);

        if (ret < 0) {
                mtd->ecc_stats.failed++;
        } else {
                mtd->ecc_stats.corrected += ret;
                *max_bitflips = max_t(unsigned int, *max_bitflips, ret);
        }
}

static int sunxi_nfc_hw_ecc_correct(struct nand_chip *nand, u8 *data, u8 *oob,
                                    int step, u32 status, u32 pattern_found,
                                    bool *erased)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        u32 tmp;

        *erased = false;

        if (status & NFC_ECC_ERR(step))
                return -EBADMSG;

        if (pattern_found & BIT(step)) {
                u8 pattern;

                if (unlikely(!(readl(nfc->regs + NFC_REG_PAT_ID(nfc)) & 0x1))) {
                        pattern = 0x0;
                } else {
                        pattern = 0xff;
                        *erased = true;
                }

                if (data)
                        memset(data, pattern, ecc->size);

                if (oob)
                        memset(oob, pattern, ecc->bytes + USER_DATA_SZ);

                return 0;
        }

        tmp = readl(nfc->regs + NFC_REG_ECC_ERR_CNT(nfc, step));

        return NFC_ECC_ERR_CNT(step, tmp);
}

static int sunxi_nfc_hw_ecc_read_chunk(struct nand_chip *nand,
                                       u8 *data, int data_off,
                                       u8 *oob, int oob_off,
                                       int *cur_off,
                                       unsigned int *max_bitflips,
                                       bool bbm, bool oob_required, int page)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        int raw_mode = 0;
        u32 pattern_found;
        bool erased;
        int ret;

        if (*cur_off != data_off)
                nand_change_read_column_op(nand, data_off, NULL, 0, false);

        sunxi_nfc_randomizer_read_buf(nand, NULL, ecc->size, false, page);

        if (data_off + ecc->size != oob_off)
                nand_change_read_column_op(nand, oob_off, NULL, 0, false);

        ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
        if (ret)
                return ret;

        sunxi_nfc_reset_user_data_len(nfc);
        sunxi_nfc_set_user_data_len(nfc, USER_DATA_SZ, 0);
        sunxi_nfc_randomizer_config(nand, page, false);
        sunxi_nfc_randomizer_enable(nand);
        writel(NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD | NFC_ECC_OP,
               nfc->regs + NFC_REG_CMD);

        ret = sunxi_nfc_wait_events(nfc, NFC_CMD_INT_FLAG, false, 0);
        sunxi_nfc_randomizer_disable(nand);
        if (ret)
                return ret;

        *cur_off = oob_off + ecc->bytes + USER_DATA_SZ;

        pattern_found = readl(nfc->regs + nfc->caps->reg_pat_found);
        pattern_found = field_get(NFC_ECC_PAT_FOUND_MSK(nfc), pattern_found);

        ret = sunxi_nfc_hw_ecc_correct(nand, data, oob_required ? oob : NULL, 0,
                                       readl(nfc->regs + NFC_REG_ECC_ST),
                                       pattern_found,
                                       &erased);
        if (erased)
                return 1;

        if (ret < 0) {
                /*
                 * Re-read the data with the randomizer disabled to identify
                 * bitflips in erased pages.
                 */
                if (nand->options & NAND_NEED_SCRAMBLING)
                        nand_change_read_column_op(nand, data_off, data,
                                                   ecc->size, false);
                else
                        memcpy_fromio(data, nfc->regs + NFC_RAM0_BASE,
                                      ecc->size);

                nand_change_read_column_op(nand, oob_off, oob,
                                           ecc->bytes + USER_DATA_SZ, false);

                ret = nand_check_erased_ecc_chunk(data, ecc->size, oob,
                                                  ecc->bytes + USER_DATA_SZ,
                                                  NULL, 0, ecc->strength);
                if (ret >= 0)
                        raw_mode = 1;
        } else {
                memcpy_fromio(data, nfc->regs + NFC_RAM0_BASE, ecc->size);

                if (oob_required) {
                        nand_change_read_column_op(nand, oob_off, NULL, 0,
                                                   false);
                        sunxi_nfc_randomizer_read_buf(nand, oob, ecc->bytes + USER_DATA_SZ,
                                                      true, page);

                        sunxi_nfc_hw_ecc_get_prot_oob_bytes(nand, oob, 0,
                                                            bbm, page);
                }
        }

        sunxi_nfc_hw_ecc_update_stats(nand, max_bitflips, ret);

        return raw_mode;
}

static void sunxi_nfc_hw_ecc_read_extra_oob(struct nand_chip *nand,
                                            u8 *oob, int *cur_off,
                                            bool randomize, int page)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        int offset = ((ecc->bytes + 4) * ecc->steps);
        int len = mtd->oobsize - offset;

        if (len <= 0)
                return;

        if (!cur_off || *cur_off != offset)
                nand_change_read_column_op(nand, mtd->writesize, NULL, 0,
                                           false);

        if (!randomize)
                sunxi_nfc_read_buf(nand, oob + offset, len);
        else
                sunxi_nfc_randomizer_read_buf(nand, oob + offset, len,
                                              false, page);

        if (cur_off)
                *cur_off = mtd->oobsize + mtd->writesize;
}

static int sunxi_nfc_hw_ecc_read_chunks_dma(struct nand_chip *nand, uint8_t *buf,
                                            int oob_required, int page,
                                            int nchunks)
{
        bool randomized = nand->options & NAND_NEED_SCRAMBLING;
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        unsigned int max_bitflips = 0;
        int ret, i, raw_mode = 0;
        struct scatterlist sg;
        u32 status, pattern_found, wait;

        ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
        if (ret)
                return ret;

        ret = sunxi_nfc_dma_op_prepare(nfc, buf, ecc->size, nchunks,
                                       DMA_FROM_DEVICE, &sg);
        if (ret)
                return ret;

        sunxi_nfc_hw_ecc_enable(nand);
        sunxi_nfc_reset_user_data_len(nfc);
        sunxi_nfc_set_user_data_len(nfc, USER_DATA_SZ, 0);
        sunxi_nfc_randomizer_config(nand, page, false);
        sunxi_nfc_randomizer_enable(nand);

        writel((NAND_CMD_RNDOUTSTART << 16) | (NAND_CMD_RNDOUT << 8) |
               NAND_CMD_READSTART, nfc->regs + NFC_REG_RCMD_SET);

        wait = NFC_CMD_INT_FLAG;

        if (nfc->caps->has_mdma)
                wait |= NFC_DMA_INT_FLAG;
        else
                dma_async_issue_pending(nfc->dmac);

        writel(NFC_PAGE_OP | NFC_DATA_SWAP_METHOD | NFC_DATA_TRANS,
               nfc->regs + NFC_REG_CMD);

        ret = sunxi_nfc_wait_events(nfc, wait, false, 0);
        if (ret && !nfc->caps->has_mdma)
                dmaengine_terminate_all(nfc->dmac);

        sunxi_nfc_randomizer_disable(nand);
        sunxi_nfc_hw_ecc_disable(nand);

        sunxi_nfc_dma_op_cleanup(nfc, DMA_FROM_DEVICE, &sg);

        if (ret)
                return ret;

        status = readl(nfc->regs + NFC_REG_ECC_ST);
        pattern_found = readl(nfc->regs + nfc->caps->reg_pat_found);
        pattern_found = field_get(NFC_ECC_PAT_FOUND_MSK(nfc), pattern_found);

        for (i = 0; i < nchunks; i++) {
                int data_off = i * ecc->size;
                int oob_off = i * (ecc->bytes + USER_DATA_SZ);
                u8 *data = buf + data_off;
                u8 *oob = nand->oob_poi + oob_off;
                bool erased;

                ret = sunxi_nfc_hw_ecc_correct(nand, randomized ? data : NULL,
                                               oob_required ? oob : NULL,
                                               i, status, pattern_found,
                                               &erased);

