/*
 * TI EDMA DMA engine driver
 *
 * Copyright 2012 Texas Instruments
 *
 * 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 version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/edma.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/of.h>

#include <linux/platform_data/edma.h>

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

/*
 * This will go away when the private EDMA API is folded
 * into this driver and the platform device(s) are
 * instantiated in the arch code. We can only get away
 * with this simplification because DA8XX may not be built
 * in the same kernel image with other DaVinci parts. This
 * avoids having to sprinkle dmaengine driver platform devices
 * and data throughout all the existing board files.
 */
#ifdef CONFIG_ARCH_DAVINCI_DA8XX
#define EDMA_CTLRS      2
#define EDMA_CHANS      32
#else
#define EDMA_CTLRS      1
#define EDMA_CHANS      64
#endif /* CONFIG_ARCH_DAVINCI_DA8XX */

/*
 * Max of 20 segments per channel to conserve PaRAM slots
 * Also note that MAX_NR_SG should be atleast the no.of periods
 * that are required for ASoC, otherwise DMA prep calls will
 * fail. Today davinci-pcm is the only user of this driver and
 * requires atleast 17 slots, so we setup the default to 20.
 */
#define MAX_NR_SG               20
#define EDMA_MAX_SLOTS          MAX_NR_SG
#define EDMA_DESCRIPTORS        16

struct edma_pset {
        u32                             len;
        dma_addr_t                      addr;
        struct edmacc_param             param;
};

struct edma_desc {
        struct virt_dma_desc            vdesc;
        struct list_head                node;
        enum dma_transfer_direction     direction;
        int                             cyclic;
        int                             absync;
        int                             pset_nr;
        struct edma_chan                *echan;
        int                             processed;

        /*
         * The following 4 elements are used for residue accounting.
         *
         * - processed_stat: the number of SG elements we have traversed
         * so far to cover accounting. This is updated directly to processed
         * during edma_callback and is always <= processed, because processed
         * refers to the number of pending transfer (programmed to EDMA
         * controller), where as processed_stat tracks number of transfers
         * accounted for so far.
         *
         * - residue: The amount of bytes we have left to transfer for this desc
         *
         * - residue_stat: The residue in bytes of data we have covered
         * so far for accounting. This is updated directly to residue
         * during callbacks to keep it current.
         *
         * - sg_len: Tracks the length of the current intermediate transfer,
         * this is required to update the residue during intermediate transfer
         * completion callback.
         */
        int                             processed_stat;
        u32                             sg_len;
        u32                             residue;
        u32                             residue_stat;

        struct edma_pset                pset[0];
};

struct edma_cc;

struct edma_chan {
        struct virt_dma_chan            vchan;
        struct list_head                node;
        struct edma_desc                *edesc;
        struct edma_cc                  *ecc;
        int                             ch_num;
        bool                            alloced;
        int                             slot[EDMA_MAX_SLOTS];
        int                             missed;
        struct dma_slave_config         cfg;
};

struct edma_cc {
        int                             ctlr;
        struct dma_device               dma_slave;
        struct edma_chan                slave_chans[EDMA_CHANS];
        int                             num_slave_chans;
        int                             dummy_slot;
};

static inline struct edma_cc *to_edma_cc(struct dma_device *d)
{
        return container_of(d, struct edma_cc, dma_slave);
}

static inline struct edma_chan *to_edma_chan(struct dma_chan *c)
{
        return container_of(c, struct edma_chan, vchan.chan);
}

static inline struct edma_desc
*to_edma_desc(struct dma_async_tx_descriptor *tx)
{
        return container_of(tx, struct edma_desc, vdesc.tx);
}

static void edma_desc_free(struct virt_dma_desc *vdesc)
{
        kfree(container_of(vdesc, struct edma_desc, vdesc));
}

/* Dispatch a queued descriptor to the controller (caller holds lock) */
static void edma_execute(struct edma_chan *echan)
{
        struct virt_dma_desc *vdesc;
        struct edma_desc *edesc;
        struct device *dev = echan->vchan.chan.device->dev;
        int i, j, left, nslots;

        /* If either we processed all psets or we're still not started */
        if (!echan->edesc ||
            echan->edesc->pset_nr == echan->edesc->processed) {
                /* Get next vdesc */
                vdesc = vchan_next_desc(&echan->vchan);
                if (!vdesc) {
                        echan->edesc = NULL;
                        return;
                }
                list_del(&vdesc->node);
                echan->edesc = to_edma_desc(&vdesc->tx);
        }

        edesc = echan->edesc;

