/*
 * Renesas USB DMA Controller Driver
 *
 * Copyright (C) 2015 Renesas Electronics Corporation
 *
 * based on rcar-dmac.c
 * Copyright (C) 2014 Renesas Electronics Inc.
 * Author: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *
 * This 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/delay.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_dma.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

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

/*
 * struct usb_dmac_sg - Descriptor for a hardware transfer
 * @mem_addr: memory address
 * @size: transfer size in bytes
 */
struct usb_dmac_sg {
        dma_addr_t mem_addr;
        u32 size;
};

/*
 * struct usb_dmac_desc - USB DMA Transfer Descriptor
 * @vd: base virtual channel DMA transaction descriptor
 * @direction: direction of the DMA transfer
 * @sg_allocated_len: length of allocated sg
 * @sg_len: length of sg
 * @sg_index: index of sg
 * @residue: residue after the DMAC completed a transfer
 * @node: node for desc_got and desc_freed
 * @done_cookie: cookie after the DMAC completed a transfer
 * @sg: information for the transfer
 */
struct usb_dmac_desc {
        struct virt_dma_desc vd;
        enum dma_transfer_direction direction;
        unsigned int sg_allocated_len;
        unsigned int sg_len;
        unsigned int sg_index;
        u32 residue;
        struct list_head node;
        dma_cookie_t done_cookie;
        struct usb_dmac_sg sg[0];
};

#define to_usb_dmac_desc(vd)    container_of(vd, struct usb_dmac_desc, vd)

/*
 * struct usb_dmac_chan - USB DMA Controller Channel
 * @vc: base virtual DMA channel object
 * @iomem: channel I/O memory base
 * @index: index of this channel in the controller
 * @irq: irq number of this channel
 * @desc: the current descriptor
 * @descs_allocated: number of descriptors allocated
 * @desc_got: got descriptors
 * @desc_freed: freed descriptors after the DMAC completed a transfer
 */
struct usb_dmac_chan {
        struct virt_dma_chan vc;
        void __iomem *iomem;
        unsigned int index;
        int irq;
        struct usb_dmac_desc *desc;
        int descs_allocated;
        struct list_head desc_got;
        struct list_head desc_freed;
};

#define to_usb_dmac_chan(c) container_of(c, struct usb_dmac_chan, vc.chan)

/*
 * struct usb_dmac - USB DMA Controller
 * @engine: base DMA engine object
 * @dev: the hardware device
 * @iomem: remapped I/O memory base
 * @n_channels: number of available channels
 * @channels: array of DMAC channels
 */
struct usb_dmac {
        struct dma_device engine;
        struct device *dev;
        void __iomem *iomem;

        unsigned int n_channels;
        struct usb_dmac_chan *channels;
};

#define to_usb_dmac(d)          container_of(d, struct usb_dmac, engine)

/* -----------------------------------------------------------------------------
 * Registers
 */

#define USB_DMAC_CHAN_OFFSET(i)         (0x20 + 0x20 * (i))

#define USB_DMASWR                      0x0008
#define USB_DMASWR_SWR                  (1 << 0)
#define USB_DMAOR                       0x0060
#define USB_DMAOR_AE                    (1 << 1)
#define USB_DMAOR_DME                   (1 << 0)

#define USB_DMASAR                      0x0000
#define USB_DMADAR                      0x0004
#define USB_DMATCR                      0x0008
#define USB_DMATCR_MASK                 0x00ffffff
#define USB_DMACHCR                     0x0014
#define USB_DMACHCR_FTE                 (1 << 24)
#define USB_DMACHCR_NULLE               (1 << 16)
#define USB_DMACHCR_NULL                (1 << 12)
#define USB_DMACHCR_TS_8B               ((0 << 7) | (0 << 6))
#define USB_DMACHCR_TS_16B              ((0 << 7) | (1 << 6))
#define USB_DMACHCR_TS_32B              ((1 << 7) | (0 << 6))
#define USB_DMACHCR_IE                  (1 << 5)
#define USB_DMACHCR_SP                  (1 << 2)
#define USB_DMACHCR_TE                  (1 << 1)
#define USB_DMACHCR_DE                  (1 << 0)
#define USB_DMATEND                     0x0018