                /* ECC errors are handled in the second loop. */
                if (ret < 0)
                        continue;

                if (oob_required && !erased) {
                        /* TODO: use DMA to retrieve OOB */
                        nand_change_read_column_op(nand,
                                                   mtd->writesize + oob_off,
                                                   oob, ecc->bytes + USER_DATA_SZ, false);

                        sunxi_nfc_hw_ecc_get_prot_oob_bytes(nand, oob, i,
                                                            !i, page);
                }

                if (erased)
                        raw_mode = 1;

                sunxi_nfc_hw_ecc_update_stats(nand, &max_bitflips, ret);
        }

        if (status & NFC_ECC_ERR_MSK(nfc)) {
                for (i = 0; i < nchunks; i++) {
                        int data_off = i * ecc->size;
                        int oob_off = i * (ecc->bytes + USER_DATA_SZ);
                        u8 *data = buf + data_off;
                        u8 *oob = nand->oob_poi + oob_off;

                        if (!(status & NFC_ECC_ERR(i)))
                                continue;

                        /*
                         * Re-read the data with the randomizer disabled to
                         * identify bitflips in erased pages.
                         * TODO: use DMA to read page in raw mode
                         */
                        if (randomized)
                                nand_change_read_column_op(nand, data_off,
                                                           data, ecc->size,
                                                           false);

                        /* TODO: use DMA to retrieve OOB */
                        nand_change_read_column_op(nand,
                                                   mtd->writesize + oob_off,
                                                   oob, ecc->bytes + USER_DATA_SZ, false);

                        ret = nand_check_erased_ecc_chunk(data, ecc->size, oob,
                                                          ecc->bytes + USER_DATA_SZ,
                                                          NULL, 0,
                                                          ecc->strength);
                        if (ret >= 0)
                                raw_mode = 1;

                        sunxi_nfc_hw_ecc_update_stats(nand, &max_bitflips, ret);
                }
        }

        if (oob_required)
                sunxi_nfc_hw_ecc_read_extra_oob(nand, nand->oob_poi,
                                                NULL, !raw_mode,
                                                page);

        return max_bitflips;
}

static int sunxi_nfc_hw_ecc_write_chunk(struct nand_chip *nand,
                                        const u8 *data, int data_off,
                                        const u8 *oob, int oob_off,
                                        int *cur_off, bool bbm,
                                        int page)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        int ret;

        if (data_off != *cur_off)
                nand_change_write_column_op(nand, data_off, NULL, 0, false);

        sunxi_nfc_randomizer_write_buf(nand, data, ecc->size, false, page);

        if (data_off + ecc->size != oob_off)
                nand_change_write_column_op(nand, oob_off, NULL, 0, false);

        ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
        if (ret)
                return ret;

        sunxi_nfc_randomizer_config(nand, page, false);
        sunxi_nfc_randomizer_enable(nand);
        sunxi_nfc_reset_user_data_len(nfc);
        sunxi_nfc_set_user_data_len(nfc, USER_DATA_SZ, 0);
        sunxi_nfc_hw_ecc_set_prot_oob_bytes(nand, oob, 0, bbm, page);

        writel(NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD |
               NFC_ACCESS_DIR | NFC_ECC_OP,
               nfc->regs + NFC_REG_CMD);

        ret = sunxi_nfc_wait_events(nfc, NFC_CMD_INT_FLAG, false, 0);
        sunxi_nfc_randomizer_disable(nand);
        if (ret)
                return ret;

        *cur_off = oob_off + ecc->bytes + USER_DATA_SZ;

        return 0;
}

static void sunxi_nfc_hw_ecc_write_extra_oob(struct nand_chip *nand,
                                             u8 *oob, int *cur_off,
                                             int page)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        int offset = ((ecc->bytes + USER_DATA_SZ) * ecc->steps);
        int len = mtd->oobsize - offset;

        if (len <= 0)
                return;

        if (!cur_off || *cur_off != offset)
                nand_change_write_column_op(nand, offset + mtd->writesize,
                                            NULL, 0, false);

        sunxi_nfc_randomizer_write_buf(nand, oob + offset, len, false, page);

        if (cur_off)
                *cur_off = mtd->oobsize + mtd->writesize;
}

static int sunxi_nfc_hw_ecc_read_page(struct nand_chip *nand, uint8_t *buf,
                                      int oob_required, int page)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        unsigned int max_bitflips = 0;
        int ret, i, cur_off = 0;
        bool raw_mode = false;

        sunxi_nfc_select_chip(nand, nand->cur_cs);

        nand_read_page_op(nand, page, 0, NULL, 0);

        sunxi_nfc_hw_ecc_enable(nand);

        for (i = 0; i < ecc->steps; i++) {
                int data_off = i * ecc->size;
                int oob_off = i * (ecc->bytes + USER_DATA_SZ);
                u8 *data = buf + data_off;
                u8 *oob = nand->oob_poi + oob_off;

                ret = sunxi_nfc_hw_ecc_read_chunk(nand, data, data_off, oob,
                                                  oob_off + mtd->writesize,
                                                  &cur_off, &max_bitflips,
                                                  !i, oob_required, page);
                if (ret < 0)
                        return ret;
                else if (ret)
                        raw_mode = true;
        }

        if (oob_required)
                sunxi_nfc_hw_ecc_read_extra_oob(nand, nand->oob_poi, &cur_off,
                                                !raw_mode, page);

        sunxi_nfc_hw_ecc_disable(nand);

        return max_bitflips;
}

static int sunxi_nfc_hw_ecc_read_page_dma(struct nand_chip *nand, u8 *buf,
                                          int oob_required, int page)
{
        int ret;

        sunxi_nfc_select_chip(nand, nand->cur_cs);

        nand_read_page_op(nand, page, 0, NULL, 0);

        ret = sunxi_nfc_hw_ecc_read_chunks_dma(nand, buf, oob_required, page,
                                               nand->ecc.steps);
        if (ret >= 0)
                return ret;

