/*
 * Copyright (C) 2013-2014 Renesas Electronics Europe Ltd.
 * Author: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 */

#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/log2.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#include <dt-bindings/dma/nbpfaxi.h>

#include "dmaengine.h"

#define NBPF_REG_CHAN_OFFSET    0
#define NBPF_REG_CHAN_SIZE      0x40

/* Channel Current Transaction Byte register */
#define NBPF_CHAN_CUR_TR_BYTE   0x20

/* Channel Status register */
#define NBPF_CHAN_STAT  0x24
#define NBPF_CHAN_STAT_EN       1
#define NBPF_CHAN_STAT_TACT     4
#define NBPF_CHAN_STAT_ERR      0x10
#define NBPF_CHAN_STAT_END      0x20
#define NBPF_CHAN_STAT_TC       0x40
#define NBPF_CHAN_STAT_DER      0x400

/* Channel Control register */
#define NBPF_CHAN_CTRL  0x28
#define NBPF_CHAN_CTRL_SETEN    1
#define NBPF_CHAN_CTRL_CLREN    2
#define NBPF_CHAN_CTRL_STG      4
#define NBPF_CHAN_CTRL_SWRST    8
#define NBPF_CHAN_CTRL_CLRRQ    0x10
#define NBPF_CHAN_CTRL_CLREND   0x20
#define NBPF_CHAN_CTRL_CLRTC    0x40
#define NBPF_CHAN_CTRL_SETSUS   0x100
#define NBPF_CHAN_CTRL_CLRSUS   0x200

/* Channel Configuration register */
#define NBPF_CHAN_CFG   0x2c
#define NBPF_CHAN_CFG_SEL       7               /* terminal SELect: 0..7 */
#define NBPF_CHAN_CFG_REQD      8               /* REQuest Direction: DMAREQ is 0: input, 1: output */
#define NBPF_CHAN_CFG_LOEN      0x10            /* LOw ENable: low DMA request line is: 0: inactive, 1: active */
#define NBPF_CHAN_CFG_HIEN      0x20            /* HIgh ENable: high DMA request line is: 0: inactive, 1: active */
#define NBPF_CHAN_CFG_LVL       0x40            /* LeVeL: DMA request line is sensed as 0: edge, 1: level */
#define NBPF_CHAN_CFG_AM        0x700           /* ACK Mode: 0: Pulse mode, 1: Level mode, b'1x: Bus Cycle */
#define NBPF_CHAN_CFG_SDS       0xf000          /* Source Data Size: 0: 8 bits,... , 7: 1024 bits */
#define NBPF_CHAN_CFG_DDS       0xf0000         /* Destination Data Size: as above */
#define NBPF_CHAN_CFG_SAD       0x100000        /* Source ADdress counting: 0: increment, 1: fixed */
#define NBPF_CHAN_CFG_DAD       0x200000        /* Destination ADdress counting: 0: increment, 1: fixed */
#define NBPF_CHAN_CFG_TM        0x400000        /* Transfer Mode: 0: single, 1: block TM */
#define NBPF_CHAN_CFG_DEM       0x1000000       /* DMAEND interrupt Mask */
#define NBPF_CHAN_CFG_TCM       0x2000000       /* DMATCO interrupt Mask */
#define NBPF_CHAN_CFG_SBE       0x8000000       /* Sweep Buffer Enable */
#define NBPF_CHAN_CFG_RSEL      0x10000000      /* RM: Register Set sELect */
#define NBPF_CHAN_CFG_RSW       0x20000000      /* RM: Register Select sWitch */
#define NBPF_CHAN_CFG_REN       0x40000000      /* RM: Register Set Enable */
#define NBPF_CHAN_CFG_DMS       0x80000000      /* 0: register mode (RM), 1: link mode (LM) */

#define NBPF_CHAN_NXLA  0x38
#define NBPF_CHAN_CRLA  0x3c

/* Link Header field */
#define NBPF_HEADER_LV  1
#define NBPF_HEADER_LE  2
#define NBPF_HEADER_WBD 4
#define NBPF_HEADER_DIM 8

#define NBPF_CTRL       0x300
#define NBPF_CTRL_PR    1               /* 0: fixed priority, 1: round robin */
#define NBPF_CTRL_LVINT 2               /* DMAEND and DMAERR signalling: 0: pulse, 1: level */

#define NBPF_DSTAT_ER   0x314
#define NBPF_DSTAT_END  0x318

#define NBPF_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) | \
         BIT(DMA_SLAVE_BUSWIDTH_8_BYTES))

struct nbpf_config {
        int num_channels;
        int buffer_size;
};

/*
 * We've got 3 types of objects, used to describe DMA transfers:
 * 1. high-level descriptor, containing a struct dma_async_tx_descriptor object
 *      in it, used to communicate with the user
 * 2. hardware DMA link descriptors, that we pass to DMAC for DMA transfer
 *      queuing, these must be DMAable, using either the streaming DMA API or
 *      allocated from coherent memory - one per SG segment
 * 3. one per SG segment descriptors, used to manage HW link descriptors from
 *      (2). They do not have to be DMAable. They can either be (a) allocated
 *      together with link descriptors as mixed (DMA / CPU) objects, or (b)
 *      separately. Even if allocated separately it would be best to link them
 *      to link descriptors once during channel resource allocation and always
 *      use them as a single object.
 * Therefore for both cases (a) and (b) at run-time objects (2) and (3) shall be
 * treated as a single SG segment descriptor.
 */

struct nbpf_link_reg {
        u32     header;
        u32     src_addr;
        u32     dst_addr;
        u32     transaction_size;
        u32     config;
        u32     interval;
        u32     extension;
        u32     next;
} __packed;

struct nbpf_device;
struct nbpf_channel;
struct nbpf_desc;

struct nbpf_link_desc {
        struct nbpf_link_reg *hwdesc;
        dma_addr_t hwdesc_dma_addr;
        struct nbpf_desc *desc;
        struct list_head node;
};

/**
 * struct nbpf_desc - DMA transfer descriptor
 * @async_tx:   dmaengine object
 * @user_wait:  waiting for a user ack
 * @length:     total transfer length
 * @sg:         list of hardware descriptors, represented by struct nbpf_link_desc
 * @node:       member in channel descriptor lists
 */
struct nbpf_desc {
        struct dma_async_tx_descriptor async_tx;
        bool user_wait;
        size_t length;
        struct nbpf_channel *chan;
        struct list_head sg;
        struct list_head node;
};