/* Hardcode the xfer_shift to 5 (32bytes) */
#define USB_DMAC_XFER_SHIFT     5
#define USB_DMAC_XFER_SIZE      (1 << USB_DMAC_XFER_SHIFT)
#define USB_DMAC_CHCR_TS        USB_DMACHCR_TS_32B
#define USB_DMAC_SLAVE_BUSWIDTH DMA_SLAVE_BUSWIDTH_32_BYTES

/* for descriptors */
#define USB_DMAC_INITIAL_NR_DESC        16
#define USB_DMAC_INITIAL_NR_SG          8

/* -----------------------------------------------------------------------------
 * Device access
 */

static void usb_dmac_write(struct usb_dmac *dmac, u32 reg, u32 data)
{
        writel(data, dmac->iomem + reg);
}

static u32 usb_dmac_read(struct usb_dmac *dmac, u32 reg)
{
        return readl(dmac->iomem + reg);
}

static u32 usb_dmac_chan_read(struct usb_dmac_chan *chan, u32 reg)
{
        return readl(chan->iomem + reg);
}

static void usb_dmac_chan_write(struct usb_dmac_chan *chan, u32 reg, u32 data)
{
        writel(data, chan->iomem + reg);
}

/* -----------------------------------------------------------------------------
 * Initialization and configuration
 */

static bool usb_dmac_chan_is_busy(struct usb_dmac_chan *chan)
{
        u32 chcr = usb_dmac_chan_read(chan, USB_DMACHCR);

        return (chcr & (USB_DMACHCR_DE | USB_DMACHCR_TE)) == USB_DMACHCR_DE;
}

static u32 usb_dmac_calc_tend(u32 size)
{
        /*
         * Please refer to the Figure "Example of Final Transaction Valid
         * Data Transfer Enable (EDTEN) Setting" in the data sheet.
         */
        return 0xffffffff << (32 - (size % USB_DMAC_XFER_SIZE ? :
                                                USB_DMAC_XFER_SIZE));
}

/* This function is already held by vc.lock */
static void usb_dmac_chan_start_sg(struct usb_dmac_chan *chan,
                                   unsigned int index)
{
        struct usb_dmac_desc *desc = chan->desc;
        struct usb_dmac_sg *sg = desc->sg + index;
        dma_addr_t src_addr = 0, dst_addr = 0;

        WARN_ON_ONCE(usb_dmac_chan_is_busy(chan));

        if (desc->direction == DMA_DEV_TO_MEM)
                dst_addr = sg->mem_addr;
        else
                src_addr = sg->mem_addr;

        dev_dbg(chan->vc.chan.device->dev,
                "chan%u: queue sg %p: %u@%pad -> %pad\n",
                chan->index, sg, sg->size, &src_addr, &dst_addr);

        usb_dmac_chan_write(chan, USB_DMASAR, src_addr & 0xffffffff);
        usb_dmac_chan_write(chan, USB_DMADAR, dst_addr & 0xffffffff);
        usb_dmac_chan_write(chan, USB_DMATCR,
                            DIV_ROUND_UP(sg->size, USB_DMAC_XFER_SIZE));
        usb_dmac_chan_write(chan, USB_DMATEND, usb_dmac_calc_tend(sg->size));

        usb_dmac_chan_write(chan, USB_DMACHCR, USB_DMAC_CHCR_TS |
                        USB_DMACHCR_NULLE | USB_DMACHCR_IE | USB_DMACHCR_DE);
}

/* This function is already held by vc.lock */
static void usb_dmac_chan_start_desc(struct usb_dmac_chan *chan)
{
        struct virt_dma_desc *vd;

        vd = vchan_next_desc(&chan->vc);
        if (!vd) {
                chan->desc = NULL;
                return;
        }

        /*
         * Remove this request from vc->desc_issued. Otherwise, this driver
         * will get the previous value from vchan_next_desc() after a transfer
         * was completed.
         */
        list_del(&vd->node);

        chan->desc = to_usb_dmac_desc(vd);
        chan->desc->sg_index = 0;
        usb_dmac_chan_start_sg(chan, 0);
}

static int usb_dmac_init(struct usb_dmac *dmac)
{
        u16 dmaor;