        /* Find out how many left */
        left = edesc->pset_nr - edesc->processed;
        nslots = min(MAX_NR_SG, left);
        edesc->sg_len = 0;

        /* Write descriptor PaRAM set(s) */
        for (i = 0; i < nslots; i++) {
                j = i + edesc->processed;
                edma_write_slot(echan->slot[i], &edesc->pset[j].param);
                edesc->sg_len += edesc->pset[j].len;
                dev_vdbg(echan->vchan.chan.device->dev,
                        "\n pset[%d]:\n"
                        "  chnum\t%d\n"
                        "  slot\t%d\n"
                        "  opt\t%08x\n"
                        "  src\t%08x\n"
                        "  dst\t%08x\n"
                        "  abcnt\t%08x\n"
                        "  ccnt\t%08x\n"
                        "  bidx\t%08x\n"
                        "  cidx\t%08x\n"
                        "  lkrld\t%08x\n",
                        j, echan->ch_num, echan->slot[i],
                        edesc->pset[j].param.opt,
                        edesc->pset[j].param.src,
                        edesc->pset[j].param.dst,
                        edesc->pset[j].param.a_b_cnt,
                        edesc->pset[j].param.ccnt,
                        edesc->pset[j].param.src_dst_bidx,
                        edesc->pset[j].param.src_dst_cidx,
                        edesc->pset[j].param.link_bcntrld);
                /* Link to the previous slot if not the last set */
                if (i != (nslots - 1))
                        edma_link(echan->slot[i], echan->slot[i+1]);
        }

        edesc->processed += nslots;

        /*
         * If this is either the last set in a set of SG-list transactions
         * then setup a link to the dummy slot, this results in all future
         * events being absorbed and that's OK because we're done
         */
        if (edesc->processed == edesc->pset_nr) {
                if (edesc->cyclic)
                        edma_link(echan->slot[nslots-1], echan->slot[1]);
                else
                        edma_link(echan->slot[nslots-1],
                                  echan->ecc->dummy_slot);
        }

        if (edesc->processed <= MAX_NR_SG) {
                dev_dbg(dev, "first transfer starting on channel %d\n",
                        echan->ch_num);
                edma_start(echan->ch_num);
        } else {
                dev_dbg(dev, "chan: %d: completed %d elements, resuming\n",
                        echan->ch_num, edesc->processed);
                edma_resume(echan->ch_num);
        }

        /*
         * This happens due to setup times between intermediate transfers
         * in long SG lists which have to be broken up into transfers of
         * MAX_NR_SG
         */
        if (echan->missed) {
                dev_dbg(dev, "missed event on channel %d\n", echan->ch_num);
                edma_clean_channel(echan->ch_num);
                edma_stop(echan->ch_num);
                edma_start(echan->ch_num);
                edma_trigger_channel(echan->ch_num);
                echan->missed = 0;
        }
}

static int edma_terminate_all(struct dma_chan *chan)
{
        struct edma_chan *echan = to_edma_chan(chan);
        unsigned long flags;
        LIST_HEAD(head);

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

        /*
         * Stop DMA activity: we assume the callback will not be called
         * after edma_dma() returns (even if it does, it will see
         * echan->edesc is NULL and exit.)
         */
        if (echan->edesc) {
                int cyclic = echan->edesc->cyclic;

                /*
                 * free the running request descriptor
                 * since it is not in any of the vdesc lists
                 */
                edma_desc_free(&echan->edesc->vdesc);

                echan->edesc = NULL;
                edma_stop(echan->ch_num);
                /* Move the cyclic channel back to default queue */
                if (cyclic)
                        edma_assign_channel_eventq(echan->ch_num,
                                                   EVENTQ_DEFAULT);
        }

        vchan_get_all_descriptors(&echan->vchan, &head);
        spin_unlock_irqrestore(&echan->vchan.lock, flags);
        vchan_dma_desc_free_list(&echan->vchan, &head);

        return 0;
}

static int edma_slave_config(struct dma_chan *chan,
        struct dma_slave_config *cfg)
{
        struct edma_chan *echan = to_edma_chan(chan);

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

        memcpy(&echan->cfg, cfg, sizeof(echan->cfg));

        return 0;
}

static int edma_dma_pause(struct dma_chan *chan)
{
        struct edma_chan *echan = to_edma_chan(chan);

        /* Pause/Resume only allowed with cyclic mode */
        if (!echan->edesc || !echan->edesc->cyclic)
                return -EINVAL;

        edma_pause(echan->ch_num);
        return 0;
}

static int edma_dma_resume(struct dma_chan *chan)
{
        struct edma_chan *echan = to_edma_chan(chan);

