/*
 * Ingenic JZ4780 DMA controller
 *
 * Copyright (c) 2015 Imagination Technologies
 * Author: Alex Smith <alex@alex-smith.me.uk>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 */

#include <linux/clk.h>
#include <linux/dmapool.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

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

#define JZ_DMA_NR_CHANNELS      32

/* Global registers. */
#define JZ_DMA_REG_DMAC         0x1000
#define JZ_DMA_REG_DIRQP        0x1004
#define JZ_DMA_REG_DDR          0x1008
#define JZ_DMA_REG_DDRS         0x100c
#define JZ_DMA_REG_DMACP        0x101c
#define JZ_DMA_REG_DSIRQP       0x1020
#define JZ_DMA_REG_DSIRQM       0x1024
#define JZ_DMA_REG_DCIRQP       0x1028
#define JZ_DMA_REG_DCIRQM       0x102c

/* Per-channel registers. */
#define JZ_DMA_REG_CHAN(n)      (n * 0x20)
#define JZ_DMA_REG_DSA(n)       (0x00 + JZ_DMA_REG_CHAN(n))
#define JZ_DMA_REG_DTA(n)       (0x04 + JZ_DMA_REG_CHAN(n))
#define JZ_DMA_REG_DTC(n)       (0x08 + JZ_DMA_REG_CHAN(n))
#define JZ_DMA_REG_DRT(n)       (0x0c + JZ_DMA_REG_CHAN(n))
#define JZ_DMA_REG_DCS(n)       (0x10 + JZ_DMA_REG_CHAN(n))
#define JZ_DMA_REG_DCM(n)       (0x14 + JZ_DMA_REG_CHAN(n))
#define JZ_DMA_REG_DDA(n)       (0x18 + JZ_DMA_REG_CHAN(n))
#define JZ_DMA_REG_DSD(n)       (0x1c + JZ_DMA_REG_CHAN(n))

#define JZ_DMA_DMAC_DMAE        BIT(0)
#define JZ_DMA_DMAC_AR          BIT(2)
#define JZ_DMA_DMAC_HLT         BIT(3)
#define JZ_DMA_DMAC_FMSC        BIT(31)

#define JZ_DMA_DRT_AUTO         0x8

#define JZ_DMA_DCS_CTE          BIT(0)
#define JZ_DMA_DCS_HLT          BIT(2)
#define JZ_DMA_DCS_TT           BIT(3)
#define JZ_DMA_DCS_AR           BIT(4)
#define JZ_DMA_DCS_DES8         BIT(30)

#define JZ_DMA_DCM_LINK         BIT(0)
#define JZ_DMA_DCM_TIE          BIT(1)
#define JZ_DMA_DCM_STDE         BIT(2)
#define JZ_DMA_DCM_TSZ_SHIFT    8
#define JZ_DMA_DCM_TSZ_MASK     (0x7 << JZ_DMA_DCM_TSZ_SHIFT)
#define JZ_DMA_DCM_DP_SHIFT     12
#define JZ_DMA_DCM_SP_SHIFT     14
#define JZ_DMA_DCM_DAI          BIT(22)
#define JZ_DMA_DCM_SAI          BIT(23)

#define JZ_DMA_SIZE_4_BYTE      0x0
#define JZ_DMA_SIZE_1_BYTE      0x1
#define JZ_DMA_SIZE_2_BYTE      0x2
#define JZ_DMA_SIZE_16_BYTE     0x3
#define JZ_DMA_SIZE_32_BYTE     0x4
#define JZ_DMA_SIZE_64_BYTE     0x5
#define JZ_DMA_SIZE_128_BYTE    0x6

#define JZ_DMA_WIDTH_32_BIT     0x0
#define JZ_DMA_WIDTH_8_BIT      0x1
#define JZ_DMA_WIDTH_16_BIT     0x2

#define JZ_DMA_BUSWIDTHS        (BIT(DMA_SLAVE_BUSWIDTH_1_BYTE)  | \
                                 BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) | \
                                 BIT(DMA_SLAVE_BUSWIDTH_4_BYTES))

