dmaengine: dw: introduce dw_dma_on() helper

[mirror_ubuntu-zesty-kernel.git] / drivers / dma / fsldma.c

/*
 * Freescale MPC85xx, MPC83xx DMA Engine support
 *
 * Copyright (C) 2007-2010 Freescale Semiconductor, Inc. All rights reserved.
 *
 * Author:
 *   Zhang Wei <wei.zhang@freescale.com>, Jul 2007
 *   Ebony Zhu <ebony.zhu@freescale.com>, May 2007
 *
 * Description:
 *   DMA engine driver for Freescale MPC8540 DMA controller, which is
 *   also fit for MPC8560, MPC8555, MPC8548, MPC8641, and etc.
 *   The support for MPC8349 DMA controller is also added.
 *
 * This driver instructs the DMA controller to issue the PCI Read Multiple
 * command for PCI read operations, instead of using the default PCI Read Line
 * command. Please be aware that this setting may result in read pre-fetching
 * on some platforms.
 *
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/dmaengine.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_platform.h>

#include "dmaengine.h"
#include "fsldma.h"

#define chan_dbg(chan, fmt, arg...)                                     \
        dev_dbg(chan->dev, "%s: " fmt, chan->name, ##arg)
#define chan_err(chan, fmt, arg...)                                     \
        dev_err(chan->dev, "%s: " fmt, chan->name, ##arg)

static const char msg_ld_oom[] = "No free memory for link descriptor";

/*
 * Register Helpers
 */

static void set_sr(struct fsldma_chan *chan, u32 val)
{
        DMA_OUT(chan, &chan->regs->sr, val, 32);
}

static u32 get_sr(struct fsldma_chan *chan)
{
        return DMA_IN(chan, &chan->regs->sr, 32);
}

static void set_mr(struct fsldma_chan *chan, u32 val)
{
        DMA_OUT(chan, &chan->regs->mr, val, 32);
}

static u32 get_mr(struct fsldma_chan *chan)
{
        return DMA_IN(chan, &chan->regs->mr, 32);
}

static void set_cdar(struct fsldma_chan *chan, dma_addr_t addr)
{
        DMA_OUT(chan, &chan->regs->cdar, addr | FSL_DMA_SNEN, 64);
}

static dma_addr_t get_cdar(struct fsldma_chan *chan)
{
        return DMA_IN(chan, &chan->regs->cdar, 64) & ~FSL_DMA_SNEN;
}

static void set_bcr(struct fsldma_chan *chan, u32 val)
{
        DMA_OUT(chan, &chan->regs->bcr, val, 32);
}

static u32 get_bcr(struct fsldma_chan *chan)
{
        return DMA_IN(chan, &chan->regs->bcr, 32);
}

/*
 * Descriptor Helpers
 */

static void set_desc_cnt(struct fsldma_chan *chan,
                                struct fsl_dma_ld_hw *hw, u32 count)
{
        hw->count = CPU_TO_DMA(chan, count, 32);
}

static void set_desc_src(struct fsldma_chan *chan,
                         struct fsl_dma_ld_hw *hw, dma_addr_t src)
{
        u64 snoop_bits;

        snoop_bits = ((chan->feature & FSL_DMA_IP_MASK) == FSL_DMA_IP_85XX)
                ? ((u64)FSL_DMA_SATR_SREADTYPE_SNOOP_READ << 32) : 0;
        hw->src_addr = CPU_TO_DMA(chan, snoop_bits | src, 64);
}

static void set_desc_dst(struct fsldma_chan *chan,
                         struct fsl_dma_ld_hw *hw, dma_addr_t dst)
{
        u64 snoop_bits;

        snoop_bits = ((chan->feature & FSL_DMA_IP_MASK) == FSL_DMA_IP_85XX)
                ? ((u64)FSL_DMA_DATR_DWRITETYPE_SNOOP_WRITE << 32) : 0;
        hw->dst_addr = CPU_TO_DMA(chan, snoop_bits | dst, 64);
}

static void set_desc_next(struct fsldma_chan *chan,
                          struct fsl_dma_ld_hw *hw, dma_addr_t next)
{
        u64 snoop_bits;

        snoop_bits = ((chan->feature & FSL_DMA_IP_MASK) == FSL_DMA_IP_83XX)
                ? FSL_DMA_SNEN : 0;
        hw->next_ln_addr = CPU_TO_DMA(chan, snoop_bits | next, 64);
}

static void set_ld_eol(struct fsldma_chan *chan, struct fsl_desc_sw *desc)
{
        u64 snoop_bits;

        snoop_bits = ((chan->feature & FSL_DMA_IP_MASK) == FSL_DMA_IP_83XX)
                ? FSL_DMA_SNEN : 0;

        desc->hw.next_ln_addr = CPU_TO_DMA(chan,
                DMA_TO_CPU(chan, desc->hw.next_ln_addr, 64) | FSL_DMA_EOL
                        | snoop_bits, 64);
}

/*
 * DMA Engine Hardware Control Helpers
 */

static void dma_init(struct fsldma_chan *chan)
{
        /* Reset the channel */
        set_mr(chan, 0);

        switch (chan->feature & FSL_DMA_IP_MASK) {
        case FSL_DMA_IP_85XX:
                /* Set the channel to below modes:
                 * EIE - Error interrupt enable
                 * EOLNIE - End of links interrupt enable
                 * BWC - Bandwidth sharing among channels
                 */
                set_mr(chan, FSL_DMA_MR_BWC | FSL_DMA_MR_EIE
                        | FSL_DMA_MR_EOLNIE);
                break;
        case FSL_DMA_IP_83XX:
                /* Set the channel to below modes:
                 * EOTIE - End-of-transfer interrupt enable
                 * PRC_RM - PCI read multiple
                 */
                set_mr(chan, FSL_DMA_MR_EOTIE | FSL_DMA_MR_PRC_RM);
                break;
        }
}

static int dma_is_idle(struct fsldma_chan *chan)
{
        u32 sr = get_sr(chan);
        return (!(sr & FSL_DMA_SR_CB)) || (sr & FSL_DMA_SR_CH);
}

