Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial

[mirror_ubuntu-artful-kernel.git] / drivers / dma / at_hdmac.c

/*
 * Driver for the Atmel AHB DMA Controller (aka HDMA or DMAC on AT91 systems)
 *
 * Copyright (C) 2008 Atmel Corporation
 *
 * 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.
 *
 *
 * This supports the Atmel AHB DMA Controller found in several Atmel SoCs.
 * The only Atmel DMA Controller that is not covered by this driver is the one
 * found on AT91SAM9263.
 */

#include <linux/clk.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>

#include "at_hdmac_regs.h"
#include "dmaengine.h"

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

#define ATC_DEFAULT_CFG         (ATC_FIFOCFG_HALFFIFO)
#define ATC_DEFAULT_CTRLB       (ATC_SIF(AT_DMA_MEM_IF) \
                                |ATC_DIF(AT_DMA_MEM_IF))

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


/* prototypes */
static dma_cookie_t atc_tx_submit(struct dma_async_tx_descriptor *tx);


/*----------------------------------------------------------------------*/

static struct at_desc *atc_first_active(struct at_dma_chan *atchan)
{
        return list_first_entry(&atchan->active_list,
                                struct at_desc, desc_node);
}

static struct at_desc *atc_first_queued(struct at_dma_chan *atchan)
{
        return list_first_entry(&atchan->queue,
                                struct at_desc, desc_node);
}

/**
 * atc_alloc_descriptor - allocate and return an initialized descriptor
 * @chan: the channel to allocate descriptors for
 * @gfp_flags: GFP allocation flags
 *
 * Note: The ack-bit is positioned in the descriptor flag at creation time
 *       to make initial allocation more convenient. This bit will be cleared
 *       and control will be given to client at usage time (during
 *       preparation functions).
 */
static struct at_desc *atc_alloc_descriptor(struct dma_chan *chan,
                                            gfp_t gfp_flags)
{
        struct at_desc  *desc = NULL;
        struct at_dma   *atdma = to_at_dma(chan->device);
        dma_addr_t phys;

        desc = dma_pool_alloc(atdma->dma_desc_pool, gfp_flags, &phys);
        if (desc) {
                memset(desc, 0, sizeof(struct at_desc));
                INIT_LIST_HEAD(&desc->tx_list);
                dma_async_tx_descriptor_init(&desc->txd, chan);
                /* txd.flags will be overwritten in prep functions */
                desc->txd.flags = DMA_CTRL_ACK;
                desc->txd.tx_submit = atc_tx_submit;
                desc->txd.phys = phys;
        }

        return desc;
}

/**
 * atc_desc_get - get an unused descriptor from free_list
 * @atchan: channel we want a new descriptor for
 */
static struct at_desc *atc_desc_get(struct at_dma_chan *atchan)
{
        struct at_desc *desc, *_desc;
        struct at_desc *ret = NULL;
        unsigned long flags;
        unsigned int i = 0;
        LIST_HEAD(tmp_list);

        spin_lock_irqsave(&atchan->lock, flags);
        list_for_each_entry_safe(desc, _desc, &atchan->free_list, desc_node) {
                i++;
                if (async_tx_test_ack(&desc->txd)) {
                        list_del(&desc->desc_node);
                        ret = desc;
                        break;
                }
                dev_dbg(chan2dev(&atchan->chan_common),
                                "desc %p not ACKed\n", desc);
        }
        spin_unlock_irqrestore(&atchan->lock, flags);
        dev_vdbg(chan2dev(&atchan->chan_common),
                "scanned %u descriptors on freelist\n", i);

        /* no more descriptor available in initial pool: create one more */
        if (!ret) {
                ret = atc_alloc_descriptor(&atchan->chan_common, GFP_ATOMIC);
                if (ret) {
                        spin_lock_irqsave(&atchan->lock, flags);
                        atchan->descs_allocated++;
                        spin_unlock_irqrestore(&atchan->lock, flags);
                } else {
                        dev_err(chan2dev(&atchan->chan_common),
                                        "not enough descriptors available\n");
                }
        }

        return ret;
}

/**
 * atc_desc_put - move a descriptor, including any children, to the free list
 * @atchan: channel we work on
 * @desc: descriptor, at the head of a chain, to move to free list
 */
static void atc_desc_put(struct at_dma_chan *atchan, struct at_desc *desc)
{
        if (desc) {
                struct at_desc *child;
                unsigned long flags;

                spin_lock_irqsave(&atchan->lock, flags);
                list_for_each_entry(child, &desc->tx_list, desc_node)
                        dev_vdbg(chan2dev(&atchan->chan_common),
                                        "moving child desc %p to freelist\n",
                                        child);
                list_splice_init(&desc->tx_list, &atchan->free_list);
                dev_vdbg(chan2dev(&atchan->chan_common),
                         "moving desc %p to freelist\n", desc);
                list_add(&desc->desc_node, &atchan->free_list);
                spin_unlock_irqrestore(&atchan->lock, flags);
        }
}