/**
 * struct jz4780_dma_hwdesc - descriptor structure read by the DMA controller.
 * @dcm: value for the DCM (channel command) register
 * @dsa: source address
 * @dta: target address
 * @dtc: transfer count (number of blocks of the transfer size specified in DCM
 * to transfer) in the low 24 bits, offset of the next descriptor from the
 * descriptor base address in the upper 8 bits.
 * @sd: target/source stride difference (in stride transfer mode).
 * @drt: request type
 */
struct jz4780_dma_hwdesc {
        uint32_t dcm;
        uint32_t dsa;
        uint32_t dta;
        uint32_t dtc;
        uint32_t sd;
        uint32_t drt;
        uint32_t reserved[2];
};

/* Size of allocations for hardware descriptor blocks. */
#define JZ_DMA_DESC_BLOCK_SIZE  PAGE_SIZE
#define JZ_DMA_MAX_DESC         \
        (JZ_DMA_DESC_BLOCK_SIZE / sizeof(struct jz4780_dma_hwdesc))

struct jz4780_dma_desc {
        struct virt_dma_desc vdesc;

        struct jz4780_dma_hwdesc *desc;
        dma_addr_t desc_phys;
        unsigned int count;
        enum dma_transaction_type type;
        uint32_t status;
};

struct jz4780_dma_chan {
        struct virt_dma_chan vchan;
        unsigned int id;
        struct dma_pool *desc_pool;

        uint32_t transfer_type;
        uint32_t transfer_shift;
        struct dma_slave_config config;

        struct jz4780_dma_desc *desc;
        unsigned int curr_hwdesc;
};

struct jz4780_dma_dev {
        struct dma_device dma_device;
        void __iomem *base;
        struct clk *clk;
        unsigned int irq;

        uint32_t chan_reserved;
        struct jz4780_dma_chan chan[JZ_DMA_NR_CHANNELS];
};

struct jz4780_dma_filter_data {
        struct device_node *of_node;
        uint32_t transfer_type;
        int channel;
};

static inline struct jz4780_dma_chan *to_jz4780_dma_chan(struct dma_chan *chan)
{
        return container_of(chan, struct jz4780_dma_chan, vchan.chan);
}

static inline struct jz4780_dma_desc *to_jz4780_dma_desc(
        struct virt_dma_desc *vdesc)
{
        return container_of(vdesc, struct jz4780_dma_desc, vdesc);
}

static inline struct jz4780_dma_dev *jz4780_dma_chan_parent(
        struct jz4780_dma_chan *jzchan)
{
        return container_of(jzchan->vchan.chan.device, struct jz4780_dma_dev,
                            dma_device);
}

static inline uint32_t jz4780_dma_readl(struct jz4780_dma_dev *jzdma,
        unsigned int reg)
{
        return readl(jzdma->base + reg);
}

static inline void jz4780_dma_writel(struct jz4780_dma_dev *jzdma,
        unsigned int reg, uint32_t val)
{
        writel(val, jzdma->base + reg);
}

static struct jz4780_dma_desc *jz4780_dma_desc_alloc(
        struct jz4780_dma_chan *jzchan, unsigned int count,
        enum dma_transaction_type type)
{
        struct jz4780_dma_desc *desc;

        if (count > JZ_DMA_MAX_DESC)
                return NULL;

        desc = kzalloc(sizeof(*desc), GFP_NOWAIT);
        if (!desc)
                return NULL;

        desc->desc = dma_pool_alloc(jzchan->desc_pool, GFP_NOWAIT,
                                    &desc->desc_phys);
        if (!desc->desc) {
                kfree(desc);
                return NULL;
        }

        desc->count = count;
        desc->type = type;
        return desc;
}

static void jz4780_dma_desc_free(struct virt_dma_desc *vdesc)
{
        struct jz4780_dma_desc *desc = to_jz4780_dma_desc(vdesc);
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(vdesc->tx.chan);

        dma_pool_free(jzchan->desc_pool, desc->desc, desc->desc_phys);
        kfree(desc);
}

static uint32_t jz4780_dma_transfer_size(unsigned long val, uint32_t *shift)
{
        int ord = ffs(val) - 1;