/* Take a wild guess: allocate 4 segments per descriptor */
#define NBPF_SEGMENTS_PER_DESC 4
#define NBPF_DESCS_PER_PAGE ((PAGE_SIZE - sizeof(struct list_head)) /   \
        (sizeof(struct nbpf_desc) +                                     \
         NBPF_SEGMENTS_PER_DESC *                                       \
         (sizeof(struct nbpf_link_desc) + sizeof(struct nbpf_link_reg))))
#define NBPF_SEGMENTS_PER_PAGE (NBPF_SEGMENTS_PER_DESC * NBPF_DESCS_PER_PAGE)

struct nbpf_desc_page {
        struct list_head node;
        struct nbpf_desc desc[NBPF_DESCS_PER_PAGE];
        struct nbpf_link_desc ldesc[NBPF_SEGMENTS_PER_PAGE];
        struct nbpf_link_reg hwdesc[NBPF_SEGMENTS_PER_PAGE];
};

/**
 * struct nbpf_channel - one DMAC channel
 * @dma_chan:   standard dmaengine channel object
 * @base:       register address base
 * @nbpf:       DMAC
 * @name:       IRQ name
 * @irq:        IRQ number
 * @slave_addr: address for slave DMA
 * @slave_width:slave data size in bytes
 * @slave_burst:maximum slave burst size in bytes
 * @terminal:   DMA terminal, assigned to this channel
 * @dmarq_cfg:  DMA request line configuration - high / low, edge / level for NBPF_CHAN_CFG
 * @flags:      configuration flags from DT
 * @lock:       protect descriptor lists
 * @free_links: list of free link descriptors
 * @free:       list of free descriptors
 * @queued:     list of queued descriptors
 * @active:     list of descriptors, scheduled for processing
 * @done:       list of completed descriptors, waiting post-processing
 * @desc_page:  list of additionally allocated descriptor pages - if any
 */
struct nbpf_channel {
        struct dma_chan dma_chan;
        struct tasklet_struct tasklet;
        void __iomem *base;
        struct nbpf_device *nbpf;
        char name[16];
        int irq;
        dma_addr_t slave_src_addr;
        size_t slave_src_width;
        size_t slave_src_burst;
        dma_addr_t slave_dst_addr;
        size_t slave_dst_width;
        size_t slave_dst_burst;
        unsigned int terminal;
        u32 dmarq_cfg;
        unsigned long flags;
        spinlock_t lock;
        struct list_head free_links;
        struct list_head free;
        struct list_head queued;
        struct list_head active;
        struct list_head done;
        struct list_head desc_page;
        struct nbpf_desc *running;
        bool paused;
};

struct nbpf_device {
        struct dma_device dma_dev;
        void __iomem *base;
        u32 max_burst_mem_read;
        u32 max_burst_mem_write;
        struct clk *clk;
        const struct nbpf_config *config;
        unsigned int eirq;
        struct nbpf_channel chan[];
};

enum nbpf_model {
        NBPF1B4,
        NBPF1B8,
        NBPF1B16,
        NBPF4B4,
        NBPF4B8,
        NBPF4B16,
        NBPF8B4,
        NBPF8B8,
        NBPF8B16,
};

static struct nbpf_config nbpf_cfg[] = {
        [NBPF1B4] = {
                .num_channels = 1,
                .buffer_size = 4,
        },
        [NBPF1B8] = {
                .num_channels = 1,
                .buffer_size = 8,
        },
        [NBPF1B16] = {
                .num_channels = 1,
                .buffer_size = 16,
        },
        [NBPF4B4] = {
                .num_channels = 4,
                .buffer_size = 4,
        },
        [NBPF4B8] = {
                .num_channels = 4,
                .buffer_size = 8,
        },
        [NBPF4B16] = {
                .num_channels = 4,
                .buffer_size = 16,
        },
        [NBPF8B4] = {
                .num_channels = 8,
                .buffer_size = 4,
        },
        [NBPF8B8] = {
                .num_channels = 8,
                .buffer_size = 8,
        },
        [NBPF8B16] = {
                .num_channels = 8,
                .buffer_size = 16,
        },
};

#define nbpf_to_chan(d) container_of(d, struct nbpf_channel, dma_chan)

/*
 * dmaengine drivers seem to have a lot in common and instead of sharing more
 * code, they reimplement those common algorithms independently. In this driver
 * we try to separate the hardware-specific part from the (largely) generic
 * part. This improves code readability and makes it possible in the future to
 * reuse the generic code in form of a helper library. That generic code should
 * be suitable for various DMA controllers, using transfer descriptors in RAM
 * and pushing one SG list at a time to the DMA controller.
 */

/*              Hardware-specific part          */

static inline u32 nbpf_chan_read(struct nbpf_channel *chan,
                                 unsigned int offset)
{
        u32 data = ioread32(chan->base + offset);
        dev_dbg(chan->dma_chan.device->dev, "%s(0x%p + 0x%x) = 0x%x\n",
                __func__, chan->base, offset, data);
        return data;
}

static inline void nbpf_chan_write(struct nbpf_channel *chan,
                                   unsigned int offset, u32 data)
{
        iowrite32(data, chan->base + offset);
        dev_dbg(chan->dma_chan.device->dev, "%s(0x%p + 0x%x) = 0x%x\n",
                __func__, chan->base, offset, data);
}

static inline u32 nbpf_read(struct nbpf_device *nbpf,
                            unsigned int offset)
{
        u32 data = ioread32(nbpf->base + offset);
        dev_dbg(nbpf->dma_dev.dev, "%s(0x%p + 0x%x) = 0x%x\n",
                __func__, nbpf->base, offset, data);
        return data;
}

static inline void nbpf_write(struct nbpf_device *nbpf,
                              unsigned int offset, u32 data)
{
        iowrite32(data, nbpf->base + offset);
        dev_dbg(nbpf->dma_dev.dev, "%s(0x%p + 0x%x) = 0x%x\n",
                __func__, nbpf->base, offset, data);
}

static void nbpf_chan_halt(struct nbpf_channel *chan)
{
        nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_CLREN);
}

static bool nbpf_status_get(struct nbpf_channel *chan)
{
        u32 status = nbpf_read(chan->nbpf, NBPF_DSTAT_END);

        return status & BIT(chan - chan->nbpf->chan);
}

static void nbpf_status_ack(struct nbpf_channel *chan)
{
        nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_CLREND);
}

static u32 nbpf_error_get(struct nbpf_device *nbpf)
{
        return nbpf_read(nbpf, NBPF_DSTAT_ER);
}

static struct nbpf_channel *nbpf_error_get_channel(struct nbpf_device *nbpf, u32 error)
{
        return nbpf->chan + __ffs(error);
}

static void nbpf_error_clear(struct nbpf_channel *chan)
{
        u32 status;
        int i;