/*
 * Start the DMA controller
 *
 * Preconditions:
 * - the CDAR register must point to the start descriptor
 * - the MRn[CS] bit must be cleared
 */
static void dma_start(struct fsldma_chan *chan)
{
        u32 mode;

        mode = get_mr(chan);

        if (chan->feature & FSL_DMA_CHAN_PAUSE_EXT) {
                set_bcr(chan, 0);
                mode |= FSL_DMA_MR_EMP_EN;
        } else {
                mode &= ~FSL_DMA_MR_EMP_EN;
        }

        if (chan->feature & FSL_DMA_CHAN_START_EXT) {
                mode |= FSL_DMA_MR_EMS_EN;
        } else {
                mode &= ~FSL_DMA_MR_EMS_EN;
                mode |= FSL_DMA_MR_CS;
        }

        set_mr(chan, mode);
}

static void dma_halt(struct fsldma_chan *chan)
{
        u32 mode;
        int i;

        /* read the mode register */
        mode = get_mr(chan);

        /*
         * The 85xx controller supports channel abort, which will stop
         * the current transfer. On 83xx, this bit is the transfer error
         * mask bit, which should not be changed.
         */
        if ((chan->feature & FSL_DMA_IP_MASK) == FSL_DMA_IP_85XX) {
                mode |= FSL_DMA_MR_CA;
                set_mr(chan, mode);

                mode &= ~FSL_DMA_MR_CA;
        }

        /* stop the DMA controller */
        mode &= ~(FSL_DMA_MR_CS | FSL_DMA_MR_EMS_EN);
        set_mr(chan, mode);

        /* wait for the DMA controller to become idle */
        for (i = 0; i < 100; i++) {
                if (dma_is_idle(chan))
                        return;

                udelay(10);
        }

        if (!dma_is_idle(chan))
                chan_err(chan, "DMA halt timeout!\n");
}

/**
 * fsl_chan_set_src_loop_size - Set source address hold transfer size
 * @chan : Freescale DMA channel
 * @size     : Address loop size, 0 for disable loop
 *
 * The set source address hold transfer size. The source
 * address hold or loop transfer size is when the DMA transfer
 * data from source address (SA), if the loop size is 4, the DMA will
 * read data from SA, SA + 1, SA + 2, SA + 3, then loop back to SA,
 * SA + 1 ... and so on.
 */
static void fsl_chan_set_src_loop_size(struct fsldma_chan *chan, int size)
{
        u32 mode;

        mode = get_mr(chan);

        switch (size) {
        case 0:
                mode &= ~FSL_DMA_MR_SAHE;
                break;
        case 1:
        case 2:
        case 4:
        case 8:
                mode |= FSL_DMA_MR_SAHE | (__ilog2(size) << 14);
                break;
        }

        set_mr(chan, mode);
}

/**
 * fsl_chan_set_dst_loop_size - Set destination address hold transfer size
 * @chan : Freescale DMA channel
 * @size     : Address loop size, 0 for disable loop
 *
 * The set destination address hold transfer size. The destination
 * address hold or loop transfer size is when the DMA transfer
 * data to destination address (TA), if the loop size is 4, the DMA will
 * write data to TA, TA + 1, TA + 2, TA + 3, then loop back to TA,
 * TA + 1 ... and so on.
 */
static void fsl_chan_set_dst_loop_size(struct fsldma_chan *chan, int size)
{
        u32 mode;

        mode = get_mr(chan);

        switch (size) {
        case 0:
                mode &= ~FSL_DMA_MR_DAHE;
                break;
        case 1:
        case 2:
        case 4:
        case 8:
                mode |= FSL_DMA_MR_DAHE | (__ilog2(size) << 16);
                break;
        }

        set_mr(chan, mode);
}

/**
 * fsl_chan_set_request_count - Set DMA Request Count for external control
 * @chan : Freescale DMA channel
 * @size     : Number of bytes to transfer in a single request
 *
 * The Freescale DMA channel can be controlled by the external signal DREQ#.
 * The DMA request count is how many bytes are allowed to transfer before
 * pausing the channel, after which a new assertion of DREQ# resumes channel
 * operation.
 *
 * A size of 0 disables external pause control. The maximum size is 1024.
 */
static void fsl_chan_set_request_count(struct fsldma_chan *chan, int size)
{
        u32 mode;

        BUG_ON(size > 1024);

        mode = get_mr(chan);
        mode |= (__ilog2(size) << 24) & 0x0f000000;

        set_mr(chan, mode);
}

/**
 * fsl_chan_toggle_ext_pause - Toggle channel external pause status
 * @chan : Freescale DMA channel
 * @enable   : 0 is disabled, 1 is enabled.
 *
 * The Freescale DMA channel can be controlled by the external signal DREQ#.
 * The DMA Request Count feature should be used in addition to this feature
 * to set the number of bytes to transfer before pausing the channel.
 */
static void fsl_chan_toggle_ext_pause(struct fsldma_chan *chan, int enable)
{
        if (enable)
                chan->feature |= FSL_DMA_CHAN_PAUSE_EXT;
        else
                chan->feature &= ~FSL_DMA_CHAN_PAUSE_EXT;
}

/**
 * fsl_chan_toggle_ext_start - Toggle channel external start status
 * @chan : Freescale DMA channel
 * @enable   : 0 is disabled, 1 is enabled.
 *
 * If enable the external start, the channel can be started by an
 * external DMA start pin. So the dma_start() does not start the
 * transfer immediately. The DMA channel will wait for the
 * control pin asserted.
 */
static void fsl_chan_toggle_ext_start(struct fsldma_chan *chan, int enable)
{
        if (enable)
                chan->feature |= FSL_DMA_CHAN_START_EXT;
        else
                chan->feature &= ~FSL_DMA_CHAN_START_EXT;
}

static void append_ld_queue(struct fsldma_chan *chan, struct fsl_desc_sw *desc)
{
        struct fsl_desc_sw *tail = to_fsl_desc(chan->ld_pending.prev);

        if (list_empty(&chan->ld_pending))
                goto out_splice;