        /* Pause/Resume only allowed with cyclic mode */
        if (!echan->edesc->cyclic)
                return -EINVAL;

        edma_resume(echan->ch_num);
        return 0;
}

/*
 * A PaRAM set configuration abstraction used by other modes
 * @chan: Channel who's PaRAM set we're configuring
 * @pset: PaRAM set to initialize and setup.
 * @src_addr: Source address of the DMA
 * @dst_addr: Destination address of the DMA
 * @burst: In units of dev_width, how much to send
 * @dev_width: How much is the dev_width
 * @dma_length: Total length of the DMA transfer
 * @direction: Direction of the transfer
 */
static int edma_config_pset(struct dma_chan *chan, struct edma_pset *epset,
        dma_addr_t src_addr, dma_addr_t dst_addr, u32 burst,
        enum dma_slave_buswidth dev_width, unsigned int dma_length,
        enum dma_transfer_direction direction)
{
        struct edma_chan *echan = to_edma_chan(chan);
        struct device *dev = chan->device->dev;
        struct edmacc_param *param = &epset->param;
        int acnt, bcnt, ccnt, cidx;
        int src_bidx, dst_bidx, src_cidx, dst_cidx;
        int absync;

        acnt = dev_width;

        /* src/dst_maxburst == 0 is the same case as src/dst_maxburst == 1 */
        if (!burst)
                burst = 1;
        /*
         * If the maxburst is equal to the fifo width, use
         * A-synced transfers. This allows for large contiguous
         * buffer transfers using only one PaRAM set.
         */
        if (burst == 1) {
                /*
                 * For the A-sync case, bcnt and ccnt are the remainder
                 * and quotient respectively of the division of:
                 * (dma_length / acnt) by (SZ_64K -1). This is so
                 * that in case bcnt over flows, we have ccnt to use.
                 * Note: In A-sync tranfer only, bcntrld is used, but it
                 * only applies for sg_dma_len(sg) >= SZ_64K.
                 * In this case, the best way adopted is- bccnt for the
                 * first frame will be the remainder below. Then for
                 * every successive frame, bcnt will be SZ_64K-1. This
                 * is assured as bcntrld = 0xffff in end of function.
                 */
                absync = false;
                ccnt = dma_length / acnt / (SZ_64K - 1);
                bcnt = dma_length / acnt - ccnt * (SZ_64K - 1);
                /*
                 * If bcnt is non-zero, we have a remainder and hence an
                 * extra frame to transfer, so increment ccnt.
                 */
                if (bcnt)
                        ccnt++;
                else
                        bcnt = SZ_64K - 1;
                cidx = acnt;
        } else {
                /*
                 * If maxburst is greater than the fifo address_width,
                 * use AB-synced transfers where A count is the fifo
                 * address_width and B count is the maxburst. In this
                 * case, we are limited to transfers of C count frames
                 * of (address_width * maxburst) where C count is limited
                 * to SZ_64K-1. This places an upper bound on the length
                 * of an SG segment that can be handled.
                 */
                absync = true;
                bcnt = burst;
                ccnt = dma_length / (acnt * bcnt);
                if (ccnt > (SZ_64K - 1)) {
                        dev_err(dev, "Exceeded max SG segment size\n");
                        return -EINVAL;
                }
                cidx = acnt * bcnt;
        }

        epset->len = dma_length;

        if (direction == DMA_MEM_TO_DEV) {
                src_bidx = acnt;
                src_cidx = cidx;
                dst_bidx = 0;
                dst_cidx = 0;
                epset->addr = src_addr;
        } else if (direction == DMA_DEV_TO_MEM)  {
                src_bidx = 0;
                src_cidx = 0;
                dst_bidx = acnt;
                dst_cidx = cidx;
                epset->addr = dst_addr;
        } else if (direction == DMA_MEM_TO_MEM)  {
                src_bidx = acnt;
                src_cidx = cidx;
                dst_bidx = acnt;
                dst_cidx = cidx;
        } else {
                dev_err(dev, "%s: direction not implemented yet\n", __func__);
                return -EINVAL;
        }

        param->opt = EDMA_TCC(EDMA_CHAN_SLOT(echan->ch_num));
        /* Configure A or AB synchronized transfers */
        if (absync)
                param->opt |= SYNCDIM;

        param->src = src_addr;
        param->dst = dst_addr;