        /* Clear all channels and enable the DMAC globally. */
        usb_dmac_write(dmac, USB_DMAOR, USB_DMAOR_DME);

        dmaor = usb_dmac_read(dmac, USB_DMAOR);
        if ((dmaor & (USB_DMAOR_AE | USB_DMAOR_DME)) != USB_DMAOR_DME) {
                dev_warn(dmac->dev, "DMAOR initialization failed.\n");
                return -EIO;
        }

        return 0;
}

/* -----------------------------------------------------------------------------
 * Descriptors allocation and free
 */
static int usb_dmac_desc_alloc(struct usb_dmac_chan *chan, unsigned int sg_len,
                               gfp_t gfp)
{
        struct usb_dmac_desc *desc;
        unsigned long flags;

        desc = kzalloc(struct_size(desc, sg, sg_len), gfp);
        if (!desc)
                return -ENOMEM;

        desc->sg_allocated_len = sg_len;
        INIT_LIST_HEAD(&desc->node);

        spin_lock_irqsave(&chan->vc.lock, flags);
        list_add_tail(&desc->node, &chan->desc_freed);
        spin_unlock_irqrestore(&chan->vc.lock, flags);

        return 0;
}

static void usb_dmac_desc_free(struct usb_dmac_chan *chan)
{
        struct usb_dmac_desc *desc, *_desc;
        LIST_HEAD(list);

        list_splice_init(&chan->desc_freed, &list);
        list_splice_init(&chan->desc_got, &list);

        list_for_each_entry_safe(desc, _desc, &list, node) {
                list_del(&desc->node);
                kfree(desc);
        }
        chan->descs_allocated = 0;
}

static struct usb_dmac_desc *usb_dmac_desc_get(struct usb_dmac_chan *chan,
                                               unsigned int sg_len, gfp_t gfp)
{
        struct usb_dmac_desc *desc = NULL;
        unsigned long flags;

        /* Get a freed descritpor */
        spin_lock_irqsave(&chan->vc.lock, flags);
        list_for_each_entry(desc, &chan->desc_freed, node) {
                if (sg_len <= desc->sg_allocated_len) {
                        list_move_tail(&desc->node, &chan->desc_got);
                        spin_unlock_irqrestore(&chan->vc.lock, flags);
                        return desc;
                }
        }
        spin_unlock_irqrestore(&chan->vc.lock, flags);

        /* Allocate a new descriptor */
        if (!usb_dmac_desc_alloc(chan, sg_len, gfp)) {
                /* If allocated the desc, it was added to tail of the list */
                spin_lock_irqsave(&chan->vc.lock, flags);
                desc = list_last_entry(&chan->desc_freed, struct usb_dmac_desc,
                                       node);
                list_move_tail(&desc->node, &chan->desc_got);
                spin_unlock_irqrestore(&chan->vc.lock, flags);
                return desc;
        }

        return NULL;
}

static void usb_dmac_desc_put(struct usb_dmac_chan *chan,
                              struct usb_dmac_desc *desc)
{
        unsigned long flags;

        spin_lock_irqsave(&chan->vc.lock, flags);
        list_move_tail(&desc->node, &chan->desc_freed);
        spin_unlock_irqrestore(&chan->vc.lock, flags);
}

/* -----------------------------------------------------------------------------
 * Stop and reset
 */

static void usb_dmac_soft_reset(struct usb_dmac_chan *uchan)
{
        struct dma_chan *chan = &uchan->vc.chan;
        struct usb_dmac *dmac = to_usb_dmac(chan->device);
        int i;

        /* Don't issue soft reset if any one of channels is busy */
        for (i = 0; i < dmac->n_channels; ++i) {
                if (usb_dmac_chan_is_busy(uchan))
                        return;
        }

        usb_dmac_write(dmac, USB_DMAOR, 0);
        usb_dmac_write(dmac, USB_DMASWR, USB_DMASWR_SWR);
        udelay(100);
        usb_dmac_write(dmac, USB_DMASWR, 0);
        usb_dmac_write(dmac, USB_DMAOR, 1);
}

static void usb_dmac_chan_halt(struct usb_dmac_chan *chan)
{
        u32 chcr = usb_dmac_chan_read(chan, USB_DMACHCR);

        chcr &= ~(USB_DMACHCR_IE | USB_DMACHCR_TE | USB_DMACHCR_DE);
        usb_dmac_chan_write(chan, USB_DMACHCR, chcr);

        usb_dmac_soft_reset(chan);
}

static void usb_dmac_stop(struct usb_dmac *dmac)
{
        usb_dmac_write(dmac, USB_DMAOR, 0);
}