        /*
         * 8 byte transfer sizes unsupported so fall back on 4. If it's larger
         * than the maximum, just limit it. It is perfectly safe to fall back
         * in this way since we won't exceed the maximum burst size supported
         * by the device, the only effect is reduced efficiency. This is better
         * than refusing to perform the request at all.
         */
        if (ord == 3)
                ord = 2;
        else if (ord > 7)
                ord = 7;

        *shift = ord;

        switch (ord) {
        case 0:
                return JZ_DMA_SIZE_1_BYTE;
        case 1:
                return JZ_DMA_SIZE_2_BYTE;
        case 2:
                return JZ_DMA_SIZE_4_BYTE;
        case 4:
                return JZ_DMA_SIZE_16_BYTE;
        case 5:
                return JZ_DMA_SIZE_32_BYTE;
        case 6:
                return JZ_DMA_SIZE_64_BYTE;
        default:
                return JZ_DMA_SIZE_128_BYTE;
        }
}

static int jz4780_dma_setup_hwdesc(struct jz4780_dma_chan *jzchan,
        struct jz4780_dma_hwdesc *desc, dma_addr_t addr, size_t len,
        enum dma_transfer_direction direction)
{
        struct dma_slave_config *config = &jzchan->config;
        uint32_t width, maxburst, tsz;

        if (direction == DMA_MEM_TO_DEV) {
                desc->dcm = JZ_DMA_DCM_SAI;
                desc->dsa = addr;
                desc->dta = config->dst_addr;
                desc->drt = jzchan->transfer_type;

                width = config->dst_addr_width;
                maxburst = config->dst_maxburst;
        } else {
                desc->dcm = JZ_DMA_DCM_DAI;
                desc->dsa = config->src_addr;
                desc->dta = addr;
                desc->drt = jzchan->transfer_type;

                width = config->src_addr_width;
                maxburst = config->src_maxburst;
        }

        /*
         * This calculates the maximum transfer size that can be used with the
         * given address, length, width and maximum burst size. The address
         * must be aligned to the transfer size, the total length must be
         * divisible by the transfer size, and we must not use more than the
         * maximum burst specified by the user.
         */
        tsz = jz4780_dma_transfer_size(addr | len | (width * maxburst),
                                       &jzchan->transfer_shift);

        switch (width) {
        case DMA_SLAVE_BUSWIDTH_1_BYTE:
        case DMA_SLAVE_BUSWIDTH_2_BYTES:
                break;
        case DMA_SLAVE_BUSWIDTH_4_BYTES:
                width = JZ_DMA_WIDTH_32_BIT;
                break;
        default:
                return -EINVAL;
        }

        desc->dcm |= tsz << JZ_DMA_DCM_TSZ_SHIFT;
        desc->dcm |= width << JZ_DMA_DCM_SP_SHIFT;
        desc->dcm |= width << JZ_DMA_DCM_DP_SHIFT;

        desc->dtc = len >> jzchan->transfer_shift;
        return 0;
}

static struct dma_async_tx_descriptor *jz4780_dma_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 jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
        struct jz4780_dma_desc *desc;
        unsigned int i;
        int err;

        desc = jz4780_dma_desc_alloc(jzchan, sg_len, DMA_SLAVE);
        if (!desc)
                return NULL;

        for (i = 0; i < sg_len; i++) {
                err = jz4780_dma_setup_hwdesc(jzchan, &desc->desc[i],
                                              sg_dma_address(&sgl[i]),
                                              sg_dma_len(&sgl[i]),
                                              direction);
                if (err < 0) {
                        jz4780_dma_desc_free(&jzchan->desc->vdesc);
                        return NULL;
                }

                desc->desc[i].dcm |= JZ_DMA_DCM_TIE;

                if (i != (sg_len - 1)) {
                        /* Automatically proceeed to the next descriptor. */
                        desc->desc[i].dcm |= JZ_DMA_DCM_LINK;