        param->src_dst_bidx = (dst_bidx << 16) | src_bidx;
        param->src_dst_cidx = (dst_cidx << 16) | src_cidx;

        param->a_b_cnt = bcnt << 16 | acnt;
        param->ccnt = ccnt;
        /*
         * Only time when (bcntrld) auto reload is required is for
         * A-sync case, and in this case, a requirement of reload value
         * of SZ_64K-1 only is assured. 'link' is initially set to NULL
         * and then later will be populated by edma_execute.
         */
        param->link_bcntrld = 0xffffffff;
        return absync;
}

static struct dma_async_tx_descriptor *edma_prep_slave_sg(
        struct dma_chan *chan, struct scatterlist *sgl,
        unsigned int sg_len, enum dma_transfer_direction direction,
        unsigned long tx_flags, void *context)
{
        struct edma_chan *echan = to_edma_chan(chan);
        struct device *dev = chan->device->dev;
        struct edma_desc *edesc;
        dma_addr_t src_addr = 0, dst_addr = 0;
        enum dma_slave_buswidth dev_width;
        u32 burst;
        struct scatterlist *sg;
        int i, nslots, ret;

        if (unlikely(!echan || !sgl || !sg_len))
                return NULL;

        if (direction == DMA_DEV_TO_MEM) {
                src_addr = echan->cfg.src_addr;
                dev_width = echan->cfg.src_addr_width;
                burst = echan->cfg.src_maxburst;
        } else if (direction == DMA_MEM_TO_DEV) {
                dst_addr = echan->cfg.dst_addr;
                dev_width = echan->cfg.dst_addr_width;
                burst = echan->cfg.dst_maxburst;
        } else {
                dev_err(dev, "%s: bad direction: %d\n", __func__, direction);
                return NULL;
        }

        if (dev_width == DMA_SLAVE_BUSWIDTH_UNDEFINED) {
                dev_err(dev, "%s: Undefined slave buswidth\n", __func__);
                return NULL;
        }

        edesc = kzalloc(sizeof(*edesc) + sg_len *
                sizeof(edesc->pset[0]), GFP_ATOMIC);
        if (!edesc) {
                dev_err(dev, "%s: Failed to allocate a descriptor\n", __func__);
                return NULL;
        }

        edesc->pset_nr = sg_len;
        edesc->residue = 0;
        edesc->direction = direction;
        edesc->echan = echan;

        /* Allocate a PaRAM slot, if needed */
        nslots = min_t(unsigned, MAX_NR_SG, sg_len);

        for (i = 0; i < nslots; i++) {
                if (echan->slot[i] < 0) {
                        echan->slot[i] =
                                edma_alloc_slot(EDMA_CTLR(echan->ch_num),
                                                EDMA_SLOT_ANY);
                        if (echan->slot[i] < 0) {
                                kfree(edesc);
                                dev_err(dev, "%s: Failed to allocate slot\n",
                                        __func__);
                                return NULL;
                        }
                }
        }

        /* Configure PaRAM sets for each SG */
        for_each_sg(sgl, sg, sg_len, i) {
                /* Get address for each SG */
                if (direction == DMA_DEV_TO_MEM)
                        dst_addr = sg_dma_address(sg);
                else
                        src_addr = sg_dma_address(sg);

                ret = edma_config_pset(chan, &edesc->pset[i], src_addr,
                                       dst_addr, burst, dev_width,
                                       sg_dma_len(sg), direction);
                if (ret < 0) {
                        kfree(edesc);
                        return NULL;
                }

                edesc->absync = ret;
                edesc->residue += sg_dma_len(sg);

                /* If this is the last in a current SG set of transactions,
                   enable interrupts so that next set is processed */
                if (!((i+1) % MAX_NR_SG))
                        edesc->pset[i].param.opt |= TCINTEN;

                /* If this is the last set, enable completion interrupt flag */
                if (i == sg_len - 1)
                        edesc->pset[i].param.opt |= TCINTEN;
        }
        edesc->residue_stat = edesc->residue;

        return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags);
}

static struct dma_async_tx_descriptor *edma_prep_dma_memcpy(
        struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
        size_t len, unsigned long tx_flags)
{
        int ret;
        struct edma_desc *edesc;
        struct device *dev = chan->device->dev;
        struct edma_chan *echan = to_edma_chan(chan);

        if (unlikely(!echan || !len))
                return NULL;

        edesc = kzalloc(sizeof(*edesc) + sizeof(edesc->pset[0]), GFP_ATOMIC);
        if (!edesc) {
                dev_dbg(dev, "Failed to allocate a descriptor\n");
                return NULL;
        }

        edesc->pset_nr = 1;

        ret = edma_config_pset(chan, &edesc->pset[0], src, dest, 1,
                               DMA_SLAVE_BUSWIDTH_4_BYTES, len, DMA_MEM_TO_MEM);
        if (ret < 0)
                return NULL;

        edesc->absync = ret;