        /* Stop the channel, make sure DMA has been aborted */
        nbpf_chan_halt(chan);

        for (i = 1000; i; i--) {
                status = nbpf_chan_read(chan, NBPF_CHAN_STAT);
                if (!(status & NBPF_CHAN_STAT_TACT))
                        break;
                cpu_relax();
        }

        if (!i)
                dev_err(chan->dma_chan.device->dev,
                        "%s(): abort timeout, channel status 0x%x\n", __func__, status);

        nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_SWRST);
}

static int nbpf_start(struct nbpf_desc *desc)
{
        struct nbpf_channel *chan = desc->chan;
        struct nbpf_link_desc *ldesc = list_first_entry(&desc->sg, struct nbpf_link_desc, node);

        nbpf_chan_write(chan, NBPF_CHAN_NXLA, (u32)ldesc->hwdesc_dma_addr);
        nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_SETEN | NBPF_CHAN_CTRL_CLRSUS);
        chan->paused = false;

        /* Software trigger MEMCPY - only MEMCPY uses the block mode */
        if (ldesc->hwdesc->config & NBPF_CHAN_CFG_TM)
                nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_STG);

        dev_dbg(chan->nbpf->dma_dev.dev, "%s(): next 0x%x, cur 0x%x\n", __func__,
                nbpf_chan_read(chan, NBPF_CHAN_NXLA), nbpf_chan_read(chan, NBPF_CHAN_CRLA));

        return 0;
}

static void nbpf_chan_prepare(struct nbpf_channel *chan)
{
        chan->dmarq_cfg = (chan->flags & NBPF_SLAVE_RQ_HIGH ? NBPF_CHAN_CFG_HIEN : 0) |
                (chan->flags & NBPF_SLAVE_RQ_LOW ? NBPF_CHAN_CFG_LOEN : 0) |
                (chan->flags & NBPF_SLAVE_RQ_LEVEL ?
                 NBPF_CHAN_CFG_LVL | (NBPF_CHAN_CFG_AM & 0x200) : 0) |
                chan->terminal;
}

static void nbpf_chan_prepare_default(struct nbpf_channel *chan)
{
        /* Don't output DMAACK */
        chan->dmarq_cfg = NBPF_CHAN_CFG_AM & 0x400;
        chan->terminal = 0;
        chan->flags = 0;
}

static void nbpf_chan_configure(struct nbpf_channel *chan)
{
        /*
         * We assume, that only the link mode and DMA request line configuration
         * have to be set in the configuration register manually. Dynamic
         * per-transfer configuration will be loaded from transfer descriptors.
         */
        nbpf_chan_write(chan, NBPF_CHAN_CFG, NBPF_CHAN_CFG_DMS | chan->dmarq_cfg);
}

static u32 nbpf_xfer_ds(struct nbpf_device *nbpf, size_t size,
                        enum dma_transfer_direction direction)
{
        int max_burst = nbpf->config->buffer_size * 8;

        if (nbpf->max_burst_mem_read || nbpf->max_burst_mem_write) {
                switch (direction) {
                case DMA_MEM_TO_MEM:
                        max_burst = min_not_zero(nbpf->max_burst_mem_read,
                                                 nbpf->max_burst_mem_write);
                        break;
                case DMA_MEM_TO_DEV:
                        if (nbpf->max_burst_mem_read)
                                max_burst = nbpf->max_burst_mem_read;
                        break;
                case DMA_DEV_TO_MEM:
                        if (nbpf->max_burst_mem_write)
                                max_burst = nbpf->max_burst_mem_write;
                        break;
                case DMA_DEV_TO_DEV:
                default:
                        break;
                }
        }

        /* Maximum supported bursts depend on the buffer size */
        return min_t(int, __ffs(size), ilog2(max_burst));
}

static size_t nbpf_xfer_size(struct nbpf_device *nbpf,
                             enum dma_slave_buswidth width, u32 burst)
{
        size_t size;

        if (!burst)
                burst = 1;

        switch (width) {
        case DMA_SLAVE_BUSWIDTH_8_BYTES:
                size = 8 * burst;
                break;

        case DMA_SLAVE_BUSWIDTH_4_BYTES:
                size = 4 * burst;
                break;

        case DMA_SLAVE_BUSWIDTH_2_BYTES:
                size = 2 * burst;
                break;

        default:
                pr_warn("%s(): invalid bus width %u\n", __func__, width);
        case DMA_SLAVE_BUSWIDTH_1_BYTE:
                size = burst;
        }

        return nbpf_xfer_ds(nbpf, size, DMA_TRANS_NONE);
}

/*
 * We need a way to recognise slaves, whose data is sent "raw" over the bus,
 * i.e. it isn't known in advance how many bytes will be received. Therefore
 * the slave driver has to provide a "large enough" buffer and either read the
 * buffer, when it is full, or detect, that some data has arrived, then wait for
 * a timeout, if no more data arrives - receive what's already there. We want to
 * handle such slaves in a special way to allow an optimised mode for other
 * users, for whom the amount of data is known in advance. So far there's no way
 * to recognise such slaves. We use a data-width check to distinguish between
 * the SD host and the PL011 UART.
 */

static int nbpf_prep_one(struct nbpf_link_desc *ldesc,
                         enum dma_transfer_direction direction,
                         dma_addr_t src, dma_addr_t dst, size_t size, bool last)
{
        struct nbpf_link_reg *hwdesc = ldesc->hwdesc;
        struct nbpf_desc *desc = ldesc->desc;
        struct nbpf_channel *chan = desc->chan;
        struct device *dev = chan->dma_chan.device->dev;
        size_t mem_xfer, slave_xfer;
        bool can_burst;

        hwdesc->header = NBPF_HEADER_WBD | NBPF_HEADER_LV |
                (last ? NBPF_HEADER_LE : 0);

        hwdesc->src_addr = src;
        hwdesc->dst_addr = dst;
        hwdesc->transaction_size = size;

        /*
         * set config: SAD, DAD, DDS, SDS, etc.
         * Note on transfer sizes: the DMAC can perform unaligned DMA transfers,
         * but it is important to have transaction size a multiple of both
         * receiver and transmitter transfer sizes. It is also possible to use
         * different RAM and device transfer sizes, and it does work well with
         * some devices, e.g. with V08R07S01E SD host controllers, which can use
         * 128 byte transfers. But this doesn't work with other devices,
         * especially when the transaction size is unknown. This is the case,
         * e.g. with serial drivers like amba-pl011.c. For reception it sets up
         * the transaction size of 4K and if fewer bytes are received, it
         * pauses DMA and reads out data received via DMA as well as those left
         * in the Rx FIFO. For this to work with the RAM side using burst
         * transfers we enable the SBE bit and terminate the transfer in our
         * .device_pause handler.
         */
        mem_xfer = nbpf_xfer_ds(chan->nbpf, size, direction);

        switch (direction) {
        case DMA_DEV_TO_MEM:
                can_burst = chan->slave_src_width >= 3;
                slave_xfer = min(mem_xfer, can_burst ?
                                 chan->slave_src_burst : chan->slave_src_width);
                /*
                 * Is the slave narrower than 64 bits, i.e. isn't using the full
                 * bus width and cannot use bursts?
                 */
                if (mem_xfer > chan->slave_src_burst && !can_burst)
                        mem_xfer = chan->slave_src_burst;
                /* Device-to-RAM DMA is unreliable without REQD set */
                hwdesc->config = NBPF_CHAN_CFG_SAD | (NBPF_CHAN_CFG_DDS & (mem_xfer << 16)) |
                        (NBPF_CHAN_CFG_SDS & (slave_xfer << 12)) | NBPF_CHAN_CFG_REQD |
                        NBPF_CHAN_CFG_SBE;
                break;

