// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for the Atmel AHB DMA Controller (aka HDMA or DMAC on AT91 systems)
 *
 * Copyright (C) 2008 Atmel Corporation
 * Copyright (C) 2022 Microchip Technology, Inc. and its subsidiaries
 *
 * This supports the Atmel AHB DMA Controller found in several Atmel SoCs.
 * The only Atmel DMA Controller that is not covered by this driver is the one
 * found on AT91SAM9263.
 */

#include <dt-bindings/dma/at91.h>
#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/dmaengine.h>
#include <linux/dmapool.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/overflow.h>
#include <linux/of_platform.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#include "dmaengine.h"
#include "virt-dma.h"

/*
 * Glossary
 * --------
 *
 * at_hdmac             : Name of the ATmel AHB DMA Controller
 * at_dma_ / atdma      : ATmel DMA controller entity related
 * atc_ / atchan        : ATmel DMA Channel entity related
 */

#define AT_DMA_MAX_NR_CHANNELS  8

/* Global Configuration Register */
#define AT_DMA_GCFG             0x00
#define AT_DMA_IF_BIGEND(i)     BIT((i))        /* AHB-Lite Interface i in Big-endian mode */
#define AT_DMA_ARB_CFG          BIT(4)          /* Arbiter mode. */

/* Controller Enable Register */
#define AT_DMA_EN               0x04
#define AT_DMA_ENABLE           BIT(0)

/* Software Single Request Register */
#define AT_DMA_SREQ             0x08
#define AT_DMA_SSREQ(x)         BIT((x) << 1)           /* Request a source single transfer on channel x */
#define AT_DMA_DSREQ(x)         BIT(1 + ((x) << 1))     /* Request a destination single transfer on channel x */

/* Software Chunk Transfer Request Register */
#define AT_DMA_CREQ             0x0c
#define AT_DMA_SCREQ(x)         BIT((x) << 1)           /* Request a source chunk transfer on channel x */
#define AT_DMA_DCREQ(x)         BIT(1 + ((x) << 1))     /* Request a destination chunk transfer on channel x */

/* Software Last Transfer Flag Register */
#define AT_DMA_LAST             0x10
#define AT_DMA_SLAST(x)         BIT((x) << 1)           /* This src rq is last tx of buffer on channel x */
#define AT_DMA_DLAST(x)         BIT(1 + ((x) << 1))     /* This dst rq is last tx of buffer on channel x */

/* Request Synchronization Register */
#define AT_DMA_SYNC             0x14
#define AT_DMA_SYR(h)           BIT((h))                /* Synchronize handshake line h */

/* Error, Chained Buffer transfer completed and Buffer transfer completed Interrupt registers */
#define AT_DMA_EBCIER           0x18                    /* Enable register */
#define AT_DMA_EBCIDR           0x1c                    /* Disable register */
#define AT_DMA_EBCIMR           0x20                    /* Mask Register */
#define AT_DMA_EBCISR           0x24                    /* Status Register */
#define AT_DMA_CBTC_OFFSET      8
#define AT_DMA_ERR_OFFSET       16
#define AT_DMA_BTC(x)           BIT((x))
#define AT_DMA_CBTC(x)          BIT(AT_DMA_CBTC_OFFSET + (x))
#define AT_DMA_ERR(x)           BIT(AT_DMA_ERR_OFFSET + (x))

/* Channel Handler Enable Register */
#define AT_DMA_CHER             0x28
#define AT_DMA_ENA(x)           BIT((x))
#define AT_DMA_SUSP(x)          BIT(8 + (x))
#define AT_DMA_KEEP(x)          BIT(24 + (x))

/* Channel Handler Disable Register */
#define AT_DMA_CHDR             0x2c
#define AT_DMA_DIS(x)           BIT(x)
#define AT_DMA_RES(x)           BIT(8 + (x))

/* Channel Handler Status Register */
#define AT_DMA_CHSR             0x30
#define AT_DMA_EMPT(x)          BIT(16 + (x))
#define AT_DMA_STAL(x)          BIT(24 + (x))

/* Channel registers base address */
#define AT_DMA_CH_REGS_BASE     0x3c
#define ch_regs(x)              (AT_DMA_CH_REGS_BASE + (x) * 0x28) /* Channel x base addr */

/* Hardware register offset for each channel */
#define ATC_SADDR_OFFSET        0x00    /* Source Address Register */
#define ATC_DADDR_OFFSET        0x04    /* Destination Address Register */
#define ATC_DSCR_OFFSET         0x08    /* Descriptor Address Register */
#define ATC_CTRLA_OFFSET        0x0c    /* Control A Register */
#define ATC_CTRLB_OFFSET        0x10    /* Control B Register */
#define ATC_CFG_OFFSET          0x14    /* Configuration Register */
#define ATC_SPIP_OFFSET         0x18    /* Src PIP Configuration Register */
#define ATC_DPIP_OFFSET         0x1c    /* Dst PIP Configuration Register */


/* Bitfield definitions */

/* Bitfields in DSCR */
#define ATC_DSCR_IF             GENMASK(1, 0)   /* Dsc feched via AHB-Lite Interface */

/* Bitfields in CTRLA */
#define ATC_BTSIZE_MAX          GENMASK(15, 0)  /* Maximum Buffer Transfer Size */
#define ATC_BTSIZE              GENMASK(15, 0)  /* Buffer Transfer Size */
#define ATC_SCSIZE              GENMASK(18, 16) /* Source Chunk Transfer Size */
#define ATC_DCSIZE              GENMASK(22, 20) /* Destination Chunk Transfer Size */
#define ATC_SRC_WIDTH           GENMASK(25, 24) /* Source Single Transfer Size */
#define ATC_DST_WIDTH           GENMASK(29, 28) /* Destination Single Transfer Size */
#define ATC_DONE                BIT(31) /* Tx Done (only written back in descriptor) */

/* Bitfields in CTRLB */
#define ATC_SIF                 GENMASK(1, 0)   /* Src tx done via AHB-Lite Interface i */
#define ATC_DIF                 GENMASK(5, 4)   /* Dst tx done via AHB-Lite Interface i */
#define AT_DMA_MEM_IF           0x0             /* interface 0 as memory interface */
#define AT_DMA_PER_IF           0x1             /* interface 1 as peripheral interface */
#define ATC_SRC_PIP             BIT(8)          /* Source Picture-in-Picture enabled */
#define ATC_DST_PIP             BIT(12)         /* Destination Picture-in-Picture enabled */
#define ATC_SRC_DSCR_DIS        BIT(16)         /* Src Descriptor fetch disable */
#define ATC_DST_DSCR_DIS        BIT(20)         /* Dst Descriptor fetch disable */
#define ATC_FC                  GENMASK(23, 21) /* Choose Flow Controller */
#define ATC_FC_MEM2MEM          0x0             /* Mem-to-Mem (DMA) */
#define ATC_FC_MEM2PER          0x1             /* Mem-to-Periph (DMA) */
#define ATC_FC_PER2MEM          0x2             /* Periph-to-Mem (DMA) */
#define ATC_FC_PER2PER          0x3             /* Periph-to-Periph (DMA) */
#define ATC_FC_PER2MEM_PER      0x4             /* Periph-to-Mem (Peripheral) */
#define ATC_FC_MEM2PER_PER      0x5             /* Mem-to-Periph (Peripheral) */
#define ATC_FC_PER2PER_SRCPER   0x6             /* Periph-to-Periph (Src Peripheral) */
#define ATC_FC_PER2PER_DSTPER   0x7             /* Periph-to-Periph (Dst Peripheral) */
#define ATC_SRC_ADDR_MODE       GENMASK(25, 24)
#define ATC_SRC_ADDR_MODE_INCR  0x0             /* Incrementing Mode */
#define ATC_SRC_ADDR_MODE_DECR  0x1             /* Decrementing Mode */
#define ATC_SRC_ADDR_MODE_FIXED 0x2             /* Fixed Mode */
#define ATC_DST_ADDR_MODE       GENMASK(29, 28)
#define ATC_DST_ADDR_MODE_INCR  0x0             /* Incrementing Mode */
#define ATC_DST_ADDR_MODE_DECR  0x1             /* Decrementing Mode */
#define ATC_DST_ADDR_MODE_FIXED 0x2             /* Fixed Mode */
#define ATC_IEN                 BIT(30)         /* BTC interrupt enable (active low) */
#define ATC_AUTO                BIT(31)         /* Auto multiple buffer tx enable */

/* Bitfields in CFG */
#define ATC_SRC_PER             GENMASK(3, 0)   /* Channel src rq associated with periph handshaking ifc h */
#define ATC_DST_PER             GENMASK(7, 4)   /* Channel dst rq associated with periph handshaking ifc h */
#define ATC_SRC_REP             BIT(8)          /* Source Replay Mod */
#define ATC_SRC_H2SEL           BIT(9)          /* Source Handshaking Mod */
#define ATC_SRC_PER_MSB         GENMASK(11, 10) /* Channel src rq (most significant bits) */
#define ATC_DST_REP             BIT(12)         /* Destination Replay Mod */
#define ATC_DST_H2SEL           BIT(13)         /* Destination Handshaking Mod */
#define ATC_DST_PER_MSB         GENMASK(15, 14) /* Channel dst rq (most significant bits) */
#define ATC_SOD                 BIT(16)         /* Stop On Done */
#define ATC_LOCK_IF             BIT(20)         /* Interface Lock */
#define ATC_LOCK_B              BIT(21)         /* AHB Bus Lock */
#define ATC_LOCK_IF_L           BIT(22)         /* Master Interface Arbiter Lock */
#define ATC_AHB_PROT            GENMASK(26, 24) /* AHB Protection */
#define ATC_FIFOCFG             GENMASK(29, 28) /* FIFO Request Configuration */
#define ATC_FIFOCFG_LARGESTBURST        0x0
#define ATC_FIFOCFG_HALFFIFO            0x1
#define ATC_FIFOCFG_ENOUGHSPACE         0x2

/* Bitfields in SPIP */
#define ATC_SPIP_HOLE           GENMASK(15, 0)
#define ATC_SPIP_BOUNDARY       GENMASK(25, 16)

/* Bitfields in DPIP */
#define ATC_DPIP_HOLE           GENMASK(15, 0)
#define ATC_DPIP_BOUNDARY       GENMASK(25, 16)