        /*
         * Enable intermediate transfer chaining to re-trigger channel
         * on completion of every TR, and enable transfer-completion
         * interrupt on completion of the whole transfer.
         */
        edesc->pset[0].param.opt |= ITCCHEN;
        edesc->pset[0].param.opt |= TCINTEN;

        return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags);
}

static struct dma_async_tx_descriptor *edma_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 tx_flags)
{
        struct edma_chan *echan = to_edma_chan(chan);
        struct device *dev = chan->device->dev;
        struct edma_desc *edesc;
        dma_addr_t src_addr, dst_addr;
        enum dma_slave_buswidth dev_width;
        u32 burst;
        int i, ret, nslots;

        if (unlikely(!echan || !buf_len || !period_len))
                return NULL;

        if (direction == DMA_DEV_TO_MEM) {
                src_addr = echan->cfg.src_addr;
                dst_addr = buf_addr;
                dev_width = echan->cfg.src_addr_width;
                burst = echan->cfg.src_maxburst;
        } else if (direction == DMA_MEM_TO_DEV) {
                src_addr = buf_addr;
                dst_addr = echan->cfg.dst_addr;
                dev_width = echan->cfg.dst_addr_width;
                burst = echan->cfg.dst_maxburst;
        } else {
                dev_err(dev, "%s: bad direction: %d\n", __func__, direction);
                return NULL;
        }

        if (dev_width == DMA_SLAVE_BUSWIDTH_UNDEFINED) {
                dev_err(dev, "%s: Undefined slave buswidth\n", __func__);
                return NULL;
        }

        if (unlikely(buf_len % period_len)) {
                dev_err(dev, "Period should be multiple of Buffer length\n");
                return NULL;
        }

        nslots = (buf_len / period_len) + 1;

        /*
         * Cyclic DMA users such as audio cannot tolerate delays introduced
         * by cases where the number of periods is more than the maximum
         * number of SGs the EDMA driver can handle at a time. For DMA types
         * such as Slave SGs, such delays are tolerable and synchronized,
         * but the synchronization is difficult to achieve with Cyclic and
         * cannot be guaranteed, so we error out early.
         */
        if (nslots > MAX_NR_SG)
                return NULL;

        edesc = kzalloc(sizeof(*edesc) + nslots *
                sizeof(edesc->pset[0]), GFP_ATOMIC);
        if (!edesc) {
                dev_err(dev, "%s: Failed to allocate a descriptor\n", __func__);
                return NULL;
        }

        edesc->cyclic = 1;
        edesc->pset_nr = nslots;
        edesc->residue = edesc->residue_stat = buf_len;
        edesc->direction = direction;
        edesc->echan = echan;

        dev_dbg(dev, "%s: channel=%d nslots=%d period_len=%zu buf_len=%zu\n",
                __func__, echan->ch_num, nslots, period_len, buf_len);

        for (i = 0; i < nslots; i++) {
                /* Allocate a PaRAM slot, if needed */
                if (echan->slot[i] < 0) {
                        echan->slot[i] =
                                edma_alloc_slot(EDMA_CTLR(echan->ch_num),
                                                EDMA_SLOT_ANY);
                        if (echan->slot[i] < 0) {
                                kfree(edesc);
                                dev_err(dev, "%s: Failed to allocate slot\n",
                                        __func__);
                                return NULL;
                        }
                }

                if (i == nslots - 1) {
                        memcpy(&edesc->pset[i], &edesc->pset[0],
                               sizeof(edesc->pset[0]));
                        break;
                }

                ret = edma_config_pset(chan, &edesc->pset[i], src_addr,
                                       dst_addr, burst, dev_width, period_len,
                                       direction);
                if (ret < 0) {
                        kfree(edesc);
                        return NULL;
                }

                if (direction == DMA_DEV_TO_MEM)
                        dst_addr += period_len;
                else
                        src_addr += period_len;