        case DMA_MEM_TO_DEV:
                slave_xfer = min(mem_xfer, chan->slave_dst_width >= 3 ?
                                 chan->slave_dst_burst : chan->slave_dst_width);
                hwdesc->config = NBPF_CHAN_CFG_DAD | (NBPF_CHAN_CFG_SDS & (mem_xfer << 12)) |
                        (NBPF_CHAN_CFG_DDS & (slave_xfer << 16)) | NBPF_CHAN_CFG_REQD;
                break;

        case DMA_MEM_TO_MEM:
                hwdesc->config = NBPF_CHAN_CFG_TCM | NBPF_CHAN_CFG_TM |
                        (NBPF_CHAN_CFG_SDS & (mem_xfer << 12)) |
                        (NBPF_CHAN_CFG_DDS & (mem_xfer << 16));
                break;

        default:
                return -EINVAL;
        }

        hwdesc->config |= chan->dmarq_cfg | (last ? 0 : NBPF_CHAN_CFG_DEM) |
                NBPF_CHAN_CFG_DMS;

        dev_dbg(dev, "%s(): desc @ %pad: hdr 0x%x, cfg 0x%x, %zu @ %pad -> %pad\n",
                __func__, &ldesc->hwdesc_dma_addr, hwdesc->header,
                hwdesc->config, size, &src, &dst);

        dma_sync_single_for_device(dev, ldesc->hwdesc_dma_addr, sizeof(*hwdesc),
                                   DMA_TO_DEVICE);

        return 0;
}

static size_t nbpf_bytes_left(struct nbpf_channel *chan)
{
        return nbpf_chan_read(chan, NBPF_CHAN_CUR_TR_BYTE);
}

static void nbpf_configure(struct nbpf_device *nbpf)
{
        nbpf_write(nbpf, NBPF_CTRL, NBPF_CTRL_LVINT);
}

/*              Generic part                    */

/* DMA ENGINE functions */
static void nbpf_issue_pending(struct dma_chan *dchan)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);
        unsigned long flags;

        dev_dbg(dchan->device->dev, "Entry %s()\n", __func__);

        spin_lock_irqsave(&chan->lock, flags);
        if (list_empty(&chan->queued))
                goto unlock;

        list_splice_tail_init(&chan->queued, &chan->active);

        if (!chan->running) {
                struct nbpf_desc *desc = list_first_entry(&chan->active,
                                                struct nbpf_desc, node);
                if (!nbpf_start(desc))
                        chan->running = desc;
        }

unlock:
        spin_unlock_irqrestore(&chan->lock, flags);
}

static enum dma_status nbpf_tx_status(struct dma_chan *dchan,
                dma_cookie_t cookie, struct dma_tx_state *state)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);
        enum dma_status status = dma_cookie_status(dchan, cookie, state);

        if (state) {
                dma_cookie_t running;
                unsigned long flags;

                spin_lock_irqsave(&chan->lock, flags);
                running = chan->running ? chan->running->async_tx.cookie : -EINVAL;

                if (cookie == running) {
                        state->residue = nbpf_bytes_left(chan);
                        dev_dbg(dchan->device->dev, "%s(): residue %u\n", __func__,
                                state->residue);
                } else if (status == DMA_IN_PROGRESS) {
                        struct nbpf_desc *desc;
                        bool found = false;

                        list_for_each_entry(desc, &chan->active, node)
                                if (desc->async_tx.cookie == cookie) {
                                        found = true;
                                        break;
                                }

                        if (!found)
                                list_for_each_entry(desc, &chan->queued, node)
                                        if (desc->async_tx.cookie == cookie) {
                                                found = true;
                                                break;

                                        }

                        state->residue = found ? desc->length : 0;
                }

                spin_unlock_irqrestore(&chan->lock, flags);
        }

        if (chan->paused)
                status = DMA_PAUSED;

        return status;
}

static dma_cookie_t nbpf_tx_submit(struct dma_async_tx_descriptor *tx)
{
        struct nbpf_desc *desc = container_of(tx, struct nbpf_desc, async_tx);
        struct nbpf_channel *chan = desc->chan;
        unsigned long flags;
        dma_cookie_t cookie;

        spin_lock_irqsave(&chan->lock, flags);
        cookie = dma_cookie_assign(tx);
        list_add_tail(&desc->node, &chan->queued);
        spin_unlock_irqrestore(&chan->lock, flags);

        dev_dbg(chan->dma_chan.device->dev, "Entry %s(%d)\n", __func__, cookie);

        return cookie;
}

static int nbpf_desc_page_alloc(struct nbpf_channel *chan)
{
        struct dma_chan *dchan = &chan->dma_chan;
        struct nbpf_desc_page *dpage = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
        struct nbpf_link_desc *ldesc;
        struct nbpf_link_reg *hwdesc;
        struct nbpf_desc *desc;
        LIST_HEAD(head);
        LIST_HEAD(lhead);
        int i;
        struct device *dev = dchan->device->dev;

        if (!dpage)
                return -ENOMEM;

        dev_dbg(dev, "%s(): alloc %lu descriptors, %lu segments, total alloc %zu\n",
                __func__, NBPF_DESCS_PER_PAGE, NBPF_SEGMENTS_PER_PAGE, sizeof(*dpage));

        for (i = 0, ldesc = dpage->ldesc, hwdesc = dpage->hwdesc;
             i < ARRAY_SIZE(dpage->ldesc);
             i++, ldesc++, hwdesc++) {
                ldesc->hwdesc = hwdesc;
                list_add_tail(&ldesc->node, &lhead);
                ldesc->hwdesc_dma_addr = dma_map_single(dchan->device->dev,
                                        hwdesc, sizeof(*hwdesc), DMA_TO_DEVICE);

                dev_dbg(dev, "%s(): mapped 0x%p to %pad\n", __func__,
                        hwdesc, &ldesc->hwdesc_dma_addr);
        }

        for (i = 0, desc = dpage->desc;
             i < ARRAY_SIZE(dpage->desc);
             i++, desc++) {
                dma_async_tx_descriptor_init(&desc->async_tx, dchan);
                desc->async_tx.tx_submit = nbpf_tx_submit;
                desc->chan = chan;
                INIT_LIST_HEAD(&desc->sg);
                list_add_tail(&desc->node, &head);
        }