                        /*
                         * The upper 8 bits of the DTC field in the descriptor
                         * must be set to (offset from descriptor base of next
                         * descriptor >> 4).
                         */
                        desc->desc[i].dtc |=
                                (((i + 1) * sizeof(*desc->desc)) >> 4) << 24;
                }
        }

        return vchan_tx_prep(&jzchan->vchan, &desc->vdesc, flags);
}

static struct dma_async_tx_descriptor *jz4780_dma_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 jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
        struct jz4780_dma_desc *desc;
        unsigned int periods, i;
        int err;

        if (buf_len % period_len)
                return NULL;

        periods = buf_len / period_len;

        desc = jz4780_dma_desc_alloc(jzchan, periods, DMA_CYCLIC);
        if (!desc)
                return NULL;

        for (i = 0; i < periods; i++) {
                err = jz4780_dma_setup_hwdesc(jzchan, &desc->desc[i], buf_addr,
                                              period_len, direction);
                if (err < 0) {
                        jz4780_dma_desc_free(&jzchan->desc->vdesc);
                        return NULL;
                }

                buf_addr += period_len;

                /*
                 * Set the link bit to indicate that the controller should
                 * automatically proceed to the next descriptor. In
                 * jz4780_dma_begin(), this will be cleared if we need to issue
                 * an interrupt after each period.
                 */
                desc->desc[i].dcm |= JZ_DMA_DCM_TIE | JZ_DMA_DCM_LINK;

                /*
                 * The upper 8 bits of the DTC field in the descriptor must be
                 * set to (offset from descriptor base of next descriptor >> 4).
                 * If this is the last descriptor, link it back to the first,
                 * i.e. leave offset set to 0, otherwise point to the next one.
                 */
                if (i != (periods - 1)) {
                        desc->desc[i].dtc |=
                                (((i + 1) * sizeof(*desc->desc)) >> 4) << 24;
                }
        }

        return vchan_tx_prep(&jzchan->vchan, &desc->vdesc, flags);
}

static struct dma_async_tx_descriptor *jz4780_dma_prep_dma_memcpy(
        struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
        size_t len, unsigned long flags)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
        struct jz4780_dma_desc *desc;
        uint32_t tsz;

        desc = jz4780_dma_desc_alloc(jzchan, 1, DMA_MEMCPY);
        if (!desc)
                return NULL;

        tsz = jz4780_dma_transfer_size(dest | src | len,
                                       &jzchan->transfer_shift);

        desc->desc[0].dsa = src;
        desc->desc[0].dta = dest;
        desc->desc[0].drt = JZ_DMA_DRT_AUTO;
        desc->desc[0].dcm = JZ_DMA_DCM_TIE | JZ_DMA_DCM_SAI | JZ_DMA_DCM_DAI |
                            tsz << JZ_DMA_DCM_TSZ_SHIFT |
                            JZ_DMA_WIDTH_32_BIT << JZ_DMA_DCM_SP_SHIFT |
                            JZ_DMA_WIDTH_32_BIT << JZ_DMA_DCM_DP_SHIFT;
        desc->desc[0].dtc = len >> jzchan->transfer_shift;

        return vchan_tx_prep(&jzchan->vchan, &desc->vdesc, flags);
}

static void jz4780_dma_begin(struct jz4780_dma_chan *jzchan)
{
        struct jz4780_dma_dev *jzdma = jz4780_dma_chan_parent(jzchan);
        struct virt_dma_desc *vdesc;
        unsigned int i;
        dma_addr_t desc_phys;

        if (!jzchan->desc) {
                vdesc = vchan_next_desc(&jzchan->vchan);
                if (!vdesc)
                        return;

                list_del(&vdesc->node);

                jzchan->desc = to_jz4780_dma_desc(vdesc);
                jzchan->curr_hwdesc = 0;