                dev_vdbg(dev, "%s: Configure period %d of buf:\n", __func__, i);
                dev_vdbg(dev,
                        "\n pset[%d]:\n"
                        "  chnum\t%d\n"
                        "  slot\t%d\n"
                        "  opt\t%08x\n"
                        "  src\t%08x\n"
                        "  dst\t%08x\n"
                        "  abcnt\t%08x\n"
                        "  ccnt\t%08x\n"
                        "  bidx\t%08x\n"
                        "  cidx\t%08x\n"
                        "  lkrld\t%08x\n",
                        i, echan->ch_num, echan->slot[i],
                        edesc->pset[i].param.opt,
                        edesc->pset[i].param.src,
                        edesc->pset[i].param.dst,
                        edesc->pset[i].param.a_b_cnt,
                        edesc->pset[i].param.ccnt,
                        edesc->pset[i].param.src_dst_bidx,
                        edesc->pset[i].param.src_dst_cidx,
                        edesc->pset[i].param.link_bcntrld);

                edesc->absync = ret;

                /*
                 * Enable period interrupt only if it is requested
                 */
                if (tx_flags & DMA_PREP_INTERRUPT)
                        edesc->pset[i].param.opt |= TCINTEN;
        }

        /* Place the cyclic channel to highest priority queue */
        edma_assign_channel_eventq(echan->ch_num, EVENTQ_0);

        return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags);
}

static void edma_callback(unsigned ch_num, u16 ch_status, void *data)
{
        struct edma_chan *echan = data;
        struct device *dev = echan->vchan.chan.device->dev;
        struct edma_desc *edesc;
        struct edmacc_param p;

        edesc = echan->edesc;

        /* Pause the channel for non-cyclic */
        if (!edesc || (edesc && !edesc->cyclic))
                edma_pause(echan->ch_num);

        switch (ch_status) {
        case EDMA_DMA_COMPLETE:
                spin_lock(&echan->vchan.lock);

                if (edesc) {
                        if (edesc->cyclic) {
                                vchan_cyclic_callback(&edesc->vdesc);
                        } else if (edesc->processed == edesc->pset_nr) {
                                dev_dbg(dev, "Transfer complete, stopping channel %d\n", ch_num);
                                edesc->residue = 0;
                                edma_stop(echan->ch_num);
                                vchan_cookie_complete(&edesc->vdesc);
                                edma_execute(echan);
                        } else {
                                dev_dbg(dev, "Intermediate transfer complete on channel %d\n", ch_num);

                                /* Update statistics for tx_status */
                                edesc->residue -= edesc->sg_len;
                                edesc->residue_stat = edesc->residue;
                                edesc->processed_stat = edesc->processed;

                                edma_execute(echan);
                        }
                }

                spin_unlock(&echan->vchan.lock);

                break;
        case EDMA_DMA_CC_ERROR:
                spin_lock(&echan->vchan.lock);

                edma_read_slot(EDMA_CHAN_SLOT(echan->slot[0]), &p);

                /*
                 * Issue later based on missed flag which will be sure
                 * to happen as:
                 * (1) we finished transmitting an intermediate slot and
                 *     edma_execute is coming up.
                 * (2) or we finished current transfer and issue will
                 *     call edma_execute.
                 *
                 * Important note: issuing can be dangerous here and
                 * lead to some nasty recursion when we are in a NULL
                 * slot. So we avoid doing so and set the missed flag.
                 */
                if (p.a_b_cnt == 0 && p.ccnt == 0) {
                        dev_dbg(dev, "Error occurred, looks like slot is null, just setting miss\n");
                        echan->missed = 1;
                } else {
                        /*
                         * The slot is already programmed but the event got
                         * missed, so its safe to issue it here.
                         */
                        dev_dbg(dev, "Error occurred but slot is non-null, TRIGGERING\n");
                        edma_clean_channel(echan->ch_num);
                        edma_stop(echan->ch_num);
                        edma_start(echan->ch_num);
                        edma_trigger_channel(echan->ch_num);
                }

                spin_unlock(&echan->vchan.lock);

                break;
        default:
                break;
        }
}

/* Alloc channel resources */
static int edma_alloc_chan_resources(struct dma_chan *chan)
{
        struct edma_chan *echan = to_edma_chan(chan);
        struct device *dev = chan->device->dev;
        int ret;
        int a_ch_num;
        LIST_HEAD(descs);

        a_ch_num = edma_alloc_channel(echan->ch_num, edma_callback,
                                        echan, EVENTQ_DEFAULT);

        if (a_ch_num < 0) {
                ret = -ENODEV;
                goto err_no_chan;
        }

        if (a_ch_num != echan->ch_num) {
                dev_err(dev, "failed to allocate requested channel %u:%u\n",
                        EDMA_CTLR(echan->ch_num),
                        EDMA_CHAN_SLOT(echan->ch_num));
                ret = -ENODEV;
                goto err_wrong_chan;
        }

        echan->alloced = true;
        echan->slot[0] = echan->ch_num;

        dev_dbg(dev, "allocated channel %d for %u:%u\n", echan->ch_num,
                EDMA_CTLR(echan->ch_num), EDMA_CHAN_SLOT(echan->ch_num));

        return 0;

err_wrong_chan:
        edma_free_channel(a_ch_num);
err_no_chan:
        return ret;
}

