// SPDX-License-Identifier: GPL-2.0-only
/*
 * (C) 2003 Red Hat, Inc.
 * (C) 2004 Dan Brown <dan_brown@ieee.org>
 * (C) 2004 Kalev Lember <kalev@smartlink.ee>
 *
 * Author: David Woodhouse <dwmw2@infradead.org>
 * Additional Diskonchip 2000 and Millennium support by Dan Brown <dan_brown@ieee.org>
 * Diskonchip Millennium Plus support by Kalev Lember <kalev@smartlink.ee>
 *
 * Error correction code lifted from the old docecc code
 * Author: Fabrice Bellard (fabrice.bellard@netgem.com)
 * Copyright (C) 2000 Netgem S.A.
 * converted to the generic Reed-Solomon library by Thomas Gleixner <tglx@kernel.org>
 *
 * Interface to generic NAND code for M-Systems DiskOnChip devices
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/rslib.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/io.h>

#include <linux/mtd/mtd.h>
#include <linux/mtd/rawnand.h>
#include <linux/mtd/doc2000.h>
#include <linux/mtd/partitions.h>
#include <linux/mtd/inftl.h>
#include <linux/module.h>

/* Where to look for the devices? */
#ifndef CONFIG_MTD_NAND_DISKONCHIP_PROBE_ADDRESS
#define CONFIG_MTD_NAND_DISKONCHIP_PROBE_ADDRESS 0
#endif

static unsigned long doc_locations[] __initdata = {
#if defined (__alpha__) || defined(__i386__) || defined(__x86_64__)
#ifdef CONFIG_MTD_NAND_DISKONCHIP_PROBE_HIGH
        0xfffc8000, 0xfffca000, 0xfffcc000, 0xfffce000,
        0xfffd0000, 0xfffd2000, 0xfffd4000, 0xfffd6000,
        0xfffd8000, 0xfffda000, 0xfffdc000, 0xfffde000,
        0xfffe0000, 0xfffe2000, 0xfffe4000, 0xfffe6000,
        0xfffe8000, 0xfffea000, 0xfffec000, 0xfffee000,
#else
        0xc8000, 0xca000, 0xcc000, 0xce000,
        0xd0000, 0xd2000, 0xd4000, 0xd6000,
        0xd8000, 0xda000, 0xdc000, 0xde000,
        0xe0000, 0xe2000, 0xe4000, 0xe6000,
        0xe8000, 0xea000, 0xec000, 0xee000,
#endif
#endif
};

static struct mtd_info *doclist = NULL;

struct doc_priv {
        struct nand_controller base;
        void __iomem *virtadr;
        unsigned long physadr;
        u_char ChipID;
        u_char CDSNControl;
        int chips_per_floor;    /* The number of chips detected on each floor */
        int curfloor;
        int curchip;
        int mh0_page;
        int mh1_page;
        struct rs_control *rs_decoder;
        struct mtd_info *nextdoc;
        bool supports_32b_reads;

        /* Handle the last stage of initialization (BBT scan, partitioning) */
        int (*late_init)(struct mtd_info *mtd);
};

/* This is the ecc value computed by the HW ecc generator upon writing an empty
   page, one with all 0xff for data. */
static u_char empty_write_ecc[6] = { 0x4b, 0x00, 0xe2, 0x0e, 0x93, 0xf7 };

#define INFTL_BBT_RESERVED_BLOCKS 4

#define DoC_is_MillenniumPlus(doc) ((doc)->ChipID == DOC_ChipID_DocMilPlus16 || (doc)->ChipID == DOC_ChipID_DocMilPlus32)
#define DoC_is_Millennium(doc) ((doc)->ChipID == DOC_ChipID_DocMil)
#define DoC_is_2000(doc) ((doc)->ChipID == DOC_ChipID_Doc2k)

static int debug = 0;
module_param(debug, int, 0);

static int try_dword = 1;
module_param(try_dword, int, 0);

static int no_ecc_failures = 0;
module_param(no_ecc_failures, int, 0);

static int no_autopart = 0;
module_param(no_autopart, int, 0);

static int show_firmware_partition = 0;
module_param(show_firmware_partition, int, 0);

#ifdef CONFIG_MTD_NAND_DISKONCHIP_BBTWRITE
static int inftl_bbt_write = 1;
#else
static int inftl_bbt_write = 0;
#endif
module_param(inftl_bbt_write, int, 0);

static unsigned long doc_config_location = CONFIG_MTD_NAND_DISKONCHIP_PROBE_ADDRESS;
module_param(doc_config_location, ulong, 0);
MODULE_PARM_DESC(doc_config_location, "Physical memory address at which to probe for DiskOnChip");

/* Sector size for HW ECC */
#define SECTOR_SIZE 512
/* The sector bytes are packed into NB_DATA 10 bit words */
#define NB_DATA (((SECTOR_SIZE + 1) * 8 + 6) / 10)
/* Number of roots */
#define NROOTS 4
/* First consective root */
#define FCR 510
/* Number of symbols */
#define NN 1023

/*
 * The HW decoder in the DoC ASIC's provides us a error syndrome,
 * which we must convert to a standard syndrome usable by the generic
 * Reed-Solomon library code.
 *
 * Fabrice Bellard figured this out in the old docecc code. I added
 * some comments, improved a minor bit and converted it to make use
 * of the generic Reed-Solomon library. tglx
 */
static int doc_ecc_decode(struct rs_control *rs, uint8_t *data, uint8_t *ecc)
{
        int i, j, nerr, errpos[8];
        uint8_t parity;
        uint16_t ds[4], s[5], tmp, errval[8], syn[4];
        struct rs_codec *cd = rs->codec;

        memset(syn, 0, sizeof(syn));
        /* Convert the ecc bytes into words */
        ds[0] = ((ecc[4] & 0xff) >> 0) | ((ecc[5] & 0x03) << 8);
        ds[1] = ((ecc[5] & 0xfc) >> 2) | ((ecc[2] & 0x0f) << 6);
        ds[2] = ((ecc[2] & 0xf0) >> 4) | ((ecc[3] & 0x3f) << 4);
        ds[3] = ((ecc[3] & 0xc0) >> 6) | ((ecc[0] & 0xff) << 2);
        parity = ecc[1];

        /* Initialize the syndrome buffer */
        for (i = 0; i < NROOTS; i++)
                s[i] = ds[0];
        /*
         *  Evaluate
         *  s[i] = ds[3]x^3 + ds[2]x^2 + ds[1]x^1 + ds[0]
         *  where x = alpha^(FCR + i)
         */
        for (j = 1; j < NROOTS; j++) {
                if (ds[j] == 0)
                        continue;
                tmp = cd->index_of[ds[j]];
                for (i = 0; i < NROOTS; i++)
                        s[i] ^= cd->alpha_to[rs_modnn(cd, tmp + (FCR + i) * j)];
        }

        /* Calc syn[i] = s[i] / alpha^(v + i) */
        for (i = 0; i < NROOTS; i++) {
                if (s[i])
                        syn[i] = rs_modnn(cd, cd->index_of[s[i]] + (NN - FCR - i));
        }
        /* Call the decoder library */
        nerr = decode_rs16(rs, NULL, NULL, 1019, syn, 0, errpos, 0, errval);