                if (jzchan->desc->type == DMA_CYCLIC && vdesc->tx.callback) {
                        /*
                         * The DMA controller doesn't support triggering an
                         * interrupt after processing each descriptor, only
                         * after processing an entire terminated list of
                         * descriptors. For a cyclic DMA setup the list of
                         * descriptors is not terminated so we can never get an
                         * interrupt.
                         *
                         * If the user requested a callback for a cyclic DMA
                         * setup then we workaround this hardware limitation
                         * here by degrading to a set of unlinked descriptors
                         * which we will submit in sequence in response to the
                         * completion of processing the previous descriptor.
                         */
                        for (i = 0; i < jzchan->desc->count; i++)
                                jzchan->desc->desc[i].dcm &= ~JZ_DMA_DCM_LINK;
                }
        } else {
                /*
                 * There is an existing transfer, therefore this must be one
                 * for which we unlinked the descriptors above. Advance to the
                 * next one in the list.
                 */
                jzchan->curr_hwdesc =
                        (jzchan->curr_hwdesc + 1) % jzchan->desc->count;
        }

        /* Use 8-word descriptors. */
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DCS(jzchan->id), JZ_DMA_DCS_DES8);

        /* Write descriptor address and initiate descriptor fetch. */
        desc_phys = jzchan->desc->desc_phys +
                    (jzchan->curr_hwdesc * sizeof(*jzchan->desc->desc));
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DDA(jzchan->id), desc_phys);
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DDRS, BIT(jzchan->id));

        /* Enable the channel. */
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DCS(jzchan->id),
                          JZ_DMA_DCS_DES8 | JZ_DMA_DCS_CTE);
}

static void jz4780_dma_issue_pending(struct dma_chan *chan)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&jzchan->vchan.lock, flags);

        if (vchan_issue_pending(&jzchan->vchan) && !jzchan->desc)
                jz4780_dma_begin(jzchan);

        spin_unlock_irqrestore(&jzchan->vchan.lock, flags);
}

static int jz4780_dma_terminate_all(struct dma_chan *chan)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
        struct jz4780_dma_dev *jzdma = jz4780_dma_chan_parent(jzchan);
        unsigned long flags;
        LIST_HEAD(head);

        spin_lock_irqsave(&jzchan->vchan.lock, flags);

        /* Clear the DMA status and stop the transfer. */
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DCS(jzchan->id), 0);
        if (jzchan->desc) {
                jz4780_dma_desc_free(&jzchan->desc->vdesc);
                jzchan->desc = NULL;
        }

        vchan_get_all_descriptors(&jzchan->vchan, &head);

        spin_unlock_irqrestore(&jzchan->vchan.lock, flags);

        vchan_dma_desc_free_list(&jzchan->vchan, &head);
        return 0;
}

static int jz4780_dma_config(struct dma_chan *chan,
        struct dma_slave_config *config)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);

        if ((config->src_addr_width == DMA_SLAVE_BUSWIDTH_8_BYTES)
           || (config->dst_addr_width == DMA_SLAVE_BUSWIDTH_8_BYTES))
                return -EINVAL;

        /* Copy the reset of the slave configuration, it is used later. */
        memcpy(&jzchan->config, config, sizeof(jzchan->config));

        return 0;
}

static size_t jz4780_dma_desc_residue(struct jz4780_dma_chan *jzchan,
        struct jz4780_dma_desc *desc, unsigned int next_sg)
{
        struct jz4780_dma_dev *jzdma = jz4780_dma_chan_parent(jzchan);
        unsigned int residue, count;
        unsigned int i;

        residue = 0;

        for (i = next_sg; i < desc->count; i++)
                residue += desc->desc[i].dtc << jzchan->transfer_shift;

        if (next_sg != 0) {
                count = jz4780_dma_readl(jzdma,
                                         JZ_DMA_REG_DTC(jzchan->id));
                residue += count << jzchan->transfer_shift;
        }