#define ATC_PER_MSB             GENMASK(5, 4)   /* Extract MSBs of a handshaking identifier */
#define ATC_SRC_PER_ID(id)                                             \
        ({ typeof(id) _id = (id);                                      \
           FIELD_PREP(ATC_SRC_PER_MSB, FIELD_GET(ATC_PER_MSB, _id)) |  \
           FIELD_PREP(ATC_SRC_PER, _id); })
#define ATC_DST_PER_ID(id)                                             \
        ({ typeof(id) _id = (id);                                      \
           FIELD_PREP(ATC_DST_PER_MSB, FIELD_GET(ATC_PER_MSB, _id)) |  \
           FIELD_PREP(ATC_DST_PER, _id); })



/*--  descriptors  -----------------------------------------------------*/

/* LLI == Linked List Item; aka DMA buffer descriptor */
struct at_lli {
        /* values that are not changed by hardware */
        u32 saddr;
        u32 daddr;
        /* value that may get written back: */
        u32 ctrla;
        /* more values that are not changed by hardware */
        u32 ctrlb;
        u32 dscr;       /* chain to next lli */
};

/**
 * struct atdma_sg - atdma scatter gather entry
 * @len: length of the current Linked List Item.
 * @lli: linked list item that is passed to the DMA controller
 * @lli_phys: physical address of the LLI.
 */
struct atdma_sg {
        unsigned int len;
        struct at_lli *lli;
        dma_addr_t lli_phys;
};

/**
 * struct at_desc - software descriptor
 * @vd: pointer to the virtual dma descriptor.
 * @atchan: pointer to the atmel dma channel.
 * @total_len: total transaction byte count
 * @sglen: number of sg entries.
 * @sg: array of sgs.
 * @boundary: number of transfers to perform before the automatic address increment operation
 * @dst_hole: value to add to the destination address when the boundary has been reached
 * @src_hole: value to add to the source address when the boundary has been reached
 * @memset_buffer: buffer used for the memset operation
 * @memset_paddr: physical address of the buffer used for the memset operation
 * @memset_vaddr: virtual address of the buffer used for the memset operation
 */
struct at_desc {
        struct                          virt_dma_desc vd;
        struct                          at_dma_chan *atchan;
        size_t                          total_len;
        unsigned int                    sglen;
        /* Interleaved data */
        size_t                          boundary;
        size_t                          dst_hole;
        size_t                          src_hole;

        /* Memset temporary buffer */
        bool                            memset_buffer;
        dma_addr_t                      memset_paddr;
        int                             *memset_vaddr;
        struct atdma_sg                 sg[] __counted_by(sglen);
};

/*--  Channels  --------------------------------------------------------*/

/**
 * enum atc_status - information bits stored in channel status flag
 *
 * @ATC_IS_PAUSED: If channel is pauses
 * @ATC_IS_CYCLIC: If channel is cyclic
 *
 * Manipulated with atomic operations.
 */
enum atc_status {
        ATC_IS_PAUSED = 1,
        ATC_IS_CYCLIC = 24,
};

/**
 * struct at_dma_chan - internal representation of an Atmel HDMAC channel
 * @vc: virtual dma channel entry.
 * @atdma: pointer to the driver data.
 * @ch_regs: memory mapped register base
 * @mask: channel index in a mask
 * @per_if: peripheral interface
 * @mem_if: memory interface
 * @status: transmit status information from irq/prep* functions
 *                to tasklet (use atomic operations)
 * @save_cfg: configuration register that is saved on suspend/resume cycle
 * @save_dscr: for cyclic operations, preserve next descriptor address in
 *             the cyclic list on suspend/resume cycle
 * @dma_sconfig: configuration for slave transfers, passed via
 * .device_config
 * @desc: pointer to the atmel dma descriptor.
 */
struct at_dma_chan {
        struct virt_dma_chan    vc;
        struct at_dma           *atdma;
        void __iomem            *ch_regs;
        u8                      mask;
        u8                      per_if;
        u8                      mem_if;
        unsigned long           status;
        u32                     save_cfg;
        u32                     save_dscr;
        struct dma_slave_config dma_sconfig;
        struct at_desc          *desc;
};

#define channel_readl(atchan, name) \
        __raw_readl((atchan)->ch_regs + ATC_##name##_OFFSET)

#define channel_writel(atchan, name, val) \
        __raw_writel((val), (atchan)->ch_regs + ATC_##name##_OFFSET)

/*
 * Fix sconfig's burst size according to at_hdmac. We need to convert them as:
 * 1 -> 0, 4 -> 1, 8 -> 2, 16 -> 3, 32 -> 4, 64 -> 5, 128 -> 6, 256 -> 7.
 *
 * This can be done by finding most significant bit set.
 */
static inline void convert_burst(u32 *maxburst)
{
        if (*maxburst > 1)
                *maxburst = fls(*maxburst) - 2;
        else
                *maxburst = 0;
}

/*
 * Fix sconfig's bus width according to at_hdmac.
 * 1 byte -> 0, 2 bytes -> 1, 4 bytes -> 2.
 */
static inline u8 convert_buswidth(enum dma_slave_buswidth addr_width)
{
        switch (addr_width) {
        case DMA_SLAVE_BUSWIDTH_2_BYTES:
                return 1;
        case DMA_SLAVE_BUSWIDTH_4_BYTES:
                return 2;
        default:
                /* For 1 byte width or fallback */
                return 0;
        }
}

/*--  Controller  ------------------------------------------------------*/

/**
 * struct at_dma - internal representation of an Atmel HDMA Controller
 * @dma_device: dmaengine dma_device object members
 * @regs: memory mapped register base
 * @clk: dma controller clock
 * @save_imr: interrupt mask register that is saved on suspend/resume cycle
 * @all_chan_mask: all channels available in a mask
 * @lli_pool: hw lli table
 * @memset_pool: hw memset pool
 * @chan: channels table to store at_dma_chan structures
 */
struct at_dma {
        struct dma_device       dma_device;
        void __iomem            *regs;
        struct clk              *clk;
        u32                     save_imr;

        u8                      all_chan_mask;

        struct dma_pool         *lli_pool;
        struct dma_pool         *memset_pool;
        /* AT THE END channels table */
        struct at_dma_chan      chan[];
};

#define dma_readl(atdma, name) \
        __raw_readl((atdma)->regs + AT_DMA_##name)
#define dma_writel(atdma, name, val) \
        __raw_writel((val), (atdma)->regs + AT_DMA_##name)

static inline struct at_desc *to_atdma_desc(struct dma_async_tx_descriptor *t)
{
        return container_of(t, struct at_desc, vd.tx);
}

static inline struct at_dma_chan *to_at_dma_chan(struct dma_chan *chan)
{
        return container_of(chan, struct at_dma_chan, vc.chan);
}

static inline struct at_dma *to_at_dma(struct dma_device *ddev)
{
        return container_of(ddev, struct at_dma, dma_device);
}


/*--  Helper functions  ------------------------------------------------*/

static struct device *chan2dev(struct dma_chan *chan)
{
        return &chan->dev->device;
}

#if defined(VERBOSE_DEBUG)
static void vdbg_dump_regs(struct at_dma_chan *atchan)
{
        struct at_dma   *atdma = to_at_dma(atchan->vc.chan.device);

        dev_err(chan2dev(&atchan->vc.chan),
                "  channel %d : imr = 0x%x, chsr = 0x%x\n",
                atchan->vc.chan.chan_id,
                dma_readl(atdma, EBCIMR),
                dma_readl(atdma, CHSR));

        dev_err(chan2dev(&atchan->vc.chan),
                "  channel: s0x%x d0x%x ctrl0x%x:0x%x cfg0x%x l0x%x\n",
                channel_readl(atchan, SADDR),
                channel_readl(atchan, DADDR),
                channel_readl(atchan, CTRLA),
                channel_readl(atchan, CTRLB),
                channel_readl(atchan, CFG),
                channel_readl(atchan, DSCR));
}
#else
static void vdbg_dump_regs(struct at_dma_chan *atchan) {}
#endif

static void atc_dump_lli(struct at_dma_chan *atchan, struct at_lli *lli)
{
        dev_crit(chan2dev(&atchan->vc.chan),
                 "desc: s%pad d%pad ctrl0x%x:0x%x l%pad\n",
                 &lli->saddr, &lli->daddr,
                 lli->ctrla, lli->ctrlb, &lli->dscr);
}


static void atc_setup_irq(struct at_dma *atdma, int chan_id, int on)
{
        u32 ebci;

        /* enable interrupts on buffer transfer completion & error */
        ebci =    AT_DMA_BTC(chan_id)
                | AT_DMA_ERR(chan_id);
        if (on)
                dma_writel(atdma, EBCIER, ebci);
        else
                dma_writel(atdma, EBCIDR, ebci);
}

static void atc_enable_chan_irq(struct at_dma *atdma, int chan_id)
{
        atc_setup_irq(atdma, chan_id, 1);
}

static void atc_disable_chan_irq(struct at_dma *atdma, int chan_id)
{
        atc_setup_irq(atdma, chan_id, 0);
}


/**
 * atc_chan_is_enabled - test if given channel is enabled
 * @atchan: channel we want to test status
 */
static inline int atc_chan_is_enabled(struct at_dma_chan *atchan)
{
        struct at_dma *atdma = to_at_dma(atchan->vc.chan.device);

        return !!(dma_readl(atdma, CHSR) & atchan->mask);
}

/**
 * atc_chan_is_paused - test channel pause/resume status
 * @atchan: channel we want to test status
 */
static inline int atc_chan_is_paused(struct at_dma_chan *atchan)
{
        return test_bit(ATC_IS_PAUSED, &atchan->status);
}

/**
 * atc_chan_is_cyclic - test if given channel has cyclic property set
 * @atchan: channel we want to test status
 */
static inline int atc_chan_is_cyclic(struct at_dma_chan *atchan)
{
        return test_bit(ATC_IS_CYCLIC, &atchan->status);
}

/**
 * set_lli_eol - set end-of-link to descriptor so it will end transfer
 * @desc: descriptor, signle or at the end of a chain, to end chain on
 * @i: index of the atmel scatter gather entry that is at the end of the chain.
 */
static void set_lli_eol(struct at_desc *desc, unsigned int i)
{
        u32 ctrlb = desc->sg[i].lli->ctrlb;

        ctrlb &= ~ATC_IEN;
        ctrlb |= ATC_SRC_DSCR_DIS | ATC_DST_DSCR_DIS;

        desc->sg[i].lli->ctrlb = ctrlb;
        desc->sg[i].lli->dscr = 0;
}

#define ATC_DEFAULT_CFG         FIELD_PREP(ATC_FIFOCFG, ATC_FIFOCFG_HALFFIFO)
#define ATC_DEFAULT_CTRLB       (FIELD_PREP(ATC_SIF, AT_DMA_MEM_IF) | \
                                 FIELD_PREP(ATC_DIF, AT_DMA_MEM_IF))
#define ATC_DMA_BUSWIDTHS\
        (BIT(DMA_SLAVE_BUSWIDTH_UNDEFINED) |\
        BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |\
        BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |\
        BIT(DMA_SLAVE_BUSWIDTH_4_BYTES))