        /* Fallback to PIO mode */
        return sunxi_nfc_hw_ecc_read_page(nand, buf, oob_required, page);
}

static int sunxi_nfc_hw_ecc_read_subpage(struct nand_chip *nand,
                                         u32 data_offs, u32 readlen,
                                         u8 *bufpoi, int page)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        int ret, i, cur_off = 0;
        unsigned int max_bitflips = 0;

        sunxi_nfc_select_chip(nand, nand->cur_cs);

        nand_read_page_op(nand, page, 0, NULL, 0);

        sunxi_nfc_hw_ecc_enable(nand);

        for (i = data_offs / ecc->size;
             i < DIV_ROUND_UP(data_offs + readlen, ecc->size); i++) {
                int data_off = i * ecc->size;
                int oob_off = i * (ecc->bytes + USER_DATA_SZ);
                u8 *data = bufpoi + data_off;
                u8 *oob = nand->oob_poi + oob_off;

                ret = sunxi_nfc_hw_ecc_read_chunk(nand, data, data_off,
                                                  oob,
                                                  oob_off + mtd->writesize,
                                                  &cur_off, &max_bitflips, !i,
                                                  false, page);
                if (ret < 0)
                        return ret;
        }

        sunxi_nfc_hw_ecc_disable(nand);

        return max_bitflips;
}

static int sunxi_nfc_hw_ecc_read_subpage_dma(struct nand_chip *nand,
                                             u32 data_offs, u32 readlen,
                                             u8 *buf, int page)
{
        int nchunks = DIV_ROUND_UP(data_offs + readlen, nand->ecc.size);
        int ret;

        sunxi_nfc_select_chip(nand, nand->cur_cs);

        nand_read_page_op(nand, page, 0, NULL, 0);

        ret = sunxi_nfc_hw_ecc_read_chunks_dma(nand, buf, false, page, nchunks);
        if (ret >= 0)
                return ret;

        /* Fallback to PIO mode */
        return sunxi_nfc_hw_ecc_read_subpage(nand, data_offs, readlen,
                                             buf, page);
}

static int sunxi_nfc_hw_ecc_write_page(struct nand_chip *nand,
                                       const uint8_t *buf, int oob_required,
                                       int page)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        int ret, i, cur_off = 0;

        sunxi_nfc_select_chip(nand, nand->cur_cs);

        nand_prog_page_begin_op(nand, page, 0, NULL, 0);

        sunxi_nfc_hw_ecc_enable(nand);

        for (i = 0; i < ecc->steps; i++) {
                int data_off = i * ecc->size;
                int oob_off = i * (ecc->bytes + USER_DATA_SZ);
                const u8 *data = buf + data_off;
                const u8 *oob = nand->oob_poi + oob_off;

                ret = sunxi_nfc_hw_ecc_write_chunk(nand, data, data_off, oob,
                                                   oob_off + mtd->writesize,
                                                   &cur_off, !i, page);
                if (ret)
                        return ret;
        }

        if (oob_required || (nand->options & NAND_NEED_SCRAMBLING))
                sunxi_nfc_hw_ecc_write_extra_oob(nand, nand->oob_poi,
                                                 &cur_off, page);

        sunxi_nfc_hw_ecc_disable(nand);

        return nand_prog_page_end_op(nand);
}

static int sunxi_nfc_hw_ecc_write_subpage(struct nand_chip *nand,
                                          u32 data_offs, u32 data_len,
                                          const u8 *buf, int oob_required,
                                          int page)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        int ret, i, cur_off = 0;

        sunxi_nfc_select_chip(nand, nand->cur_cs);

        nand_prog_page_begin_op(nand, page, 0, NULL, 0);

        sunxi_nfc_hw_ecc_enable(nand);

        for (i = data_offs / ecc->size;
             i < DIV_ROUND_UP(data_offs + data_len, ecc->size); i++) {
                int data_off = i * ecc->size;
                int oob_off = i * (ecc->bytes + USER_DATA_SZ);
                const u8 *data = buf + data_off;
                const u8 *oob = nand->oob_poi + oob_off;

                ret = sunxi_nfc_hw_ecc_write_chunk(nand, data, data_off, oob,
                                                   oob_off + mtd->writesize,
                                                   &cur_off, !i, page);
                if (ret)
                        return ret;
        }

        sunxi_nfc_hw_ecc_disable(nand);

        return nand_prog_page_end_op(nand);
}

static int sunxi_nfc_hw_ecc_write_page_dma(struct nand_chip *nand,
                                           const u8 *buf,
                                           int oob_required,
                                           int page)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        struct scatterlist sg;
        u32 wait;
        int ret, i;

        sunxi_nfc_select_chip(nand, nand->cur_cs);

        ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
        if (ret)
                return ret;

        ret = sunxi_nfc_dma_op_prepare(nfc, buf, ecc->size, ecc->steps,
                                       DMA_TO_DEVICE, &sg);
        if (ret)
                goto pio_fallback;

        sunxi_nfc_reset_user_data_len(nfc);
        for (i = 0; i < ecc->steps; i++) {
                const u8 *oob = nand->oob_poi + (i * (ecc->bytes + USER_DATA_SZ));

                sunxi_nfc_hw_ecc_set_prot_oob_bytes(nand, oob, i, !i, page);
                sunxi_nfc_set_user_data_len(nfc, USER_DATA_SZ, i);
        }

        nand_prog_page_begin_op(nand, page, 0, NULL, 0);

        sunxi_nfc_hw_ecc_enable(nand);
        sunxi_nfc_randomizer_config(nand, page, false);
        sunxi_nfc_randomizer_enable(nand);

        writel((NAND_CMD_RNDIN << 8) | NAND_CMD_PAGEPROG,
               nfc->regs + NFC_REG_WCMD_SET);

        wait = NFC_CMD_INT_FLAG;

        if (nfc->caps->has_mdma)
                wait |= NFC_DMA_INT_FLAG;
        else
                dma_async_issue_pending(nfc->dmac);

        writel(NFC_PAGE_OP | NFC_DATA_SWAP_METHOD |
               NFC_DATA_TRANS | NFC_ACCESS_DIR,
               nfc->regs + NFC_REG_CMD);

        ret = sunxi_nfc_wait_events(nfc, wait, false, 0);
        if (ret && !nfc->caps->has_mdma)
                dmaengine_terminate_all(nfc->dmac);

        sunxi_nfc_randomizer_disable(nand);
        sunxi_nfc_hw_ecc_disable(nand);

        sunxi_nfc_dma_op_cleanup(nfc, DMA_TO_DEVICE, &sg);

        if (ret)
                return ret;

        if (oob_required || (nand->options & NAND_NEED_SCRAMBLING))
                /* TODO: use DMA to transfer extra OOB bytes ? */
                sunxi_nfc_hw_ecc_write_extra_oob(nand, nand->oob_poi,
                                                 NULL, page);

        return nand_prog_page_end_op(nand);

pio_fallback:
        return sunxi_nfc_hw_ecc_write_page(nand, buf, oob_required, page);
}

static int sunxi_nfc_hw_ecc_read_oob(struct nand_chip *nand, int page)
{
        u8 *buf = nand_get_data_buf(nand);

        return nand->ecc.read_page(nand, buf, 1, page);
}

static int sunxi_nfc_hw_ecc_write_oob(struct nand_chip *nand, int page)
{
        struct mtd_info *mtd = nand_to_mtd(nand);
        u8 *buf = nand_get_data_buf(nand);
        int ret;

        memset(buf, 0xff, mtd->writesize);
        ret = nand->ecc.write_page(nand, buf, 1, page);
        if (ret)
                return ret;