/* -----------------------------------------------------------------------------
 * DMA engine operations
 */

static int usb_dmac_alloc_chan_resources(struct dma_chan *chan)
{
        struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
        int ret;

        while (uchan->descs_allocated < USB_DMAC_INITIAL_NR_DESC) {
                ret = usb_dmac_desc_alloc(uchan, USB_DMAC_INITIAL_NR_SG,
                                          GFP_KERNEL);
                if (ret < 0) {
                        usb_dmac_desc_free(uchan);
                        return ret;
                }
                uchan->descs_allocated++;
        }

        return pm_runtime_get_sync(chan->device->dev);
}

static void usb_dmac_free_chan_resources(struct dma_chan *chan)
{
        struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
        unsigned long flags;

        /* Protect against ISR */
        spin_lock_irqsave(&uchan->vc.lock, flags);
        usb_dmac_chan_halt(uchan);
        spin_unlock_irqrestore(&uchan->vc.lock, flags);

        usb_dmac_desc_free(uchan);
        vchan_free_chan_resources(&uchan->vc);

        pm_runtime_put(chan->device->dev);
}

static struct dma_async_tx_descriptor *
usb_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
                       unsigned int sg_len, enum dma_transfer_direction dir,
                       unsigned long dma_flags, void *context)
{
        struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
        struct usb_dmac_desc *desc;
        struct scatterlist *sg;
        int i;

        if (!sg_len) {
                dev_warn(chan->device->dev,
                         "%s: bad parameter: len=%d\n", __func__, sg_len);
                return NULL;
        }

        desc = usb_dmac_desc_get(uchan, sg_len, GFP_NOWAIT);
        if (!desc)
                return NULL;

        desc->direction = dir;
        desc->sg_len = sg_len;
        for_each_sg(sgl, sg, sg_len, i) {
                desc->sg[i].mem_addr = sg_dma_address(sg);
                desc->sg[i].size = sg_dma_len(sg);
        }

        return vchan_tx_prep(&uchan->vc, &desc->vd, dma_flags);
}

static int usb_dmac_chan_terminate_all(struct dma_chan *chan)
{
        struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
        struct usb_dmac_desc *desc, *_desc;
        unsigned long flags;
        LIST_HEAD(head);
        LIST_HEAD(list);

        spin_lock_irqsave(&uchan->vc.lock, flags);
        usb_dmac_chan_halt(uchan);
        vchan_get_all_descriptors(&uchan->vc, &head);
        if (uchan->desc)
                uchan->desc = NULL;
        list_splice_init(&uchan->desc_got, &list);
        list_for_each_entry_safe(desc, _desc, &list, node)
                list_move_tail(&desc->node, &uchan->desc_freed);
        spin_unlock_irqrestore(&uchan->vc.lock, flags);
        vchan_dma_desc_free_list(&uchan->vc, &head);

        return 0;
}

static unsigned int usb_dmac_get_current_residue(struct usb_dmac_chan *chan,
                                                 struct usb_dmac_desc *desc,
                                                 int sg_index)
{
        struct usb_dmac_sg *sg = desc->sg + sg_index;
        u32 mem_addr = sg->mem_addr & 0xffffffff;
        unsigned int residue = sg->size;

        /*
         * We cannot use USB_DMATCR to calculate residue because USB_DMATCR
         * has unsuited value to calculate.
         */
        if (desc->direction == DMA_DEV_TO_MEM)
                residue -= usb_dmac_chan_read(chan, USB_DMADAR) - mem_addr;
        else
                residue -= usb_dmac_chan_read(chan, USB_DMASAR) - mem_addr;

        return residue;
}

static u32 usb_dmac_chan_get_residue_if_complete(struct usb_dmac_chan *chan,
                                                 dma_cookie_t cookie)
{
        struct usb_dmac_desc *desc;
        u32 residue = 0;

        list_for_each_entry_reverse(desc, &chan->desc_freed, node) {
                if (desc->done_cookie == cookie) {
                        residue = desc->residue;
                        break;
                }
        }

        return residue;
}

static u32 usb_dmac_chan_get_residue(struct usb_dmac_chan *chan,
                                     dma_cookie_t cookie)
{
        u32 residue = 0;
        struct virt_dma_desc *vd;
        struct usb_dmac_desc *desc = chan->desc;
        int i;

        if (!desc) {
                vd = vchan_find_desc(&chan->vc, cookie);
                if (!vd)
                        return 0;
                desc = to_usb_dmac_desc(vd);
        }