#define ATC_MAX_DSCR_TRIALS     10

/*
 * Initial number of descriptors to allocate for each channel. This could
 * be increased during dma usage.
 */
static unsigned int init_nr_desc_per_channel = 64;
module_param(init_nr_desc_per_channel, uint, 0644);
MODULE_PARM_DESC(init_nr_desc_per_channel,
                 "initial descriptors per channel (default: 64)");

/**
 * struct at_dma_platform_data - Controller configuration parameters
 * @nr_channels: Number of channels supported by hardware (max 8)
 * @cap_mask: dma_capability flags supported by the platform
 */
struct at_dma_platform_data {
        unsigned int    nr_channels;
        dma_cap_mask_t  cap_mask;
};

/**
 * struct at_dma_slave - Controller-specific information about a slave
 * @dma_dev: required DMA master device
 * @cfg: Platform-specific initializer for the CFG register
 */
struct at_dma_slave {
        struct device           *dma_dev;
        u32                     cfg;
};

static inline unsigned int atc_get_xfer_width(dma_addr_t src, dma_addr_t dst,
                                                size_t len)
{
        unsigned int width;

        if (!((src | dst  | len) & 3))
                width = 2;
        else if (!((src | dst | len) & 1))
                width = 1;
        else
                width = 0;

        return width;
}

static void atdma_lli_chain(struct at_desc *desc, unsigned int i)
{
        struct atdma_sg *atdma_sg = &desc->sg[i];

        if (i)
                desc->sg[i - 1].lli->dscr = atdma_sg->lli_phys;
}

/**
 * atc_dostart - starts the DMA engine for real
 * @atchan: the channel we want to start
 */
static void atc_dostart(struct at_dma_chan *atchan)
{
        struct virt_dma_desc *vd = vchan_next_desc(&atchan->vc);
        struct at_desc *desc;

        if (!vd) {
                atchan->desc = NULL;
                return;
        }

        vdbg_dump_regs(atchan);

        list_del(&vd->node);
        atchan->desc = desc = to_atdma_desc(&vd->tx);

        channel_writel(atchan, SADDR, 0);
        channel_writel(atchan, DADDR, 0);
        channel_writel(atchan, CTRLA, 0);
        channel_writel(atchan, CTRLB, 0);
        channel_writel(atchan, DSCR, desc->sg[0].lli_phys);
        channel_writel(atchan, SPIP,
                       FIELD_PREP(ATC_SPIP_HOLE, desc->src_hole) |
                       FIELD_PREP(ATC_SPIP_BOUNDARY, desc->boundary));
        channel_writel(atchan, DPIP,
                       FIELD_PREP(ATC_DPIP_HOLE, desc->dst_hole) |
                       FIELD_PREP(ATC_DPIP_BOUNDARY, desc->boundary));

        /* Don't allow CPU to reorder channel enable. */
        wmb();
        dma_writel(atchan->atdma, CHER, atchan->mask);

        vdbg_dump_regs(atchan);
}

static void atdma_desc_free(struct virt_dma_desc *vd)
{
        struct at_dma *atdma = to_at_dma(vd->tx.chan->device);
        struct at_desc *desc = to_atdma_desc(&vd->tx);
        unsigned int i;

        for (i = 0; i < desc->sglen; i++) {
                if (desc->sg[i].lli)
                        dma_pool_free(atdma->lli_pool, desc->sg[i].lli,
                                      desc->sg[i].lli_phys);
        }

        /* If the transfer was a memset, free our temporary buffer */
        if (desc->memset_buffer) {
                dma_pool_free(atdma->memset_pool, desc->memset_vaddr,
                              desc->memset_paddr);
                desc->memset_buffer = false;
        }

        kfree(desc);
}

/**
 * atc_calc_bytes_left - calculates the number of bytes left according to the
 * value read from CTRLA.
 *
 * @current_len: the number of bytes left before reading CTRLA
 * @ctrla: the value of CTRLA
 */
static inline u32 atc_calc_bytes_left(u32 current_len, u32 ctrla)
{
        u32 btsize = FIELD_GET(ATC_BTSIZE, ctrla);
        u32 src_width = FIELD_GET(ATC_SRC_WIDTH, ctrla);

        /*
         * According to the datasheet, when reading the Control A Register
         * (ctrla), the Buffer Transfer Size (btsize) bitfield refers to the
         * number of transfers completed on the Source Interface.
         * So btsize is always a number of source width transfers.
         */
        return current_len - (btsize << src_width);
}

/**
 * atc_get_llis_residue - Get residue for a hardware linked list transfer
 * @atchan: pointer to an atmel hdmac channel.
 * @desc: pointer to the descriptor for which the residue is calculated.
 * @residue: residue to be set to dma_tx_state.
 *
 * Calculate the residue by removing the length of the Linked List Item (LLI)
 * already transferred from the total length. To get the current LLI we can use
 * the value of the channel's DSCR register and compare it against the DSCR
 * value of each LLI.
 *
 * The CTRLA register provides us with the amount of data already read from the
 * source for the LLI. So we can compute a more accurate residue by also
 * removing the number of bytes corresponding to this amount of data.
 *
 * However, the DSCR and CTRLA registers cannot be read both atomically. Hence a
 * race condition may occur: the first read register may refer to one LLI
 * whereas the second read may refer to a later LLI in the list because of the
 * DMA transfer progression inbetween the two reads.
 *
 * One solution could have been to pause the DMA transfer, read the DSCR and
 * CTRLA then resume the DMA transfer. Nonetheless, this approach presents some
 * drawbacks:
 * - If the DMA transfer is paused, RX overruns or TX underruns are more likey
 *   to occur depending on the system latency. Taking the USART driver as an
 *   example, it uses a cyclic DMA transfer to read data from the Receive
 *   Holding Register (RHR) to avoid RX overruns since the RHR is not protected
 *   by any FIFO on most Atmel SoCs. So pausing the DMA transfer to compute the
 *   residue would break the USART driver design.
 * - The atc_pause() function masks interrupts but we'd rather avoid to do so
 * for system latency purpose.
 *
 * Then we'd rather use another solution: the DSCR is read a first time, the
 * CTRLA is read in turn, next the DSCR is read a second time. If the two
 * consecutive read values of the DSCR are the same then we assume both refers
 * to the very same LLI as well as the CTRLA value read inbetween does. For
 * cyclic transfers, the assumption is that a full loop is "not so fast". If the
 * two DSCR values are different, we read again the CTRLA then the DSCR till two
 * consecutive read values from DSCR are equal or till the maximum trials is
 * reach. This algorithm is very unlikely not to find a stable value for DSCR.
 *
 * Returns: %0 on success, -errno otherwise.
 */
static int atc_get_llis_residue(struct at_dma_chan *atchan,
                                struct at_desc *desc, u32 *residue)
{
        u32 len, ctrla, dscr;
        unsigned int i;

        len = desc->total_len;
        dscr = channel_readl(atchan, DSCR);
        rmb(); /* ensure DSCR is read before CTRLA */
        ctrla = channel_readl(atchan, CTRLA);
        for (i = 0; i < ATC_MAX_DSCR_TRIALS; ++i) {
                u32 new_dscr;

                rmb(); /* ensure DSCR is read after CTRLA */
                new_dscr = channel_readl(atchan, DSCR);

                /*
                 * If the DSCR register value has not changed inside the DMA
                 * controller since the previous read, we assume that both the
                 * dscr and ctrla values refers to the very same descriptor.
                 */
                if (likely(new_dscr == dscr))
                        break;

                /*
                 * DSCR has changed inside the DMA controller, so the previously
                 * read value of CTRLA may refer to an already processed
                 * descriptor hence could be outdated. We need to update ctrla
                 * to match the current descriptor.
                 */
                dscr = new_dscr;
                rmb(); /* ensure DSCR is read before CTRLA */
                ctrla = channel_readl(atchan, CTRLA);
        }
        if (unlikely(i == ATC_MAX_DSCR_TRIALS))
                return -ETIMEDOUT;

        /* For the first descriptor we can be more accurate. */
        if (desc->sg[0].lli->dscr == dscr) {
                *residue = atc_calc_bytes_left(len, ctrla);
                return 0;
        }
        len -= desc->sg[0].len;

        for (i = 1; i < desc->sglen; i++) {
                if (desc->sg[i].lli && desc->sg[i].lli->dscr == dscr)
                        break;
                len -= desc->sg[i].len;
        }

        /*
         * For the current LLI in the chain we can calculate the remaining bytes
         * using the channel's CTRLA register.
         */
        *residue = atc_calc_bytes_left(len, ctrla);
        return 0;

}

/**
 * atc_get_residue - get the number of bytes residue for a cookie.
 * The residue is passed by address and updated on success.
 * @chan: DMA channel
 * @cookie: transaction identifier to check status of
 * @residue: residue to be updated.
 *
 * Return: %0 on success, -errno otherwise.
 */
static int atc_get_residue(struct dma_chan *chan, dma_cookie_t cookie,
                           u32 *residue)
{
        struct at_dma_chan *atchan = to_at_dma_chan(chan);
        struct virt_dma_desc *vd;
        struct at_desc *desc = NULL;
        u32 len, ctrla;

        vd = vchan_find_desc(&atchan->vc, cookie);
        if (vd)
                desc = to_atdma_desc(&vd->tx);
        else if (atchan->desc && atchan->desc->vd.tx.cookie == cookie)
                desc = atchan->desc;

        if (!desc)
                return -EINVAL;

        if (desc->sg[0].lli->dscr)
                /* hardware linked list transfer */
                return atc_get_llis_residue(atchan, desc, residue);

        /* single transfer */
        len = desc->total_len;
        ctrla = channel_readl(atchan, CTRLA);
        *residue = atc_calc_bytes_left(len, ctrla);
        return 0;
}