        /* Incorrectable errors ? */
        if (nerr < 0)
                return nerr;

        /*
         * Correct the errors. The bitpositions are a bit of magic,
         * but they are given by the design of the de/encoder circuit
         * in the DoC ASIC's.
         */
        for (i = 0; i < nerr; i++) {
                int index, bitpos, pos = 1015 - errpos[i];
                uint8_t val;
                if (pos >= NB_DATA && pos < 1019)
                        continue;
                if (pos < NB_DATA) {
                        /* extract bit position (MSB first) */
                        pos = 10 * (NB_DATA - 1 - pos) - 6;
                        /* now correct the following 10 bits. At most two bytes
                           can be modified since pos is even */
                        index = (pos >> 3) ^ 1;
                        bitpos = pos & 7;
                        if ((index >= 0 && index < SECTOR_SIZE) || index == (SECTOR_SIZE + 1)) {
                                val = (uint8_t) (errval[i] >> (2 + bitpos));
                                parity ^= val;
                                if (index < SECTOR_SIZE)
                                        data[index] ^= val;
                        }
                        index = ((pos >> 3) + 1) ^ 1;
                        bitpos = (bitpos + 10) & 7;
                        if (bitpos == 0)
                                bitpos = 8;
                        if ((index >= 0 && index < SECTOR_SIZE) || index == (SECTOR_SIZE + 1)) {
                                val = (uint8_t) (errval[i] << (8 - bitpos));
                                parity ^= val;
                                if (index < SECTOR_SIZE)
                                        data[index] ^= val;
                        }
                }
        }
        /* If the parity is wrong, no rescue possible */
        return parity ? -EBADMSG : nerr;
}

static void DoC_Delay(struct doc_priv *doc, unsigned short cycles)
{
        volatile char __always_unused dummy;
        int i;

        for (i = 0; i < cycles; i++) {
                if (DoC_is_Millennium(doc))
                        dummy = ReadDOC(doc->virtadr, NOP);
                else if (DoC_is_MillenniumPlus(doc))
                        dummy = ReadDOC(doc->virtadr, Mplus_NOP);
                else
                        dummy = ReadDOC(doc->virtadr, DOCStatus);
        }

}

#define CDSN_CTRL_FR_B_MASK     (CDSN_CTRL_FR_B0 | CDSN_CTRL_FR_B1)

/* DOC_WaitReady: Wait for RDY line to be asserted by the flash chip */
static int _DoC_WaitReady(struct doc_priv *doc)
{
        void __iomem *docptr = doc->virtadr;
        unsigned long timeo = jiffies + (HZ * 10);

        if (debug)
                printk("_DoC_WaitReady...\n");
        /* Out-of-line routine to wait for chip response */
        if (DoC_is_MillenniumPlus(doc)) {
                while ((ReadDOC(docptr, Mplus_FlashControl) & CDSN_CTRL_FR_B_MASK) != CDSN_CTRL_FR_B_MASK) {
                        if (time_after(jiffies, timeo)) {
                                printk("_DoC_WaitReady timed out.\n");
                                return -EIO;
                        }
                        udelay(1);
                        cond_resched();
                }
        } else {
                while (!(ReadDOC(docptr, CDSNControl) & CDSN_CTRL_FR_B)) {
                        if (time_after(jiffies, timeo)) {
                                printk("_DoC_WaitReady timed out.\n");
                                return -EIO;
                        }
                        udelay(1);
                        cond_resched();
                }
        }

        return 0;
}

static inline int DoC_WaitReady(struct doc_priv *doc)
{
        void __iomem *docptr = doc->virtadr;
        int ret = 0;

        if (DoC_is_MillenniumPlus(doc)) {
                DoC_Delay(doc, 4);

                if ((ReadDOC(docptr, Mplus_FlashControl) & CDSN_CTRL_FR_B_MASK) != CDSN_CTRL_FR_B_MASK)
                        /* Call the out-of-line routine to wait */
                        ret = _DoC_WaitReady(doc);
        } else {
                DoC_Delay(doc, 4);

                if (!(ReadDOC(docptr, CDSNControl) & CDSN_CTRL_FR_B))
                        /* Call the out-of-line routine to wait */
                        ret = _DoC_WaitReady(doc);
                DoC_Delay(doc, 2);
        }

        if (debug)
                printk("DoC_WaitReady OK\n");
        return ret;
}

static void doc2000_write_byte(struct nand_chip *this, u_char datum)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;

        if (debug)
                printk("write_byte %02x\n", datum);
        WriteDOC(datum, docptr, CDSNSlowIO);
        WriteDOC(datum, docptr, 2k_CDSN_IO);
}

static void doc2000_writebuf(struct nand_chip *this, const u_char *buf,
                             int len)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        int i;
        if (debug)
                printk("writebuf of %d bytes: ", len);
        for (i = 0; i < len; i++) {
                WriteDOC_(buf[i], docptr, DoC_2k_CDSN_IO + i);
                if (debug && i < 16)
                        printk("%02x ", buf[i]);
        }
        if (debug)
                printk("\n");
}

static void doc2000_readbuf(struct nand_chip *this, u_char *buf, int len)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        u32 *buf32 = (u32 *)buf;
        int i;

        if (debug)
                printk("readbuf of %d bytes: ", len);

        if (!doc->supports_32b_reads ||
            ((((unsigned long)buf) | len) & 3)) {
                for (i = 0; i < len; i++)
                        buf[i] = ReadDOC(docptr, 2k_CDSN_IO + i);
        } else {
                for (i = 0; i < len / 4; i++)
                        buf32[i] = readl(docptr + DoC_2k_CDSN_IO + i);
        }
}

/*
 * We need our own readid() here because it's called before the NAND chip
 * has been initialized, and calling nand_op_readid() would lead to a NULL
 * pointer exception when dereferencing the NAND timings.
 */
static void doc200x_readid(struct nand_chip *this, unsigned int cs, u8 *id)
{
        u8 addr = 0;
        struct nand_op_instr instrs[] = {
                NAND_OP_CMD(NAND_CMD_READID, 0),
                NAND_OP_ADDR(1, &addr, 50),
                NAND_OP_8BIT_DATA_IN(2, id, 0),
        };

        struct nand_operation op = NAND_OPERATION(cs, instrs);

        if (!id)
                op.ninstrs--;

        this->controller->ops->exec_op(this, &op, false);
}

static uint16_t __init doc200x_ident_chip(struct mtd_info *mtd, int nr)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);
        uint16_t ret;
        u8 id[2];

        doc200x_readid(this, nr, id);

        ret = ((u16)id[0] << 8) | id[1];

        if (doc->ChipID == DOC_ChipID_Doc2k && try_dword && !nr) {
                /* First chip probe. See if we get same results by 32-bit access */
                union {
                        uint32_t dword;
                        uint8_t byte[4];
                } ident;
                void __iomem *docptr = doc->virtadr;

                doc200x_readid(this, nr, NULL);

                ident.dword = readl(docptr + DoC_2k_CDSN_IO);
                if (((ident.byte[0] << 8) | ident.byte[1]) == ret) {
                        pr_info("DiskOnChip 2000 responds to DWORD access\n");
                        doc->supports_32b_reads = true;
                }
        }

        return ret;
}

static void __init doc2000_count_chips(struct mtd_info *mtd)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);
        uint16_t mfrid;
        int i;