        /* Compute the size of all usb_dmac_sg still to be transferred */
        for (i = desc->sg_index + 1; i < desc->sg_len; i++)
                residue += desc->sg[i].size;

        /* Add the residue for the current sg */
        residue += usb_dmac_get_current_residue(chan, desc, desc->sg_index);

        return residue;
}

static enum dma_status usb_dmac_tx_status(struct dma_chan *chan,
                                          dma_cookie_t cookie,
                                          struct dma_tx_state *txstate)
{
        struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
        enum dma_status status;
        unsigned int residue = 0;
        unsigned long flags;

        status = dma_cookie_status(chan, cookie, txstate);
        /* a client driver will get residue after DMA_COMPLETE */
        if (!txstate)
                return status;

        spin_lock_irqsave(&uchan->vc.lock, flags);
        if (status == DMA_COMPLETE)
                residue = usb_dmac_chan_get_residue_if_complete(uchan, cookie);
        else
                residue = usb_dmac_chan_get_residue(uchan, cookie);
        spin_unlock_irqrestore(&uchan->vc.lock, flags);

        dma_set_residue(txstate, residue);

        return status;
}

static void usb_dmac_issue_pending(struct dma_chan *chan)
{
        struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&uchan->vc.lock, flags);
        if (vchan_issue_pending(&uchan->vc) && !uchan->desc)
                usb_dmac_chan_start_desc(uchan);
        spin_unlock_irqrestore(&uchan->vc.lock, flags);
}

static void usb_dmac_virt_desc_free(struct virt_dma_desc *vd)
{
        struct usb_dmac_desc *desc = to_usb_dmac_desc(vd);
        struct usb_dmac_chan *chan = to_usb_dmac_chan(vd->tx.chan);

        usb_dmac_desc_put(chan, desc);
}

/* -----------------------------------------------------------------------------
 * IRQ handling
 */

static void usb_dmac_isr_transfer_end(struct usb_dmac_chan *chan)
{
        struct usb_dmac_desc *desc = chan->desc;

        BUG_ON(!desc);

        if (++desc->sg_index < desc->sg_len) {
                usb_dmac_chan_start_sg(chan, desc->sg_index);
        } else {
                desc->residue = usb_dmac_get_current_residue(chan, desc,
                                                        desc->sg_index - 1);
                desc->done_cookie = desc->vd.tx.cookie;
                vchan_cookie_complete(&desc->vd);

                /* Restart the next transfer if this driver has a next desc */
                usb_dmac_chan_start_desc(chan);
        }
}

static irqreturn_t usb_dmac_isr_channel(int irq, void *dev)
{
        struct usb_dmac_chan *chan = dev;
        irqreturn_t ret = IRQ_NONE;
        u32 mask = 0;
        u32 chcr;
        bool xfer_end = false;

        spin_lock(&chan->vc.lock);

        chcr = usb_dmac_chan_read(chan, USB_DMACHCR);
        if (chcr & (USB_DMACHCR_TE | USB_DMACHCR_SP)) {
                mask |= USB_DMACHCR_DE | USB_DMACHCR_TE | USB_DMACHCR_SP;
                if (chcr & USB_DMACHCR_DE)
                        xfer_end = true;
                ret |= IRQ_HANDLED;
        }
        if (chcr & USB_DMACHCR_NULL) {
                /* An interruption of TE will happen after we set FTE */
                mask |= USB_DMACHCR_NULL;
                chcr |= USB_DMACHCR_FTE;
                ret |= IRQ_HANDLED;
        }
        if (mask)
                usb_dmac_chan_write(chan, USB_DMACHCR, chcr & ~mask);

        if (xfer_end)
                usb_dmac_isr_transfer_end(chan);

        spin_unlock(&chan->vc.lock);

        return ret;
}

/* -----------------------------------------------------------------------------
 * OF xlate and channel filter
 */

static bool usb_dmac_chan_filter(struct dma_chan *chan, void *arg)
{
        struct usb_dmac_chan *uchan = to_usb_dmac_chan(chan);
        struct of_phandle_args *dma_spec = arg;

        if (dma_spec->np != chan->device->dev->of_node)
                return false;