        /*
         * Add the hardware descriptor to the chain of hardware descriptors
         * that already exists in memory.
         *
         * This will un-set the EOL bit of the existing transaction, and the
         * last link in this transaction will become the EOL descriptor.
         */
        set_desc_next(chan, &tail->hw, desc->async_tx.phys);

        /*
         * Add the software descriptor and all children to the list
         * of pending transactions
         */
out_splice:
        list_splice_tail_init(&desc->tx_list, &chan->ld_pending);
}

static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
{
        struct fsldma_chan *chan = to_fsl_chan(tx->chan);
        struct fsl_desc_sw *desc = tx_to_fsl_desc(tx);
        struct fsl_desc_sw *child;
        dma_cookie_t cookie = -EINVAL;

        spin_lock_bh(&chan->desc_lock);

#ifdef CONFIG_PM
        if (unlikely(chan->pm_state != RUNNING)) {
                chan_dbg(chan, "cannot submit due to suspend\n");
                spin_unlock_bh(&chan->desc_lock);
                return -1;
        }
#endif

        /*
         * assign cookies to all of the software descriptors
         * that make up this transaction
         */
        list_for_each_entry(child, &desc->tx_list, node) {
                cookie = dma_cookie_assign(&child->async_tx);
        }

        /* put this transaction onto the tail of the pending queue */
        append_ld_queue(chan, desc);

        spin_unlock_bh(&chan->desc_lock);

        return cookie;
}

/**
 * fsl_dma_free_descriptor - Free descriptor from channel's DMA pool.
 * @chan : Freescale DMA channel
 * @desc: descriptor to be freed
 */
static void fsl_dma_free_descriptor(struct fsldma_chan *chan,
                struct fsl_desc_sw *desc)
{
        list_del(&desc->node);
        chan_dbg(chan, "LD %p free\n", desc);
        dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
}

/**
 * fsl_dma_alloc_descriptor - Allocate descriptor from channel's DMA pool.
 * @chan : Freescale DMA channel
 *
 * Return - The descriptor allocated. NULL for failed.
 */
static struct fsl_desc_sw *fsl_dma_alloc_descriptor(struct fsldma_chan *chan)
{
        struct fsl_desc_sw *desc;
        dma_addr_t pdesc;

        desc = dma_pool_alloc(chan->desc_pool, GFP_ATOMIC, &pdesc);
        if (!desc) {
                chan_dbg(chan, "out of memory for link descriptor\n");
                return NULL;
        }

        memset(desc, 0, sizeof(*desc));
        INIT_LIST_HEAD(&desc->tx_list);
        dma_async_tx_descriptor_init(&desc->async_tx, &chan->common);
        desc->async_tx.tx_submit = fsl_dma_tx_submit;
        desc->async_tx.phys = pdesc;

        chan_dbg(chan, "LD %p allocated\n", desc);

        return desc;
}

/**
 * fsldma_clean_completed_descriptor - free all descriptors which
 * has been completed and acked
 * @chan: Freescale DMA channel
 *
 * This function is used on all completed and acked descriptors.
 * All descriptors should only be freed in this function.
 */
static void fsldma_clean_completed_descriptor(struct fsldma_chan *chan)
{
        struct fsl_desc_sw *desc, *_desc;

        /* Run the callback for each descriptor, in order */
        list_for_each_entry_safe(desc, _desc, &chan->ld_completed, node)
                if (async_tx_test_ack(&desc->async_tx))
                        fsl_dma_free_descriptor(chan, desc);
}

/**
 * fsldma_run_tx_complete_actions - cleanup a single link descriptor
 * @chan: Freescale DMA channel
 * @desc: descriptor to cleanup and free
 * @cookie: Freescale DMA transaction identifier
 *
 * This function is used on a descriptor which has been executed by the DMA
 * controller. It will run any callbacks, submit any dependencies.
 */
static dma_cookie_t fsldma_run_tx_complete_actions(struct fsldma_chan *chan,
                struct fsl_desc_sw *desc, dma_cookie_t cookie)
{
        struct dma_async_tx_descriptor *txd = &desc->async_tx;
        dma_cookie_t ret = cookie;

        BUG_ON(txd->cookie < 0);

        if (txd->cookie > 0) {
                ret = txd->cookie;

                /* Run the link descriptor callback function */
                if (txd->callback) {
                        chan_dbg(chan, "LD %p callback\n", desc);
                        txd->callback(txd->callback_param);
                }
        }

        /* Run any dependencies */
        dma_run_dependencies(txd);

        return ret;
}

/**
 * fsldma_clean_running_descriptor - move the completed descriptor from
 * ld_running to ld_completed
 * @chan: Freescale DMA channel
 * @desc: the descriptor which is completed
 *
 * Free the descriptor directly if acked by async_tx api, or move it to
 * queue ld_completed.
 */
static void fsldma_clean_running_descriptor(struct fsldma_chan *chan,
                struct fsl_desc_sw *desc)
{
        /* Remove from the list of transactions */
        list_del(&desc->node);

        /*
         * the client is allowed to attach dependent operations
         * until 'ack' is set
         */
        if (!async_tx_test_ack(&desc->async_tx)) {
                /*
                 * Move this descriptor to the list of descriptors which is
                 * completed, but still awaiting the 'ack' bit to be set.
                 */
                list_add_tail(&desc->node, &chan->ld_completed);
                return;
        }

        dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
}

/**
 * fsl_chan_xfer_ld_queue - transfer any pending transactions
 * @chan : Freescale DMA channel
 *
 * HARDWARE STATE: idle
 * LOCKING: must hold chan->desc_lock
 */
static void fsl_chan_xfer_ld_queue(struct fsldma_chan *chan)
{
        struct fsl_desc_sw *desc;

        /*
         * If the list of pending descriptors is empty, then we
         * don't need to do any work at all
         */
        if (list_empty(&chan->ld_pending)) {
                chan_dbg(chan, "no pending LDs\n");
                return;
        }