        /* Max 4 chips per floor on DiskOnChip 2000 */
        doc->chips_per_floor = 4;

        /* Find out what the first chip is */
        mfrid = doc200x_ident_chip(mtd, 0);

        /* Find how many chips in each floor. */
        for (i = 1; i < 4; i++) {
                if (doc200x_ident_chip(mtd, i) != mfrid)
                        break;
        }
        doc->chips_per_floor = i;
        pr_debug("Detected %d chips per floor.\n", i);
}

static void doc2001_write_byte(struct nand_chip *this, u_char datum)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;

        WriteDOC(datum, docptr, CDSNSlowIO);
        WriteDOC(datum, docptr, Mil_CDSN_IO);
        WriteDOC(datum, docptr, WritePipeTerm);
}

static void doc2001_writebuf(struct nand_chip *this, const u_char *buf, int len)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        int i;

        for (i = 0; i < len; i++)
                WriteDOC_(buf[i], docptr, DoC_Mil_CDSN_IO + i);
        /* Terminate write pipeline */
        WriteDOC(0x00, docptr, WritePipeTerm);
}

static void doc2001_readbuf(struct nand_chip *this, u_char *buf, int len)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        int i;

        /* Start read pipeline */
        ReadDOC(docptr, ReadPipeInit);

        for (i = 0; i < len - 1; i++)
                buf[i] = ReadDOC(docptr, Mil_CDSN_IO + (i & 0xff));

        /* Terminate read pipeline */
        buf[i] = ReadDOC(docptr, LastDataRead);
}

static void doc2001plus_writebuf(struct nand_chip *this, const u_char *buf, int len)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        int i;

        if (debug)
                printk("writebuf of %d bytes: ", len);
        for (i = 0; i < len; i++) {
                WriteDOC_(buf[i], docptr, DoC_Mil_CDSN_IO + i);
                if (debug && i < 16)
                        printk("%02x ", buf[i]);
        }
        if (debug)
                printk("\n");
}

static void doc2001plus_readbuf(struct nand_chip *this, u_char *buf, int len)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        int i;

        if (debug)
                printk("readbuf of %d bytes: ", len);

        /* Start read pipeline */
        ReadDOC(docptr, Mplus_ReadPipeInit);
        ReadDOC(docptr, Mplus_ReadPipeInit);

        for (i = 0; i < len - 2; i++) {
                buf[i] = ReadDOC(docptr, Mil_CDSN_IO);
                if (debug && i < 16)
                        printk("%02x ", buf[i]);
        }

        /* Terminate read pipeline */
        if (len >= 2) {
                buf[len - 2] = ReadDOC(docptr, Mplus_LastDataRead);
                if (debug && i < 16)
                        printk("%02x ", buf[len - 2]);
        }

        buf[len - 1] = ReadDOC(docptr, Mplus_LastDataRead);
        if (debug && i < 16)
                printk("%02x ", buf[len - 1]);
        if (debug)
                printk("\n");
}

static void doc200x_write_control(struct doc_priv *doc, u8 value)
{
        WriteDOC(value, doc->virtadr, CDSNControl);
        /* 11.4.3 -- 4 NOPs after CSDNControl write */
        DoC_Delay(doc, 4);
}

static void doc200x_exec_instr(struct nand_chip *this,
                               const struct nand_op_instr *instr)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        unsigned int i;

        switch (instr->type) {
        case NAND_OP_CMD_INSTR:
                doc200x_write_control(doc, CDSN_CTRL_CE | CDSN_CTRL_CLE);
                doc2000_write_byte(this, instr->ctx.cmd.opcode);
                break;

        case NAND_OP_ADDR_INSTR:
                doc200x_write_control(doc, CDSN_CTRL_CE | CDSN_CTRL_ALE);
                for (i = 0; i < instr->ctx.addr.naddrs; i++) {
                        u8 addr = instr->ctx.addr.addrs[i];

                        if (DoC_is_2000(doc))
                                doc2000_write_byte(this, addr);
                        else
                                doc2001_write_byte(this, addr);
                }
                break;

        case NAND_OP_DATA_IN_INSTR:
                doc200x_write_control(doc, CDSN_CTRL_CE);
                if (DoC_is_2000(doc))
                        doc2000_readbuf(this, instr->ctx.data.buf.in,
                                        instr->ctx.data.len);
                else
                        doc2001_readbuf(this, instr->ctx.data.buf.in,
                                        instr->ctx.data.len);
                break;

        case NAND_OP_DATA_OUT_INSTR:
                doc200x_write_control(doc, CDSN_CTRL_CE);
                if (DoC_is_2000(doc))
                        doc2000_writebuf(this, instr->ctx.data.buf.out,
                                         instr->ctx.data.len);
                else
                        doc2001_writebuf(this, instr->ctx.data.buf.out,
                                         instr->ctx.data.len);
                break;

        case NAND_OP_WAITRDY_INSTR:
                DoC_WaitReady(doc);
                break;
        }

        if (instr->delay_ns)
                ndelay(instr->delay_ns);
}

static int doc200x_exec_op(struct nand_chip *this,
                           const struct nand_operation *op,
                           bool check_only)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        unsigned int i;

        if (check_only)
                return true;

        doc->curchip = op->cs % doc->chips_per_floor;
        doc->curfloor = op->cs / doc->chips_per_floor;

        WriteDOC(doc->curfloor, doc->virtadr, FloorSelect);
        WriteDOC(doc->curchip, doc->virtadr, CDSNDeviceSelect);

        /* Assert CE pin */
        doc200x_write_control(doc, CDSN_CTRL_CE);

        for (i = 0; i < op->ninstrs; i++)
                doc200x_exec_instr(this, &op->instrs[i]);

        /* De-assert CE pin */
        doc200x_write_control(doc, 0);

        return 0;
}

static void doc2001plus_write_pipe_term(struct doc_priv *doc)
{
        WriteDOC(0x00, doc->virtadr, Mplus_WritePipeTerm);
        WriteDOC(0x00, doc->virtadr, Mplus_WritePipeTerm);
}

static void doc2001plus_exec_instr(struct nand_chip *this,
                                   const struct nand_op_instr *instr)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        unsigned int i;

        switch (instr->type) {
        case NAND_OP_CMD_INSTR:
                WriteDOC(instr->ctx.cmd.opcode, doc->virtadr, Mplus_FlashCmd);
                doc2001plus_write_pipe_term(doc);
                break;

        case NAND_OP_ADDR_INSTR:
                for (i = 0; i < instr->ctx.addr.naddrs; i++) {
                        u8 addr = instr->ctx.addr.addrs[i];