        /* Send command to program the OOB data */
        return nand_prog_page_end_op(nand);
}

static const s32 tWB_lut[] = {6, 12, 16, 20};
static const s32 tRHW_lut[] = {4, 8, 12, 20};

static int _sunxi_nand_lookup_timing(const s32 *lut, int lut_size, u32 duration,
                u32 clk_period)
{
        u32 clk_cycles = DIV_ROUND_UP(duration, clk_period);
        int i;

        for (i = 0; i < lut_size; i++) {
                if (clk_cycles <= lut[i])
                        return i;
        }

        /* Doesn't fit */
        return -EINVAL;
}

#define sunxi_nand_lookup_timing(l, p, c) \
                        _sunxi_nand_lookup_timing(l, ARRAY_SIZE(l), p, c)

static int sunxi_nfc_setup_interface(struct nand_chip *nand, int csline,
                                     const struct nand_interface_config *conf)
{
        struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
        struct sunxi_nfc *nfc = to_sunxi_nfc(sunxi_nand->nand.controller);
        const struct nand_sdr_timings *timings;
        u32 min_clk_period = 0;
        s32 tWB, tADL, tWHR, tRHW, tCAD;
        long real_clk_rate;

        timings = nand_get_sdr_timings(conf);
        if (IS_ERR(timings))
                return -ENOTSUPP;

        /* T1 <=> tCLS */
        if (timings->tCLS_min > min_clk_period)
                min_clk_period = timings->tCLS_min;

        /* T2 <=> tCLH */
        if (timings->tCLH_min > min_clk_period)
                min_clk_period = timings->tCLH_min;

        /* T3 <=> tCS */
        if (timings->tCS_min > min_clk_period)
                min_clk_period = timings->tCS_min;

        /* T4 <=> tCH */
        if (timings->tCH_min > min_clk_period)
                min_clk_period = timings->tCH_min;

        /* T5 <=> tWP */
        if (timings->tWP_min > min_clk_period)
                min_clk_period = timings->tWP_min;

        /* T6 <=> tWH */
        if (timings->tWH_min > min_clk_period)
                min_clk_period = timings->tWH_min;

        /* T7 <=> tALS */
        if (timings->tALS_min > min_clk_period)
                min_clk_period = timings->tALS_min;

        /* T8 <=> tDS */
        if (timings->tDS_min > min_clk_period)
                min_clk_period = timings->tDS_min;

        /* T9 <=> tDH */
        if (timings->tDH_min > min_clk_period)
                min_clk_period = timings->tDH_min;

        /* T10 <=> tRR */
        if (timings->tRR_min > (min_clk_period * 3))
                min_clk_period = DIV_ROUND_UP(timings->tRR_min, 3);

        /* T11 <=> tALH */
        if (timings->tALH_min > min_clk_period)
                min_clk_period = timings->tALH_min;

        /* T12 <=> tRP */
        if (timings->tRP_min > min_clk_period)
                min_clk_period = timings->tRP_min;

        /* T13 <=> tREH */
        if (timings->tREH_min > min_clk_period)
                min_clk_period = timings->tREH_min;

        /* T14 <=> tRC */
        if (timings->tRC_min > (min_clk_period * 2))
                min_clk_period = DIV_ROUND_UP(timings->tRC_min, 2);

        /* T15 <=> tWC */
        if (timings->tWC_min > (min_clk_period * 2))
                min_clk_period = DIV_ROUND_UP(timings->tWC_min, 2);

        /* T16 - T19 + tCAD */
        if (timings->tWB_max > (min_clk_period * 20))
                min_clk_period = DIV_ROUND_UP(timings->tWB_max, 20);

        if (timings->tADL_min > (min_clk_period * 32))
                min_clk_period = DIV_ROUND_UP(timings->tADL_min, 32);

        if (timings->tWHR_min > (min_clk_period * 32))
                min_clk_period = DIV_ROUND_UP(timings->tWHR_min, 32);

        if (timings->tRHW_min > (min_clk_period * 20))
                min_clk_period = DIV_ROUND_UP(timings->tRHW_min, 20);

        /*
         * In non-EDO, tREA should be less than tRP to guarantee that the
         * controller does not sample the IO lines too early. Unfortunately,
         * the sunxi NAND controller does not allow us to have different
         * values for tRP and tREH (tRP = tREH = tRW / 2).
         *
         * We have 2 options to overcome this limitation:
         *
         * 1/ Extend tRC to fulfil the tREA <= tRC / 2 constraint
         * 2/ Use EDO mode (only works if timings->tRLOH > 0)
         */
        if (timings->tREA_max > min_clk_period && !timings->tRLOH_min)
                min_clk_period = timings->tREA_max;

        tWB  = sunxi_nand_lookup_timing(tWB_lut, timings->tWB_max,
                                        min_clk_period);
        if (tWB < 0) {
                dev_err(nfc->dev, "unsupported tWB\n");
                return tWB;
        }

        tADL = DIV_ROUND_UP(timings->tADL_min, min_clk_period) >> 3;
        if (tADL > 3) {
                dev_err(nfc->dev, "unsupported tADL\n");
                return -EINVAL;
        }

        tWHR = DIV_ROUND_UP(timings->tWHR_min, min_clk_period) >> 3;
        if (tWHR > 3) {
                dev_err(nfc->dev, "unsupported tWHR\n");
                return -EINVAL;
        }

        tRHW = sunxi_nand_lookup_timing(tRHW_lut, timings->tRHW_min,
                                        min_clk_period);
        if (tRHW < 0) {
                dev_err(nfc->dev, "unsupported tRHW\n");
                return tRHW;
        }

        if (csline == NAND_DATA_IFACE_CHECK_ONLY)
                return 0;

        /*
         * TODO: according to ONFI specs this value only applies for DDR NAND,
         * but Allwinner seems to set this to 0x7. Mimic them for now.
         */
        tCAD = 0x7;

        /* TODO: A83 has some more bits for CDQSS, CS, CLHZ, CCS, WC */
        sunxi_nand->timing_cfg = NFC_TIMING_CFG(tWB, tADL, tWHR, tRHW, tCAD);

        /* Convert min_clk_period from picoseconds to nanoseconds */
        min_clk_period = DIV_ROUND_UP(min_clk_period, 1000);