        /*
         * This function cannot be called from interrupt context, so, no need to
         * save flags
         */
        spin_lock_irq(&chan->lock);
        list_splice_tail(&lhead, &chan->free_links);
        list_splice_tail(&head, &chan->free);
        list_add(&dpage->node, &chan->desc_page);
        spin_unlock_irq(&chan->lock);

        return ARRAY_SIZE(dpage->desc);
}

static void nbpf_desc_put(struct nbpf_desc *desc)
{
        struct nbpf_channel *chan = desc->chan;
        struct nbpf_link_desc *ldesc, *tmp;
        unsigned long flags;

        spin_lock_irqsave(&chan->lock, flags);
        list_for_each_entry_safe(ldesc, tmp, &desc->sg, node)
                list_move(&ldesc->node, &chan->free_links);

        list_add(&desc->node, &chan->free);
        spin_unlock_irqrestore(&chan->lock, flags);
}

static void nbpf_scan_acked(struct nbpf_channel *chan)
{
        struct nbpf_desc *desc, *tmp;
        unsigned long flags;
        LIST_HEAD(head);

        spin_lock_irqsave(&chan->lock, flags);
        list_for_each_entry_safe(desc, tmp, &chan->done, node)
                if (async_tx_test_ack(&desc->async_tx) && desc->user_wait) {
                        list_move(&desc->node, &head);
                        desc->user_wait = false;
                }
        spin_unlock_irqrestore(&chan->lock, flags);

        list_for_each_entry_safe(desc, tmp, &head, node) {
                list_del(&desc->node);
                nbpf_desc_put(desc);
        }
}

/*
 * We have to allocate descriptors with the channel lock dropped. This means,
 * before we re-acquire the lock buffers can be taken already, so we have to
 * re-check after re-acquiring the lock and possibly retry, if buffers are gone
 * again.
 */
static struct nbpf_desc *nbpf_desc_get(struct nbpf_channel *chan, size_t len)
{
        struct nbpf_desc *desc = NULL;
        struct nbpf_link_desc *ldesc, *prev = NULL;

        nbpf_scan_acked(chan);

        spin_lock_irq(&chan->lock);

        do {
                int i = 0, ret;

                if (list_empty(&chan->free)) {
                        /* No more free descriptors */
                        spin_unlock_irq(&chan->lock);
                        ret = nbpf_desc_page_alloc(chan);
                        if (ret < 0)
                                return NULL;
                        spin_lock_irq(&chan->lock);
                        continue;
                }
                desc = list_first_entry(&chan->free, struct nbpf_desc, node);
                list_del(&desc->node);

                do {
                        if (list_empty(&chan->free_links)) {
                                /* No more free link descriptors */
                                spin_unlock_irq(&chan->lock);
                                ret = nbpf_desc_page_alloc(chan);
                                if (ret < 0) {
                                        nbpf_desc_put(desc);
                                        return NULL;
                                }
                                spin_lock_irq(&chan->lock);
                                continue;
                        }

                        ldesc = list_first_entry(&chan->free_links,
                                                 struct nbpf_link_desc, node);
                        ldesc->desc = desc;
                        if (prev)
                                prev->hwdesc->next = (u32)ldesc->hwdesc_dma_addr;

                        prev = ldesc;
                        list_move_tail(&ldesc->node, &desc->sg);

                        i++;
                } while (i < len);
        } while (!desc);

        prev->hwdesc->next = 0;

        spin_unlock_irq(&chan->lock);

        return desc;
}

static void nbpf_chan_idle(struct nbpf_channel *chan)
{
        struct nbpf_desc *desc, *tmp;
        unsigned long flags;
        LIST_HEAD(head);

        spin_lock_irqsave(&chan->lock, flags);

        list_splice_init(&chan->done, &head);
        list_splice_init(&chan->active, &head);
        list_splice_init(&chan->queued, &head);

        chan->running = NULL;

        spin_unlock_irqrestore(&chan->lock, flags);

        list_for_each_entry_safe(desc, tmp, &head, node) {
                dev_dbg(chan->nbpf->dma_dev.dev, "%s(): force-free desc %p cookie %d\n",
                        __func__, desc, desc->async_tx.cookie);
                list_del(&desc->node);
                nbpf_desc_put(desc);
        }
}

static int nbpf_pause(struct dma_chan *dchan)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);

        dev_dbg(dchan->device->dev, "Entry %s\n", __func__);

        chan->paused = true;
        nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_SETSUS);
        /* See comment in nbpf_prep_one() */
        nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_CLREN);

        return 0;
}

static int nbpf_terminate_all(struct dma_chan *dchan)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);

        dev_dbg(dchan->device->dev, "Entry %s\n", __func__);
        dev_dbg(dchan->device->dev, "Terminating\n");

        nbpf_chan_halt(chan);
        nbpf_chan_idle(chan);

        return 0;
}

static int nbpf_config(struct dma_chan *dchan,
                       struct dma_slave_config *config)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);

        dev_dbg(dchan->device->dev, "Entry %s\n", __func__);

        /*
         * We could check config->slave_id to match chan->terminal here,
         * but with DT they would be coming from the same source, so
         * such a check would be superflous
         */

        chan->slave_dst_addr = config->dst_addr;
        chan->slave_dst_width = nbpf_xfer_size(chan->nbpf,
                                               config->dst_addr_width, 1);
        chan->slave_dst_burst = nbpf_xfer_size(chan->nbpf,
                                               config->dst_addr_width,
                                               config->dst_maxburst);
        chan->slave_src_addr = config->src_addr;
        chan->slave_src_width = nbpf_xfer_size(chan->nbpf,
                                               config->src_addr_width, 1);
        chan->slave_src_burst = nbpf_xfer_size(chan->nbpf,
                                               config->src_addr_width,
                                               config->src_maxburst);

        return 0;
}

static struct dma_async_tx_descriptor *nbpf_prep_sg(struct nbpf_channel *chan,
                struct scatterlist *src_sg, struct scatterlist *dst_sg,
                size_t len, enum dma_transfer_direction direction,
                unsigned long flags)
{
        struct nbpf_link_desc *ldesc;
        struct scatterlist *mem_sg;
        struct nbpf_desc *desc;
        bool inc_src, inc_dst;
        size_t data_len = 0;
        int i = 0;

        switch (direction) {
        case DMA_DEV_TO_MEM:
                mem_sg = dst_sg;
                inc_src = false;
                inc_dst = true;
                break;

        case DMA_MEM_TO_DEV:
                mem_sg = src_sg;
                inc_src = true;
                inc_dst = false;
                break;

        default:
        case DMA_MEM_TO_MEM:
                mem_sg = src_sg;
                inc_src = true;
                inc_dst = true;
        }

        desc = nbpf_desc_get(chan, len);
        if (!desc)
                return NULL;

        desc->async_tx.flags = flags;
        desc->async_tx.cookie = -EBUSY;
        desc->user_wait = false;