        /*
         * The DMA controller is not idle, which means that the interrupt
         * handler will start any queued transactions when it runs after
         * this transaction finishes
         */
        if (!chan->idle) {
                chan_dbg(chan, "DMA controller still busy\n");
                return;
        }

        /*
         * If there are some link descriptors which have not been
         * transferred, we need to start the controller
         */

        /*
         * Move all elements from the queue of pending transactions
         * onto the list of running transactions
         */
        chan_dbg(chan, "idle, starting controller\n");
        desc = list_first_entry(&chan->ld_pending, struct fsl_desc_sw, node);
        list_splice_tail_init(&chan->ld_pending, &chan->ld_running);

        /*
         * The 85xx DMA controller doesn't clear the channel start bit
         * automatically at the end of a transfer. Therefore we must clear
         * it in software before starting the transfer.
         */
        if ((chan->feature & FSL_DMA_IP_MASK) == FSL_DMA_IP_85XX) {
                u32 mode;

                mode = get_mr(chan);
                mode &= ~FSL_DMA_MR_CS;
                set_mr(chan, mode);
        }

        /*
         * Program the descriptor's address into the DMA controller,
         * then start the DMA transaction
         */
        set_cdar(chan, desc->async_tx.phys);
        get_cdar(chan);

        dma_start(chan);
        chan->idle = false;
}

/**
 * fsldma_cleanup_descriptors - cleanup link descriptors which are completed
 * and move them to ld_completed to free until flag 'ack' is set
 * @chan: Freescale DMA channel
 *
 * This function is used on descriptors which have been executed by the DMA
 * controller. It will run any callbacks, submit any dependencies, then
 * free these descriptors if flag 'ack' is set.
 */
static void fsldma_cleanup_descriptors(struct fsldma_chan *chan)
{
        struct fsl_desc_sw *desc, *_desc;
        dma_cookie_t cookie = 0;
        dma_addr_t curr_phys = get_cdar(chan);
        int seen_current = 0;

        fsldma_clean_completed_descriptor(chan);

        /* Run the callback for each descriptor, in order */
        list_for_each_entry_safe(desc, _desc, &chan->ld_running, node) {
                /*
                 * do not advance past the current descriptor loaded into the
                 * hardware channel, subsequent descriptors are either in
                 * process or have not been submitted
                 */
                if (seen_current)
                        break;

                /*
                 * stop the search if we reach the current descriptor and the
                 * channel is busy
                 */
                if (desc->async_tx.phys == curr_phys) {
                        seen_current = 1;
                        if (!dma_is_idle(chan))
                                break;
                }

                cookie = fsldma_run_tx_complete_actions(chan, desc, cookie);

                fsldma_clean_running_descriptor(chan, desc);
        }

        /*
         * Start any pending transactions automatically
         *
         * In the ideal case, we keep the DMA controller busy while we go
         * ahead and free the descriptors below.
         */
        fsl_chan_xfer_ld_queue(chan);

        if (cookie > 0)
                chan->common.completed_cookie = cookie;
}

/**
 * fsl_dma_alloc_chan_resources - Allocate resources for DMA channel.
 * @chan : Freescale DMA channel
 *
 * This function will create a dma pool for descriptor allocation.
 *
 * Return - The number of descriptors allocated.
 */
static int fsl_dma_alloc_chan_resources(struct dma_chan *dchan)
{
        struct fsldma_chan *chan = to_fsl_chan(dchan);

        /* Has this channel already been allocated? */
        if (chan->desc_pool)
                return 1;

        /*
         * We need the descriptor to be aligned to 32bytes
         * for meeting FSL DMA specification requirement.
         */
        chan->desc_pool = dma_pool_create(chan->name, chan->dev,
                                          sizeof(struct fsl_desc_sw),
                                          __alignof__(struct fsl_desc_sw), 0);
        if (!chan->desc_pool) {
                chan_err(chan, "unable to allocate descriptor pool\n");
                return -ENOMEM;
        }

        /* there is at least one descriptor free to be allocated */
        return 1;
}

/**
 * fsldma_free_desc_list - Free all descriptors in a queue
 * @chan: Freescae DMA channel
 * @list: the list to free
 *
 * LOCKING: must hold chan->desc_lock
 */
static void fsldma_free_desc_list(struct fsldma_chan *chan,
                                  struct list_head *list)
{
        struct fsl_desc_sw *desc, *_desc;

        list_for_each_entry_safe(desc, _desc, list, node)
                fsl_dma_free_descriptor(chan, desc);
}

static void fsldma_free_desc_list_reverse(struct fsldma_chan *chan,
                                          struct list_head *list)
{
        struct fsl_desc_sw *desc, *_desc;

        list_for_each_entry_safe_reverse(desc, _desc, list, node)
                fsl_dma_free_descriptor(chan, desc);
}

/**
 * fsl_dma_free_chan_resources - Free all resources of the channel.
 * @chan : Freescale DMA channel
 */
static void fsl_dma_free_chan_resources(struct dma_chan *dchan)
{
        struct fsldma_chan *chan = to_fsl_chan(dchan);

        chan_dbg(chan, "free all channel resources\n");
        spin_lock_bh(&chan->desc_lock);
        fsldma_cleanup_descriptors(chan);
        fsldma_free_desc_list(chan, &chan->ld_pending);
        fsldma_free_desc_list(chan, &chan->ld_running);
        fsldma_free_desc_list(chan, &chan->ld_completed);
        spin_unlock_bh(&chan->desc_lock);

        dma_pool_destroy(chan->desc_pool);
        chan->desc_pool = NULL;
}

static struct dma_async_tx_descriptor *
fsl_dma_prep_memcpy(struct dma_chan *dchan,
        dma_addr_t dma_dst, dma_addr_t dma_src,
        size_t len, unsigned long flags)
{
        struct fsldma_chan *chan;
        struct fsl_desc_sw *first = NULL, *prev = NULL, *new;
        size_t copy;

        if (!dchan)
                return NULL;

        if (!len)
                return NULL;

        chan = to_fsl_chan(dchan);

        do {

                /* Allocate the link descriptor from DMA pool */
                new = fsl_dma_alloc_descriptor(chan);
                if (!new) {
                        chan_err(chan, "%s\n", msg_ld_oom);
                        goto fail;
                }

                copy = min(len, (size_t)FSL_DMA_BCR_MAX_CNT);

                set_desc_cnt(chan, &new->hw, copy);
                set_desc_src(chan, &new->hw, dma_src);
                set_desc_dst(chan, &new->hw, dma_dst);

                if (!first)
                        first = new;
                else
                        set_desc_next(chan, &prev->hw, new->async_tx.phys);

                new->async_tx.cookie = 0;
                async_tx_ack(&new->async_tx);

                prev = new;
                len -= copy;
                dma_src += copy;
                dma_dst += copy;