/**
 * atc_desc_chain - build chain adding a descriptor
 * @first: address of first descriptor of the chain
 * @prev: address of previous descriptor of the chain
 * @desc: descriptor to queue
 *
 * Called from prep_* functions
 */
static void atc_desc_chain(struct at_desc **first, struct at_desc **prev,
                           struct at_desc *desc)
{
        if (!(*first)) {
                *first = desc;
        } else {
                /* inform the HW lli about chaining */
                (*prev)->lli.dscr = desc->txd.phys;
                /* insert the link descriptor to the LD ring */
                list_add_tail(&desc->desc_node,
                                &(*first)->tx_list);
        }
        *prev = desc;
}

/**
 * atc_dostart - starts the DMA engine for real
 * @atchan: the channel we want to start
 * @first: first descriptor in the list we want to begin with
 *
 * Called with atchan->lock held and bh disabled
 */
static void atc_dostart(struct at_dma_chan *atchan, struct at_desc *first)
{
        struct at_dma   *atdma = to_at_dma(atchan->chan_common.device);

        /* ASSERT:  channel is idle */
        if (atc_chan_is_enabled(atchan)) {
                dev_err(chan2dev(&atchan->chan_common),
                        "BUG: Attempted to start non-idle channel\n");
                dev_err(chan2dev(&atchan->chan_common),
                        "  channel: s0x%x d0x%x ctrl0x%x:0x%x l0x%x\n",
                        channel_readl(atchan, SADDR),
                        channel_readl(atchan, DADDR),
                        channel_readl(atchan, CTRLA),
                        channel_readl(atchan, CTRLB),
                        channel_readl(atchan, DSCR));

                /* The tasklet will hopefully advance the queue... */
                return;
        }

        vdbg_dump_regs(atchan);

        channel_writel(atchan, SADDR, 0);
        channel_writel(atchan, DADDR, 0);
        channel_writel(atchan, CTRLA, 0);
        channel_writel(atchan, CTRLB, 0);
        channel_writel(atchan, DSCR, first->txd.phys);
        dma_writel(atdma, CHER, atchan->mask);

        vdbg_dump_regs(atchan);
}

/**
 * atc_chain_complete - finish work for one transaction chain
 * @atchan: channel we work on
 * @desc: descriptor at the head of the chain we want do complete
 *
 * Called with atchan->lock held and bh disabled */
static void
atc_chain_complete(struct at_dma_chan *atchan, struct at_desc *desc)
{
        struct dma_async_tx_descriptor  *txd = &desc->txd;

        dev_vdbg(chan2dev(&atchan->chan_common),
                "descriptor %u complete\n", txd->cookie);

        /* mark the descriptor as complete for non cyclic cases only */
        if (!atc_chan_is_cyclic(atchan))
                dma_cookie_complete(txd);

        /* move children to free_list */
        list_splice_init(&desc->tx_list, &atchan->free_list);
        /* move myself to free_list */
        list_move(&desc->desc_node, &atchan->free_list);

        /* unmap dma addresses (not on slave channels) */
        if (!atchan->chan_common.private) {
                struct device *parent = chan2parent(&atchan->chan_common);
                if (!(txd->flags & DMA_COMPL_SKIP_DEST_UNMAP)) {
                        if (txd->flags & DMA_COMPL_DEST_UNMAP_SINGLE)
                                dma_unmap_single(parent,
                                                desc->lli.daddr,
                                                desc->len, DMA_FROM_DEVICE);
                        else
                                dma_unmap_page(parent,
                                                desc->lli.daddr,
                                                desc->len, DMA_FROM_DEVICE);
                }
                if (!(txd->flags & DMA_COMPL_SKIP_SRC_UNMAP)) {
                        if (txd->flags & DMA_COMPL_SRC_UNMAP_SINGLE)
                                dma_unmap_single(parent,
                                                desc->lli.saddr,
                                                desc->len, DMA_TO_DEVICE);
                        else
                                dma_unmap_page(parent,
                                                desc->lli.saddr,
                                                desc->len, DMA_TO_DEVICE);
                }
        }