        /*
         * Unlike what is stated in Allwinner datasheet, the clk_rate should
         * be set to (1 / min_clk_period), and not (2 / min_clk_period).
         * This new formula was verified with a scope and validated by
         * Allwinner engineers.
         */
        sunxi_nand->clk_rate = NSEC_PER_SEC / min_clk_period;
        real_clk_rate = clk_round_rate(nfc->mod_clk, sunxi_nand->clk_rate);
        if (real_clk_rate <= 0) {
                dev_err(nfc->dev, "Unable to round clk %lu\n",
                        sunxi_nand->clk_rate);
                return -EINVAL;
        }

        sunxi_nand->timing_ctl = 0;

        /*
         * ONFI specification 3.1, paragraph 4.15.2 dictates that EDO data
         * output cycle timings shall be used if the host drives tRC less than
         * 30 ns. We should also use EDO mode if tREA is bigger than tRP.
         */
        min_clk_period = NSEC_PER_SEC / real_clk_rate;
        if (min_clk_period * 2 < 30 || min_clk_period * 1000 < timings->tREA_max)
                sunxi_nand->timing_ctl = NFC_TIMING_CTL_EDO;

        return 0;
}

static int sunxi_nand_ooblayout_ecc(struct mtd_info *mtd, int section,
                                    struct mtd_oob_region *oobregion)
{
        struct nand_chip *nand = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &nand->ecc;

        if (section >= ecc->steps)
                return -ERANGE;

        oobregion->offset = section * (ecc->bytes + USER_DATA_SZ) + 4;
        oobregion->length = ecc->bytes;

        return 0;
}

static int sunxi_nand_ooblayout_free(struct mtd_info *mtd, int section,
                                     struct mtd_oob_region *oobregion)
{
        struct nand_chip *nand = mtd_to_nand(mtd);
        struct nand_ecc_ctrl *ecc = &nand->ecc;

        if (section > ecc->steps)
                return -ERANGE;

        /*
         * The first 2 bytes are used for BB markers, hence we
         * only have 2 bytes available in the first user data
         * section.
         */
        if (!section && ecc->engine_type == NAND_ECC_ENGINE_TYPE_ON_HOST) {
                oobregion->offset = 2;
                oobregion->length = 2;

                return 0;
        }

        /*
         * The controller does not provide access to OOB bytes
         * past the end of the ECC data.
         */
        if (section == ecc->steps && ecc->engine_type == NAND_ECC_ENGINE_TYPE_ON_HOST)
                return -ERANGE;

        oobregion->offset = section * (ecc->bytes + USER_DATA_SZ);

        if (section < ecc->steps)
                oobregion->length = USER_DATA_SZ;
        else
                oobregion->length = mtd->oobsize - oobregion->offset;

        return 0;
}

static const struct mtd_ooblayout_ops sunxi_nand_ooblayout_ops = {
        .ecc = sunxi_nand_ooblayout_ecc,
        .free = sunxi_nand_ooblayout_free,
};

static int sunxi_nand_hw_ecc_ctrl_init(struct nand_chip *nand,
                                       struct nand_ecc_ctrl *ecc,
                                       struct device_node *np)
{
        struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        const u8 *strengths = nfc->caps->ecc_strengths;
        struct mtd_info *mtd = nand_to_mtd(nand);
        struct nand_device *nanddev = mtd_to_nanddev(mtd);
        int nsectors;
        int i;

        if (nanddev->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) {
                int bytes;

                ecc->size = 1024;
                nsectors = mtd->writesize / ecc->size;

                /* Reserve 2 bytes for the BBM */
                bytes = (mtd->oobsize - 2) / nsectors;

                /* 4 non-ECC bytes are added before each ECC bytes section */
                bytes -= USER_DATA_SZ;

                /* and bytes has to be even. */
                if (bytes % 2)
                        bytes--;

                ecc->strength = bytes * 8 / fls(8 * ecc->size);

                for (i = 0; i < nfc->caps->nstrengths; i++) {
                        if (strengths[i] > ecc->strength)
                                break;
                }

                if (!i)
                        ecc->strength = 0;
                else
                        ecc->strength = strengths[i - 1];
        }

        if (ecc->size != 512 && ecc->size != 1024)
                return -EINVAL;

        /* Prefer 1k ECC chunk over 512 ones */
        if (ecc->size == 512 && mtd->writesize > 512) {
                ecc->size = 1024;
                ecc->strength *= 2;
        }

        /* Add ECC info retrieval from DT */
        for (i = 0; i < nfc->caps->nstrengths; i++) {
                if (ecc->strength <= strengths[i]) {
                        /*
                         * Update ecc->strength value with the actual strength
                         * that will be used by the ECC engine.
                         */
                        ecc->strength = strengths[i];
                        break;
                }
        }

        if (i >= nfc->caps->nstrengths) {
                dev_err(nfc->dev, "unsupported strength\n");
                return -ENOTSUPP;
        }

        /* HW ECC always request ECC bytes for 1024 bytes blocks */
        ecc->bytes = DIV_ROUND_UP(ecc->strength * fls(8 * 1024), 8);

        /* HW ECC always work with even numbers of ECC bytes */
        ecc->bytes = ALIGN(ecc->bytes, 2);

        nsectors = mtd->writesize / ecc->size;

        if (mtd->oobsize < ((ecc->bytes + USER_DATA_SZ) * nsectors))
                return -EINVAL;

        ecc->read_oob = sunxi_nfc_hw_ecc_read_oob;
        ecc->write_oob = sunxi_nfc_hw_ecc_write_oob;
        mtd_set_ooblayout(mtd, &sunxi_nand_ooblayout_ops);

        if (nfc->dmac || nfc->caps->has_mdma) {
                ecc->read_page = sunxi_nfc_hw_ecc_read_page_dma;
                ecc->read_subpage = sunxi_nfc_hw_ecc_read_subpage_dma;
                ecc->write_page = sunxi_nfc_hw_ecc_write_page_dma;
                nand->options |= NAND_USES_DMA;
        } else {
                ecc->read_page = sunxi_nfc_hw_ecc_read_page;
                ecc->read_subpage = sunxi_nfc_hw_ecc_read_subpage;
                ecc->write_page = sunxi_nfc_hw_ecc_write_page;
        }