/**
 * atc_handle_error - handle errors reported by DMA controller
 * @atchan: channel where error occurs.
 * @i: channel index
 */
static void atc_handle_error(struct at_dma_chan *atchan, unsigned int i)
{
        struct at_desc *desc = atchan->desc;

        /* Disable channel on AHB error */
        dma_writel(atchan->atdma, CHDR, AT_DMA_RES(i) | atchan->mask);

        /*
         * KERN_CRITICAL may seem harsh, but since this only happens
         * when someone submits a bad physical address in a
         * descriptor, we should consider ourselves lucky that the
         * controller flagged an error instead of scribbling over
         * random memory locations.
         */
        dev_crit(chan2dev(&atchan->vc.chan), "Bad descriptor submitted for DMA!\n");
        dev_crit(chan2dev(&atchan->vc.chan), "cookie: %d\n",
                 desc->vd.tx.cookie);
        for (i = 0; i < desc->sglen; i++)
                atc_dump_lli(atchan, desc->sg[i].lli);
}

static void atdma_handle_chan_done(struct at_dma_chan *atchan, u32 pending,
                                   unsigned int i)
{
        struct at_desc *desc;

        spin_lock(&atchan->vc.lock);
        desc = atchan->desc;

        if (desc) {
                if (pending & AT_DMA_ERR(i)) {
                        atc_handle_error(atchan, i);
                        /* Pretend the descriptor completed successfully */
                }

                if (atc_chan_is_cyclic(atchan)) {
                        vchan_cyclic_callback(&desc->vd);
                } else {
                        vchan_cookie_complete(&desc->vd);
                        atchan->desc = NULL;
                        if (!(atc_chan_is_enabled(atchan)))
                                atc_dostart(atchan);
                }
        }
        spin_unlock(&atchan->vc.lock);
}

static irqreturn_t at_dma_interrupt(int irq, void *dev_id)
{
        struct at_dma           *atdma = dev_id;
        struct at_dma_chan      *atchan;
        int                     i;
        u32                     status, pending, imr;
        int                     ret = IRQ_NONE;

        do {
                imr = dma_readl(atdma, EBCIMR);
                status = dma_readl(atdma, EBCISR);
                pending = status & imr;

                if (!pending)
                        break;

                dev_vdbg(atdma->dma_device.dev,
                        "interrupt: status = 0x%08x, 0x%08x, 0x%08x\n",
                         status, imr, pending);

                for (i = 0; i < atdma->dma_device.chancnt; i++) {
                        atchan = &atdma->chan[i];
                        if (!(pending & (AT_DMA_BTC(i) | AT_DMA_ERR(i))))
                                continue;
                        atdma_handle_chan_done(atchan, pending, i);
                        ret = IRQ_HANDLED;
                }

        } while (pending);

        return ret;
}

/*--  DMA Engine API  --------------------------------------------------*/
/**
 * atc_prep_dma_interleaved - prepare memory to memory interleaved operation
 * @chan: the channel to prepare operation on
 * @xt: Interleaved transfer template
 * @flags: tx descriptor status flags
 */
static struct dma_async_tx_descriptor *
atc_prep_dma_interleaved(struct dma_chan *chan,
                         struct dma_interleaved_template *xt,
                         unsigned long flags)
{
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct data_chunk       *first;
        struct atdma_sg         *atdma_sg;
        struct at_desc          *desc;
        struct at_lli           *lli;
        size_t                  xfer_count;
        unsigned int            dwidth;
        u32                     ctrla;
        u32                     ctrlb;
        size_t                  len = 0;
        int                     i;

        if (unlikely(!xt || xt->numf != 1 || !xt->frame_size))
                return NULL;

        first = xt->sgl;

        dev_info(chan2dev(chan),
                 "%s: src=%pad, dest=%pad, numf=%zu, frame_size=%zu, flags=0x%lx\n",
                __func__, &xt->src_start, &xt->dst_start, xt->numf,
                xt->frame_size, flags);

        /*
         * The controller can only "skip" X bytes every Y bytes, so we
         * need to make sure we are given a template that fit that
         * description, ie a template with chunks that always have the
         * same size, with the same ICGs.
         */
        for (i = 0; i < xt->frame_size; i++) {
                struct data_chunk *chunk = xt->sgl + i;

                if ((chunk->size != xt->sgl->size) ||
                    (dmaengine_get_dst_icg(xt, chunk) != dmaengine_get_dst_icg(xt, first)) ||
                    (dmaengine_get_src_icg(xt, chunk) != dmaengine_get_src_icg(xt, first))) {
                        dev_err(chan2dev(chan),
                                "%s: the controller can transfer only identical chunks\n",
                                __func__);
                        return NULL;
                }

                len += chunk->size;
        }

        dwidth = atc_get_xfer_width(xt->src_start, xt->dst_start, len);

        xfer_count = len >> dwidth;
        if (xfer_count > ATC_BTSIZE_MAX) {
                dev_err(chan2dev(chan), "%s: buffer is too big\n", __func__);
                return NULL;
        }

        ctrla = FIELD_PREP(ATC_SRC_WIDTH, dwidth) |
                FIELD_PREP(ATC_DST_WIDTH, dwidth);

        ctrlb = ATC_DEFAULT_CTRLB | ATC_IEN |
                FIELD_PREP(ATC_SRC_ADDR_MODE, ATC_SRC_ADDR_MODE_INCR) |
                FIELD_PREP(ATC_DST_ADDR_MODE, ATC_DST_ADDR_MODE_INCR) |
                ATC_SRC_PIP | ATC_DST_PIP |
                FIELD_PREP(ATC_FC, ATC_FC_MEM2MEM);

        desc = kzalloc_flex(*desc, sg, 1, GFP_ATOMIC);
        if (!desc)
                return NULL;
        desc->sglen = 1;

        atdma_sg = desc->sg;
        atdma_sg->lli = dma_pool_alloc(atdma->lli_pool, GFP_NOWAIT,
                                       &atdma_sg->lli_phys);
        if (!atdma_sg->lli) {
                kfree(desc);
                return NULL;
        }
        lli = atdma_sg->lli;

        lli->saddr = xt->src_start;
        lli->daddr = xt->dst_start;
        lli->ctrla = ctrla | xfer_count;
        lli->ctrlb = ctrlb;

        desc->boundary = first->size >> dwidth;
        desc->dst_hole = (dmaengine_get_dst_icg(xt, first) >> dwidth) + 1;
        desc->src_hole = (dmaengine_get_src_icg(xt, first) >> dwidth) + 1;

        atdma_sg->len = len;
        desc->total_len = len;

        set_lli_eol(desc, 0);
        return vchan_tx_prep(&atchan->vc, &desc->vd, flags);
}

/**
 * atc_prep_dma_memcpy - prepare a memcpy operation
 * @chan: the channel to prepare operation on
 * @dest: operation virtual destination address
 * @src: operation virtual source address
 * @len: operation length
 * @flags: tx descriptor status flags
 */
static struct dma_async_tx_descriptor *
atc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
                size_t len, unsigned long flags)
{
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_desc          *desc = NULL;
        size_t                  xfer_count;
        size_t                  offset;
        size_t                  sg_len;
        unsigned int            src_width;
        unsigned int            dst_width;
        unsigned int            i;
        u32                     ctrla;
        u32                     ctrlb;

        dev_dbg(chan2dev(chan), "prep_dma_memcpy: d%pad s%pad l0x%zx f0x%lx\n",
                &dest, &src, len, flags);

        if (unlikely(!len)) {
                dev_err(chan2dev(chan), "prep_dma_memcpy: length is zero!\n");
                return NULL;
        }

        sg_len = DIV_ROUND_UP(len, ATC_BTSIZE_MAX);
        desc = kzalloc_flex(*desc, sg, sg_len, GFP_ATOMIC);
        if (!desc)
                return NULL;
        desc->sglen = sg_len;

        ctrlb = ATC_DEFAULT_CTRLB | ATC_IEN |
                FIELD_PREP(ATC_SRC_ADDR_MODE, ATC_SRC_ADDR_MODE_INCR) |
                FIELD_PREP(ATC_DST_ADDR_MODE, ATC_DST_ADDR_MODE_INCR) |
                FIELD_PREP(ATC_FC, ATC_FC_MEM2MEM);

        /*
         * We can be a lot more clever here, but this should take care
         * of the most common optimization.
         */
        src_width = dst_width = atc_get_xfer_width(src, dest, len);

        ctrla = FIELD_PREP(ATC_SRC_WIDTH, src_width) |
                FIELD_PREP(ATC_DST_WIDTH, dst_width);

        for (offset = 0, i = 0; offset < len;
             offset += xfer_count << src_width, i++) {
                struct atdma_sg *atdma_sg = &desc->sg[i];
                struct at_lli *lli;

                atdma_sg->lli = dma_pool_alloc(atdma->lli_pool, GFP_NOWAIT,
                                               &atdma_sg->lli_phys);
                if (!atdma_sg->lli)
                        goto err_desc_get;
                lli = atdma_sg->lli;

                xfer_count = min_t(size_t, (len - offset) >> src_width,
                                   ATC_BTSIZE_MAX);

                lli->saddr = src + offset;
                lli->daddr = dest + offset;
                lli->ctrla = ctrla | xfer_count;
                lli->ctrlb = ctrlb;

                desc->sg[i].len = xfer_count << src_width;

                atdma_lli_chain(desc, i);
        }

        desc->total_len = len;