        /* for cyclic transfers,
         * no need to replay callback function while stopping */
        if (!atc_chan_is_cyclic(atchan)) {
                dma_async_tx_callback   callback = txd->callback;
                void                    *param = txd->callback_param;

                /*
                 * The API requires that no submissions are done from a
                 * callback, so we don't need to drop the lock here
                 */
                if (callback)
                        callback(param);
        }

        dma_run_dependencies(txd);
}

/**
 * atc_complete_all - finish work for all transactions
 * @atchan: channel to complete transactions for
 *
 * Eventually submit queued descriptors if any
 *
 * Assume channel is idle while calling this function
 * Called with atchan->lock held and bh disabled
 */
static void atc_complete_all(struct at_dma_chan *atchan)
{
        struct at_desc *desc, *_desc;
        LIST_HEAD(list);

        dev_vdbg(chan2dev(&atchan->chan_common), "complete all\n");

        BUG_ON(atc_chan_is_enabled(atchan));

        /*
         * Submit queued descriptors ASAP, i.e. before we go through
         * the completed ones.
         */
        if (!list_empty(&atchan->queue))
                atc_dostart(atchan, atc_first_queued(atchan));
        /* empty active_list now it is completed */
        list_splice_init(&atchan->active_list, &list);
        /* empty queue list by moving descriptors (if any) to active_list */
        list_splice_init(&atchan->queue, &atchan->active_list);

        list_for_each_entry_safe(desc, _desc, &list, desc_node)
                atc_chain_complete(atchan, desc);
}

/**
 * atc_cleanup_descriptors - cleanup up finished descriptors in active_list
 * @atchan: channel to be cleaned up
 *
 * Called with atchan->lock held and bh disabled
 */
static void atc_cleanup_descriptors(struct at_dma_chan *atchan)
{
        struct at_desc  *desc, *_desc;
        struct at_desc  *child;

        dev_vdbg(chan2dev(&atchan->chan_common), "cleanup descriptors\n");

        list_for_each_entry_safe(desc, _desc, &atchan->active_list, desc_node) {
                if (!(desc->lli.ctrla & ATC_DONE))
                        /* This one is currently in progress */
                        return;

                list_for_each_entry(child, &desc->tx_list, desc_node)
                        if (!(child->lli.ctrla & ATC_DONE))
                                /* Currently in progress */
                                return;

                /*
                 * No descriptors so far seem to be in progress, i.e.
                 * this chain must be done.
                 */
                atc_chain_complete(atchan, desc);
        }
}

/**
 * atc_advance_work - at the end of a transaction, move forward
 * @atchan: channel where the transaction ended
 *
 * Called with atchan->lock held and bh disabled
 */
static void atc_advance_work(struct at_dma_chan *atchan)
{
        dev_vdbg(chan2dev(&atchan->chan_common), "advance_work\n");

        if (list_empty(&atchan->active_list) ||
            list_is_singular(&atchan->active_list)) {
                atc_complete_all(atchan);
        } else {
                atc_chain_complete(atchan, atc_first_active(atchan));
                /* advance work */
                atc_dostart(atchan, atc_first_active(atchan));
        }
}


/**
 * atc_handle_error - handle errors reported by DMA controller
 * @atchan: channel where error occurs
 *
 * Called with atchan->lock held and bh disabled
 */
static void atc_handle_error(struct at_dma_chan *atchan)
{
        struct at_desc *bad_desc;
        struct at_desc *child;

        /*
         * The descriptor currently at the head of the active list is
         * broked. Since we don't have any way to report errors, we'll
         * just have to scream loudly and try to carry on.
         */
        bad_desc = atc_first_active(atchan);
        list_del_init(&bad_desc->desc_node);

        /* As we are stopped, take advantage to push queued descriptors
         * in active_list */
        list_splice_init(&atchan->queue, atchan->active_list.prev);

        /* Try to restart the controller */
        if (!list_empty(&atchan->active_list))
                atc_dostart(atchan, atc_first_active(atchan));