                        WriteDOC(addr, doc->virtadr, Mplus_FlashAddress);
                }
                doc2001plus_write_pipe_term(doc);
                /* deassert ALE */
                WriteDOC(0, doc->virtadr, Mplus_FlashControl);
                break;

        case NAND_OP_DATA_IN_INSTR:
                doc2001plus_readbuf(this, instr->ctx.data.buf.in,
                                    instr->ctx.data.len);
                break;
        case NAND_OP_DATA_OUT_INSTR:
                doc2001plus_writebuf(this, instr->ctx.data.buf.out,
                                     instr->ctx.data.len);
                doc2001plus_write_pipe_term(doc);
                break;
        case NAND_OP_WAITRDY_INSTR:
                DoC_WaitReady(doc);
                break;
        }

        if (instr->delay_ns)
                ndelay(instr->delay_ns);
}

static int doc2001plus_exec_op(struct nand_chip *this,
                               const struct nand_operation *op,
                               bool check_only)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        unsigned int i;

        if (check_only)
                return true;

        doc->curchip = op->cs % doc->chips_per_floor;
        doc->curfloor = op->cs / doc->chips_per_floor;

        /* Assert ChipEnable and deassert WriteProtect */
        WriteDOC(DOC_FLASH_CE, doc->virtadr, Mplus_FlashSelect);

        for (i = 0; i < op->ninstrs; i++)
                doc2001plus_exec_instr(this, &op->instrs[i]);

        /* De-assert ChipEnable */
        WriteDOC(0, doc->virtadr, Mplus_FlashSelect);

        return 0;
}

static void doc200x_enable_hwecc(struct nand_chip *this, int mode)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;

        /* Prime the ECC engine */
        switch (mode) {
        case NAND_ECC_READ:
                WriteDOC(DOC_ECC_RESET, docptr, ECCConf);
                WriteDOC(DOC_ECC_EN, docptr, ECCConf);
                break;
        case NAND_ECC_WRITE:
                WriteDOC(DOC_ECC_RESET, docptr, ECCConf);
                WriteDOC(DOC_ECC_EN | DOC_ECC_RW, docptr, ECCConf);
                break;
        }
}

static void doc2001plus_enable_hwecc(struct nand_chip *this, int mode)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;

        /* Prime the ECC engine */
        switch (mode) {
        case NAND_ECC_READ:
                WriteDOC(DOC_ECC_RESET, docptr, Mplus_ECCConf);
                WriteDOC(DOC_ECC_EN, docptr, Mplus_ECCConf);
                break;
        case NAND_ECC_WRITE:
                WriteDOC(DOC_ECC_RESET, docptr, Mplus_ECCConf);
                WriteDOC(DOC_ECC_EN | DOC_ECC_RW, docptr, Mplus_ECCConf);
                break;
        }
}

/* This code is only called on write */
static int doc200x_calculate_ecc(struct nand_chip *this, const u_char *dat,
                                 unsigned char *ecc_code)
{
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        int i;
        int __always_unused emptymatch = 1;

        /* flush the pipeline */
        if (DoC_is_2000(doc)) {
                WriteDOC(doc->CDSNControl & ~CDSN_CTRL_FLASH_IO, docptr, CDSNControl);
                WriteDOC(0, docptr, 2k_CDSN_IO);
                WriteDOC(0, docptr, 2k_CDSN_IO);
                WriteDOC(0, docptr, 2k_CDSN_IO);
                WriteDOC(doc->CDSNControl, docptr, CDSNControl);
        } else if (DoC_is_MillenniumPlus(doc)) {
                WriteDOC(0, docptr, Mplus_NOP);
                WriteDOC(0, docptr, Mplus_NOP);
                WriteDOC(0, docptr, Mplus_NOP);
        } else {
                WriteDOC(0, docptr, NOP);
                WriteDOC(0, docptr, NOP);
                WriteDOC(0, docptr, NOP);
        }

        for (i = 0; i < 6; i++) {
                if (DoC_is_MillenniumPlus(doc))
                        ecc_code[i] = ReadDOC_(docptr, DoC_Mplus_ECCSyndrome0 + i);
                else
                        ecc_code[i] = ReadDOC_(docptr, DoC_ECCSyndrome0 + i);
                if (ecc_code[i] != empty_write_ecc[i])
                        emptymatch = 0;
        }
        if (DoC_is_MillenniumPlus(doc))
                WriteDOC(DOC_ECC_DIS, docptr, Mplus_ECCConf);
        else
                WriteDOC(DOC_ECC_DIS, docptr, ECCConf);
#if 0
        /* If emptymatch=1, we might have an all-0xff data buffer.  Check. */
        if (emptymatch) {
                /* Note: this somewhat expensive test should not be triggered
                   often.  It could be optimized away by examining the data in
                   the writebuf routine, and remembering the result. */
                for (i = 0; i < 512; i++) {
                        if (dat[i] == 0xff)
                                continue;
                        emptymatch = 0;
                        break;
                }
        }
        /* If emptymatch still =1, we do have an all-0xff data buffer.
           Return all-0xff ecc value instead of the computed one, so
           it'll look just like a freshly-erased page. */
        if (emptymatch)
                memset(ecc_code, 0xff, 6);
#endif
        return 0;
}

static int doc200x_correct_data(struct nand_chip *this, u_char *dat,
                                u_char *read_ecc, u_char *isnull)
{
        int i, ret = 0;
        struct doc_priv *doc = nand_get_controller_data(this);
        void __iomem *docptr = doc->virtadr;
        uint8_t calc_ecc[6];
        volatile u_char dummy;

        /* flush the pipeline */
        if (DoC_is_2000(doc)) {
                dummy = ReadDOC(docptr, 2k_ECCStatus);
                dummy = ReadDOC(docptr, 2k_ECCStatus);
                dummy = ReadDOC(docptr, 2k_ECCStatus);
        } else if (DoC_is_MillenniumPlus(doc)) {
                dummy = ReadDOC(docptr, Mplus_ECCConf);
                dummy = ReadDOC(docptr, Mplus_ECCConf);
                dummy = ReadDOC(docptr, Mplus_ECCConf);
        } else {
                dummy = ReadDOC(docptr, ECCConf);
                dummy = ReadDOC(docptr, ECCConf);
                dummy = ReadDOC(docptr, ECCConf);
        }

        /* Error occurred ? */
        if (dummy & 0x80) {
                for (i = 0; i < 6; i++) {
                        if (DoC_is_MillenniumPlus(doc))
                                calc_ecc[i] = ReadDOC_(docptr, DoC_Mplus_ECCSyndrome0 + i);
                        else
                                calc_ecc[i] = ReadDOC_(docptr, DoC_ECCSyndrome0 + i);
                }

                ret = doc_ecc_decode(doc->rs_decoder, dat, calc_ecc);
                if (ret > 0)
                        pr_err("doc200x_correct_data corrected %d errors\n",
                               ret);
        }
        if (DoC_is_MillenniumPlus(doc))
                WriteDOC(DOC_ECC_DIS, docptr, Mplus_ECCConf);
        else
                WriteDOC(DOC_ECC_DIS, docptr, ECCConf);
        if (no_ecc_failures && mtd_is_eccerr(ret)) {
                pr_err("suppressing ECC failure\n");
                ret = 0;
        }
        return ret;
}

//u_char mydatabuf[528];

static int doc200x_ooblayout_ecc(struct mtd_info *mtd, int section,
                                 struct mtd_oob_region *oobregion)
{
        if (section)
                return -ERANGE;

        oobregion->offset = 0;
        oobregion->length = 6;

        return 0;
}

static int doc200x_ooblayout_free(struct mtd_info *mtd, int section,
                                  struct mtd_oob_region *oobregion)
{
        if (section > 1)
                return -ERANGE;