                /* Insert the link descriptor to the LD ring */
                list_add_tail(&new->node, &first->tx_list);
        } while (len);

        new->async_tx.flags = flags; /* client is in control of this ack */
        new->async_tx.cookie = -EBUSY;

        /* Set End-of-link to the last link descriptor of new list */
        set_ld_eol(chan, new);

        return &first->async_tx;

fail:
        if (!first)
                return NULL;

        fsldma_free_desc_list_reverse(chan, &first->tx_list);
        return NULL;
}

static struct dma_async_tx_descriptor *fsl_dma_prep_sg(struct dma_chan *dchan,
        struct scatterlist *dst_sg, unsigned int dst_nents,
        struct scatterlist *src_sg, unsigned int src_nents,
        unsigned long flags)
{
        struct fsl_desc_sw *first = NULL, *prev = NULL, *new = NULL;
        struct fsldma_chan *chan = to_fsl_chan(dchan);
        size_t dst_avail, src_avail;
        dma_addr_t dst, src;
        size_t len;

        /* basic sanity checks */
        if (dst_nents == 0 || src_nents == 0)
                return NULL;

        if (dst_sg == NULL || src_sg == NULL)
                return NULL;

        /*
         * TODO: should we check that both scatterlists have the same
         * TODO: number of bytes in total? Is that really an error?
         */

        /* get prepared for the loop */
        dst_avail = sg_dma_len(dst_sg);
        src_avail = sg_dma_len(src_sg);

        /* run until we are out of scatterlist entries */
        while (true) {

                /* create the largest transaction possible */
                len = min_t(size_t, src_avail, dst_avail);
                len = min_t(size_t, len, FSL_DMA_BCR_MAX_CNT);
                if (len == 0)
                        goto fetch;

                dst = sg_dma_address(dst_sg) + sg_dma_len(dst_sg) - dst_avail;
                src = sg_dma_address(src_sg) + sg_dma_len(src_sg) - src_avail;

                /* allocate and populate the descriptor */
                new = fsl_dma_alloc_descriptor(chan);
                if (!new) {
                        chan_err(chan, "%s\n", msg_ld_oom);
                        goto fail;
                }

                set_desc_cnt(chan, &new->hw, len);
                set_desc_src(chan, &new->hw, src);
                set_desc_dst(chan, &new->hw, dst);

                if (!first)
                        first = new;
                else
                        set_desc_next(chan, &prev->hw, new->async_tx.phys);

                new->async_tx.cookie = 0;
                async_tx_ack(&new->async_tx);
                prev = new;

                /* Insert the link descriptor to the LD ring */
                list_add_tail(&new->node, &first->tx_list);

                /* update metadata */
                dst_avail -= len;
                src_avail -= len;

fetch:
                /* fetch the next dst scatterlist entry */
                if (dst_avail == 0) {

                        /* no more entries: we're done */
                        if (dst_nents == 0)
                                break;

                        /* fetch the next entry: if there are no more: done */
                        dst_sg = sg_next(dst_sg);
                        if (dst_sg == NULL)
                                break;

                        dst_nents--;
                        dst_avail = sg_dma_len(dst_sg);
                }

                /* fetch the next src scatterlist entry */
                if (src_avail == 0) {

                        /* no more entries: we're done */
                        if (src_nents == 0)
                                break;

                        /* fetch the next entry: if there are no more: done */
                        src_sg = sg_next(src_sg);
                        if (src_sg == NULL)
                                break;

                        src_nents--;
                        src_avail = sg_dma_len(src_sg);
                }
        }

        new->async_tx.flags = flags; /* client is in control of this ack */
        new->async_tx.cookie = -EBUSY;

        /* Set End-of-link to the last link descriptor of new list */
        set_ld_eol(chan, new);

        return &first->async_tx;

fail:
        if (!first)
                return NULL;

        fsldma_free_desc_list_reverse(chan, &first->tx_list);
        return NULL;
}

/**
 * fsl_dma_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: DMAEngine flags
 * @context: transaction context (ignored)
 *
 * Prepare a set of descriptors for a DMA_SLAVE transaction. Following the
 * DMA_SLAVE API, this gets the device-specific information from the
 * chan->private variable.
 */
static struct dma_async_tx_descriptor *fsl_dma_prep_slave_sg(
        struct dma_chan *dchan, struct scatterlist *sgl, unsigned int sg_len,
        enum dma_transfer_direction direction, unsigned long flags,
        void *context)
{
        /*
         * This operation is not supported on the Freescale DMA controller
         *
         * However, we need to provide the function pointer to allow the
         * device_control() method to work.
         */
        return NULL;
}

static int fsl_dma_device_control(struct dma_chan *dchan,
                                  enum dma_ctrl_cmd cmd, unsigned long arg)
{
        struct dma_slave_config *config;
        struct fsldma_chan *chan;
        int size;

        if (!dchan)
                return -EINVAL;

        chan = to_fsl_chan(dchan);

        switch (cmd) {
        case DMA_TERMINATE_ALL:
                spin_lock_bh(&chan->desc_lock);

                /* Halt the DMA engine */
                dma_halt(chan);

                /* Remove and free all of the descriptors in the LD queue */
                fsldma_free_desc_list(chan, &chan->ld_pending);
                fsldma_free_desc_list(chan, &chan->ld_running);
                fsldma_free_desc_list(chan, &chan->ld_completed);
                chan->idle = true;

                spin_unlock_bh(&chan->desc_lock);
                return 0;

        case DMA_SLAVE_CONFIG:
                config = (struct dma_slave_config *)arg;