        return residue;
}

static enum dma_status jz4780_dma_tx_status(struct dma_chan *chan,
        dma_cookie_t cookie, struct dma_tx_state *txstate)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
        struct virt_dma_desc *vdesc;
        enum dma_status status;
        unsigned long flags;

        status = dma_cookie_status(chan, cookie, txstate);
        if ((status == DMA_COMPLETE) || (txstate == NULL))
                return status;

        spin_lock_irqsave(&jzchan->vchan.lock, flags);

        vdesc = vchan_find_desc(&jzchan->vchan, cookie);
        if (vdesc) {
                /* On the issued list, so hasn't been processed yet */
                txstate->residue = jz4780_dma_desc_residue(jzchan,
                                        to_jz4780_dma_desc(vdesc), 0);
        } else if (cookie == jzchan->desc->vdesc.tx.cookie) {
                txstate->residue = jz4780_dma_desc_residue(jzchan, jzchan->desc,
                          (jzchan->curr_hwdesc + 1) % jzchan->desc->count);
        } else
                txstate->residue = 0;

        if (vdesc && jzchan->desc && vdesc == &jzchan->desc->vdesc
            && jzchan->desc->status & (JZ_DMA_DCS_AR | JZ_DMA_DCS_HLT))
                status = DMA_ERROR;

        spin_unlock_irqrestore(&jzchan->vchan.lock, flags);
        return status;
}

static void jz4780_dma_chan_irq(struct jz4780_dma_dev *jzdma,
        struct jz4780_dma_chan *jzchan)
{
        uint32_t dcs;

        spin_lock(&jzchan->vchan.lock);

        dcs = jz4780_dma_readl(jzdma, JZ_DMA_REG_DCS(jzchan->id));
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DCS(jzchan->id), 0);

        if (dcs & JZ_DMA_DCS_AR) {
                dev_warn(&jzchan->vchan.chan.dev->device,
                         "address error (DCS=0x%x)\n", dcs);
        }

        if (dcs & JZ_DMA_DCS_HLT) {
                dev_warn(&jzchan->vchan.chan.dev->device,
                         "channel halt (DCS=0x%x)\n", dcs);
        }

        if (jzchan->desc) {
                jzchan->desc->status = dcs;

                if ((dcs & (JZ_DMA_DCS_AR | JZ_DMA_DCS_HLT)) == 0) {
                        if (jzchan->desc->type == DMA_CYCLIC) {
                                vchan_cyclic_callback(&jzchan->desc->vdesc);
                        } else {
                                vchan_cookie_complete(&jzchan->desc->vdesc);
                                jzchan->desc = NULL;
                        }

                        jz4780_dma_begin(jzchan);
                }
        } else {
                dev_err(&jzchan->vchan.chan.dev->device,
                        "channel IRQ with no active transfer\n");
        }

        spin_unlock(&jzchan->vchan.lock);
}

static irqreturn_t jz4780_dma_irq_handler(int irq, void *data)
{
        struct jz4780_dma_dev *jzdma = data;
        uint32_t pending, dmac;
        int i;

        pending = jz4780_dma_readl(jzdma, JZ_DMA_REG_DIRQP);

        for (i = 0; i < JZ_DMA_NR_CHANNELS; i++) {
                if (!(pending & (1<<i)))
                        continue;

                jz4780_dma_chan_irq(jzdma, &jzdma->chan[i]);
        }

        /* Clear halt and address error status of all channels. */
        dmac = jz4780_dma_readl(jzdma, JZ_DMA_REG_DMAC);
        dmac &= ~(JZ_DMA_DMAC_HLT | JZ_DMA_DMAC_AR);
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DMAC, dmac);