        /*
         * The strange out-of-order free bytes definition is a (possibly
         * unneeded) attempt to retain compatibility.  It used to read:
         *      .oobfree = { {8, 8} }
         * Since that leaves two bytes unusable, it was changed.  But the
         * following scheme might affect existing jffs2 installs by moving the
         * cleanmarker:
         *      .oobfree = { {6, 10} }
         * jffs2 seems to handle the above gracefully, but the current scheme
         * seems safer. The only problem with it is that any code retrieving
         * free bytes position must be able to handle out-of-order segments.
         */
        if (!section) {
                oobregion->offset = 8;
                oobregion->length = 8;
        } else {
                oobregion->offset = 6;
                oobregion->length = 2;
        }

        return 0;
}

static const struct mtd_ooblayout_ops doc200x_ooblayout_ops = {
        .ecc = doc200x_ooblayout_ecc,
        .free = doc200x_ooblayout_free,
};

/* Find the (I)NFTL Media Header, and optionally also the mirror media header.
   On successful return, buf will contain a copy of the media header for
   further processing.  id is the string to scan for, and will presumably be
   either "ANAND" or "BNAND".  If findmirror=1, also look for the mirror media
   header.  The page #s of the found media headers are placed in mh0_page and
   mh1_page in the DOC private structure. */
static int __init find_media_headers(struct mtd_info *mtd, u_char *buf, const char *id, int findmirror)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);
        unsigned offs;
        int ret;
        size_t retlen;

        for (offs = 0; offs < mtd->size; offs += mtd->erasesize) {
                ret = mtd_read(mtd, offs, mtd->writesize, &retlen, buf);
                if (retlen != mtd->writesize)
                        continue;
                if (ret) {
                        pr_warn("ECC error scanning DOC at 0x%x\n", offs);
                }
                if (memcmp(buf, id, 6))
                        continue;
                pr_info("Found DiskOnChip %s Media Header at 0x%x\n", id, offs);
                if (doc->mh0_page == -1) {
                        doc->mh0_page = offs >> this->page_shift;
                        if (!findmirror)
                                return 1;
                        continue;
                }
                doc->mh1_page = offs >> this->page_shift;
                return 2;
        }
        if (doc->mh0_page == -1) {
                pr_warn("DiskOnChip %s Media Header not found.\n", id);
                return 0;
        }
        /* Only one mediaheader was found.  We want buf to contain a
           mediaheader on return, so we'll have to re-read the one we found. */
        offs = doc->mh0_page << this->page_shift;
        ret = mtd_read(mtd, offs, mtd->writesize, &retlen, buf);
        if (retlen != mtd->writesize) {
                /* Insanity.  Give up. */
                pr_err("Read DiskOnChip Media Header once, but can't reread it???\n");
                return 0;
        }
        return 1;
}

static inline int __init nftl_partscan(struct mtd_info *mtd, struct mtd_partition *parts)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);
        struct nand_memory_organization *memorg;
        int ret = 0;
        u_char *buf;
        struct NFTLMediaHeader *mh;
        const unsigned psize = 1 << this->page_shift;
        int numparts = 0;
        unsigned blocks, maxblocks;
        int offs, numheaders;

        memorg = nanddev_get_memorg(&this->base);

        buf = kmalloc(mtd->writesize, GFP_KERNEL);
        if (!buf) {
                return 0;
        }
        if (!(numheaders = find_media_headers(mtd, buf, "ANAND", 1)))
                goto out;
        mh = (struct NFTLMediaHeader *)buf;

        le16_to_cpus(&mh->NumEraseUnits);
        le16_to_cpus(&mh->FirstPhysicalEUN);
        le32_to_cpus(&mh->FormattedSize);

        pr_info("    DataOrgID        = %s\n"
                "    NumEraseUnits    = %d\n"
                "    FirstPhysicalEUN = %d\n"
                "    FormattedSize    = %d\n"
                "    UnitSizeFactor   = %d\n",
                mh->DataOrgID, mh->NumEraseUnits,
                mh->FirstPhysicalEUN, mh->FormattedSize,
                mh->UnitSizeFactor);

        blocks = mtd->size >> this->phys_erase_shift;
        maxblocks = min(32768U, mtd->erasesize - psize);

        if (mh->UnitSizeFactor == 0x00) {
                /* Auto-determine UnitSizeFactor.  The constraints are:
                   - There can be at most 32768 virtual blocks.
                   - There can be at most (virtual block size - page size)
                   virtual blocks (because MediaHeader+BBT must fit in 1).
                 */
                mh->UnitSizeFactor = 0xff;
                while (blocks > maxblocks) {
                        blocks >>= 1;
                        maxblocks = min(32768U, (maxblocks << 1) + psize);
                        mh->UnitSizeFactor--;
                }
                pr_warn("UnitSizeFactor=0x00 detected.  Correct value is assumed to be 0x%02x.\n", mh->UnitSizeFactor);
        }

        /* NOTE: The lines below modify internal variables of the NAND and MTD
           layers; variables with have already been configured by nand_scan.
           Unfortunately, we didn't know before this point what these values
           should be.  Thus, this code is somewhat dependent on the exact
           implementation of the NAND layer.  */
        if (mh->UnitSizeFactor != 0xff) {
                this->bbt_erase_shift += (0xff - mh->UnitSizeFactor);
                memorg->pages_per_eraseblock <<= (0xff - mh->UnitSizeFactor);
                mtd->erasesize <<= (0xff - mh->UnitSizeFactor);
                pr_info("Setting virtual erase size to %d\n", mtd->erasesize);
                blocks = mtd->size >> this->bbt_erase_shift;
                maxblocks = min(32768U, mtd->erasesize - psize);
        }

        if (blocks > maxblocks) {
                pr_err("UnitSizeFactor of 0x%02x is inconsistent with device size.  Aborting.\n", mh->UnitSizeFactor);
                goto out;
        }

        /* Skip past the media headers. */
        offs = max(doc->mh0_page, doc->mh1_page);
        offs <<= this->page_shift;
        offs += mtd->erasesize;

        if (show_firmware_partition == 1) {
                parts[0].name = " DiskOnChip Firmware / Media Header partition";
                parts[0].offset = 0;
                parts[0].size = offs;
                numparts = 1;
        }

        parts[numparts].name = " DiskOnChip BDTL partition";
        parts[numparts].offset = offs;
        parts[numparts].size = (mh->NumEraseUnits - numheaders) << this->bbt_erase_shift;

        offs += parts[numparts].size;
        numparts++;

        if (offs < mtd->size) {
                parts[numparts].name = " DiskOnChip Remainder partition";
                parts[numparts].offset = offs;
                parts[numparts].size = mtd->size - offs;
                numparts++;
        }

        ret = numparts;
 out:
        kfree(buf);
        return ret;
}

/* This is a stripped-down copy of the code in inftlmount.c */
static inline int __init inftl_partscan(struct mtd_info *mtd, struct mtd_partition *parts)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);
        int ret = 0;
        u_char *buf;
        struct INFTLMediaHeader *mh;
        struct INFTLPartition *ip;
        int numparts = 0;
        int blocks;
        int vshift, lastvunit = 0;
        int i;
        int end = mtd->size;