        /*
         * This is a private descriptor list, and we own the descriptor. No need
         * to lock.
         */
        list_for_each_entry(ldesc, &desc->sg, node) {
                int ret = nbpf_prep_one(ldesc, direction,
                                        sg_dma_address(src_sg),
                                        sg_dma_address(dst_sg),
                                        sg_dma_len(mem_sg),
                                        i == len - 1);
                if (ret < 0) {
                        nbpf_desc_put(desc);
                        return NULL;
                }
                data_len += sg_dma_len(mem_sg);
                if (inc_src)
                        src_sg = sg_next(src_sg);
                if (inc_dst)
                        dst_sg = sg_next(dst_sg);
                mem_sg = direction == DMA_DEV_TO_MEM ? dst_sg : src_sg;
                i++;
        }

        desc->length = data_len;

        /* The user has to return the descriptor to us ASAP via .tx_submit() */
        return &desc->async_tx;
}

static struct dma_async_tx_descriptor *nbpf_prep_memcpy(
        struct dma_chan *dchan, dma_addr_t dst, dma_addr_t src,
        size_t len, unsigned long flags)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);
        struct scatterlist dst_sg;
        struct scatterlist src_sg;

        sg_init_table(&dst_sg, 1);
        sg_init_table(&src_sg, 1);

        sg_dma_address(&dst_sg) = dst;
        sg_dma_address(&src_sg) = src;

        sg_dma_len(&dst_sg) = len;
        sg_dma_len(&src_sg) = len;

        dev_dbg(dchan->device->dev, "%s(): %zu @ %pad -> %pad\n",
                __func__, len, &src, &dst);

        return nbpf_prep_sg(chan, &src_sg, &dst_sg, 1,
                            DMA_MEM_TO_MEM, flags);
}

static struct dma_async_tx_descriptor *nbpf_prep_memcpy_sg(
        struct dma_chan *dchan,
        struct scatterlist *dst_sg, unsigned int dst_nents,
        struct scatterlist *src_sg, unsigned int src_nents,
        unsigned long flags)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);

        if (dst_nents != src_nents)
                return NULL;

        return nbpf_prep_sg(chan, src_sg, dst_sg, src_nents,
                            DMA_MEM_TO_MEM, flags);
}

static struct dma_async_tx_descriptor *nbpf_prep_slave_sg(
        struct dma_chan *dchan, struct scatterlist *sgl, unsigned int sg_len,
        enum dma_transfer_direction direction, unsigned long flags, void *context)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);
        struct scatterlist slave_sg;

        dev_dbg(dchan->device->dev, "Entry %s()\n", __func__);

        sg_init_table(&slave_sg, 1);

        switch (direction) {
        case DMA_MEM_TO_DEV:
                sg_dma_address(&slave_sg) = chan->slave_dst_addr;
                return nbpf_prep_sg(chan, sgl, &slave_sg, sg_len,
                                    direction, flags);

        case DMA_DEV_TO_MEM:
                sg_dma_address(&slave_sg) = chan->slave_src_addr;
                return nbpf_prep_sg(chan, &slave_sg, sgl, sg_len,
                                    direction, flags);

        default:
                return NULL;
        }
}

static int nbpf_alloc_chan_resources(struct dma_chan *dchan)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);
        int ret;

        INIT_LIST_HEAD(&chan->free);
        INIT_LIST_HEAD(&chan->free_links);
        INIT_LIST_HEAD(&chan->queued);
        INIT_LIST_HEAD(&chan->active);
        INIT_LIST_HEAD(&chan->done);

        ret = nbpf_desc_page_alloc(chan);
        if (ret < 0)
                return ret;

        dev_dbg(dchan->device->dev, "Entry %s(): terminal %u\n", __func__,
                chan->terminal);

        nbpf_chan_configure(chan);

        return ret;
}

static void nbpf_free_chan_resources(struct dma_chan *dchan)
{
        struct nbpf_channel *chan = nbpf_to_chan(dchan);
        struct nbpf_desc_page *dpage, *tmp;

        dev_dbg(dchan->device->dev, "Entry %s()\n", __func__);

        nbpf_chan_halt(chan);
        nbpf_chan_idle(chan);
        /* Clean up for if a channel is re-used for MEMCPY after slave DMA */
        nbpf_chan_prepare_default(chan);

        list_for_each_entry_safe(dpage, tmp, &chan->desc_page, node) {
                struct nbpf_link_desc *ldesc;
                int i;
                list_del(&dpage->node);
                for (i = 0, ldesc = dpage->ldesc;
                     i < ARRAY_SIZE(dpage->ldesc);
                     i++, ldesc++)
                        dma_unmap_single(dchan->device->dev, ldesc->hwdesc_dma_addr,
                                         sizeof(*ldesc->hwdesc), DMA_TO_DEVICE);
                free_page((unsigned long)dpage);
        }
}

static struct dma_chan *nbpf_of_xlate(struct of_phandle_args *dma_spec,
                                      struct of_dma *ofdma)
{
        struct nbpf_device *nbpf = ofdma->of_dma_data;
        struct dma_chan *dchan;
        struct nbpf_channel *chan;

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

        dchan = dma_get_any_slave_channel(&nbpf->dma_dev);
        if (!dchan)
                return NULL;

        dev_dbg(dchan->device->dev, "Entry %s(%s)\n", __func__,
                dma_spec->np->name);

        chan = nbpf_to_chan(dchan);

        chan->terminal = dma_spec->args[0];
        chan->flags = dma_spec->args[1];

        nbpf_chan_prepare(chan);
        nbpf_chan_configure(chan);

        return dchan;
}

static void nbpf_chan_tasklet(unsigned long data)
{
        struct nbpf_channel *chan = (struct nbpf_channel *)data;
        struct nbpf_desc *desc, *tmp;
        struct dmaengine_desc_callback cb;

        while (!list_empty(&chan->done)) {
                bool found = false, must_put, recycling = false;

                spin_lock_irq(&chan->lock);

                list_for_each_entry_safe(desc, tmp, &chan->done, node) {
                        if (!desc->user_wait) {
                                /* Newly completed descriptor, have to process */
                                found = true;
                                break;
                        } else if (async_tx_test_ack(&desc->async_tx)) {
                                /*
                                 * This descriptor was waiting for a user ACK,
                                 * it can be recycled now.
                                 */
                                list_del(&desc->node);
                                spin_unlock_irq(&chan->lock);
                                nbpf_desc_put(desc);
                                recycling = true;
                                break;
                        }
                }

                if (recycling)
                        continue;

                if (!found) {
                        /* This can happen if TERMINATE_ALL has been called */
                        spin_unlock_irq(&chan->lock);
                        break;
                }

                dma_cookie_complete(&desc->async_tx);

                /*
                 * With released lock we cannot dereference desc, maybe it's
                 * still on the "done" list
                 */
                if (async_tx_test_ack(&desc->async_tx)) {
                        list_del(&desc->node);
                        must_put = true;
                } else {
                        desc->user_wait = true;
                        must_put = false;
                }

                dmaengine_desc_get_callback(&desc->async_tx, &cb);