        /* Clear interrupt pending status. */
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DIRQP, 0);

        return IRQ_HANDLED;
}

static int jz4780_dma_alloc_chan_resources(struct dma_chan *chan)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);

        jzchan->desc_pool = dma_pool_create(dev_name(&chan->dev->device),
                                            chan->device->dev,
                                            JZ_DMA_DESC_BLOCK_SIZE,
                                            PAGE_SIZE, 0);
        if (!jzchan->desc_pool) {
                dev_err(&chan->dev->device,
                        "failed to allocate descriptor pool\n");
                return -ENOMEM;
        }

        return 0;
}

static void jz4780_dma_free_chan_resources(struct dma_chan *chan)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);

        vchan_free_chan_resources(&jzchan->vchan);
        dma_pool_destroy(jzchan->desc_pool);
        jzchan->desc_pool = NULL;
}

static bool jz4780_dma_filter_fn(struct dma_chan *chan, void *param)
{
        struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
        struct jz4780_dma_dev *jzdma = jz4780_dma_chan_parent(jzchan);
        struct jz4780_dma_filter_data *data = param;

        if (jzdma->dma_device.dev->of_node != data->of_node)
                return false;

        if (data->channel > -1) {
                if (data->channel != jzchan->id)
                        return false;
        } else if (jzdma->chan_reserved & BIT(jzchan->id)) {
                return false;
        }

        jzchan->transfer_type = data->transfer_type;

        return true;
}

static struct dma_chan *jz4780_of_dma_xlate(struct of_phandle_args *dma_spec,
        struct of_dma *ofdma)
{
        struct jz4780_dma_dev *jzdma = ofdma->of_dma_data;
        dma_cap_mask_t mask = jzdma->dma_device.cap_mask;
        struct jz4780_dma_filter_data data;

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

        data.of_node = ofdma->of_node;
        data.transfer_type = dma_spec->args[0];
        data.channel = dma_spec->args[1];

        if (data.channel > -1) {
                if (data.channel >= JZ_DMA_NR_CHANNELS) {
                        dev_err(jzdma->dma_device.dev,
                                "device requested non-existent channel %u\n",
                                data.channel);
                        return NULL;
                }

                /* Can only select a channel marked as reserved. */
                if (!(jzdma->chan_reserved & BIT(data.channel))) {
                        dev_err(jzdma->dma_device.dev,
                                "device requested unreserved channel %u\n",
                                data.channel);
                        return NULL;
                }

                jzdma->chan[data.channel].transfer_type = data.transfer_type;

                return dma_get_slave_channel(
                        &jzdma->chan[data.channel].vchan.chan);
        } else {
                return dma_request_channel(mask, jz4780_dma_filter_fn, &data);
        }
}

static int jz4780_dma_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct jz4780_dma_dev *jzdma;
        struct jz4780_dma_chan *jzchan;
        struct dma_device *dd;
        struct resource *res;
        int i, ret;

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

        platform_set_drvdata(pdev, jzdma);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res) {
                dev_err(dev, "failed to get I/O memory\n");
                return -EINVAL;
        }

        jzdma->base = devm_ioremap_resource(dev, res);
        if (IS_ERR(jzdma->base))
                return PTR_ERR(jzdma->base);

        ret = platform_get_irq(pdev, 0);
        if (ret < 0) {
                dev_err(dev, "failed to get IRQ: %d\n", ret);
                return ret;
        }

        jzdma->irq = ret;

        ret = request_irq(jzdma->irq, jz4780_dma_irq_handler, 0, dev_name(dev),
                          jzdma);
        if (ret) {
                dev_err(dev, "failed to request IRQ %u!\n", jzdma->irq);
                return ret;
        }

        jzdma->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(jzdma->clk)) {
                dev_err(dev, "failed to get clock\n");
                ret = PTR_ERR(jzdma->clk);
                goto err_free_irq;
        }

        clk_prepare_enable(jzdma->clk);