        if (inftl_bbt_write)
                end -= (INFTL_BBT_RESERVED_BLOCKS << this->phys_erase_shift);

        buf = kmalloc(mtd->writesize, GFP_KERNEL);
        if (!buf) {
                return 0;
        }

        if (!find_media_headers(mtd, buf, "BNAND", 0))
                goto out;
        doc->mh1_page = doc->mh0_page + (4096 >> this->page_shift);
        mh = (struct INFTLMediaHeader *)buf;

        le32_to_cpus(&mh->NoOfBootImageBlocks);
        le32_to_cpus(&mh->NoOfBinaryPartitions);
        le32_to_cpus(&mh->NoOfBDTLPartitions);
        le32_to_cpus(&mh->BlockMultiplierBits);
        le32_to_cpus(&mh->FormatFlags);
        le32_to_cpus(&mh->PercentUsed);

        pr_info("    bootRecordID          = %s\n"
                "    NoOfBootImageBlocks   = %d\n"
                "    NoOfBinaryPartitions  = %d\n"
                "    NoOfBDTLPartitions    = %d\n"
                "    BlockMultiplierBits   = %d\n"
                "    FormatFlgs            = %d\n"
                "    OsakVersion           = %d.%d.%d.%d\n"
                "    PercentUsed           = %d\n",
                mh->bootRecordID, mh->NoOfBootImageBlocks,
                mh->NoOfBinaryPartitions,
                mh->NoOfBDTLPartitions,
                mh->BlockMultiplierBits, mh->FormatFlags,
                ((unsigned char *) &mh->OsakVersion)[0] & 0xf,
                ((unsigned char *) &mh->OsakVersion)[1] & 0xf,
                ((unsigned char *) &mh->OsakVersion)[2] & 0xf,
                ((unsigned char *) &mh->OsakVersion)[3] & 0xf,
                mh->PercentUsed);

        vshift = this->phys_erase_shift + mh->BlockMultiplierBits;

        blocks = mtd->size >> vshift;
        if (blocks > 32768) {
                pr_err("BlockMultiplierBits=%d is inconsistent with device size.  Aborting.\n", mh->BlockMultiplierBits);
                goto out;
        }

        blocks = doc->chips_per_floor << (this->chip_shift - this->phys_erase_shift);
        if (inftl_bbt_write && (blocks > mtd->erasesize)) {
                pr_err("Writeable BBTs spanning more than one erase block are not yet supported.  FIX ME!\n");
                goto out;
        }

        /* Scan the partitions */
        for (i = 0; (i < 4); i++) {
                ip = &(mh->Partitions[i]);
                le32_to_cpus(&ip->virtualUnits);
                le32_to_cpus(&ip->firstUnit);
                le32_to_cpus(&ip->lastUnit);
                le32_to_cpus(&ip->flags);
                le32_to_cpus(&ip->spareUnits);
                le32_to_cpus(&ip->Reserved0);

                pr_info("    PARTITION[%d] ->\n"
                        "        virtualUnits    = %d\n"
                        "        firstUnit       = %d\n"
                        "        lastUnit        = %d\n"
                        "        flags           = 0x%x\n"
                        "        spareUnits      = %d\n",
                        i, ip->virtualUnits, ip->firstUnit,
                        ip->lastUnit, ip->flags,
                        ip->spareUnits);

                if ((show_firmware_partition == 1) &&
                    (i == 0) && (ip->firstUnit > 0)) {
                        parts[0].name = " DiskOnChip IPL / Media Header partition";
                        parts[0].offset = 0;
                        parts[0].size = (uint64_t)mtd->erasesize * ip->firstUnit;
                        numparts = 1;
                }

                if (ip->flags & INFTL_BINARY)
                        parts[numparts].name = " DiskOnChip BDK partition";
                else
                        parts[numparts].name = " DiskOnChip BDTL partition";
                parts[numparts].offset = ip->firstUnit << vshift;
                parts[numparts].size = (1 + ip->lastUnit - ip->firstUnit) << vshift;
                numparts++;
                if (ip->lastUnit > lastvunit)
                        lastvunit = ip->lastUnit;
                if (ip->flags & INFTL_LAST)
                        break;
        }
        lastvunit++;
        if ((lastvunit << vshift) < end) {
                parts[numparts].name = " DiskOnChip Remainder partition";
                parts[numparts].offset = lastvunit << vshift;
                parts[numparts].size = end - parts[numparts].offset;
                numparts++;
        }
        ret = numparts;
 out:
        kfree(buf);
        return ret;
}

static int __init nftl_scan_bbt(struct mtd_info *mtd)
{
        int ret, numparts;
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);
        struct mtd_partition parts[2];

        memset((char *)parts, 0, sizeof(parts));
        /* On NFTL, we have to find the media headers before we can read the
           BBTs, since they're stored in the media header eraseblocks. */
        numparts = nftl_partscan(mtd, parts);
        if (!numparts)
                return -EIO;
        this->bbt_td->options = NAND_BBT_ABSPAGE | NAND_BBT_8BIT |
                                NAND_BBT_SAVECONTENT | NAND_BBT_WRITE |
                                NAND_BBT_VERSION;
        this->bbt_td->veroffs = 7;
        this->bbt_td->pages[0] = doc->mh0_page + 1;
        if (doc->mh1_page != -1) {
                this->bbt_md->options = NAND_BBT_ABSPAGE | NAND_BBT_8BIT |
                                        NAND_BBT_SAVECONTENT | NAND_BBT_WRITE |
                                        NAND_BBT_VERSION;
                this->bbt_md->veroffs = 7;
                this->bbt_md->pages[0] = doc->mh1_page + 1;
        } else {
                this->bbt_md = NULL;
        }

        ret = nand_create_bbt(this);
        if (ret)
                return ret;

        return mtd_device_register(mtd, parts, no_autopart ? 0 : numparts);
}

static int __init inftl_scan_bbt(struct mtd_info *mtd)
{
        int ret, numparts;
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);
        struct mtd_partition parts[5];

        if (nanddev_ntargets(&this->base) > doc->chips_per_floor) {
                pr_err("Multi-floor INFTL devices not yet supported.\n");
                return -EIO;
        }

        if (DoC_is_MillenniumPlus(doc)) {
                this->bbt_td->options = NAND_BBT_2BIT | NAND_BBT_ABSPAGE;
                if (inftl_bbt_write)
                        this->bbt_td->options |= NAND_BBT_WRITE;
                this->bbt_td->pages[0] = 2;
                this->bbt_md = NULL;
        } else {
                this->bbt_td->options = NAND_BBT_LASTBLOCK | NAND_BBT_8BIT | NAND_BBT_VERSION;
                if (inftl_bbt_write)
                        this->bbt_td->options |= NAND_BBT_WRITE;
                this->bbt_td->offs = 8;
                this->bbt_td->len = 8;
                this->bbt_td->veroffs = 7;
                this->bbt_td->maxblocks = INFTL_BBT_RESERVED_BLOCKS;
                this->bbt_td->reserved_block_code = 0x01;
                this->bbt_td->pattern = "MSYS_BBT";