        /* set end-of-link to the last link descriptor of list*/
        set_lli_eol(desc, i - 1);

        return vchan_tx_prep(&atchan->vc, &desc->vd, flags);

err_desc_get:
        atdma_desc_free(&desc->vd);
        return NULL;
}

static int atdma_create_memset_lli(struct dma_chan *chan,
                                   struct atdma_sg *atdma_sg,
                                   dma_addr_t psrc, dma_addr_t pdst, size_t len)
{
        struct at_dma *atdma = to_at_dma(chan->device);
        struct at_lli *lli;
        size_t xfer_count;
        u32 ctrla = FIELD_PREP(ATC_SRC_WIDTH, 2) | FIELD_PREP(ATC_DST_WIDTH, 2);
        u32 ctrlb = ATC_DEFAULT_CTRLB | ATC_IEN |
                    FIELD_PREP(ATC_SRC_ADDR_MODE, ATC_SRC_ADDR_MODE_FIXED) |
                    FIELD_PREP(ATC_DST_ADDR_MODE, ATC_DST_ADDR_MODE_INCR) |
                    FIELD_PREP(ATC_FC, ATC_FC_MEM2MEM);

        xfer_count = len >> 2;
        if (xfer_count > ATC_BTSIZE_MAX) {
                dev_err(chan2dev(chan), "%s: buffer is too big\n", __func__);
                return -EINVAL;
        }

        atdma_sg->lli = dma_pool_alloc(atdma->lli_pool, GFP_NOWAIT,
                                       &atdma_sg->lli_phys);
        if (!atdma_sg->lli)
                return -ENOMEM;
        lli = atdma_sg->lli;

        lli->saddr = psrc;
        lli->daddr = pdst;
        lli->ctrla = ctrla | xfer_count;
        lli->ctrlb = ctrlb;

        atdma_sg->len = len;

        return 0;
}

/**
 * atc_prep_dma_memset - prepare a memcpy operation
 * @chan: the channel to prepare operation on
 * @dest: operation virtual destination address
 * @value: value to set memory buffer to
 * @len: operation length
 * @flags: tx descriptor status flags
 */
static struct dma_async_tx_descriptor *
atc_prep_dma_memset(struct dma_chan *chan, dma_addr_t dest, int value,
                    size_t len, unsigned long flags)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_desc          *desc;
        void __iomem            *vaddr;
        dma_addr_t              paddr;
        char                    fill_pattern;
        int                     ret;

        dev_vdbg(chan2dev(chan), "%s: d%pad v0x%x l0x%zx f0x%lx\n", __func__,
                &dest, value, len, flags);

        if (unlikely(!len)) {
                dev_dbg(chan2dev(chan), "%s: length is zero!\n", __func__);
                return NULL;
        }

        if (!is_dma_fill_aligned(chan->device, dest, 0, len)) {
                dev_dbg(chan2dev(chan), "%s: buffer is not aligned\n",
                        __func__);
                return NULL;
        }

        vaddr = dma_pool_alloc(atdma->memset_pool, GFP_NOWAIT, &paddr);
        if (!vaddr) {
                dev_err(chan2dev(chan), "%s: couldn't allocate buffer\n",
                        __func__);
                return NULL;
        }

        /* Only the first byte of value is to be used according to dmaengine */
        fill_pattern = (char)value;

        *(u32*)vaddr = (fill_pattern << 24) |
                       (fill_pattern << 16) |
                       (fill_pattern << 8) |
                       fill_pattern;

        desc = kzalloc_flex(*desc, sg, 1, GFP_ATOMIC);
        if (!desc)
                goto err_free_buffer;
        desc->sglen = 1;

        ret = atdma_create_memset_lli(chan, desc->sg, paddr, dest, len);
        if (ret)
                goto err_free_desc;

        desc->memset_paddr = paddr;
        desc->memset_vaddr = vaddr;
        desc->memset_buffer = true;

        desc->total_len = len;

        /* set end-of-link on the descriptor */
        set_lli_eol(desc, 0);

        return vchan_tx_prep(&atchan->vc, &desc->vd, flags);

err_free_desc:
        kfree(desc);
err_free_buffer:
        dma_pool_free(atdma->memset_pool, vaddr, paddr);
        return NULL;
}

static struct dma_async_tx_descriptor *
atc_prep_dma_memset_sg(struct dma_chan *chan,
                       struct scatterlist *sgl,
                       unsigned int sg_len, int value,
                       unsigned long flags)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_desc          *desc;
        struct scatterlist      *sg;
        void __iomem            *vaddr;
        dma_addr_t              paddr;
        size_t                  total_len = 0;
        int                     i;
        int                     ret;

        dev_vdbg(chan2dev(chan), "%s: v0x%x l0x%x f0x%lx\n", __func__,
                 value, sg_len, flags);

        if (unlikely(!sgl || !sg_len)) {
                dev_dbg(chan2dev(chan), "%s: scatterlist is empty!\n",
                        __func__);
                return NULL;
        }

        vaddr = dma_pool_alloc(atdma->memset_pool, GFP_NOWAIT, &paddr);
        if (!vaddr) {
                dev_err(chan2dev(chan), "%s: couldn't allocate buffer\n",
                        __func__);
                return NULL;
        }
        *(u32*)vaddr = value;

        desc = kzalloc_flex(*desc, sg, sg_len, GFP_ATOMIC);
        if (!desc)
                goto err_free_dma_buf;
        desc->sglen = sg_len;

        for_each_sg(sgl, sg, sg_len, i) {
                dma_addr_t dest = sg_dma_address(sg);
                size_t len = sg_dma_len(sg);

                dev_vdbg(chan2dev(chan), "%s: d%pad, l0x%zx\n",
                         __func__, &dest, len);

                if (!is_dma_fill_aligned(chan->device, dest, 0, len)) {
                        dev_err(chan2dev(chan), "%s: buffer is not aligned\n",
                                __func__);
                        goto err_free_desc;
                }

                ret = atdma_create_memset_lli(chan, &desc->sg[i], paddr, dest,
                                              len);
                if (ret)
                        goto err_free_desc;

                atdma_lli_chain(desc, i);
                total_len += len;
        }

        desc->memset_paddr = paddr;
        desc->memset_vaddr = vaddr;
        desc->memset_buffer = true;

        desc->total_len = total_len;

        /* set end-of-link on the descriptor */
        set_lli_eol(desc, i - 1);

        return vchan_tx_prep(&atchan->vc, &desc->vd, flags);

err_free_desc:
        atdma_desc_free(&desc->vd);
err_free_dma_buf:
        dma_pool_free(atdma->memset_pool, vaddr, paddr);
        return NULL;
}

/**
 * atc_prep_slave_sg - prepare descriptors for a DMA_SLAVE transaction
 * @chan: DMA channel
 * @sgl: scatterlist to transfer to/from
 * @sg_len: number of entries in @scatterlist
 * @direction: DMA direction
 * @flags: tx descriptor status flags
 * @context: transaction context (ignored)
 */
static struct dma_async_tx_descriptor *
atc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
                unsigned int sg_len, enum dma_transfer_direction direction,
                unsigned long flags, void *context)
{
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma_slave     *atslave = chan->private;
        struct dma_slave_config *sconfig = &atchan->dma_sconfig;
        struct at_desc          *desc;
        u32                     ctrla;
        u32                     ctrlb;
        dma_addr_t              reg;
        unsigned int            reg_width;
        unsigned int            mem_width;
        unsigned int            i;
        struct scatterlist      *sg;
        size_t                  total_len = 0;

        dev_vdbg(chan2dev(chan), "prep_slave_sg (%d): %s f0x%lx\n",
                        sg_len,
                        direction == DMA_MEM_TO_DEV ? "TO DEVICE" : "FROM DEVICE",
                        flags);

        if (unlikely(!atslave || !sg_len)) {
                dev_dbg(chan2dev(chan), "prep_slave_sg: sg length is zero!\n");
                return NULL;
        }

        desc = kzalloc_flex(*desc, sg, sg_len, GFP_ATOMIC);
        if (!desc)
                return NULL;
        desc->sglen = sg_len;

        ctrla = FIELD_PREP(ATC_SCSIZE, sconfig->src_maxburst) |
                FIELD_PREP(ATC_DCSIZE, sconfig->dst_maxburst);
        ctrlb = ATC_IEN;

        switch (direction) {
        case DMA_MEM_TO_DEV:
                reg_width = convert_buswidth(sconfig->dst_addr_width);
                ctrla |= FIELD_PREP(ATC_DST_WIDTH, reg_width);
                ctrlb |= FIELD_PREP(ATC_DST_ADDR_MODE,
                                    ATC_DST_ADDR_MODE_FIXED) |
                         FIELD_PREP(ATC_SRC_ADDR_MODE, ATC_SRC_ADDR_MODE_INCR) |
                         FIELD_PREP(ATC_FC, ATC_FC_MEM2PER) |
                         FIELD_PREP(ATC_SIF, atchan->mem_if) |
                         FIELD_PREP(ATC_DIF, atchan->per_if);
                reg = sconfig->dst_addr;
                for_each_sg(sgl, sg, sg_len, i) {
                        struct atdma_sg *atdma_sg = &desc->sg[i];
                        struct at_lli *lli;
                        u32             len;
                        u32             mem;

                        atdma_sg->lli = dma_pool_alloc(atdma->lli_pool,
                                                       GFP_NOWAIT,
                                                       &atdma_sg->lli_phys);
                        if (!atdma_sg->lli)
                                goto err_desc_get;
                        lli = atdma_sg->lli;

                        mem = sg_dma_address(sg);
                        len = sg_dma_len(sg);
                        if (unlikely(!len)) {
                                dev_dbg(chan2dev(chan),
                                        "prep_slave_sg: sg(%d) data length is zero\n", i);
                                goto err;
                        }
                        mem_width = 2;
                        if (unlikely(mem & 3 || len & 3))
                                mem_width = 0;

                        lli->saddr = mem;
                        lli->daddr = reg;
                        lli->ctrla = ctrla |
                                     FIELD_PREP(ATC_SRC_WIDTH, mem_width) |
                                     len >> mem_width;
                        lli->ctrlb = ctrlb;

                        atdma_sg->len = len;
                        total_len += len;

                        desc->sg[i].len = len;
                        atdma_lli_chain(desc, i);
                }
                break;
        case DMA_DEV_TO_MEM:
                reg_width = convert_buswidth(sconfig->src_addr_width);
                ctrla |= FIELD_PREP(ATC_SRC_WIDTH, reg_width);
                ctrlb |= FIELD_PREP(ATC_DST_ADDR_MODE, ATC_DST_ADDR_MODE_INCR) |
                         FIELD_PREP(ATC_SRC_ADDR_MODE,
                                    ATC_SRC_ADDR_MODE_FIXED) |
                         FIELD_PREP(ATC_FC, ATC_FC_PER2MEM) |
                         FIELD_PREP(ATC_SIF, atchan->per_if) |
                         FIELD_PREP(ATC_DIF, atchan->mem_if);

                reg = sconfig->src_addr;
                for_each_sg(sgl, sg, sg_len, i) {
                        struct atdma_sg *atdma_sg = &desc->sg[i];
                        struct at_lli *lli;
                        u32             len;
                        u32             mem;

                        atdma_sg->lli = dma_pool_alloc(atdma->lli_pool,
                                                       GFP_NOWAIT,
                                                       &atdma_sg->lli_phys);
                        if (!atdma_sg->lli)
                                goto err_desc_get;
                        lli = atdma_sg->lli;