        /* USB-DMAC should be used with fixed usb controller's FIFO */
        if (uchan->index != dma_spec->args[0])
                return false;

        return true;
}

static struct dma_chan *usb_dmac_of_xlate(struct of_phandle_args *dma_spec,
                                          struct of_dma *ofdma)
{
        struct dma_chan *chan;
        dma_cap_mask_t mask;

        if (dma_spec->args_count != 1)
                return NULL;

        /* Only slave DMA channels can be allocated via DT */
        dma_cap_zero(mask);
        dma_cap_set(DMA_SLAVE, mask);

        chan = dma_request_channel(mask, usb_dmac_chan_filter, dma_spec);
        if (!chan)
                return NULL;

        return chan;
}

/* -----------------------------------------------------------------------------
 * Power management
 */

#ifdef CONFIG_PM
static int usb_dmac_runtime_suspend(struct device *dev)
{
        struct usb_dmac *dmac = dev_get_drvdata(dev);
        int i;

        for (i = 0; i < dmac->n_channels; ++i) {
                if (!dmac->channels[i].iomem)
                        break;
                usb_dmac_chan_halt(&dmac->channels[i]);
        }

        return 0;
}

static int usb_dmac_runtime_resume(struct device *dev)
{
        struct usb_dmac *dmac = dev_get_drvdata(dev);

        return usb_dmac_init(dmac);
}
#endif /* CONFIG_PM */

static const struct dev_pm_ops usb_dmac_pm = {
        SET_RUNTIME_PM_OPS(usb_dmac_runtime_suspend, usb_dmac_runtime_resume,
                           NULL)
};

/* -----------------------------------------------------------------------------
 * Probe and remove
 */

static int usb_dmac_chan_probe(struct usb_dmac *dmac,
                               struct usb_dmac_chan *uchan,
                               unsigned int index)
{
        struct platform_device *pdev = to_platform_device(dmac->dev);
        char pdev_irqname[5];
        char *irqname;
        int ret;

        uchan->index = index;
        uchan->iomem = dmac->iomem + USB_DMAC_CHAN_OFFSET(index);

        /* Request the channel interrupt. */
        sprintf(pdev_irqname, "ch%u", index);
        uchan->irq = platform_get_irq_byname(pdev, pdev_irqname);
        if (uchan->irq < 0) {
                dev_err(dmac->dev, "no IRQ specified for channel %u\n", index);
                return -ENODEV;
        }

        irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
                                 dev_name(dmac->dev), index);
        if (!irqname)
                return -ENOMEM;

        ret = devm_request_irq(dmac->dev, uchan->irq, usb_dmac_isr_channel,
                               IRQF_SHARED, irqname, uchan);
        if (ret) {
                dev_err(dmac->dev, "failed to request IRQ %u (%d)\n",
                        uchan->irq, ret);
                return ret;
        }

        uchan->vc.desc_free = usb_dmac_virt_desc_free;
        vchan_init(&uchan->vc, &dmac->engine);
        INIT_LIST_HEAD(&uchan->desc_freed);
        INIT_LIST_HEAD(&uchan->desc_got);

        return 0;
}

static int usb_dmac_parse_of(struct device *dev, struct usb_dmac *dmac)
{
        struct device_node *np = dev->of_node;
        int ret;

        ret = of_property_read_u32(np, "dma-channels", &dmac->n_channels);
        if (ret < 0) {
                dev_err(dev, "unable to read dma-channels property\n");
                return ret;
        }

        if (dmac->n_channels <= 0 || dmac->n_channels >= 100) {
                dev_err(dev, "invalid number of channels %u\n",
                        dmac->n_channels);
                return -EINVAL;
        }

        return 0;
}

static int usb_dmac_probe(struct platform_device *pdev)
{
        const enum dma_slave_buswidth widths = USB_DMAC_SLAVE_BUSWIDTH;
        struct dma_device *engine;
        struct usb_dmac *dmac;
        struct resource *mem;
        unsigned int i;
        int ret;

        dmac = devm_kzalloc(&pdev->dev, sizeof(*dmac), GFP_KERNEL);
        if (!dmac)
                return -ENOMEM;

        dmac->dev = &pdev->dev;
        platform_set_drvdata(pdev, dmac);

        ret = usb_dmac_parse_of(&pdev->dev, dmac);
        if (ret < 0)
                return ret;

        dmac->channels = devm_kcalloc(&pdev->dev, dmac->n_channels,
                                      sizeof(*dmac->channels), GFP_KERNEL);
        if (!dmac->channels)
                return -ENOMEM;