        /* TODO: support DMA for raw accesses and subpage write */
        ecc->write_subpage = sunxi_nfc_hw_ecc_write_subpage;
        ecc->read_oob_raw = nand_read_oob_std;
        ecc->write_oob_raw = nand_write_oob_std;

        sunxi_nand->ecc.ecc_ctl = NFC_ECC_MODE(nfc, i) | NFC_ECC_EXCEPTION |
                                  NFC_ECC_PIPELINE | NFC_ECC_EN;

        if (ecc->size == 512) {
                if (nfc->caps->has_ecc_block_512) {
                        sunxi_nand->ecc.ecc_ctl |= NFC_ECC_BLOCK_512;
                } else {
                        dev_err(nfc->dev, "512B ECC block not supported\n");
                        return -EOPNOTSUPP;
                }
        }

        return 0;
}

static int sunxi_nand_attach_chip(struct nand_chip *nand)
{
        const struct nand_ecc_props *requirements =
                nanddev_get_ecc_requirements(&nand->base);
        struct nand_ecc_ctrl *ecc = &nand->ecc;
        struct device_node *np = nand_get_flash_node(nand);
        int ret;

        if (nand->bbt_options & NAND_BBT_USE_FLASH)
                nand->bbt_options |= NAND_BBT_NO_OOB;

        if (nand->options & NAND_NEED_SCRAMBLING)
                nand->options |= NAND_NO_SUBPAGE_WRITE;

        nand->options |= NAND_SUBPAGE_READ;

        if (!ecc->size) {
                ecc->size = requirements->step_size;
                ecc->strength = requirements->strength;
        }

        if (!ecc->size || !ecc->strength)
                return -EINVAL;

        switch (ecc->engine_type) {
        case NAND_ECC_ENGINE_TYPE_ON_HOST:
                ret = sunxi_nand_hw_ecc_ctrl_init(nand, ecc, np);
                if (ret)
                        return ret;
                break;
        case NAND_ECC_ENGINE_TYPE_NONE:
        case NAND_ECC_ENGINE_TYPE_SOFT:
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int sunxi_nfc_exec_subop(struct nand_chip *nand,
                                const struct nand_subop *subop)
{
        struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
        u32 cmd = 0, extcmd = 0, cnt = 0, addrs[2] = { };
        unsigned int i, j, remaining, start;
        void *inbuf = NULL;
        int ret;

        for (i = 0; i < subop->ninstrs; i++) {
                const struct nand_op_instr *instr = &subop->instrs[i];

                switch (instr->type) {
                case NAND_OP_CMD_INSTR:
                        if (cmd & NFC_SEND_CMD1) {
                                if (WARN_ON(cmd & NFC_SEND_CMD2))
                                        return -EINVAL;

                                cmd |= NFC_SEND_CMD2;
                                extcmd |= instr->ctx.cmd.opcode;
                        } else {
                                cmd |= NFC_SEND_CMD1 |
                                       NFC_CMD(instr->ctx.cmd.opcode);
                        }
                        break;

                case NAND_OP_ADDR_INSTR:
                        remaining = nand_subop_get_num_addr_cyc(subop, i);
                        start = nand_subop_get_addr_start_off(subop, i);
                        for (j = 0; j < 8 && j + start < remaining; j++) {
                                u32 addr = instr->ctx.addr.addrs[j + start];

                                addrs[j / 4] |= addr << (j % 4) * 8;
                        }

                        if (j)
                                cmd |= NFC_SEND_ADR | NFC_ADR_NUM(j);

                        break;

                case NAND_OP_DATA_IN_INSTR:
                case NAND_OP_DATA_OUT_INSTR:
                        start = nand_subop_get_data_start_off(subop, i);
                        remaining = nand_subop_get_data_len(subop, i);
                        cnt = min_t(u32, remaining, nfc->caps->sram_size);
                        cmd |= NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD;

                        if (instr->type == NAND_OP_DATA_OUT_INSTR) {
                                cmd |= NFC_ACCESS_DIR;
                                memcpy_toio(nfc->regs + NFC_RAM0_BASE,
                                            instr->ctx.data.buf.out + start,
                                            cnt);
                        } else {
                                inbuf = instr->ctx.data.buf.in + start;
                        }

                        break;

                case NAND_OP_WAITRDY_INSTR:
                        cmd |= NFC_WAIT_FLAG;
                        break;
                }
        }

        ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
        if (ret)
                return ret;

        if (cmd & NFC_SEND_ADR) {
                writel(addrs[0], nfc->regs + NFC_REG_ADDR_LOW);
                writel(addrs[1], nfc->regs + NFC_REG_ADDR_HIGH);
        }

        if (cmd & NFC_SEND_CMD2)
                writel(extcmd,
                       nfc->regs +
                       (cmd & NFC_ACCESS_DIR ?
                        NFC_REG_WCMD_SET : NFC_REG_RCMD_SET));

        if (cmd & NFC_DATA_TRANS)
                writel(cnt, nfc->regs + NFC_REG_CNT);

        writel(cmd, nfc->regs + NFC_REG_CMD);

        ret = sunxi_nfc_wait_events(nfc, NFC_CMD_INT_FLAG,
                                    !(cmd & NFC_WAIT_FLAG) && cnt < 64,
                                    0);
        if (ret)
                return ret;

        if (inbuf)
                memcpy_fromio(inbuf, nfc->regs + NFC_RAM0_BASE, cnt);

        return 0;
}

static int sunxi_nfc_soft_waitrdy(struct nand_chip *nand,
                                  const struct nand_subop *subop)
{
        return nand_soft_waitrdy(nand,
                                 subop->instrs[0].ctx.waitrdy.timeout_ms);
}

static const struct nand_op_parser sunxi_nfc_op_parser = NAND_OP_PARSER(
        NAND_OP_PARSER_PATTERN(sunxi_nfc_exec_subop,
                               NAND_OP_PARSER_PAT_CMD_ELEM(true),
                               NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8),
                               NAND_OP_PARSER_PAT_CMD_ELEM(true),
                               NAND_OP_PARSER_PAT_WAITRDY_ELEM(true),
                               NAND_OP_PARSER_PAT_DATA_IN_ELEM(true, 1024)),
        NAND_OP_PARSER_PATTERN(sunxi_nfc_exec_subop,
                               NAND_OP_PARSER_PAT_CMD_ELEM(true),
                               NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8),
                               NAND_OP_PARSER_PAT_DATA_OUT_ELEM(true, 1024),
                               NAND_OP_PARSER_PAT_CMD_ELEM(true),
                               NAND_OP_PARSER_PAT_WAITRDY_ELEM(true)),
);

static const struct nand_op_parser sunxi_nfc_norb_op_parser = NAND_OP_PARSER(
        NAND_OP_PARSER_PATTERN(sunxi_nfc_exec_subop,
                               NAND_OP_PARSER_PAT_CMD_ELEM(true),
                               NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8),
                               NAND_OP_PARSER_PAT_CMD_ELEM(true),
                               NAND_OP_PARSER_PAT_DATA_IN_ELEM(true, 1024)),
        NAND_OP_PARSER_PATTERN(sunxi_nfc_exec_subop,
                               NAND_OP_PARSER_PAT_CMD_ELEM(true),
                               NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8),
                               NAND_OP_PARSER_PAT_DATA_OUT_ELEM(true, 1024),
                               NAND_OP_PARSER_PAT_CMD_ELEM(true)),
        NAND_OP_PARSER_PATTERN(sunxi_nfc_soft_waitrdy,
                               NAND_OP_PARSER_PAT_WAITRDY_ELEM(false)),
);