                        mem = sg_dma_address(sg);
                        len = sg_dma_len(sg);
                        if (unlikely(!len)) {
                                dev_dbg(chan2dev(chan),
                                        "prep_slave_sg: sg(%d) data length is zero\n", i);
                                goto err;
                        }
                        mem_width = 2;
                        if (unlikely(mem & 3 || len & 3))
                                mem_width = 0;

                        lli->saddr = reg;
                        lli->daddr = mem;
                        lli->ctrla = ctrla |
                                     FIELD_PREP(ATC_DST_WIDTH, mem_width) |
                                     len >> reg_width;
                        lli->ctrlb = ctrlb;

                        desc->sg[i].len = len;
                        total_len += len;

                        atdma_lli_chain(desc, i);
                }
                break;
        default:
                return NULL;
        }

        /* set end-of-link to the last link descriptor of list*/
        set_lli_eol(desc, i - 1);

        desc->total_len = total_len;

        return vchan_tx_prep(&atchan->vc, &desc->vd, flags);

err_desc_get:
        dev_err(chan2dev(chan), "not enough descriptors available\n");
err:
        atdma_desc_free(&desc->vd);
        return NULL;
}

/*
 * atc_dma_cyclic_check_values
 * Check for too big/unaligned periods and unaligned DMA buffer
 */
static int
atc_dma_cyclic_check_values(unsigned int reg_width, dma_addr_t buf_addr,
                size_t period_len)
{
        if (period_len > (ATC_BTSIZE_MAX << reg_width))
                goto err_out;
        if (unlikely(period_len & ((1 << reg_width) - 1)))
                goto err_out;
        if (unlikely(buf_addr & ((1 << reg_width) - 1)))
                goto err_out;

        return 0;

err_out:
        return -EINVAL;
}

/*
 * atc_dma_cyclic_fill_desc - Fill one period descriptor
 */
static int
atc_dma_cyclic_fill_desc(struct dma_chan *chan, struct at_desc *desc,
                unsigned int i, dma_addr_t buf_addr,
                unsigned int reg_width, size_t period_len,
                enum dma_transfer_direction direction)
{
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct dma_slave_config *sconfig = &atchan->dma_sconfig;
        struct atdma_sg         *atdma_sg = &desc->sg[i];
        struct at_lli           *lli;

        atdma_sg->lli = dma_pool_alloc(atdma->lli_pool, GFP_ATOMIC,
                                       &atdma_sg->lli_phys);
        if (!atdma_sg->lli)
                return -ENOMEM;
        lli = atdma_sg->lli;

        switch (direction) {
        case DMA_MEM_TO_DEV:
                lli->saddr = buf_addr + (period_len * i);
                lli->daddr = sconfig->dst_addr;
                lli->ctrlb = FIELD_PREP(ATC_DST_ADDR_MODE,
                                        ATC_DST_ADDR_MODE_FIXED) |
                             FIELD_PREP(ATC_SRC_ADDR_MODE,
                                        ATC_SRC_ADDR_MODE_INCR) |
                             FIELD_PREP(ATC_FC, ATC_FC_MEM2PER) |
                             FIELD_PREP(ATC_SIF, atchan->mem_if) |
                             FIELD_PREP(ATC_DIF, atchan->per_if);

                break;

        case DMA_DEV_TO_MEM:
                lli->saddr = sconfig->src_addr;
                lli->daddr = buf_addr + (period_len * i);
                lli->ctrlb = FIELD_PREP(ATC_DST_ADDR_MODE,
                                        ATC_DST_ADDR_MODE_INCR) |
                             FIELD_PREP(ATC_SRC_ADDR_MODE,
                                        ATC_SRC_ADDR_MODE_FIXED) |
                             FIELD_PREP(ATC_FC, ATC_FC_PER2MEM) |
                             FIELD_PREP(ATC_SIF, atchan->per_if) |
                             FIELD_PREP(ATC_DIF, atchan->mem_if);
                break;

        default:
                return -EINVAL;
        }

        lli->ctrla = FIELD_PREP(ATC_SCSIZE, sconfig->src_maxburst) |
                     FIELD_PREP(ATC_DCSIZE, sconfig->dst_maxburst) |
                     FIELD_PREP(ATC_DST_WIDTH, reg_width) |
                     FIELD_PREP(ATC_SRC_WIDTH, reg_width) |
                     period_len >> reg_width;
        desc->sg[i].len = period_len;

        return 0;
}

/**
 * atc_prep_dma_cyclic - prepare the cyclic DMA transfer
 * @chan: the DMA channel to prepare
 * @buf_addr: physical DMA address where the buffer starts
 * @buf_len: total number of bytes for the entire buffer
 * @period_len: number of bytes for each period
 * @direction: transfer direction, to or from device
 * @flags: tx descriptor status flags
 */
static struct dma_async_tx_descriptor *
atc_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
                size_t period_len, enum dma_transfer_direction direction,
                unsigned long flags)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma_slave     *atslave = chan->private;
        struct dma_slave_config *sconfig = &atchan->dma_sconfig;
        struct at_desc          *desc;
        unsigned long           was_cyclic;
        unsigned int            reg_width;
        unsigned int            periods = buf_len / period_len;
        unsigned int            i;

        dev_vdbg(chan2dev(chan), "prep_dma_cyclic: %s buf@%pad - %d (%zu/%zu)\n",
                        direction == DMA_MEM_TO_DEV ? "TO DEVICE" : "FROM DEVICE",
                        &buf_addr,
                        periods, buf_len, period_len);

        if (unlikely(!atslave || !buf_len || !period_len)) {
                dev_dbg(chan2dev(chan), "prep_dma_cyclic: length is zero!\n");
                return NULL;
        }

        was_cyclic = test_and_set_bit(ATC_IS_CYCLIC, &atchan->status);
        if (was_cyclic) {
                dev_dbg(chan2dev(chan), "prep_dma_cyclic: channel in use!\n");
                return NULL;
        }

        if (unlikely(!is_slave_direction(direction)))
                goto err_out;

        if (direction == DMA_MEM_TO_DEV)
                reg_width = convert_buswidth(sconfig->dst_addr_width);
        else
                reg_width = convert_buswidth(sconfig->src_addr_width);

        /* Check for too big/unaligned periods and unaligned DMA buffer */
        if (atc_dma_cyclic_check_values(reg_width, buf_addr, period_len))
                goto err_out;

        desc = kzalloc_flex(*desc, sg, periods, GFP_ATOMIC);
        if (!desc)
                goto err_out;
        desc->sglen = periods;

        /* build cyclic linked list */
        for (i = 0; i < periods; i++) {
                if (atc_dma_cyclic_fill_desc(chan, desc, i, buf_addr,
                                             reg_width, period_len, direction))
                        goto err_fill_desc;
                atdma_lli_chain(desc, i);
        }
        desc->total_len = buf_len;
        /* lets make a cyclic list */
        desc->sg[i - 1].lli->dscr = desc->sg[0].lli_phys;

        return vchan_tx_prep(&atchan->vc, &desc->vd, flags);

err_fill_desc:
        atdma_desc_free(&desc->vd);
err_out:
        clear_bit(ATC_IS_CYCLIC, &atchan->status);
        return NULL;
}

static int atc_config(struct dma_chan *chan,
                      struct dma_slave_config *sconfig)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);

        dev_vdbg(chan2dev(chan), "%s\n", __func__);

        /* Check if it is chan is configured for slave transfers */
        if (!chan->private)
                return -EINVAL;

        memcpy(&atchan->dma_sconfig, sconfig, sizeof(*sconfig));

        convert_burst(&atchan->dma_sconfig.src_maxburst);
        convert_burst(&atchan->dma_sconfig.dst_maxburst);

        return 0;
}

static int atc_pause(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        int                     chan_id = atchan->vc.chan.chan_id;
        unsigned long           flags;

        dev_vdbg(chan2dev(chan), "%s\n", __func__);

        spin_lock_irqsave(&atchan->vc.lock, flags);

        dma_writel(atdma, CHER, AT_DMA_SUSP(chan_id));
        set_bit(ATC_IS_PAUSED, &atchan->status);

        spin_unlock_irqrestore(&atchan->vc.lock, flags);

        return 0;
}

static int atc_resume(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        int                     chan_id = atchan->vc.chan.chan_id;
        unsigned long           flags;

        dev_vdbg(chan2dev(chan), "%s\n", __func__);

        if (!atc_chan_is_paused(atchan))
                return 0;

        spin_lock_irqsave(&atchan->vc.lock, flags);

        dma_writel(atdma, CHDR, AT_DMA_RES(chan_id));
        clear_bit(ATC_IS_PAUSED, &atchan->status);

        spin_unlock_irqrestore(&atchan->vc.lock, flags);

        return 0;
}

static int atc_terminate_all(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        int                     chan_id = atchan->vc.chan.chan_id;
        unsigned long           flags;

        LIST_HEAD(list);

        dev_vdbg(chan2dev(chan), "%s\n", __func__);

        /*
         * This is only called when something went wrong elsewhere, so
         * we don't really care about the data. Just disable the
         * channel. We still have to poll the channel enable bit due
         * to AHB/HSB limitations.
         */
        spin_lock_irqsave(&atchan->vc.lock, flags);

        /* disabling channel: must also remove suspend state */
        dma_writel(atdma, CHDR, AT_DMA_RES(chan_id) | atchan->mask);