                this->bbt_md->options = NAND_BBT_LASTBLOCK | NAND_BBT_8BIT | NAND_BBT_VERSION;
                if (inftl_bbt_write)
                        this->bbt_md->options |= NAND_BBT_WRITE;
                this->bbt_md->offs = 8;
                this->bbt_md->len = 8;
                this->bbt_md->veroffs = 7;
                this->bbt_md->maxblocks = INFTL_BBT_RESERVED_BLOCKS;
                this->bbt_md->reserved_block_code = 0x01;
                this->bbt_md->pattern = "TBB_SYSM";
        }

        ret = nand_create_bbt(this);
        if (ret)
                return ret;

        memset((char *)parts, 0, sizeof(parts));
        numparts = inftl_partscan(mtd, parts);
        /* At least for now, require the INFTL Media Header.  We could probably
           do without it for non-INFTL use, since all it gives us is
           autopartitioning, but I want to give it more thought. */
        if (!numparts)
                return -EIO;
        return mtd_device_register(mtd, parts, no_autopart ? 0 : numparts);
}

static inline int __init doc2000_init(struct mtd_info *mtd)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);

        doc->late_init = nftl_scan_bbt;

        doc->CDSNControl = CDSN_CTRL_FLASH_IO | CDSN_CTRL_ECC_IO;
        doc2000_count_chips(mtd);
        mtd->name = "DiskOnChip 2000 (NFTL Model)";
        return (4 * doc->chips_per_floor);
}

static inline int __init doc2001_init(struct mtd_info *mtd)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);

        ReadDOC(doc->virtadr, ChipID);
        ReadDOC(doc->virtadr, ChipID);
        ReadDOC(doc->virtadr, ChipID);
        if (ReadDOC(doc->virtadr, ChipID) != DOC_ChipID_DocMil) {
                /* It's not a Millennium; it's one of the newer
                   DiskOnChip 2000 units with a similar ASIC.
                   Treat it like a Millennium, except that it
                   can have multiple chips. */
                doc2000_count_chips(mtd);
                mtd->name = "DiskOnChip 2000 (INFTL Model)";
                doc->late_init = inftl_scan_bbt;
                return (4 * doc->chips_per_floor);
        } else {
                /* Bog-standard Millennium */
                doc->chips_per_floor = 1;
                mtd->name = "DiskOnChip Millennium";
                doc->late_init = nftl_scan_bbt;
                return 1;
        }
}

static inline int __init doc2001plus_init(struct mtd_info *mtd)
{
        struct nand_chip *this = mtd_to_nand(mtd);
        struct doc_priv *doc = nand_get_controller_data(this);

        doc->late_init = inftl_scan_bbt;
        this->ecc.hwctl = doc2001plus_enable_hwecc;

        doc->chips_per_floor = 1;
        mtd->name = "DiskOnChip Millennium Plus";

        return 1;
}

static int doc200x_attach_chip(struct nand_chip *chip)
{
        if (chip->ecc.engine_type != NAND_ECC_ENGINE_TYPE_ON_HOST)
                return 0;

        chip->ecc.placement = NAND_ECC_PLACEMENT_INTERLEAVED;
        chip->ecc.size = 512;
        chip->ecc.bytes = 6;
        chip->ecc.strength = 2;
        chip->ecc.options = NAND_ECC_GENERIC_ERASED_CHECK;
        chip->ecc.hwctl = doc200x_enable_hwecc;
        chip->ecc.calculate = doc200x_calculate_ecc;
        chip->ecc.correct = doc200x_correct_data;

        return 0;
}

static const struct nand_controller_ops doc200x_ops = {
        .exec_op = doc200x_exec_op,
        .attach_chip = doc200x_attach_chip,
};

static const struct nand_controller_ops doc2001plus_ops = {
        .exec_op = doc2001plus_exec_op,
        .attach_chip = doc200x_attach_chip,
};

static int __init doc_probe(unsigned long physadr)
{
        struct nand_chip *nand = NULL;
        struct doc_priv *doc = NULL;
        unsigned char ChipID;
        struct mtd_info *mtd;
        void __iomem *virtadr;
        unsigned char save_control;
        unsigned char tmp, tmpb, tmpc;
        int reg, len, numchips;
        int ret = 0;

        if (!request_mem_region(physadr, DOC_IOREMAP_LEN, "DiskOnChip"))
                return -EBUSY;
        virtadr = ioremap(physadr, DOC_IOREMAP_LEN);
        if (!virtadr) {
                pr_err("Diskonchip ioremap failed: 0x%x bytes at 0x%lx\n",
                       DOC_IOREMAP_LEN, physadr);
                ret = -EIO;
                goto error_ioremap;
        }

        /* It's not possible to cleanly detect the DiskOnChip - the
         * bootup procedure will put the device into reset mode, and
         * it's not possible to talk to it without actually writing
         * to the DOCControl register. So we store the current contents
         * of the DOCControl register's location, in case we later decide
         * that it's not a DiskOnChip, and want to put it back how we
         * found it.
         */
        save_control = ReadDOC(virtadr, DOCControl);

        /* Reset the DiskOnChip ASIC */
        WriteDOC(DOC_MODE_CLR_ERR | DOC_MODE_MDWREN | DOC_MODE_RESET, virtadr, DOCControl);
        WriteDOC(DOC_MODE_CLR_ERR | DOC_MODE_MDWREN | DOC_MODE_RESET, virtadr, DOCControl);

        /* Enable the DiskOnChip ASIC */
        WriteDOC(DOC_MODE_CLR_ERR | DOC_MODE_MDWREN | DOC_MODE_NORMAL, virtadr, DOCControl);
        WriteDOC(DOC_MODE_CLR_ERR | DOC_MODE_MDWREN | DOC_MODE_NORMAL, virtadr, DOCControl);

        ChipID = ReadDOC(virtadr, ChipID);

        switch (ChipID) {
        case DOC_ChipID_Doc2k:
                reg = DoC_2k_ECCStatus;
                break;
        case DOC_ChipID_DocMil:
                reg = DoC_ECCConf;
                break;
        case DOC_ChipID_DocMilPlus16:
        case DOC_ChipID_DocMilPlus32:
        case 0:
                /* Possible Millennium Plus, need to do more checks */
                /* Possibly release from power down mode */
                for (tmp = 0; (tmp < 4); tmp++)
                        ReadDOC(virtadr, Mplus_Power);

                /* Reset the Millennium Plus ASIC */
                tmp = DOC_MODE_RESET | DOC_MODE_MDWREN | DOC_MODE_RST_LAT | DOC_MODE_BDECT;
                WriteDOC(tmp, virtadr, Mplus_DOCControl);
                WriteDOC(~tmp, virtadr, Mplus_CtrlConfirm);

                usleep_range(1000, 2000);
                /* Enable the Millennium Plus ASIC */
                tmp = DOC_MODE_NORMAL | DOC_MODE_MDWREN | DOC_MODE_RST_LAT | DOC_MODE_BDECT;
                WriteDOC(tmp, virtadr, Mplus_DOCControl);
                WriteDOC(~tmp, virtadr, Mplus_CtrlConfirm);
                usleep_range(1000, 2000);