        /*
         * KERN_CRITICAL may seem harsh, but since this only happens
         * when someone submits a bad physical address in a
         * descriptor, we should consider ourselves lucky that the
         * controller flagged an error instead of scribbling over
         * random memory locations.
         */
        dev_crit(chan2dev(&atchan->chan_common),
                        "Bad descriptor submitted for DMA!\n");
        dev_crit(chan2dev(&atchan->chan_common),
                        "  cookie: %d\n", bad_desc->txd.cookie);
        atc_dump_lli(atchan, &bad_desc->lli);
        list_for_each_entry(child, &bad_desc->tx_list, desc_node)
                atc_dump_lli(atchan, &child->lli);

        /* Pretend the descriptor completed successfully */
        atc_chain_complete(atchan, bad_desc);
}

/**
 * atc_handle_cyclic - at the end of a period, run callback function
 * @atchan: channel used for cyclic operations
 *
 * Called with atchan->lock held and bh disabled
 */
static void atc_handle_cyclic(struct at_dma_chan *atchan)
{
        struct at_desc                  *first = atc_first_active(atchan);
        struct dma_async_tx_descriptor  *txd = &first->txd;
        dma_async_tx_callback           callback = txd->callback;
        void                            *param = txd->callback_param;

        dev_vdbg(chan2dev(&atchan->chan_common),
                        "new cyclic period llp 0x%08x\n",
                        channel_readl(atchan, DSCR));

        if (callback)
                callback(param);
}

/*--  IRQ & Tasklet  ---------------------------------------------------*/

static void atc_tasklet(unsigned long data)
{
        struct at_dma_chan *atchan = (struct at_dma_chan *)data;
        unsigned long flags;

        spin_lock_irqsave(&atchan->lock, flags);
        if (test_and_clear_bit(ATC_IS_ERROR, &atchan->status))
                atc_handle_error(atchan);
        else if (atc_chan_is_cyclic(atchan))
                atc_handle_cyclic(atchan);
        else
                atc_advance_work(atchan);

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

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

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

                if (!pending)
                        break;

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

                for (i = 0; i < atdma->dma_common.chancnt; i++) {
                        atchan = &atdma->chan[i];
                        if (pending & (AT_DMA_BTC(i) | AT_DMA_ERR(i))) {
                                if (pending & AT_DMA_ERR(i)) {
                                        /* Disable channel on AHB error */
                                        dma_writel(atdma, CHDR,
                                                AT_DMA_RES(i) | atchan->mask);
                                        /* Give information to tasklet */
                                        set_bit(ATC_IS_ERROR, &atchan->status);
                                }
                                tasklet_schedule(&atchan->tasklet);
                                ret = IRQ_HANDLED;
                        }
                }

        } while (pending);

        return ret;
}


/*--  DMA Engine API  --------------------------------------------------*/

/**
 * atc_tx_submit - set the prepared descriptor(s) to be executed by the engine
 * @desc: descriptor at the head of the transaction chain
 *
 * Queue chain if DMA engine is working already
 *
 * Cookie increment and adding to active_list or queue must be atomic
 */
static dma_cookie_t atc_tx_submit(struct dma_async_tx_descriptor *tx)
{
        struct at_desc          *desc = txd_to_at_desc(tx);
        struct at_dma_chan      *atchan = to_at_dma_chan(tx->chan);
        dma_cookie_t            cookie;
        unsigned long           flags;

        spin_lock_irqsave(&atchan->lock, flags);
        cookie = dma_cookie_assign(tx);

        if (list_empty(&atchan->active_list)) {
                dev_vdbg(chan2dev(tx->chan), "tx_submit: started %u\n",
                                desc->txd.cookie);
                atc_dostart(atchan, desc);
                list_add_tail(&desc->desc_node, &atchan->active_list);
        } else {
                dev_vdbg(chan2dev(tx->chan), "tx_submit: queued %u\n",
                                desc->txd.cookie);
                list_add_tail(&desc->desc_node, &atchan->queue);
        }

        spin_unlock_irqrestore(&atchan->lock, flags);

        return cookie;
}

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

        dev_vdbg(chan2dev(chan), "prep_dma_memcpy: d0x%x s0x%x l0x%zx f0x%lx\n",
                        dest, src, len, flags);

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

        ctrlb =   ATC_DEFAULT_CTRLB | ATC_IEN
                | ATC_SRC_ADDR_MODE_INCR
                | ATC_DST_ADDR_MODE_INCR
                | ATC_FC_MEM2MEM;