/* Free channel resources */
static void edma_free_chan_resources(struct dma_chan *chan)
{
        struct edma_chan *echan = to_edma_chan(chan);
        struct device *dev = chan->device->dev;
        int i;

        /* Terminate transfers */
        edma_stop(echan->ch_num);

        vchan_free_chan_resources(&echan->vchan);

        /* Free EDMA PaRAM slots */
        for (i = 1; i < EDMA_MAX_SLOTS; i++) {
                if (echan->slot[i] >= 0) {
                        edma_free_slot(echan->slot[i]);
                        echan->slot[i] = -1;
                }
        }

        /* Free EDMA channel */
        if (echan->alloced) {
                edma_free_channel(echan->ch_num);
                echan->alloced = false;
        }

        dev_dbg(dev, "freeing channel for %u\n", echan->ch_num);
}

/* Send pending descriptor to hardware */
static void edma_issue_pending(struct dma_chan *chan)
{
        struct edma_chan *echan = to_edma_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&echan->vchan.lock, flags);
        if (vchan_issue_pending(&echan->vchan) && !echan->edesc)
                edma_execute(echan);
        spin_unlock_irqrestore(&echan->vchan.lock, flags);
}

static u32 edma_residue(struct edma_desc *edesc)
{
        bool dst = edesc->direction == DMA_DEV_TO_MEM;
        struct edma_pset *pset = edesc->pset;
        dma_addr_t done, pos;
        int i;

        /*
         * We always read the dst/src position from the first RamPar
         * pset. That's the one which is active now.
         */
        pos = edma_get_position(edesc->echan->slot[0], dst);

        /*
         * Cyclic is simple. Just subtract pset[0].addr from pos.
         *
         * We never update edesc->residue in the cyclic case, so we
         * can tell the remaining room to the end of the circular
         * buffer.
         */
        if (edesc->cyclic) {
                done = pos - pset->addr;
                edesc->residue_stat = edesc->residue - done;
                return edesc->residue_stat;
        }

        /*
         * For SG operation we catch up with the last processed
         * status.
         */
        pset += edesc->processed_stat;

        for (i = edesc->processed_stat; i < edesc->processed; i++, pset++) {
                /*
                 * If we are inside this pset address range, we know
                 * this is the active one. Get the current delta and
                 * stop walking the psets.
                 */
                if (pos >= pset->addr && pos < pset->addr + pset->len)
                        return edesc->residue_stat - (pos - pset->addr);

                /* Otherwise mark it done and update residue_stat. */
                edesc->processed_stat++;
                edesc->residue_stat -= pset->len;
        }
        return edesc->residue_stat;
}

/* Check request completion status */
static enum dma_status edma_tx_status(struct dma_chan *chan,
                                      dma_cookie_t cookie,
                                      struct dma_tx_state *txstate)
{
        struct edma_chan *echan = to_edma_chan(chan);
        struct virt_dma_desc *vdesc;
        enum dma_status ret;
        unsigned long flags;

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

        spin_lock_irqsave(&echan->vchan.lock, flags);
        if (echan->edesc && echan->edesc->vdesc.tx.cookie == cookie)
                txstate->residue = edma_residue(echan->edesc);
        else if ((vdesc = vchan_find_desc(&echan->vchan, cookie)))
                txstate->residue = to_edma_desc(&vdesc->tx)->residue;
        spin_unlock_irqrestore(&echan->vchan.lock, flags);

        return ret;
}

static void __init edma_chan_init(struct edma_cc *ecc,
                                  struct dma_device *dma,
                                  struct edma_chan *echans)
{
        int i, j;

        for (i = 0; i < EDMA_CHANS; i++) {
                struct edma_chan *echan = &echans[i];
                echan->ch_num = EDMA_CTLR_CHAN(ecc->ctlr, i);
                echan->ecc = ecc;
                echan->vchan.desc_free = edma_desc_free;

                vchan_init(&echan->vchan, dma);