                /* make sure the channel supports setting burst size */
                if (!chan->set_request_count)
                        return -ENXIO;

                /* we set the controller burst size depending on direction */
                if (config->direction == DMA_MEM_TO_DEV)
                        size = config->dst_addr_width * config->dst_maxburst;
                else
                        size = config->src_addr_width * config->src_maxburst;

                chan->set_request_count(chan, size);
                return 0;

        case FSLDMA_EXTERNAL_START:

                /* make sure the channel supports external start */
                if (!chan->toggle_ext_start)
                        return -ENXIO;

                chan->toggle_ext_start(chan, arg);
                return 0;

        default:
                return -ENXIO;
        }

        return 0;
}

/**
 * fsl_dma_memcpy_issue_pending - Issue the DMA start command
 * @chan : Freescale DMA channel
 */
static void fsl_dma_memcpy_issue_pending(struct dma_chan *dchan)
{
        struct fsldma_chan *chan = to_fsl_chan(dchan);

        spin_lock_bh(&chan->desc_lock);
        fsl_chan_xfer_ld_queue(chan);
        spin_unlock_bh(&chan->desc_lock);
}

/**
 * fsl_tx_status - Determine the DMA status
 * @chan : Freescale DMA channel
 */
static enum dma_status fsl_tx_status(struct dma_chan *dchan,
                                        dma_cookie_t cookie,
                                        struct dma_tx_state *txstate)
{
        struct fsldma_chan *chan = to_fsl_chan(dchan);
        enum dma_status ret;

        ret = dma_cookie_status(dchan, cookie, txstate);
        if (ret == DMA_COMPLETE)
                return ret;

        spin_lock_bh(&chan->desc_lock);
        fsldma_cleanup_descriptors(chan);
        spin_unlock_bh(&chan->desc_lock);

        return dma_cookie_status(dchan, cookie, txstate);
}

/*----------------------------------------------------------------------------*/
/* Interrupt Handling                                                         */
/*----------------------------------------------------------------------------*/

static irqreturn_t fsldma_chan_irq(int irq, void *data)
{
        struct fsldma_chan *chan = data;
        u32 stat;

        /* save and clear the status register */
        stat = get_sr(chan);
        set_sr(chan, stat);
        chan_dbg(chan, "irq: stat = 0x%x\n", stat);

        /* check that this was really our device */
        stat &= ~(FSL_DMA_SR_CB | FSL_DMA_SR_CH);
        if (!stat)
                return IRQ_NONE;

        if (stat & FSL_DMA_SR_TE)
                chan_err(chan, "Transfer Error!\n");

        /*
         * Programming Error
         * The DMA_INTERRUPT async_tx is a NULL transfer, which will
         * trigger a PE interrupt.
         */
        if (stat & FSL_DMA_SR_PE) {
                chan_dbg(chan, "irq: Programming Error INT\n");
                stat &= ~FSL_DMA_SR_PE;
                if (get_bcr(chan) != 0)
                        chan_err(chan, "Programming Error!\n");
        }

        /*
         * For MPC8349, EOCDI event need to update cookie
         * and start the next transfer if it exist.
         */
        if (stat & FSL_DMA_SR_EOCDI) {
                chan_dbg(chan, "irq: End-of-Chain link INT\n");
                stat &= ~FSL_DMA_SR_EOCDI;
        }

        /*
         * If it current transfer is the end-of-transfer,
         * we should clear the Channel Start bit for
         * prepare next transfer.
         */
        if (stat & FSL_DMA_SR_EOLNI) {
                chan_dbg(chan, "irq: End-of-link INT\n");
                stat &= ~FSL_DMA_SR_EOLNI;
        }

        /* check that the DMA controller is really idle */
        if (!dma_is_idle(chan))
                chan_err(chan, "irq: controller not idle!\n");

        /* check that we handled all of the bits */
        if (stat)
                chan_err(chan, "irq: unhandled sr 0x%08x\n", stat);

        /*
         * Schedule the tasklet to handle all cleanup of the current
         * transaction. It will start a new transaction if there is
         * one pending.
         */
        tasklet_schedule(&chan->tasklet);
        chan_dbg(chan, "irq: Exit\n");
        return IRQ_HANDLED;
}

static void dma_do_tasklet(unsigned long data)
{
        struct fsldma_chan *chan = (struct fsldma_chan *)data;

        chan_dbg(chan, "tasklet entry\n");

        spin_lock_bh(&chan->desc_lock);

        /* the hardware is now idle and ready for more */
        chan->idle = true;

        /* Run all cleanup for descriptors which have been completed */
        fsldma_cleanup_descriptors(chan);

        spin_unlock_bh(&chan->desc_lock);

        chan_dbg(chan, "tasklet exit\n");
}

static irqreturn_t fsldma_ctrl_irq(int irq, void *data)
{
        struct fsldma_device *fdev = data;
        struct fsldma_chan *chan;
        unsigned int handled = 0;
        u32 gsr, mask;
        int i;

        gsr = (fdev->feature & FSL_DMA_BIG_ENDIAN) ? in_be32(fdev->regs)
                                                   : in_le32(fdev->regs);
        mask = 0xff000000;
        dev_dbg(fdev->dev, "IRQ: gsr 0x%.8x\n", gsr);

        for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
                chan = fdev->chan[i];
                if (!chan)
                        continue;

                if (gsr & mask) {
                        dev_dbg(fdev->dev, "IRQ: chan %d\n", chan->id);
                        fsldma_chan_irq(irq, chan);
                        handled++;
                }

                gsr &= ~mask;
                mask >>= 8;
        }

        return IRQ_RETVAL(handled);
}

static void fsldma_free_irqs(struct fsldma_device *fdev)
{
        struct fsldma_chan *chan;
        int i;

        if (fdev->irq != NO_IRQ) {
                dev_dbg(fdev->dev, "free per-controller IRQ\n");
                free_irq(fdev->irq, fdev);
                return;
        }

        for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
                chan = fdev->chan[i];
                if (chan && chan->irq != NO_IRQ) {
                        chan_dbg(chan, "free per-channel IRQ\n");
                        free_irq(chan->irq, chan);
                }
        }
}

static int fsldma_request_irqs(struct fsldma_device *fdev)
{
        struct fsldma_chan *chan;
        int ret;
        int i;