                ChipID = ReadDOC(virtadr, ChipID);

                switch (ChipID) {
                case DOC_ChipID_DocMilPlus16:
                        reg = DoC_Mplus_Toggle;
                        break;
                case DOC_ChipID_DocMilPlus32:
                        pr_err("DiskOnChip Millennium Plus 32MB is not supported, ignoring.\n");
                        fallthrough;
                default:
                        ret = -ENODEV;
                        goto notfound;
                }
                break;

        default:
                ret = -ENODEV;
                goto notfound;
        }
        /* Check the TOGGLE bit in the ECC register */
        tmp = ReadDOC_(virtadr, reg) & DOC_TOGGLE_BIT;
        tmpb = ReadDOC_(virtadr, reg) & DOC_TOGGLE_BIT;
        tmpc = ReadDOC_(virtadr, reg) & DOC_TOGGLE_BIT;
        if ((tmp == tmpb) || (tmp != tmpc)) {
                pr_warn("Possible DiskOnChip at 0x%lx failed TOGGLE test, dropping.\n", physadr);
                ret = -ENODEV;
                goto notfound;
        }

        for (mtd = doclist; mtd; mtd = doc->nextdoc) {
                unsigned char oldval;
                unsigned char newval;
                nand = mtd_to_nand(mtd);
                doc = nand_get_controller_data(nand);
                /* Use the alias resolution register to determine if this is
                   in fact the same DOC aliased to a new address.  If writes
                   to one chip's alias resolution register change the value on
                   the other chip, they're the same chip. */
                if (ChipID == DOC_ChipID_DocMilPlus16) {
                        oldval = ReadDOC(doc->virtadr, Mplus_AliasResolution);
                        newval = ReadDOC(virtadr, Mplus_AliasResolution);
                } else {
                        oldval = ReadDOC(doc->virtadr, AliasResolution);
                        newval = ReadDOC(virtadr, AliasResolution);
                }
                if (oldval != newval)
                        continue;
                if (ChipID == DOC_ChipID_DocMilPlus16) {
                        WriteDOC(~newval, virtadr, Mplus_AliasResolution);
                        oldval = ReadDOC(doc->virtadr, Mplus_AliasResolution);
                        WriteDOC(newval, virtadr, Mplus_AliasResolution);       // restore it
                } else {
                        WriteDOC(~newval, virtadr, AliasResolution);
                        oldval = ReadDOC(doc->virtadr, AliasResolution);
                        WriteDOC(newval, virtadr, AliasResolution);     // restore it
                }
                newval = ~newval;
                if (oldval == newval) {
                        pr_debug("Found alias of DOC at 0x%lx to 0x%lx\n",
                                 doc->physadr, physadr);
                        goto notfound;
                }
        }

        pr_notice("DiskOnChip found at 0x%lx\n", physadr);

        len = sizeof(struct nand_chip) + sizeof(struct doc_priv) +
              (2 * sizeof(struct nand_bbt_descr));
        nand = kzalloc(len, GFP_KERNEL);
        if (!nand) {
                ret = -ENOMEM;
                goto fail;
        }

        /*
         * Allocate a RS codec instance
         *
         * Symbolsize is 10 (bits)
         * Primitve polynomial is x^10+x^3+1
         * First consecutive root is 510
         * Primitve element to generate roots = 1
         * Generator polinomial degree = 4
         */
        doc = (struct doc_priv *) (nand + 1);
        doc->rs_decoder = init_rs(10, 0x409, FCR, 1, NROOTS);
        if (!doc->rs_decoder) {
                pr_err("DiskOnChip: Could not create a RS codec\n");
                ret = -ENOMEM;
                goto fail;
        }

        nand_controller_init(&doc->base);
        if (ChipID == DOC_ChipID_DocMilPlus16)
                doc->base.ops = &doc2001plus_ops;
        else
                doc->base.ops = &doc200x_ops;

        mtd                     = nand_to_mtd(nand);
        nand->bbt_td            = (struct nand_bbt_descr *) (doc + 1);
        nand->bbt_md            = nand->bbt_td + 1;

        mtd->owner              = THIS_MODULE;
        mtd_set_ooblayout(mtd, &doc200x_ooblayout_ops);

        nand->controller        = &doc->base;
        nand_set_controller_data(nand, doc);
        nand->bbt_options       = NAND_BBT_USE_FLASH;
        /* Skip the automatic BBT scan so we can run it manually */
        nand->options           |= NAND_SKIP_BBTSCAN | NAND_NO_BBM_QUIRK;

        doc->physadr            = physadr;
        doc->virtadr            = virtadr;
        doc->ChipID             = ChipID;
        doc->curfloor           = -1;
        doc->curchip            = -1;
        doc->mh0_page           = -1;
        doc->mh1_page           = -1;
        doc->nextdoc            = doclist;

        if (ChipID == DOC_ChipID_Doc2k)
                numchips = doc2000_init(mtd);
        else if (ChipID == DOC_ChipID_DocMilPlus16)
                numchips = doc2001plus_init(mtd);
        else
                numchips = doc2001_init(mtd);

        ret = nand_scan(nand, numchips);
        if (ret)
                goto fail;

        ret = doc->late_init(mtd);
        if (ret) {
                nand_cleanup(nand);
                goto fail;
        }

        /* Success! */
        doclist = mtd;
        return 0;

 notfound:
        /* Put back the contents of the DOCControl register, in case it's not
           actually a DiskOnChip.  */
        WriteDOC(save_control, virtadr, DOCControl);
 fail:
        if (doc)
                free_rs(doc->rs_decoder);
        kfree(nand);
        iounmap(virtadr);

error_ioremap:
        release_mem_region(physadr, DOC_IOREMAP_LEN);

        return ret;
}

static void release_nanddoc(void)
{
        struct mtd_info *mtd, *nextmtd;
        struct nand_chip *nand;
        struct doc_priv *doc;
        int ret;

        for (mtd = doclist; mtd; mtd = nextmtd) {
                nand = mtd_to_nand(mtd);
                doc = nand_get_controller_data(nand);

                nextmtd = doc->nextdoc;
                ret = mtd_device_unregister(mtd);
                WARN_ON(ret);
                nand_cleanup(nand);
                iounmap(doc->virtadr);
                release_mem_region(doc->physadr, DOC_IOREMAP_LEN);
                free_rs(doc->rs_decoder);
                kfree(nand);
        }
}

static int __init init_nanddoc(void)
{
        int i, ret = 0;

        if (doc_config_location) {
                pr_info("Using configured DiskOnChip probe address 0x%lx\n",
                        doc_config_location);
                ret = doc_probe(doc_config_location);
                if (ret < 0)
                        return ret;
        } else {
                for (i = 0; i < ARRAY_SIZE(doc_locations); i++) {
                        doc_probe(doc_locations[i]);
                }
        }
        /* No banner message any more. Print a message if no DiskOnChip
           found, so the user knows we at least tried. */
        if (!doclist) {
                pr_info("No valid DiskOnChip devices found\n");
                ret = -ENODEV;
        }
        return ret;
}

static void __exit cleanup_nanddoc(void)
{
        /* Cleanup the nand/DoC resources */
        release_nanddoc();
}

module_init(init_nanddoc);
module_exit(cleanup_nanddoc);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
MODULE_DESCRIPTION("M-Systems DiskOnChip 2000, Millennium and Millennium Plus device driver");