static int sunxi_nfc_exec_op(struct nand_chip *nand,
                             const struct nand_operation *op, bool check_only)
{
        struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
        const struct nand_op_parser *parser;

        if (!check_only)
                sunxi_nfc_select_chip(nand, op->cs);

        if (sunxi_nand->sels[op->cs].rb >= 0)
                parser = &sunxi_nfc_op_parser;
        else
                parser = &sunxi_nfc_norb_op_parser;

        return nand_op_parser_exec_op(nand, parser, op, check_only);
}

static const struct nand_controller_ops sunxi_nand_controller_ops = {
        .attach_chip = sunxi_nand_attach_chip,
        .setup_interface = sunxi_nfc_setup_interface,
        .exec_op = sunxi_nfc_exec_op,
};

static void sunxi_nand_chips_cleanup(struct sunxi_nfc *nfc)
{
        struct sunxi_nand_chip *sunxi_nand;
        struct nand_chip *chip;
        int ret;

        while (!list_empty(&nfc->chips)) {
                sunxi_nand = list_first_entry(&nfc->chips,
                                              struct sunxi_nand_chip,
                                              node);
                chip = &sunxi_nand->nand;
                ret = mtd_device_unregister(nand_to_mtd(chip));
                WARN_ON(ret);
                nand_cleanup(chip);
                list_del(&sunxi_nand->node);
        }
}

static int sunxi_nand_chip_init(struct device *dev, struct sunxi_nfc *nfc,
                                struct device_node *np)
{
        struct sunxi_nand_chip *sunxi_nand;
        struct mtd_info *mtd;
        struct nand_chip *nand;
        int nsels;
        int ret;
        int i;
        u32 tmp;

        if (!of_get_property(np, "reg", &nsels))
                return -EINVAL;

        nsels /= sizeof(u32);
        if (!nsels) {
                dev_err(dev, "invalid reg property size\n");
                return -EINVAL;
        }

        sunxi_nand = devm_kzalloc(dev, struct_size(sunxi_nand, sels, nsels),
                                  GFP_KERNEL);
        if (!sunxi_nand)
                return -ENOMEM;

        sunxi_nand->nsels = nsels;

        for (i = 0; i < nsels; i++) {
                ret = of_property_read_u32_index(np, "reg", i, &tmp);
                if (ret) {
                        dev_err(dev, "could not retrieve reg property: %d\n",
                                ret);
                        return ret;
                }

                if (tmp > NFC_MAX_CS) {
                        dev_err(dev,
                                "invalid reg value: %u (max CS = 7)\n",
                                tmp);
                        return -EINVAL;
                }

                if (test_and_set_bit(tmp, &nfc->assigned_cs)) {
                        dev_err(dev, "CS %d already assigned\n", tmp);
                        return -EINVAL;
                }

                sunxi_nand->sels[i].cs = tmp;

                if (!of_property_read_u32_index(np, "allwinner,rb", i, &tmp) &&
                    tmp < 2)
                        sunxi_nand->sels[i].rb = tmp;
                else
                        sunxi_nand->sels[i].rb = -1;
        }

        nand = &sunxi_nand->nand;
        /* Default tR value specified in the ONFI spec (chapter 4.15.1) */
        nand->controller = &nfc->controller;
        nand->controller->ops = &sunxi_nand_controller_ops;

        /*
         * Set the ECC mode to the default value in case nothing is specified
         * in the DT.
         */
        nand->ecc.engine_type = NAND_ECC_ENGINE_TYPE_ON_HOST;
        nand_set_flash_node(nand, np);

        mtd = nand_to_mtd(nand);
        mtd->dev.parent = dev;

        ret = nand_scan(nand, nsels);
        if (ret)
                return ret;

        ret = mtd_device_register(mtd, NULL, 0);
        if (ret) {
                dev_err(dev, "failed to register mtd device: %d\n", ret);
                nand_cleanup(nand);
                return ret;
        }

        list_add_tail(&sunxi_nand->node, &nfc->chips);

        return 0;
}

static int sunxi_nand_chips_init(struct device *dev, struct sunxi_nfc *nfc)
{
        struct device_node *np = dev->of_node;
        int ret;

        for_each_child_of_node_scoped(np, nand_np) {
                ret = sunxi_nand_chip_init(dev, nfc, nand_np);
                if (ret) {
                        sunxi_nand_chips_cleanup(nfc);
                        return ret;
                }
        }

        return 0;
}

static int sunxi_nfc_dma_init(struct sunxi_nfc *nfc, struct resource *r)
{
        int ret;

        if (nfc->caps->has_mdma)
                return 0;

        nfc->dmac = dma_request_chan(nfc->dev, "rxtx");
        if (IS_ERR(nfc->dmac)) {
                ret = PTR_ERR(nfc->dmac);
                if (ret == -EPROBE_DEFER)
                        return ret;

                /* Ignore errors to fall back to PIO mode */
                dev_warn(nfc->dev, "failed to request rxtx DMA channel: %d\n", ret);
                nfc->dmac = NULL;
        } else {
                struct dma_slave_config dmac_cfg = { };

                dmac_cfg.src_addr = r->start + nfc->caps->reg_io_data;
                dmac_cfg.dst_addr = dmac_cfg.src_addr;
                dmac_cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
                dmac_cfg.dst_addr_width = dmac_cfg.src_addr_width;
                dmac_cfg.src_maxburst = nfc->caps->dma_maxburst;
                dmac_cfg.dst_maxburst = nfc->caps->dma_maxburst;
                dmaengine_slave_config(nfc->dmac, &dmac_cfg);
        }
        return 0;
}

static int sunxi_nfc_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct resource *r;
        struct sunxi_nfc *nfc;
        int irq;
        int ret;

        nfc = devm_kzalloc(dev, sizeof(*nfc), GFP_KERNEL);
        if (!nfc)
                return -ENOMEM;

        nfc->dev = dev;
        nand_controller_init(&nfc->controller);
        INIT_LIST_HEAD(&nfc->chips);

        nfc->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &r);
        if (IS_ERR(nfc->regs))
                return PTR_ERR(nfc->regs);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        nfc->caps = of_device_get_match_data(dev);
        if (!nfc->caps)
                return -EINVAL;

        nfc->ahb_clk = devm_clk_get_enabled(dev, "ahb");
        if (IS_ERR(nfc->ahb_clk)) {
                dev_err(dev, "failed to retrieve ahb clk\n");
                return PTR_ERR(nfc->ahb_clk);
        }

        nfc->mod_clk = devm_clk_get_enabled(dev, "mod");
        if (IS_ERR(nfc->mod_clk)) {
                dev_err(dev, "failed to retrieve mod clk\n");
                return PTR_ERR(nfc->mod_clk);
        }