        /* confirm that this channel is disabled */
        while (dma_readl(atdma, CHSR) & atchan->mask)
                cpu_relax();

        if (atchan->desc) {
                vchan_terminate_vdesc(&atchan->desc->vd);
                atchan->desc = NULL;
        }

        vchan_get_all_descriptors(&atchan->vc, &list);

        clear_bit(ATC_IS_PAUSED, &atchan->status);
        /* if channel dedicated to cyclic operations, free it */
        clear_bit(ATC_IS_CYCLIC, &atchan->status);

        spin_unlock_irqrestore(&atchan->vc.lock, flags);

        vchan_dma_desc_free_list(&atchan->vc, &list);

        return 0;
}

/**
 * atc_tx_status - poll for transaction completion
 * @chan: DMA channel
 * @cookie: transaction identifier to check status of
 * @txstate: if not %NULL updated with transaction state
 *
 * If @txstate is passed in, upon return it reflect the driver
 * internal state and can be used with dma_async_is_complete() to check
 * the status of multiple cookies without re-checking hardware state.
 */
static enum dma_status
atc_tx_status(struct dma_chan *chan,
                dma_cookie_t cookie,
                struct dma_tx_state *txstate)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        unsigned long           flags;
        enum dma_status         dma_status;
        u32 residue;
        int ret;

        dma_status = dma_cookie_status(chan, cookie, txstate);
        if (dma_status == DMA_COMPLETE || !txstate)
                return dma_status;

        spin_lock_irqsave(&atchan->vc.lock, flags);
        /*  Get number of bytes left in the active transactions */
        ret = atc_get_residue(chan, cookie, &residue);
        spin_unlock_irqrestore(&atchan->vc.lock, flags);

        if (unlikely(ret < 0)) {
                dev_vdbg(chan2dev(chan), "get residual bytes error\n");
                return DMA_ERROR;
        } else {
                dma_set_residue(txstate, residue);
        }

        dev_vdbg(chan2dev(chan), "tx_status %d: cookie = %d residue = %u\n",
                 dma_status, cookie, residue);

        return dma_status;
}

static void atc_issue_pending(struct dma_chan *chan)
{
        struct at_dma_chan *atchan = to_at_dma_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&atchan->vc.lock, flags);
        if (vchan_issue_pending(&atchan->vc) && !atchan->desc) {
                if (!(atc_chan_is_enabled(atchan)))
                        atc_dostart(atchan);
        }
        spin_unlock_irqrestore(&atchan->vc.lock, flags);
}

/**
 * atc_alloc_chan_resources - allocate resources for DMA channel
 * @chan: allocate descriptor resources for this channel
 *
 * Return: the number of allocated descriptors
 */
static int atc_alloc_chan_resources(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_dma_slave     *atslave;
        u32                     cfg;

        dev_vdbg(chan2dev(chan), "alloc_chan_resources\n");

        /* ASSERT:  channel is idle */
        if (atc_chan_is_enabled(atchan)) {
                dev_dbg(chan2dev(chan), "DMA channel not idle ?\n");
                return -EIO;
        }

        cfg = ATC_DEFAULT_CFG;

        atslave = chan->private;
        if (atslave) {
                /*
                 * We need controller-specific data to set up slave
                 * transfers.
                 */
                BUG_ON(!atslave->dma_dev || atslave->dma_dev != atdma->dma_device.dev);

                /* if cfg configuration specified take it instead of default */
                if (atslave->cfg)
                        cfg = atslave->cfg;
        }

        /* channel parameters */
        channel_writel(atchan, CFG, cfg);

        return 0;
}

/**
 * atc_free_chan_resources - free all channel resources
 * @chan: DMA channel
 */
static void atc_free_chan_resources(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma_slave     *atslave;

        BUG_ON(atc_chan_is_enabled(atchan));

        vchan_free_chan_resources(to_virt_chan(chan));
        atchan->status = 0;

        /*
         * Free atslave allocated in at_dma_xlate()
         */
        atslave = chan->private;
        if (atslave) {
                put_device(atslave->dma_dev);
                kfree(atslave);
                chan->private = NULL;
        }

        dev_vdbg(chan2dev(chan), "free_chan_resources: done\n");
}

#ifdef CONFIG_OF
static bool at_dma_filter(struct dma_chan *chan, void *slave)
{
        struct at_dma_slave *atslave = slave;

        if (atslave->dma_dev == chan->device->dev) {
                chan->private = atslave;
                return true;
        } else {
                return false;
        }
}

static struct dma_chan *at_dma_xlate(struct of_phandle_args *dma_spec,
                                     struct of_dma *of_dma)
{
        struct dma_chan *chan;
        struct at_dma_chan *atchan;
        struct at_dma_slave *atslave;
        dma_cap_mask_t mask;
        unsigned int per_id;
        struct platform_device *dmac_pdev;

        if (dma_spec->args_count != 2)
                return NULL;

        dmac_pdev = of_find_device_by_node(dma_spec->np);
        if (!dmac_pdev)
                return NULL;

        dma_cap_zero(mask);
        dma_cap_set(DMA_SLAVE, mask);

        atslave = kmalloc_obj(*atslave);
        if (!atslave) {
                put_device(&dmac_pdev->dev);
                return NULL;
        }

        atslave->cfg = ATC_DST_H2SEL | ATC_SRC_H2SEL;
        /*
         * We can fill both SRC_PER and DST_PER, one of these fields will be
         * ignored depending on DMA transfer direction.
         */
        per_id = dma_spec->args[1] & AT91_DMA_CFG_PER_ID_MASK;
        atslave->cfg |= ATC_DST_PER_ID(per_id) |  ATC_SRC_PER_ID(per_id);
        /*
         * We have to translate the value we get from the device tree since
         * the half FIFO configuration value had to be 0 to keep backward
         * compatibility.
         */
        switch (dma_spec->args[1] & AT91_DMA_CFG_FIFOCFG_MASK) {
        case AT91_DMA_CFG_FIFOCFG_ALAP:
                atslave->cfg |= FIELD_PREP(ATC_FIFOCFG,
                                           ATC_FIFOCFG_LARGESTBURST);
                break;
        case AT91_DMA_CFG_FIFOCFG_ASAP:
                atslave->cfg |= FIELD_PREP(ATC_FIFOCFG,
                                           ATC_FIFOCFG_ENOUGHSPACE);
                break;
        case AT91_DMA_CFG_FIFOCFG_HALF:
        default:
                atslave->cfg |= FIELD_PREP(ATC_FIFOCFG, ATC_FIFOCFG_HALFFIFO);
        }
        atslave->dma_dev = &dmac_pdev->dev;

        chan = dma_request_channel(mask, at_dma_filter, atslave);
        if (!chan) {
                put_device(&dmac_pdev->dev);
                kfree(atslave);
                return NULL;
        }

        atchan = to_at_dma_chan(chan);
        atchan->per_if = dma_spec->args[0] & 0xff;
        atchan->mem_if = (dma_spec->args[0] >> 16) & 0xff;

        return chan;
}
#else
static struct dma_chan *at_dma_xlate(struct of_phandle_args *dma_spec,
                                     struct of_dma *of_dma)
{
        return NULL;
}
#endif

/*--  Module Management  -----------------------------------------------*/

/* cap_mask is a multi-u32 bitfield, fill it with proper C code. */
static struct at_dma_platform_data at91sam9rl_config = {
        .nr_channels = 2,
};
static struct at_dma_platform_data at91sam9g45_config = {
        .nr_channels = 8,
};

#if defined(CONFIG_OF)
static const struct of_device_id atmel_dma_dt_ids[] = {
        {
                .compatible = "atmel,at91sam9rl-dma",
                .data = &at91sam9rl_config,
        }, {
                .compatible = "atmel,at91sam9g45-dma",
                .data = &at91sam9g45_config,
        }, {
                /* sentinel */
        }
};

MODULE_DEVICE_TABLE(of, atmel_dma_dt_ids);
#endif

static const struct platform_device_id atdma_devtypes[] = {
        {
                .name = "at91sam9rl_dma",
                .driver_data = (unsigned long) &at91sam9rl_config,
        }, {
                .name = "at91sam9g45_dma",
                .driver_data = (unsigned long) &at91sam9g45_config,
        }, {
                /* sentinel */
        }
};

static inline const struct at_dma_platform_data * __init at_dma_get_driver_data(
                                                struct platform_device *pdev)
{
        if (pdev->dev.of_node) {
                const struct of_device_id *match;
                match = of_match_node(atmel_dma_dt_ids, pdev->dev.of_node);
                if (match == NULL)
                        return NULL;
                return match->data;
        }
        return (struct at_dma_platform_data *)
                        platform_get_device_id(pdev)->driver_data;
}

/**
 * at_dma_off - disable DMA controller
 * @atdma: the Atmel HDAMC device
 */
static void at_dma_off(struct at_dma *atdma)
{
        dma_writel(atdma, EN, 0);

        /* disable all interrupts */
        dma_writel(atdma, EBCIDR, -1L);

        /* confirm that all channels are disabled */
        while (dma_readl(atdma, CHSR) & atdma->all_chan_mask)
                cpu_relax();
}

static int __init at_dma_probe(struct platform_device *pdev)
{
        struct at_dma           *atdma;
        int                     irq;
        int                     err;
        int                     i;
        const struct at_dma_platform_data *plat_dat;

        /* setup platform data for each SoC */
        dma_cap_set(DMA_MEMCPY, at91sam9rl_config.cap_mask);
        dma_cap_set(DMA_INTERLEAVE, at91sam9g45_config.cap_mask);
        dma_cap_set(DMA_MEMCPY, at91sam9g45_config.cap_mask);
        dma_cap_set(DMA_MEMSET, at91sam9g45_config.cap_mask);
        dma_cap_set(DMA_MEMSET_SG, at91sam9g45_config.cap_mask);
        dma_cap_set(DMA_PRIVATE, at91sam9g45_config.cap_mask);
        dma_cap_set(DMA_SLAVE, at91sam9g45_config.cap_mask);

        /* get DMA parameters from controller type */
        plat_dat = at_dma_get_driver_data(pdev);
        if (!plat_dat)
                return -ENODEV;

        atdma = devm_kzalloc(&pdev->dev,
                             struct_size(atdma, chan, plat_dat->nr_channels),
                             GFP_KERNEL);
        if (!atdma)
                return -ENOMEM;

        atdma->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(atdma->regs))
                return PTR_ERR(atdma->regs);

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

        /* discover transaction capabilities */
        atdma->dma_device.cap_mask = plat_dat->cap_mask;
        atdma->all_chan_mask = (1 << plat_dat->nr_channels) - 1;

        atdma->clk = devm_clk_get(&pdev->dev, "dma_clk");
        if (IS_ERR(atdma->clk))
                return PTR_ERR(atdma->clk);

        err = clk_prepare_enable(atdma->clk);
        if (err)
                return err;

        /* force dma off, just in case */
        at_dma_off(atdma);

        err = request_irq(irq, at_dma_interrupt, 0, "at_hdmac", atdma);
        if (err)
                goto err_irq;

        platform_set_drvdata(pdev, atdma);

        /* create a pool of consistent memory blocks for hardware descriptors */
        atdma->lli_pool = dma_pool_create("at_hdmac_lli_pool",
                                          &pdev->dev, sizeof(struct at_lli),
                                          4 /* word alignment */, 0);
        if (!atdma->lli_pool) {
                dev_err(&pdev->dev, "Unable to allocate DMA LLI descriptor pool\n");
                err = -ENOMEM;
                goto err_desc_pool_create;
        }