                /* ack and callback completed descriptor */
                spin_unlock_irq(&chan->lock);

                dmaengine_desc_callback_invoke(&cb, NULL);

                if (must_put)
                        nbpf_desc_put(desc);
        }
}

static irqreturn_t nbpf_chan_irq(int irq, void *dev)
{
        struct nbpf_channel *chan = dev;
        bool done = nbpf_status_get(chan);
        struct nbpf_desc *desc;
        irqreturn_t ret;
        bool bh = false;

        if (!done)
                return IRQ_NONE;

        nbpf_status_ack(chan);

        dev_dbg(&chan->dma_chan.dev->device, "%s()\n", __func__);

        spin_lock(&chan->lock);
        desc = chan->running;
        if (WARN_ON(!desc)) {
                ret = IRQ_NONE;
                goto unlock;
        } else {
                ret = IRQ_HANDLED;
                bh = true;
        }

        list_move_tail(&desc->node, &chan->done);
        chan->running = NULL;

        if (!list_empty(&chan->active)) {
                desc = list_first_entry(&chan->active,
                                        struct nbpf_desc, node);
                if (!nbpf_start(desc))
                        chan->running = desc;
        }

unlock:
        spin_unlock(&chan->lock);

        if (bh)
                tasklet_schedule(&chan->tasklet);

        return ret;
}

static irqreturn_t nbpf_err_irq(int irq, void *dev)
{
        struct nbpf_device *nbpf = dev;
        u32 error = nbpf_error_get(nbpf);

        dev_warn(nbpf->dma_dev.dev, "DMA error IRQ %u\n", irq);

        if (!error)
                return IRQ_NONE;

        do {
                struct nbpf_channel *chan = nbpf_error_get_channel(nbpf, error);
                /* On error: abort all queued transfers, no callback */
                nbpf_error_clear(chan);
                nbpf_chan_idle(chan);
                error = nbpf_error_get(nbpf);
        } while (error);

        return IRQ_HANDLED;
}

static int nbpf_chan_probe(struct nbpf_device *nbpf, int n)
{
        struct dma_device *dma_dev = &nbpf->dma_dev;
        struct nbpf_channel *chan = nbpf->chan + n;
        int ret;

        chan->nbpf = nbpf;
        chan->base = nbpf->base + NBPF_REG_CHAN_OFFSET + NBPF_REG_CHAN_SIZE * n;
        INIT_LIST_HEAD(&chan->desc_page);
        spin_lock_init(&chan->lock);
        chan->dma_chan.device = dma_dev;
        dma_cookie_init(&chan->dma_chan);
        nbpf_chan_prepare_default(chan);

        dev_dbg(dma_dev->dev, "%s(): channel %d: -> %p\n", __func__, n, chan->base);

        snprintf(chan->name, sizeof(chan->name), "nbpf %d", n);

        tasklet_init(&chan->tasklet, nbpf_chan_tasklet, (unsigned long)chan);
        ret = devm_request_irq(dma_dev->dev, chan->irq,
                        nbpf_chan_irq, IRQF_SHARED,
                        chan->name, chan);
        if (ret < 0)
                return ret;

        /* Add the channel to DMA device channel list */
        list_add_tail(&chan->dma_chan.device_node,
                      &dma_dev->channels);

        return 0;
}

static const struct of_device_id nbpf_match[] = {
        {.compatible = "renesas,nbpfaxi64dmac1b4",      .data = &nbpf_cfg[NBPF1B4]},
        {.compatible = "renesas,nbpfaxi64dmac1b8",      .data = &nbpf_cfg[NBPF1B8]},
        {.compatible = "renesas,nbpfaxi64dmac1b16",     .data = &nbpf_cfg[NBPF1B16]},
        {.compatible = "renesas,nbpfaxi64dmac4b4",      .data = &nbpf_cfg[NBPF4B4]},
        {.compatible = "renesas,nbpfaxi64dmac4b8",      .data = &nbpf_cfg[NBPF4B8]},
        {.compatible = "renesas,nbpfaxi64dmac4b16",     .data = &nbpf_cfg[NBPF4B16]},
        {.compatible = "renesas,nbpfaxi64dmac8b4",      .data = &nbpf_cfg[NBPF8B4]},
        {.compatible = "renesas,nbpfaxi64dmac8b8",      .data = &nbpf_cfg[NBPF8B8]},
        {.compatible = "renesas,nbpfaxi64dmac8b16",     .data = &nbpf_cfg[NBPF8B16]},
        {}
};
MODULE_DEVICE_TABLE(of, nbpf_match);

static int nbpf_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        const struct of_device_id *of_id = of_match_device(nbpf_match, dev);
        struct device_node *np = dev->of_node;
        struct nbpf_device *nbpf;
        struct dma_device *dma_dev;
        struct resource *iomem, *irq_res;
        const struct nbpf_config *cfg;
        int num_channels;
        int ret, irq, eirq, i;
        int irqbuf[9] /* maximum 8 channels + error IRQ */;
        unsigned int irqs = 0;

        BUILD_BUG_ON(sizeof(struct nbpf_desc_page) > PAGE_SIZE);

        /* DT only */
        if (!np || !of_id || !of_id->data)
                return -ENODEV;

        cfg = of_id->data;
        num_channels = cfg->num_channels;

        nbpf = devm_kzalloc(dev, sizeof(*nbpf) + num_channels *
                            sizeof(nbpf->chan[0]), GFP_KERNEL);
        if (!nbpf)
                return -ENOMEM;

        dma_dev = &nbpf->dma_dev;
        dma_dev->dev = dev;

        iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        nbpf->base = devm_ioremap_resource(dev, iomem);
        if (IS_ERR(nbpf->base))
                return PTR_ERR(nbpf->base);

        nbpf->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(nbpf->clk))
                return PTR_ERR(nbpf->clk);

        of_property_read_u32(np, "max-burst-mem-read",
                             &nbpf->max_burst_mem_read);
        of_property_read_u32(np, "max-burst-mem-write",
                             &nbpf->max_burst_mem_write);

        nbpf->config = cfg;

        for (i = 0; irqs < ARRAY_SIZE(irqbuf); i++) {
                irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, i);
                if (!irq_res)
                        break;

                for (irq = irq_res->start; irq <= irq_res->end;
                     irq++, irqs++)
                        irqbuf[irqs] = irq;
        }