        /* if we have a per-controller IRQ, use that */
        if (fdev->irq != NO_IRQ) {
                dev_dbg(fdev->dev, "request per-controller IRQ\n");
                ret = request_irq(fdev->irq, fsldma_ctrl_irq, IRQF_SHARED,
                                  "fsldma-controller", fdev);
                return ret;
        }

        /* no per-controller IRQ, use the per-channel IRQs */
        for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
                chan = fdev->chan[i];
                if (!chan)
                        continue;

                if (chan->irq == NO_IRQ) {
                        chan_err(chan, "interrupts property missing in device tree\n");
                        ret = -ENODEV;
                        goto out_unwind;
                }

                chan_dbg(chan, "request per-channel IRQ\n");
                ret = request_irq(chan->irq, fsldma_chan_irq, IRQF_SHARED,
                                  "fsldma-chan", chan);
                if (ret) {
                        chan_err(chan, "unable to request per-channel IRQ\n");
                        goto out_unwind;
                }
        }

        return 0;

out_unwind:
        for (/* none */; i >= 0; i--) {
                chan = fdev->chan[i];
                if (!chan)
                        continue;

                if (chan->irq == NO_IRQ)
                        continue;

                free_irq(chan->irq, chan);
        }

        return ret;
}

/*----------------------------------------------------------------------------*/
/* OpenFirmware Subsystem                                                     */
/*----------------------------------------------------------------------------*/

static int fsl_dma_chan_probe(struct fsldma_device *fdev,
        struct device_node *node, u32 feature, const char *compatible)
{
        struct fsldma_chan *chan;
        struct resource res;
        int err;

        /* alloc channel */
        chan = kzalloc(sizeof(*chan), GFP_KERNEL);
        if (!chan) {
                dev_err(fdev->dev, "no free memory for DMA channels!\n");
                err = -ENOMEM;
                goto out_return;
        }

        /* ioremap registers for use */
        chan->regs = of_iomap(node, 0);
        if (!chan->regs) {
                dev_err(fdev->dev, "unable to ioremap registers\n");
                err = -ENOMEM;
                goto out_free_chan;
        }

        err = of_address_to_resource(node, 0, &res);
        if (err) {
                dev_err(fdev->dev, "unable to find 'reg' property\n");
                goto out_iounmap_regs;
        }

        chan->feature = feature;
        if (!fdev->feature)
                fdev->feature = chan->feature;

        /*
         * If the DMA device's feature is different than the feature
         * of its channels, report the bug
         */
        WARN_ON(fdev->feature != chan->feature);

        chan->dev = fdev->dev;
        chan->id = (res.start & 0xfff) < 0x300 ?
                   ((res.start - 0x100) & 0xfff) >> 7 :
                   ((res.start - 0x200) & 0xfff) >> 7;
        if (chan->id >= FSL_DMA_MAX_CHANS_PER_DEVICE) {
                dev_err(fdev->dev, "too many channels for device\n");
                err = -EINVAL;
                goto out_iounmap_regs;
        }

        fdev->chan[chan->id] = chan;
        tasklet_init(&chan->tasklet, dma_do_tasklet, (unsigned long)chan);
        snprintf(chan->name, sizeof(chan->name), "chan%d", chan->id);

        /* Initialize the channel */
        dma_init(chan);

        /* Clear cdar registers */
        set_cdar(chan, 0);

        switch (chan->feature & FSL_DMA_IP_MASK) {
        case FSL_DMA_IP_85XX:
                chan->toggle_ext_pause = fsl_chan_toggle_ext_pause;
        case FSL_DMA_IP_83XX:
                chan->toggle_ext_start = fsl_chan_toggle_ext_start;
                chan->set_src_loop_size = fsl_chan_set_src_loop_size;
                chan->set_dst_loop_size = fsl_chan_set_dst_loop_size;
                chan->set_request_count = fsl_chan_set_request_count;
        }

        spin_lock_init(&chan->desc_lock);
        INIT_LIST_HEAD(&chan->ld_pending);
        INIT_LIST_HEAD(&chan->ld_running);
        INIT_LIST_HEAD(&chan->ld_completed);
        chan->idle = true;
#ifdef CONFIG_PM
        chan->pm_state = RUNNING;
#endif

        chan->common.device = &fdev->common;
        dma_cookie_init(&chan->common);

        /* find the IRQ line, if it exists in the device tree */
        chan->irq = irq_of_parse_and_map(node, 0);

        /* Add the channel to DMA device channel list */
        list_add_tail(&chan->common.device_node, &fdev->common.channels);
        fdev->common.chancnt++;

        dev_info(fdev->dev, "#%d (%s), irq %d\n", chan->id, compatible,
                 chan->irq != NO_IRQ ? chan->irq : fdev->irq);

        return 0;

out_iounmap_regs:
        iounmap(chan->regs);
out_free_chan:
        kfree(chan);
out_return:
        return err;
}

static void fsl_dma_chan_remove(struct fsldma_chan *chan)
{
        irq_dispose_mapping(chan->irq);
        list_del(&chan->common.device_node);
        iounmap(chan->regs);
        kfree(chan);
}

static int fsldma_of_probe(struct platform_device *op)
{
        struct fsldma_device *fdev;
        struct device_node *child;
        int err;

        fdev = kzalloc(sizeof(*fdev), GFP_KERNEL);
        if (!fdev) {
                dev_err(&op->dev, "No enough memory for 'priv'\n");
                err = -ENOMEM;
                goto out_return;
        }

        fdev->dev = &op->dev;
        INIT_LIST_HEAD(&fdev->common.channels);