        /*
         * We can be a lot more clever here, but this should take care
         * of the most common optimization.
         */
        if (!((src | dest  | len) & 3)) {
                ctrla = ATC_SRC_WIDTH_WORD | ATC_DST_WIDTH_WORD;
                src_width = dst_width = 2;
        } else if (!((src | dest | len) & 1)) {
                ctrla = ATC_SRC_WIDTH_HALFWORD | ATC_DST_WIDTH_HALFWORD;
                src_width = dst_width = 1;
        } else {
                ctrla = ATC_SRC_WIDTH_BYTE | ATC_DST_WIDTH_BYTE;
                src_width = dst_width = 0;
        }

        for (offset = 0; offset < len; offset += xfer_count << src_width) {
                xfer_count = min_t(size_t, (len - offset) >> src_width,
                                ATC_BTSIZE_MAX);

                desc = atc_desc_get(atchan);
                if (!desc)
                        goto err_desc_get;

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

                desc->txd.cookie = 0;

                atc_desc_chain(&first, &prev, desc);
        }

        /* First descriptor of the chain embedds additional information */
        first->txd.cookie = -EBUSY;
        first->len = len;

        /* set end-of-link to the last link descriptor of list*/
        set_desc_eol(desc);

        first->txd.flags = flags; /* client is in control of this ack */

        return &first->txd;

err_desc_get:
        atc_desc_put(atchan, first);
        return NULL;
}


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

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

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

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

        switch (direction) {
        case DMA_MEM_TO_DEV:
                reg_width = convert_buswidth(sconfig->dst_addr_width);
                ctrla |=  ATC_DST_WIDTH(reg_width);
                ctrlb |=  ATC_DST_ADDR_MODE_FIXED
                        | ATC_SRC_ADDR_MODE_INCR
                        | ATC_FC_MEM2PER
                        | ATC_SIF(AT_DMA_MEM_IF) | ATC_DIF(AT_DMA_PER_IF);
                reg = sconfig->dst_addr;
                for_each_sg(sgl, sg, sg_len, i) {
                        struct at_desc  *desc;
                        u32             len;
                        u32             mem;

                        desc = atc_desc_get(atchan);
                        if (!desc)
                                goto err_desc_get;

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

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

                        atc_desc_chain(&first, &prev, desc);
                        total_len += len;
                }
                break;
        case DMA_DEV_TO_MEM:
                reg_width = convert_buswidth(sconfig->src_addr_width);
                ctrla |=  ATC_SRC_WIDTH(reg_width);
                ctrlb |=  ATC_DST_ADDR_MODE_INCR
                        | ATC_SRC_ADDR_MODE_FIXED
                        | ATC_FC_PER2MEM
                        | ATC_SIF(AT_DMA_PER_IF) | ATC_DIF(AT_DMA_MEM_IF);

                reg = sconfig->src_addr;
                for_each_sg(sgl, sg, sg_len, i) {
                        struct at_desc  *desc;
                        u32             len;
                        u32             mem;

                        desc = atc_desc_get(atchan);
                        if (!desc)
                                goto err_desc_get;

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

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

                        atc_desc_chain(&first, &prev, desc);
                        total_len += len;
                }
                break;
        default:
                return NULL;
        }

        /* set end-of-link to the last link descriptor of list*/
        set_desc_eol(prev);

        /* First descriptor of the chain embedds additional information */
        first->txd.cookie = -EBUSY;
        first->len = total_len;

        /* first link descriptor of list is responsible of flags */
        first->txd.flags = flags; /* client is in control of this ack */

        return &first->txd;

err_desc_get:
        dev_err(chan2dev(chan), "not enough descriptors available\n");
err:
        atc_desc_put(atchan, first);
        return NULL;
}

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

        return 0;

err_out:
        return -EINVAL;
}

/**
 * atc_dma_cyclic_fill_desc - Fill one period descriptor
 */
static int
atc_dma_cyclic_fill_desc(struct dma_chan *chan, struct at_desc *desc,
                unsigned int period_index, dma_addr_t buf_addr,
                unsigned int reg_width, size_t period_len,
                enum dma_transfer_direction direction)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct dma_slave_config *sconfig = &atchan->dma_sconfig;
        u32                     ctrla;