        /*
         * 3 IRQ resource schemes are supported:
         * 1. 1 shared IRQ for error and all channels
         * 2. 2 IRQs: one for error and one shared for all channels
         * 3. 1 IRQ for error and an own IRQ for each channel
         */
        if (irqs != 1 && irqs != 2 && irqs != num_channels + 1)
                return -ENXIO;

        if (irqs == 1) {
                eirq = irqbuf[0];

                for (i = 0; i <= num_channels; i++)
                        nbpf->chan[i].irq = irqbuf[0];
        } else {
                eirq = platform_get_irq_byname(pdev, "error");
                if (eirq < 0)
                        return eirq;

                if (irqs == num_channels + 1) {
                        struct nbpf_channel *chan;

                        for (i = 0, chan = nbpf->chan; i <= num_channels;
                             i++, chan++) {
                                /* Skip the error IRQ */
                                if (irqbuf[i] == eirq)
                                        i++;
                                chan->irq = irqbuf[i];
                        }

                        if (chan != nbpf->chan + num_channels)
                                return -EINVAL;
                } else {
                        /* 2 IRQs and more than one channel */
                        if (irqbuf[0] == eirq)
                                irq = irqbuf[1];
                        else
                                irq = irqbuf[0];

                        for (i = 0; i <= num_channels; i++)
                                nbpf->chan[i].irq = irq;
                }
        }

        ret = devm_request_irq(dev, eirq, nbpf_err_irq,
                               IRQF_SHARED, "dma error", nbpf);
        if (ret < 0)
                return ret;
        nbpf->eirq = eirq;

        INIT_LIST_HEAD(&dma_dev->channels);

        /* Create DMA Channel */
        for (i = 0; i < num_channels; i++) {
                ret = nbpf_chan_probe(nbpf, i);
                if (ret < 0)
                        return ret;
        }

        dma_cap_set(DMA_MEMCPY, dma_dev->cap_mask);
        dma_cap_set(DMA_SLAVE, dma_dev->cap_mask);
        dma_cap_set(DMA_PRIVATE, dma_dev->cap_mask);
        dma_cap_set(DMA_SG, dma_dev->cap_mask);

        /* Common and MEMCPY operations */
        dma_dev->device_alloc_chan_resources
                = nbpf_alloc_chan_resources;
        dma_dev->device_free_chan_resources = nbpf_free_chan_resources;
        dma_dev->device_prep_dma_sg = nbpf_prep_memcpy_sg;
        dma_dev->device_prep_dma_memcpy = nbpf_prep_memcpy;
        dma_dev->device_tx_status = nbpf_tx_status;
        dma_dev->device_issue_pending = nbpf_issue_pending;

        /*
         * If we drop support for unaligned MEMCPY buffer addresses and / or
         * lengths by setting
         * dma_dev->copy_align = 4;
         * then we can set transfer length to 4 bytes in nbpf_prep_one() for
         * DMA_MEM_TO_MEM
         */

        /* Compulsory for DMA_SLAVE fields */
        dma_dev->device_prep_slave_sg = nbpf_prep_slave_sg;
        dma_dev->device_config = nbpf_config;
        dma_dev->device_pause = nbpf_pause;
        dma_dev->device_terminate_all = nbpf_terminate_all;

        dma_dev->src_addr_widths = NBPF_DMA_BUSWIDTHS;
        dma_dev->dst_addr_widths = NBPF_DMA_BUSWIDTHS;
        dma_dev->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);

        platform_set_drvdata(pdev, nbpf);

        ret = clk_prepare_enable(nbpf->clk);
        if (ret < 0)
                return ret;

        nbpf_configure(nbpf);

        ret = dma_async_device_register(dma_dev);
        if (ret < 0)
                goto e_clk_off;

        ret = of_dma_controller_register(np, nbpf_of_xlate, nbpf);
        if (ret < 0)
                goto e_dma_dev_unreg;

        return 0;

e_dma_dev_unreg:
        dma_async_device_unregister(dma_dev);
e_clk_off:
        clk_disable_unprepare(nbpf->clk);

        return ret;
}

static int nbpf_remove(struct platform_device *pdev)
{
        struct nbpf_device *nbpf = platform_get_drvdata(pdev);
        int i;

        devm_free_irq(&pdev->dev, nbpf->eirq, nbpf);

        for (i = 0; i < nbpf->config->num_channels; i++) {
                struct nbpf_channel *chan = nbpf->chan + i;

                devm_free_irq(&pdev->dev, chan->irq, chan);

                tasklet_kill(&chan->tasklet);
        }

        of_dma_controller_free(pdev->dev.of_node);
        dma_async_device_unregister(&nbpf->dma_dev);
        clk_disable_unprepare(nbpf->clk);

        return 0;
}

static const struct platform_device_id nbpf_ids[] = {
        {"nbpfaxi64dmac1b4",    (kernel_ulong_t)&nbpf_cfg[NBPF1B4]},
        {"nbpfaxi64dmac1b8",    (kernel_ulong_t)&nbpf_cfg[NBPF1B8]},
        {"nbpfaxi64dmac1b16",   (kernel_ulong_t)&nbpf_cfg[NBPF1B16]},
        {"nbpfaxi64dmac4b4",    (kernel_ulong_t)&nbpf_cfg[NBPF4B4]},
        {"nbpfaxi64dmac4b8",    (kernel_ulong_t)&nbpf_cfg[NBPF4B8]},
        {"nbpfaxi64dmac4b16",   (kernel_ulong_t)&nbpf_cfg[NBPF4B16]},
        {"nbpfaxi64dmac8b4",    (kernel_ulong_t)&nbpf_cfg[NBPF8B4]},
        {"nbpfaxi64dmac8b8",    (kernel_ulong_t)&nbpf_cfg[NBPF8B8]},
        {"nbpfaxi64dmac8b16",   (kernel_ulong_t)&nbpf_cfg[NBPF8B16]},
        {},
};
MODULE_DEVICE_TABLE(platform, nbpf_ids);

#ifdef CONFIG_PM
static int nbpf_runtime_suspend(struct device *dev)
{
        struct nbpf_device *nbpf = platform_get_drvdata(to_platform_device(dev));
        clk_disable_unprepare(nbpf->clk);
        return 0;
}

static int nbpf_runtime_resume(struct device *dev)
{
        struct nbpf_device *nbpf = platform_get_drvdata(to_platform_device(dev));
        return clk_prepare_enable(nbpf->clk);
}
#endif

static const struct dev_pm_ops nbpf_pm_ops = {
        SET_RUNTIME_PM_OPS(nbpf_runtime_suspend, nbpf_runtime_resume, NULL)
};

static struct platform_driver nbpf_driver = {
        .driver = {
                .name = "dma-nbpf",
                .of_match_table = nbpf_match,
                .pm = &nbpf_pm_ops,
        },
        .id_table = nbpf_ids,
        .probe = nbpf_probe,
        .remove = nbpf_remove,
};

module_platform_driver(nbpf_driver);

MODULE_AUTHOR("Guennadi Liakhovetski <g.liakhovetski@gmx.de>");
MODULE_DESCRIPTION("dmaengine driver for NBPFAXI64* DMACs");
MODULE_LICENSE("GPL v2");