        /* ioremap the registers for use */
        fdev->regs = of_iomap(op->dev.of_node, 0);
        if (!fdev->regs) {
                dev_err(&op->dev, "unable to ioremap registers\n");
                err = -ENOMEM;
                goto out_free_fdev;
        }

        /* map the channel IRQ if it exists, but don't hookup the handler yet */
        fdev->irq = irq_of_parse_and_map(op->dev.of_node, 0);

        dma_cap_set(DMA_MEMCPY, fdev->common.cap_mask);
        dma_cap_set(DMA_SG, fdev->common.cap_mask);
        dma_cap_set(DMA_SLAVE, fdev->common.cap_mask);
        fdev->common.device_alloc_chan_resources = fsl_dma_alloc_chan_resources;
        fdev->common.device_free_chan_resources = fsl_dma_free_chan_resources;
        fdev->common.device_prep_dma_memcpy = fsl_dma_prep_memcpy;
        fdev->common.device_prep_dma_sg = fsl_dma_prep_sg;
        fdev->common.device_tx_status = fsl_tx_status;
        fdev->common.device_issue_pending = fsl_dma_memcpy_issue_pending;
        fdev->common.device_prep_slave_sg = fsl_dma_prep_slave_sg;
        fdev->common.device_control = fsl_dma_device_control;
        fdev->common.dev = &op->dev;

        dma_set_mask(&(op->dev), DMA_BIT_MASK(36));

        platform_set_drvdata(op, fdev);

        /*
         * We cannot use of_platform_bus_probe() because there is no
         * of_platform_bus_remove(). Instead, we manually instantiate every DMA
         * channel object.
         */
        for_each_child_of_node(op->dev.of_node, child) {
                if (of_device_is_compatible(child, "fsl,eloplus-dma-channel")) {
                        fsl_dma_chan_probe(fdev, child,
                                FSL_DMA_IP_85XX | FSL_DMA_BIG_ENDIAN,
                                "fsl,eloplus-dma-channel");
                }

                if (of_device_is_compatible(child, "fsl,elo-dma-channel")) {
                        fsl_dma_chan_probe(fdev, child,
                                FSL_DMA_IP_83XX | FSL_DMA_LITTLE_ENDIAN,
                                "fsl,elo-dma-channel");
                }
        }

        /*
         * Hookup the IRQ handler(s)
         *
         * If we have a per-controller interrupt, we prefer that to the
         * per-channel interrupts to reduce the number of shared interrupt
         * handlers on the same IRQ line
         */
        err = fsldma_request_irqs(fdev);
        if (err) {
                dev_err(fdev->dev, "unable to request IRQs\n");
                goto out_free_fdev;
        }

        dma_async_device_register(&fdev->common);
        return 0;

out_free_fdev:
        irq_dispose_mapping(fdev->irq);
        kfree(fdev);
out_return:
        return err;
}

static int fsldma_of_remove(struct platform_device *op)
{
        struct fsldma_device *fdev;
        unsigned int i;

        fdev = platform_get_drvdata(op);
        dma_async_device_unregister(&fdev->common);

        fsldma_free_irqs(fdev);

        for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
                if (fdev->chan[i])
                        fsl_dma_chan_remove(fdev->chan[i]);
        }

        iounmap(fdev->regs);
        kfree(fdev);

        return 0;
}

#ifdef CONFIG_PM
static int fsldma_suspend_late(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct fsldma_device *fdev = platform_get_drvdata(pdev);
        struct fsldma_chan *chan;
        int i;

        for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
                chan = fdev->chan[i];
                if (!chan)
                        continue;

                spin_lock_bh(&chan->desc_lock);
                if (unlikely(!chan->idle))
                        goto out;
                chan->regs_save.mr = get_mr(chan);
                chan->pm_state = SUSPENDED;
                spin_unlock_bh(&chan->desc_lock);
        }
        return 0;

out:
        for (; i >= 0; i--) {
                chan = fdev->chan[i];
                if (!chan)
                        continue;
                chan->pm_state = RUNNING;
                spin_unlock_bh(&chan->desc_lock);
        }
        return -EBUSY;
}

static int fsldma_resume_early(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct fsldma_device *fdev = platform_get_drvdata(pdev);
        struct fsldma_chan *chan;
        u32 mode;
        int i;

        for (i = 0; i < FSL_DMA_MAX_CHANS_PER_DEVICE; i++) {
                chan = fdev->chan[i];
                if (!chan)
                        continue;

                spin_lock_bh(&chan->desc_lock);
                mode = chan->regs_save.mr
                        & ~FSL_DMA_MR_CS & ~FSL_DMA_MR_CC & ~FSL_DMA_MR_CA;
                set_mr(chan, mode);
                chan->pm_state = RUNNING;
                spin_unlock_bh(&chan->desc_lock);
        }

        return 0;
}

static const struct dev_pm_ops fsldma_pm_ops = {
        .suspend_late   = fsldma_suspend_late,
        .resume_early   = fsldma_resume_early,
};
#endif

static const struct of_device_id fsldma_of_ids[] = {
        { .compatible = "fsl,elo3-dma", },
        { .compatible = "fsl,eloplus-dma", },
        { .compatible = "fsl,elo-dma", },
        {}
};

static struct platform_driver fsldma_of_driver = {
        .driver = {
                .name = "fsl-elo-dma",
                .owner = THIS_MODULE,
                .of_match_table = fsldma_of_ids,
#ifdef CONFIG_PM
                .pm = &fsldma_pm_ops,
#endif
        },
        .probe = fsldma_of_probe,
        .remove = fsldma_of_remove,
};

/*----------------------------------------------------------------------------*/
/* Module Init / Exit                                                         */
/*----------------------------------------------------------------------------*/

static __init int fsldma_init(void)
{
        pr_info("Freescale Elo series DMA driver\n");
        return platform_driver_register(&fsldma_of_driver);
}

static void __exit fsldma_exit(void)
{
        platform_driver_unregister(&fsldma_of_driver);
}

subsys_initcall(fsldma_init);
module_exit(fsldma_exit);

MODULE_DESCRIPTION("Freescale Elo series DMA driver");
MODULE_LICENSE("GPL");