        /* prepare common CRTLA value */
        ctrla =   ATC_SCSIZE(sconfig->src_maxburst)
                | ATC_DCSIZE(sconfig->dst_maxburst)
                | ATC_DST_WIDTH(reg_width)
                | ATC_SRC_WIDTH(reg_width)
                | period_len >> reg_width;

        switch (direction) {
        case DMA_MEM_TO_DEV:
                desc->lli.saddr = buf_addr + (period_len * period_index);
                desc->lli.daddr = sconfig->dst_addr;
                desc->lli.ctrla = ctrla;
                desc->lli.ctrlb = ATC_DST_ADDR_MODE_FIXED
                                | ATC_SRC_ADDR_MODE_INCR
                                | ATC_FC_MEM2PER
                                | ATC_SIF(AT_DMA_MEM_IF)
                                | ATC_DIF(AT_DMA_PER_IF);
                break;

        case DMA_DEV_TO_MEM:
                desc->lli.saddr = sconfig->src_addr;
                desc->lli.daddr = buf_addr + (period_len * period_index);
                desc->lli.ctrla = ctrla;
                desc->lli.ctrlb = ATC_DST_ADDR_MODE_INCR
                                | ATC_SRC_ADDR_MODE_FIXED
                                | ATC_FC_PER2MEM
                                | ATC_SIF(AT_DMA_PER_IF)
                                | ATC_DIF(AT_DMA_MEM_IF);
                break;

        default:
                return -EINVAL;
        }

        return 0;
}

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

        dev_vdbg(chan2dev(chan), "prep_dma_cyclic: %s buf@0x%08x - %d (%d/%d)\n",
                        direction == DMA_MEM_TO_DEV ? "TO DEVICE" : "FROM DEVICE",
                        buf_addr,
                        periods, buf_len, period_len);

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

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

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

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

        /* build cyclic linked list */
        for (i = 0; i < periods; i++) {
                struct at_desc  *desc;

                desc = atc_desc_get(atchan);
                if (!desc)
                        goto err_desc_get;

                if (atc_dma_cyclic_fill_desc(chan, desc, i, buf_addr,
                                             reg_width, period_len, direction))
                        goto err_desc_get;

                atc_desc_chain(&first, &prev, desc);
        }

        /* lets make a cyclic list */
        prev->lli.dscr = first->txd.phys;

        /* First descriptor of the chain embedds additional information */
        first->txd.cookie = -EBUSY;
        first->len = buf_len;

        return &first->txd;

err_desc_get:
        dev_err(chan2dev(chan), "not enough descriptors available\n");
        atc_desc_put(atchan, first);
err_out:
        clear_bit(ATC_IS_CYCLIC, &atchan->status);
        return NULL;
}

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

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

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

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

        return 0;
}


static int atc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
                       unsigned long arg)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        int                     chan_id = atchan->chan_common.chan_id;
        unsigned long           flags;

        LIST_HEAD(list);

        dev_vdbg(chan2dev(chan), "atc_control (%d)\n", cmd);

        if (cmd == DMA_PAUSE) {
                spin_lock_irqsave(&atchan->lock, flags);

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

                spin_unlock_irqrestore(&atchan->lock, flags);
        } else if (cmd == DMA_RESUME) {
                if (!atc_chan_is_paused(atchan))
                        return 0;

                spin_lock_irqsave(&atchan->lock, flags);

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

                spin_unlock_irqrestore(&atchan->lock, flags);
        } else if (cmd == DMA_TERMINATE_ALL) {
                struct at_desc  *desc, *_desc;
                /*
                 * This is only called when something went wrong elsewhere, so
                 * we don't really care about the data. Just disable the
                 * channel. We still have to poll the channel enable bit due
                 * to AHB/HSB limitations.
                 */
                spin_lock_irqsave(&atchan->lock, flags);

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

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

                /* active_list entries will end up before queued entries */
                list_splice_init(&atchan->queue, &list);
                list_splice_init(&atchan->active_list, &list);

                /* Flush all pending and queued descriptors */
                list_for_each_entry_safe(desc, _desc, &list, desc_node)
                        atc_chain_complete(atchan, desc);

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

                spin_unlock_irqrestore(&atchan->lock, flags);
        } else if (cmd == DMA_SLAVE_CONFIG) {
                return set_runtime_config(chan, (struct dma_slave_config *)arg);
        } else {
                return -ENXIO;
        }

        return 0;
}

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

        spin_lock_irqsave(&atchan->lock, flags);

        ret = dma_cookie_status(chan, cookie, txstate);
        if (ret != DMA_SUCCESS) {
                atc_cleanup_descriptors(atchan);

                ret = dma_cookie_status(chan, cookie, txstate);
        }

        last_complete = chan->completed_cookie;
        last_used = chan->cookie;

        spin_unlock_irqrestore(&atchan->lock, flags);

        if (ret != DMA_SUCCESS)
                dma_set_residue(txstate, atc_first_active(atchan)->len);

        if (atc_chan_is_paused(atchan))
                ret = DMA_PAUSED;

        dev_vdbg(chan2dev(chan), "tx_status %d: cookie = %d (d%d, u%d)\n",
                 ret, cookie, last_complete ? last_complete : 0,
                 last_used ? last_used : 0);

        return ret;
}

/**
 * atc_issue_pending - try to finish work
 * @chan: target DMA channel
 */
static void atc_issue_pending(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        unsigned long           flags;