                INIT_LIST_HEAD(&echan->node);
                for (j = 0; j < EDMA_MAX_SLOTS; j++)
                        echan->slot[j] = -1;
        }
}

#define EDMA_DMA_BUSWIDTHS      (BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) | \
                                 BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) | \
                                 BIT(DMA_SLAVE_BUSWIDTH_3_BYTES) | \
                                 BIT(DMA_SLAVE_BUSWIDTH_4_BYTES))

static void edma_dma_init(struct edma_cc *ecc, struct dma_device *dma,
                          struct device *dev)
{
        dma->device_prep_slave_sg = edma_prep_slave_sg;
        dma->device_prep_dma_cyclic = edma_prep_dma_cyclic;
        dma->device_prep_dma_memcpy = edma_prep_dma_memcpy;
        dma->device_alloc_chan_resources = edma_alloc_chan_resources;
        dma->device_free_chan_resources = edma_free_chan_resources;
        dma->device_issue_pending = edma_issue_pending;
        dma->device_tx_status = edma_tx_status;
        dma->device_config = edma_slave_config;
        dma->device_pause = edma_dma_pause;
        dma->device_resume = edma_dma_resume;
        dma->device_terminate_all = edma_terminate_all;

        dma->src_addr_widths = EDMA_DMA_BUSWIDTHS;
        dma->dst_addr_widths = EDMA_DMA_BUSWIDTHS;
        dma->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
        dma->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;

        dma->dev = dev;

        /*
         * code using dma memcpy must make sure alignment of
         * length is at dma->copy_align boundary.
         */
        dma->copy_align = DMA_SLAVE_BUSWIDTH_4_BYTES;

        INIT_LIST_HEAD(&dma->channels);
}

static int edma_probe(struct platform_device *pdev)
{
        struct edma_cc *ecc;
        int ret;

        ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
        if (ret)
                return ret;

        ecc = devm_kzalloc(&pdev->dev, sizeof(*ecc), GFP_KERNEL);
        if (!ecc) {
                dev_err(&pdev->dev, "Can't allocate controller\n");
                return -ENOMEM;
        }

        ecc->ctlr = pdev->id;
        ecc->dummy_slot = edma_alloc_slot(ecc->ctlr, EDMA_SLOT_ANY);
        if (ecc->dummy_slot < 0) {
                dev_err(&pdev->dev, "Can't allocate PaRAM dummy slot\n");
                return ecc->dummy_slot;
        }

        dma_cap_zero(ecc->dma_slave.cap_mask);
        dma_cap_set(DMA_SLAVE, ecc->dma_slave.cap_mask);
        dma_cap_set(DMA_CYCLIC, ecc->dma_slave.cap_mask);
        dma_cap_set(DMA_MEMCPY, ecc->dma_slave.cap_mask);

        edma_dma_init(ecc, &ecc->dma_slave, &pdev->dev);

        edma_chan_init(ecc, &ecc->dma_slave, ecc->slave_chans);

        ret = dma_async_device_register(&ecc->dma_slave);
        if (ret)
                goto err_reg1;

        platform_set_drvdata(pdev, ecc);

        dev_info(&pdev->dev, "TI EDMA DMA engine driver\n");

        return 0;

err_reg1:
        edma_free_slot(ecc->dummy_slot);
        return ret;
}

static int edma_remove(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct edma_cc *ecc = dev_get_drvdata(dev);

        dma_async_device_unregister(&ecc->dma_slave);
        edma_free_slot(ecc->dummy_slot);

        return 0;
}

static struct platform_driver edma_driver = {
        .probe          = edma_probe,
        .remove         = edma_remove,
        .driver = {
                .name = "edma-dma-engine",
        },
};

bool edma_filter_fn(struct dma_chan *chan, void *param)
{
        if (chan->device->dev->driver == &edma_driver.driver) {
                struct edma_chan *echan = to_edma_chan(chan);
                unsigned ch_req = *(unsigned *)param;
                return ch_req == echan->ch_num;
        }
        return false;
}
EXPORT_SYMBOL(edma_filter_fn);

static int edma_init(void)
{
        return platform_driver_register(&edma_driver);
}
subsys_initcall(edma_init);

static void __exit edma_exit(void)
{
        platform_driver_unregister(&edma_driver);
}
module_exit(edma_exit);

MODULE_AUTHOR("Matt Porter <matt.porter@linaro.org>");
MODULE_DESCRIPTION("TI EDMA DMA engine driver");
MODULE_LICENSE("GPL v2");