        if (nfc->caps->has_ecc_clk) {
                nfc->ecc_clk = devm_clk_get_enabled(dev, "ecc");
                if (IS_ERR(nfc->ecc_clk)) {
                        dev_err(dev, "failed to retrieve ecc clk\n");
                        return PTR_ERR(nfc->ecc_clk);
                }
        }

        if (nfc->caps->has_mbus_clk) {
                nfc->mbus_clk = devm_clk_get_enabled(dev, "mbus");
                if (IS_ERR(nfc->mbus_clk)) {
                        dev_err(dev, "failed to retrieve mbus clk\n");
                        return PTR_ERR(nfc->mbus_clk);
                }
        }

        nfc->reset = devm_reset_control_get_optional_exclusive(dev, "ahb");
        if (IS_ERR(nfc->reset))
                return PTR_ERR(nfc->reset);

        ret = reset_control_deassert(nfc->reset);
        if (ret) {
                dev_err(dev, "reset err %d\n", ret);
                return ret;
        }

        ret = sunxi_nfc_rst(nfc);
        if (ret)
                goto out_ahb_reset_reassert;

        writel(0, nfc->regs + NFC_REG_INT);
        ret = devm_request_irq(dev, irq, sunxi_nfc_interrupt,
                               0, "sunxi-nand", nfc);
        if (ret)
                goto out_ahb_reset_reassert;

        ret = sunxi_nfc_dma_init(nfc, r);

        if (ret)
                goto out_ahb_reset_reassert;

        platform_set_drvdata(pdev, nfc);

        ret = sunxi_nand_chips_init(dev, nfc);
        if (ret) {
                dev_err(dev, "failed to init nand chips\n");
                goto out_release_dmac;
        }

        return 0;

out_release_dmac:
        if (nfc->dmac)
                dma_release_channel(nfc->dmac);
out_ahb_reset_reassert:
        reset_control_assert(nfc->reset);

        return ret;
}

static void sunxi_nfc_remove(struct platform_device *pdev)
{
        struct sunxi_nfc *nfc = platform_get_drvdata(pdev);

        sunxi_nand_chips_cleanup(nfc);

        reset_control_assert(nfc->reset);

        if (nfc->dmac)
                dma_release_channel(nfc->dmac);
}

static const u8 sunxi_ecc_strengths_a10[] = {
        16, 24, 28, 32, 40, 48, 56, 60, 64
};

static const u8 sunxi_ecc_strengths_h6[] = {
        16, 24, 28, 32, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80
};

static const u8 sunxi_user_data_len_h6[] = {
        0, 4, 8, 12, 16, 20, 24, 28, 32
};

static const struct sunxi_nfc_caps sunxi_nfc_a10_caps = {
        .has_ecc_block_512 = true,
        .reg_io_data = NFC_REG_A10_IO_DATA,
        .reg_ecc_err_cnt = NFC_REG_A10_ECC_ERR_CNT,
        .reg_user_data = NFC_REG_A10_USER_DATA,
        .reg_spare_area = NFC_REG_A10_SPARE_AREA,
        .reg_pat_id = NFC_REG_A10_PAT_ID,
        .reg_pat_found = NFC_REG_ECC_ST,
        .random_en_mask = BIT(9),
        .random_dir_mask = BIT(10),
        .ecc_mode_mask = GENMASK(15, 12),
        .ecc_err_mask = GENMASK(15, 0),
        .pat_found_mask = GENMASK(31, 16),
        .dma_maxburst = 4,
        .ecc_strengths = sunxi_ecc_strengths_a10,
        .nstrengths = ARRAY_SIZE(sunxi_ecc_strengths_a10),
        .max_ecc_steps = 16,
        .sram_size = 1024,
};

static const struct sunxi_nfc_caps sunxi_nfc_a23_caps = {
        .has_mdma = true,
        .has_ecc_block_512 = true,
        .reg_io_data = NFC_REG_A23_IO_DATA,
        .reg_ecc_err_cnt = NFC_REG_A10_ECC_ERR_CNT,
        .reg_user_data = NFC_REG_A10_USER_DATA,
        .reg_spare_area = NFC_REG_A10_SPARE_AREA,
        .reg_pat_id = NFC_REG_A10_PAT_ID,
        .reg_pat_found = NFC_REG_ECC_ST,
        .random_en_mask = BIT(9),
        .random_dir_mask = BIT(10),
        .ecc_mode_mask = GENMASK(15, 12),
        .ecc_err_mask = GENMASK(15, 0),
        .pat_found_mask = GENMASK(31, 16),
        .dma_maxburst = 8,
        .ecc_strengths = sunxi_ecc_strengths_a10,
        .nstrengths = ARRAY_SIZE(sunxi_ecc_strengths_a10),
        .max_ecc_steps = 16,
        .sram_size = 1024,
};

static const struct sunxi_nfc_caps sunxi_nfc_h616_caps = {
        .has_ecc_clk = true,
        .has_mbus_clk = true,
        .reg_io_data = NFC_REG_A23_IO_DATA,
        .reg_ecc_err_cnt = NFC_REG_H6_ECC_ERR_CNT,
        .reg_user_data = NFC_REG_H6_USER_DATA,
        .reg_user_data_len = NFC_REG_H6_USER_DATA_LEN,
        .reg_spare_area = NFC_REG_H6_SPARE_AREA,
        .reg_pat_id = NFC_REG_H6_PAT_ID,
        .reg_pat_found = NFC_REG_H6_PAT_FOUND,
        .random_en_mask = BIT(5),
        .random_dir_mask = BIT(6),
        .ecc_mode_mask = GENMASK(15, 8),
        .ecc_err_mask = GENMASK(31, 0),
        .pat_found_mask = GENMASK(31, 0),
        .dma_maxburst = 8,
        .ecc_strengths = sunxi_ecc_strengths_h6,
        .nstrengths = ARRAY_SIZE(sunxi_ecc_strengths_h6),
        .user_data_len_tab = sunxi_user_data_len_h6,
        .nuser_data_tab = ARRAY_SIZE(sunxi_user_data_len_h6),
        .max_ecc_steps = 32,
        .sram_size = 8192,
};

static const struct of_device_id sunxi_nfc_ids[] = {
        {
                .compatible = "allwinner,sun4i-a10-nand",
                .data = &sunxi_nfc_a10_caps,
        },
        {
                .compatible = "allwinner,sun8i-a23-nand-controller",
                .data = &sunxi_nfc_a23_caps,
        },
        {
                .compatible = "allwinner,sun50i-h616-nand-controller",
                .data = &sunxi_nfc_h616_caps,
        },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, sunxi_nfc_ids);

static struct platform_driver sunxi_nfc_driver = {
        .driver = {
                .name = "sunxi_nand",
                .of_match_table = sunxi_nfc_ids,
        },
        .probe = sunxi_nfc_probe,
        .remove = sunxi_nfc_remove,
};
module_platform_driver(sunxi_nfc_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Boris BREZILLON");
MODULE_DESCRIPTION("Allwinner NAND Flash Controller driver");