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

        /* Not needed for cyclic transfers */
        if (atc_chan_is_cyclic(atchan))
                return;

        spin_lock_irqsave(&atchan->lock, flags);
        if (!atc_chan_is_enabled(atchan)) {
                atc_advance_work(atchan);
        }
        spin_unlock_irqrestore(&atchan->lock, flags);
}

/**
 * atc_alloc_chan_resources - allocate resources for DMA channel
 * @chan: allocate descriptor resources for this channel
 * @client: current client requesting the channel be ready for requests
 *
 * return - the number of allocated descriptors
 */
static int atc_alloc_chan_resources(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_desc          *desc;
        struct at_dma_slave     *atslave;
        unsigned long           flags;
        int                     i;
        u32                     cfg;
        LIST_HEAD(tmp_list);

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

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

        cfg = ATC_DEFAULT_CFG;

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

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

        /* have we already been set up?
         * reconfigure channel but no need to reallocate descriptors */
        if (!list_empty(&atchan->free_list))
                return atchan->descs_allocated;

        /* Allocate initial pool of descriptors */
        for (i = 0; i < init_nr_desc_per_channel; i++) {
                desc = atc_alloc_descriptor(chan, GFP_KERNEL);
                if (!desc) {
                        dev_err(atdma->dma_common.dev,
                                "Only %d initial descriptors\n", i);
                        break;
                }
                list_add_tail(&desc->desc_node, &tmp_list);
        }

        spin_lock_irqsave(&atchan->lock, flags);
        atchan->descs_allocated = i;
        list_splice(&tmp_list, &atchan->free_list);
        dma_cookie_init(chan);
        spin_unlock_irqrestore(&atchan->lock, flags);

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

        dev_dbg(chan2dev(chan),
                "alloc_chan_resources: allocated %d descriptors\n",
                atchan->descs_allocated);

        return atchan->descs_allocated;
}

/**
 * atc_free_chan_resources - free all channel resources
 * @chan: DMA channel
 */
static void atc_free_chan_resources(struct dma_chan *chan)
{
        struct at_dma_chan      *atchan = to_at_dma_chan(chan);
        struct at_dma           *atdma = to_at_dma(chan->device);
        struct at_desc          *desc, *_desc;
        LIST_HEAD(list);

        dev_dbg(chan2dev(chan), "free_chan_resources: (descs allocated=%u)\n",
                atchan->descs_allocated);

        /* ASSERT:  channel is idle */
        BUG_ON(!list_empty(&atchan->active_list));
        BUG_ON(!list_empty(&atchan->queue));
        BUG_ON(atc_chan_is_enabled(atchan));

        list_for_each_entry_safe(desc, _desc, &atchan->free_list, desc_node) {
                dev_vdbg(chan2dev(chan), "  freeing descriptor %p\n", desc);
                list_del(&desc->desc_node);
                /* free link descriptor */
                dma_pool_free(atdma->dma_desc_pool, desc, desc->txd.phys);
        }
        list_splice_init(&atchan->free_list, &list);
        atchan->descs_allocated = 0;
        atchan->status = 0;

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


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

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

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

MODULE_DEVICE_TABLE(of, atmel_dma_dt_ids);
#endif

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

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

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

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

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

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

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

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

        io = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!io)
                return -EINVAL;

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

        size = sizeof(struct at_dma);
        size += plat_dat->nr_channels * sizeof(struct at_dma_chan);
        atdma = kzalloc(size, GFP_KERNEL);
        if (!atdma)
                return -ENOMEM;

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

        size = resource_size(io);
        if (!request_mem_region(io->start, size, pdev->dev.driver->name)) {
                err = -EBUSY;
                goto err_kfree;
        }

        atdma->regs = ioremap(io->start, size);
        if (!atdma->regs) {
                err = -ENOMEM;
                goto err_release_r;
        }

        atdma->clk = clk_get(&pdev->dev, "dma_clk");
        if (IS_ERR(atdma->clk)) {
                err = PTR_ERR(atdma->clk);
                goto err_clk;
        }
        clk_enable(atdma->clk);