        /* Request resources. */
        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        dmac->iomem = devm_ioremap_resource(&pdev->dev, mem);
        if (IS_ERR(dmac->iomem))
                return PTR_ERR(dmac->iomem);

        /* Enable runtime PM and initialize the device. */
        pm_runtime_enable(&pdev->dev);
        ret = pm_runtime_get_sync(&pdev->dev);
        if (ret < 0) {
                dev_err(&pdev->dev, "runtime PM get sync failed (%d)\n", ret);
                goto error_pm;
        }

        ret = usb_dmac_init(dmac);

        if (ret) {
                dev_err(&pdev->dev, "failed to reset device\n");
                goto error;
        }

        /* Initialize the channels. */
        INIT_LIST_HEAD(&dmac->engine.channels);

        for (i = 0; i < dmac->n_channels; ++i) {
                ret = usb_dmac_chan_probe(dmac, &dmac->channels[i], i);
                if (ret < 0)
                        goto error;
        }

        /* Register the DMAC as a DMA provider for DT. */
        ret = of_dma_controller_register(pdev->dev.of_node, usb_dmac_of_xlate,
                                         NULL);
        if (ret < 0)
                goto error;

        /*
         * Register the DMA engine device.
         *
         * Default transfer size of 32 bytes requires 32-byte alignment.
         */
        engine = &dmac->engine;
        dma_cap_set(DMA_SLAVE, engine->cap_mask);

        engine->dev = &pdev->dev;

        engine->src_addr_widths = widths;
        engine->dst_addr_widths = widths;
        engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
        engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;

        engine->device_alloc_chan_resources = usb_dmac_alloc_chan_resources;
        engine->device_free_chan_resources = usb_dmac_free_chan_resources;
        engine->device_prep_slave_sg = usb_dmac_prep_slave_sg;
        engine->device_terminate_all = usb_dmac_chan_terminate_all;
        engine->device_tx_status = usb_dmac_tx_status;
        engine->device_issue_pending = usb_dmac_issue_pending;

        ret = dma_async_device_register(engine);
        if (ret < 0)
                goto error;

        pm_runtime_put(&pdev->dev);
        return 0;

error:
        of_dma_controller_free(pdev->dev.of_node);
        pm_runtime_put(&pdev->dev);
error_pm:
        pm_runtime_disable(&pdev->dev);
        return ret;
}

static void usb_dmac_chan_remove(struct usb_dmac *dmac,
                                 struct usb_dmac_chan *uchan)
{
        usb_dmac_chan_halt(uchan);
        devm_free_irq(dmac->dev, uchan->irq, uchan);
}

static int usb_dmac_remove(struct platform_device *pdev)
{
        struct usb_dmac *dmac = platform_get_drvdata(pdev);
        int i;

        for (i = 0; i < dmac->n_channels; ++i)
                usb_dmac_chan_remove(dmac, &dmac->channels[i]);
        of_dma_controller_free(pdev->dev.of_node);
        dma_async_device_unregister(&dmac->engine);

        pm_runtime_disable(&pdev->dev);

        return 0;
}

static void usb_dmac_shutdown(struct platform_device *pdev)
{
        struct usb_dmac *dmac = platform_get_drvdata(pdev);

        usb_dmac_stop(dmac);
}

static const struct of_device_id usb_dmac_of_ids[] = {
        { .compatible = "renesas,usb-dmac", },
        { /* Sentinel */ }
};
MODULE_DEVICE_TABLE(of, usb_dmac_of_ids);

static struct platform_driver usb_dmac_driver = {
        .driver         = {
                .pm     = &usb_dmac_pm,
                .name   = "usb-dmac",
                .of_match_table = usb_dmac_of_ids,
        },
        .probe          = usb_dmac_probe,
        .remove         = usb_dmac_remove,
        .shutdown       = usb_dmac_shutdown,
};

module_platform_driver(usb_dmac_driver);

MODULE_DESCRIPTION("Renesas USB DMA Controller Driver");
MODULE_AUTHOR("Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>");
MODULE_LICENSE("GPL v2");