        /* create a pool of consistent memory blocks for memset blocks */
        atdma->memset_pool = dma_pool_create("at_hdmac_memset_pool",
                                             &pdev->dev, sizeof(int), 4, 0);
        if (!atdma->memset_pool) {
                dev_err(&pdev->dev, "No memory for memset dma pool\n");
                err = -ENOMEM;
                goto err_memset_pool_create;
        }

        /* clear any pending interrupt */
        while (dma_readl(atdma, EBCISR))
                cpu_relax();

        /* initialize channels related values */
        INIT_LIST_HEAD(&atdma->dma_device.channels);
        for (i = 0; i < plat_dat->nr_channels; i++) {
                struct at_dma_chan      *atchan = &atdma->chan[i];

                atchan->mem_if = AT_DMA_MEM_IF;
                atchan->per_if = AT_DMA_PER_IF;

                atchan->ch_regs = atdma->regs + ch_regs(i);
                atchan->mask = 1 << i;

                atchan->atdma = atdma;
                atchan->vc.desc_free = atdma_desc_free;
                vchan_init(&atchan->vc, &atdma->dma_device);
                atc_enable_chan_irq(atdma, i);
        }

        /* set base routines */
        atdma->dma_device.device_alloc_chan_resources = atc_alloc_chan_resources;
        atdma->dma_device.device_free_chan_resources = atc_free_chan_resources;
        atdma->dma_device.device_tx_status = atc_tx_status;
        atdma->dma_device.device_issue_pending = atc_issue_pending;
        atdma->dma_device.dev = &pdev->dev;

        /* set prep routines based on capability */
        if (dma_has_cap(DMA_INTERLEAVE, atdma->dma_device.cap_mask))
                atdma->dma_device.device_prep_interleaved_dma = atc_prep_dma_interleaved;

        if (dma_has_cap(DMA_MEMCPY, atdma->dma_device.cap_mask))
                atdma->dma_device.device_prep_dma_memcpy = atc_prep_dma_memcpy;

        if (dma_has_cap(DMA_MEMSET, atdma->dma_device.cap_mask)) {
                atdma->dma_device.device_prep_dma_memset = atc_prep_dma_memset;
                atdma->dma_device.device_prep_dma_memset_sg = atc_prep_dma_memset_sg;
                atdma->dma_device.fill_align = DMAENGINE_ALIGN_4_BYTES;
        }

        if (dma_has_cap(DMA_SLAVE, atdma->dma_device.cap_mask)) {
                atdma->dma_device.device_prep_slave_sg = atc_prep_slave_sg;
                /* controller can do slave DMA: can trigger cyclic transfers */
                dma_cap_set(DMA_CYCLIC, atdma->dma_device.cap_mask);
                atdma->dma_device.device_prep_dma_cyclic = atc_prep_dma_cyclic;
                atdma->dma_device.device_config = atc_config;
                atdma->dma_device.device_pause = atc_pause;
                atdma->dma_device.device_resume = atc_resume;
                atdma->dma_device.device_terminate_all = atc_terminate_all;
                atdma->dma_device.src_addr_widths = ATC_DMA_BUSWIDTHS;
                atdma->dma_device.dst_addr_widths = ATC_DMA_BUSWIDTHS;
                atdma->dma_device.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
                atdma->dma_device.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
        }

        dma_writel(atdma, EN, AT_DMA_ENABLE);

        dev_info(&pdev->dev, "Atmel AHB DMA Controller ( %s%s%s), %d channels\n",
          dma_has_cap(DMA_MEMCPY, atdma->dma_device.cap_mask) ? "cpy " : "",
          dma_has_cap(DMA_MEMSET, atdma->dma_device.cap_mask) ? "set " : "",
          dma_has_cap(DMA_SLAVE, atdma->dma_device.cap_mask)  ? "slave " : "",
          plat_dat->nr_channels);

        err = dma_async_device_register(&atdma->dma_device);
        if (err) {
                dev_err(&pdev->dev, "Unable to register: %d.\n", err);
                goto err_dma_async_device_register;
        }

        /*
         * Do not return an error if the dmac node is not present in order to
         * not break the existing way of requesting channel with
         * dma_request_channel().
         */
        if (pdev->dev.of_node) {
                err = of_dma_controller_register(pdev->dev.of_node,
                                                 at_dma_xlate, atdma);
                if (err) {
                        dev_err(&pdev->dev, "could not register of_dma_controller\n");
                        goto err_of_dma_controller_register;
                }
        }

        return 0;

err_of_dma_controller_register:
        dma_async_device_unregister(&atdma->dma_device);
err_dma_async_device_register:
        dma_pool_destroy(atdma->memset_pool);
err_memset_pool_create:
        dma_pool_destroy(atdma->lli_pool);
err_desc_pool_create:
        free_irq(platform_get_irq(pdev, 0), atdma);
err_irq:
        clk_disable_unprepare(atdma->clk);
        return err;
}

static void at_dma_remove(struct platform_device *pdev)
{
        struct at_dma           *atdma = platform_get_drvdata(pdev);
        struct dma_chan         *chan, *_chan;

        at_dma_off(atdma);
        if (pdev->dev.of_node)
                of_dma_controller_free(pdev->dev.of_node);
        dma_async_device_unregister(&atdma->dma_device);

        dma_pool_destroy(atdma->memset_pool);
        dma_pool_destroy(atdma->lli_pool);
        free_irq(platform_get_irq(pdev, 0), atdma);

        list_for_each_entry_safe(chan, _chan, &atdma->dma_device.channels,
                        device_node) {
                /* Disable interrupts */
                atc_disable_chan_irq(atdma, chan->chan_id);
                list_del(&chan->device_node);
        }

        clk_disable_unprepare(atdma->clk);
}

static void at_dma_shutdown(struct platform_device *pdev)
{
        struct at_dma   *atdma = platform_get_drvdata(pdev);

        at_dma_off(platform_get_drvdata(pdev));
        clk_disable_unprepare(atdma->clk);
}

static int at_dma_prepare(struct device *dev)
{
        struct at_dma *atdma = dev_get_drvdata(dev);
        struct dma_chan *chan, *_chan;

        list_for_each_entry_safe(chan, _chan, &atdma->dma_device.channels,
                        device_node) {
                struct at_dma_chan *atchan = to_at_dma_chan(chan);
                /* wait for transaction completion (except in cyclic case) */
                if (atc_chan_is_enabled(atchan) && !atc_chan_is_cyclic(atchan))
                        return -EAGAIN;
        }
        return 0;
}

static void atc_suspend_cyclic(struct at_dma_chan *atchan)
{
        struct dma_chan *chan = &atchan->vc.chan;

        /* Channel should be paused by user
         * do it anyway even if it is not done already */
        if (!atc_chan_is_paused(atchan)) {
                dev_warn(chan2dev(chan),
                "cyclic channel not paused, should be done by channel user\n");
                atc_pause(chan);
        }

        /* now preserve additional data for cyclic operations */
        /* next descriptor address in the cyclic list */
        atchan->save_dscr = channel_readl(atchan, DSCR);

        vdbg_dump_regs(atchan);
}

static int at_dma_suspend_noirq(struct device *dev)
{
        struct at_dma *atdma = dev_get_drvdata(dev);
        struct dma_chan *chan, *_chan;

        /* preserve data */
        list_for_each_entry_safe(chan, _chan, &atdma->dma_device.channels,
                        device_node) {
                struct at_dma_chan *atchan = to_at_dma_chan(chan);

                if (atc_chan_is_cyclic(atchan))
                        atc_suspend_cyclic(atchan);
                atchan->save_cfg = channel_readl(atchan, CFG);
        }
        atdma->save_imr = dma_readl(atdma, EBCIMR);

        /* disable DMA controller */
        at_dma_off(atdma);
        clk_disable_unprepare(atdma->clk);
        return 0;
}

static void atc_resume_cyclic(struct at_dma_chan *atchan)
{
        struct at_dma   *atdma = to_at_dma(atchan->vc.chan.device);

        /* restore channel status for cyclic descriptors list:
         * next descriptor in the cyclic list at the time of suspend */
        channel_writel(atchan, SADDR, 0);
        channel_writel(atchan, DADDR, 0);
        channel_writel(atchan, CTRLA, 0);
        channel_writel(atchan, CTRLB, 0);
        channel_writel(atchan, DSCR, atchan->save_dscr);
        dma_writel(atdma, CHER, atchan->mask);

        /* channel pause status should be removed by channel user
         * We cannot take the initiative to do it here */

        vdbg_dump_regs(atchan);
}

static int at_dma_resume_noirq(struct device *dev)
{
        struct at_dma *atdma = dev_get_drvdata(dev);
        struct dma_chan *chan, *_chan;

        /* bring back DMA controller */
        clk_prepare_enable(atdma->clk);
        dma_writel(atdma, EN, AT_DMA_ENABLE);

        /* clear any pending interrupt */
        while (dma_readl(atdma, EBCISR))
                cpu_relax();

        /* restore saved data */
        dma_writel(atdma, EBCIER, atdma->save_imr);
        list_for_each_entry_safe(chan, _chan, &atdma->dma_device.channels,
                        device_node) {
                struct at_dma_chan *atchan = to_at_dma_chan(chan);

                channel_writel(atchan, CFG, atchan->save_cfg);
                if (atc_chan_is_cyclic(atchan))
                        atc_resume_cyclic(atchan);
        }
        return 0;
}

static const struct dev_pm_ops __maybe_unused at_dma_dev_pm_ops = {
        .prepare = at_dma_prepare,
        .suspend_noirq = at_dma_suspend_noirq,
        .resume_noirq = at_dma_resume_noirq,
};

static struct platform_driver at_dma_driver = {
        .remove         = at_dma_remove,
        .shutdown       = at_dma_shutdown,
        .id_table       = atdma_devtypes,
        .driver = {
                .name   = "at_hdmac",
                .pm     = pm_ptr(&at_dma_dev_pm_ops),
                .of_match_table = of_match_ptr(atmel_dma_dt_ids),
        },
};

static int __init at_dma_init(void)
{
        return platform_driver_probe(&at_dma_driver, at_dma_probe);
}
subsys_initcall(at_dma_init);

static void __exit at_dma_exit(void)
{
        platform_driver_unregister(&at_dma_driver);
}
module_exit(at_dma_exit);

MODULE_DESCRIPTION("Atmel AHB DMA Controller driver");
MODULE_AUTHOR("Nicolas Ferre <nicolas.ferre@atmel.com>");
MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:at_hdmac");