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

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

        platform_set_drvdata(pdev, atdma);

        /* create a pool of consistent memory blocks for hardware descriptors */
        atdma->dma_desc_pool = dma_pool_create("at_hdmac_desc_pool",
                        &pdev->dev, sizeof(struct at_desc),
                        4 /* word alignment */, 0);
        if (!atdma->dma_desc_pool) {
                dev_err(&pdev->dev, "No memory for descriptors dma pool\n");
                err = -ENOMEM;
                goto err_pool_create;
        }

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

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

                atchan->chan_common.device = &atdma->dma_common;
                dma_cookie_init(&atchan->chan_common);
                list_add_tail(&atchan->chan_common.device_node,
                                &atdma->dma_common.channels);

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

                INIT_LIST_HEAD(&atchan->active_list);
                INIT_LIST_HEAD(&atchan->queue);
                INIT_LIST_HEAD(&atchan->free_list);

                tasklet_init(&atchan->tasklet, atc_tasklet,
                                (unsigned long)atchan);
                atc_enable_chan_irq(atdma, i);
        }

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

        /* set prep routines based on capability */
        if (dma_has_cap(DMA_MEMCPY, atdma->dma_common.cap_mask))
                atdma->dma_common.device_prep_dma_memcpy = atc_prep_dma_memcpy;

        if (dma_has_cap(DMA_SLAVE, atdma->dma_common.cap_mask)) {
                atdma->dma_common.device_prep_slave_sg = atc_prep_slave_sg;
                /* controller can do slave DMA: can trigger cyclic transfers */
                dma_cap_set(DMA_CYCLIC, atdma->dma_common.cap_mask);
                atdma->dma_common.device_prep_dma_cyclic = atc_prep_dma_cyclic;
                atdma->dma_common.device_control = atc_control;
        }

        dma_writel(atdma, EN, AT_DMA_ENABLE);

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

        dma_async_device_register(&atdma->dma_common);

        return 0;

err_pool_create:
        platform_set_drvdata(pdev, NULL);
        free_irq(platform_get_irq(pdev, 0), atdma);
err_irq:
        clk_disable(atdma->clk);
        clk_put(atdma->clk);
err_clk:
        iounmap(atdma->regs);
        atdma->regs = NULL;
err_release_r:
        release_mem_region(io->start, size);
err_kfree:
        kfree(atdma);
        return err;
}

static int __exit at_dma_remove(struct platform_device *pdev)
{
        struct at_dma           *atdma = platform_get_drvdata(pdev);
        struct dma_chan         *chan, *_chan;
        struct resource         *io;

        at_dma_off(atdma);
        dma_async_device_unregister(&atdma->dma_common);

        dma_pool_destroy(atdma->dma_desc_pool);
        platform_set_drvdata(pdev, NULL);
        free_irq(platform_get_irq(pdev, 0), atdma);

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

                /* Disable interrupts */
                atc_disable_chan_irq(atdma, chan->chan_id);
                tasklet_disable(&atchan->tasklet);

                tasklet_kill(&atchan->tasklet);
                list_del(&chan->device_node);
        }

        clk_disable(atdma->clk);
        clk_put(atdma->clk);

        iounmap(atdma->regs);
        atdma->regs = NULL;

        io = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        release_mem_region(io->start, resource_size(io));

        kfree(atdma);

        return 0;
}

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

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

static int at_dma_prepare(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct at_dma *atdma = platform_get_drvdata(pdev);
        struct dma_chan *chan, *_chan;

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

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

        /* Channel should be paused by user
         * do it anyway even if it is not done already */
        if (!atc_chan_is_paused(atchan)) {
                dev_warn(chan2dev(chan),
                "cyclic channel not paused, should be done by channel user\n");
                atc_control(chan, DMA_PAUSE, 0);
        }

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

        vdbg_dump_regs(atchan);
}

static int at_dma_suspend_noirq(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct at_dma *atdma = platform_get_drvdata(pdev);
        struct dma_chan *chan, *_chan;

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

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

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

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

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

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

        vdbg_dump_regs(atchan);
}

static int at_dma_resume_noirq(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct at_dma *atdma = platform_get_drvdata(pdev);
        struct dma_chan *chan, *_chan;

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

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

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

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

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

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

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

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

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