        /* Property is optional, if it doesn't exist the value will remain 0. */
        of_property_read_u32_index(dev->of_node, "ingenic,reserved-channels",
                                   0, &jzdma->chan_reserved);

        dd = &jzdma->dma_device;

        dma_cap_set(DMA_MEMCPY, dd->cap_mask);
        dma_cap_set(DMA_SLAVE, dd->cap_mask);
        dma_cap_set(DMA_CYCLIC, dd->cap_mask);

        dd->dev = dev;
        dd->copy_align = DMAENGINE_ALIGN_4_BYTES;
        dd->device_alloc_chan_resources = jz4780_dma_alloc_chan_resources;
        dd->device_free_chan_resources = jz4780_dma_free_chan_resources;
        dd->device_prep_slave_sg = jz4780_dma_prep_slave_sg;
        dd->device_prep_dma_cyclic = jz4780_dma_prep_dma_cyclic;
        dd->device_prep_dma_memcpy = jz4780_dma_prep_dma_memcpy;
        dd->device_config = jz4780_dma_config;
        dd->device_terminate_all = jz4780_dma_terminate_all;
        dd->device_tx_status = jz4780_dma_tx_status;
        dd->device_issue_pending = jz4780_dma_issue_pending;
        dd->src_addr_widths = JZ_DMA_BUSWIDTHS;
        dd->dst_addr_widths = JZ_DMA_BUSWIDTHS;
        dd->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
        dd->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;

        /*
         * Enable DMA controller, mark all channels as not programmable.
         * Also set the FMSC bit - it increases MSC performance, so it makes
         * little sense not to enable it.
         */
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DMAC,
                          JZ_DMA_DMAC_DMAE | JZ_DMA_DMAC_FMSC);
        jz4780_dma_writel(jzdma, JZ_DMA_REG_DMACP, 0);

        INIT_LIST_HEAD(&dd->channels);

        for (i = 0; i < JZ_DMA_NR_CHANNELS; i++) {
                jzchan = &jzdma->chan[i];
                jzchan->id = i;

                vchan_init(&jzchan->vchan, dd);
                jzchan->vchan.desc_free = jz4780_dma_desc_free;
        }

        ret = dma_async_device_register(dd);
        if (ret) {
                dev_err(dev, "failed to register device\n");
                goto err_disable_clk;
        }

        /* Register with OF DMA helpers. */
        ret = of_dma_controller_register(dev->of_node, jz4780_of_dma_xlate,
                                         jzdma);
        if (ret) {
                dev_err(dev, "failed to register OF DMA controller\n");
                goto err_unregister_dev;
        }

        dev_info(dev, "JZ4780 DMA controller initialised\n");
        return 0;

err_unregister_dev:
        dma_async_device_unregister(dd);

err_disable_clk:
        clk_disable_unprepare(jzdma->clk);

err_free_irq:
        free_irq(jzdma->irq, jzdma);
        return ret;
}

static int jz4780_dma_remove(struct platform_device *pdev)
{
        struct jz4780_dma_dev *jzdma = platform_get_drvdata(pdev);
        int i;

        of_dma_controller_free(pdev->dev.of_node);

        free_irq(jzdma->irq, jzdma);

        for (i = 0; i < JZ_DMA_NR_CHANNELS; i++)
                tasklet_kill(&jzdma->chan[i].vchan.task);

        dma_async_device_unregister(&jzdma->dma_device);
        return 0;
}

static const struct of_device_id jz4780_dma_dt_match[] = {
        { .compatible = "ingenic,jz4780-dma", .data = NULL },
        {},
};
MODULE_DEVICE_TABLE(of, jz4780_dma_dt_match);

static struct platform_driver jz4780_dma_driver = {
        .probe          = jz4780_dma_probe,
        .remove         = jz4780_dma_remove,
        .driver = {
                .name   = "jz4780-dma",
                .of_match_table = of_match_ptr(jz4780_dma_dt_match),
        },
};

static int __init jz4780_dma_init(void)
{
        return platform_driver_register(&jz4780_dma_driver);
}
subsys_initcall(jz4780_dma_init);

static void __exit jz4780_dma_exit(void)
{
        platform_driver_unregister(&jz4780_dma_driver);
}
module_exit(jz4780_dma_exit);

MODULE_AUTHOR("Alex Smith <alex@alex-smith.me.uk>");
MODULE_DESCRIPTION("Ingenic JZ4780 DMA controller driver");
MODULE_LICENSE("GPL");