pids: improve get_task_pid() to fix the unsafe sys_wait4()->task_pgrp()

[linux-2.6/mini2440.git] / drivers / dma / dw_dmac.c

/*
 * Driver for the Synopsys DesignWare DMA Controller (aka DMACA on
 * AVR32 systems.)
 *
 * Copyright (C) 2007-2008 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#include "dw_dmac_regs.h"

/*
 * This supports the Synopsys "DesignWare AHB Central DMA Controller",
 * (DW_ahb_dmac) which is used with various AMBA 2.0 systems (not all
 * of which use ARM any more).  See the "Databook" from Synopsys for
 * information beyond what licensees probably provide.
 *
 * The driver has currently been tested only with the Atmel AT32AP7000,
 * which does not support descriptor writeback.
 */

/* NOTE:  DMS+SMS is system-specific. We should get this information
 * from the platform code somehow.
 */
#define DWC_DEFAULT_CTLLO       (DWC_CTLL_DST_MSIZE(0)          \
                                | DWC_CTLL_SRC_MSIZE(0)         \
                                | DWC_CTLL_DMS(0)               \
                                | DWC_CTLL_SMS(1)               \
                                | DWC_CTLL_LLP_D_EN             \
                                | DWC_CTLL_LLP_S_EN)

/*
 * This is configuration-dependent and usually a funny size like 4095.
 * Let's round it down to the nearest power of two.
 *
 * Note that this is a transfer count, i.e. if we transfer 32-bit
 * words, we can do 8192 bytes per descriptor.
 *
 * This parameter is also system-specific.
 */
#define DWC_MAX_COUNT   2048U

/*
 * Number of descriptors to allocate for each channel. This should be
 * made configurable somehow; preferably, the clients (at least the
 * ones using slave transfers) should be able to give us a hint.
 */
#define NR_DESCS_PER_CHANNEL    64

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

/*
 * Because we're not relying on writeback from the controller (it may not
 * even be configured into the core!) we don't need to use dma_pool.  These
 * descriptors -- and associated data -- are cacheable.  We do need to make
 * sure their dcache entries are written back before handing them off to
 * the controller, though.
 */

static struct device *chan2dev(struct dma_chan *chan)
{
        return &chan->dev->device;
}
static struct device *chan2parent(struct dma_chan *chan)
{
        return chan->dev->device.parent;
}

static struct dw_desc *dwc_first_active(struct dw_dma_chan *dwc)
{
        return list_entry(dwc->active_list.next, struct dw_desc, desc_node);
}

static struct dw_desc *dwc_first_queued(struct dw_dma_chan *dwc)
{
        return list_entry(dwc->queue.next, struct dw_desc, desc_node);
}

static struct dw_desc *dwc_desc_get(struct dw_dma_chan *dwc)
{
        struct dw_desc *desc, *_desc;
        struct dw_desc *ret = NULL;
        unsigned int i = 0;

        spin_lock_bh(&dwc->lock);
        list_for_each_entry_safe(desc, _desc, &dwc->free_list, desc_node) {
                if (async_tx_test_ack(&desc->txd)) {
                        list_del(&desc->desc_node);
                        ret = desc;
                        break;
                }
                dev_dbg(chan2dev(&dwc->chan), "desc %p not ACKed\n", desc);
                i++;
        }
        spin_unlock_bh(&dwc->lock);

        dev_vdbg(chan2dev(&dwc->chan), "scanned %u descriptors on freelist\n", i);

        return ret;
}

static void dwc_sync_desc_for_cpu(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
        struct dw_desc  *child;

        list_for_each_entry(child, &desc->txd.tx_list, desc_node)
                dma_sync_single_for_cpu(chan2parent(&dwc->chan),
                                child->txd.phys, sizeof(child->lli),
                                DMA_TO_DEVICE);
        dma_sync_single_for_cpu(chan2parent(&dwc->chan),
                        desc->txd.phys, sizeof(desc->lli),
                        DMA_TO_DEVICE);
}

/*
 * Move a descriptor, including any children, to the free list.
 * `desc' must not be on any lists.
 */
static void dwc_desc_put(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
        if (desc) {
                struct dw_desc *child;

                dwc_sync_desc_for_cpu(dwc, desc);

                spin_lock_bh(&dwc->lock);
                list_for_each_entry(child, &desc->txd.tx_list, desc_node)
                        dev_vdbg(chan2dev(&dwc->chan),
                                        "moving child desc %p to freelist\n",
                                        child);
                list_splice_init(&desc->txd.tx_list, &dwc->free_list);
                dev_vdbg(chan2dev(&dwc->chan), "moving desc %p to freelist\n", desc);
                list_add(&desc->desc_node, &dwc->free_list);
                spin_unlock_bh(&dwc->lock);
        }
}

/* Called with dwc->lock held and bh disabled */
static dma_cookie_t
dwc_assign_cookie(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
        dma_cookie_t cookie = dwc->chan.cookie;

        if (++cookie < 0)
                cookie = 1;

        dwc->chan.cookie = cookie;
        desc->txd.cookie = cookie;

        return cookie;
}

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

/* Called with dwc->lock held and bh disabled */
static void dwc_dostart(struct dw_dma_chan *dwc, struct dw_desc *first)
{
        struct dw_dma   *dw = to_dw_dma(dwc->chan.device);

        /* ASSERT:  channel is idle */
        if (dma_readl(dw, CH_EN) & dwc->mask) {
                dev_err(chan2dev(&dwc->chan),
                        "BUG: Attempted to start non-idle channel\n");
                dev_err(chan2dev(&dwc->chan),
                        "  SAR: 0x%x DAR: 0x%x LLP: 0x%x CTL: 0x%x:%08x\n",
                        channel_readl(dwc, SAR),
                        channel_readl(dwc, DAR),
                        channel_readl(dwc, LLP),
                        channel_readl(dwc, CTL_HI),
                        channel_readl(dwc, CTL_LO));

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

        channel_writel(dwc, LLP, first->txd.phys);
        channel_writel(dwc, CTL_LO,
                        DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN);
        channel_writel(dwc, CTL_HI, 0);
        channel_set_bit(dw, CH_EN, dwc->mask);
}

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

static void
dwc_descriptor_complete(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
        dma_async_tx_callback           callback;
        void                            *param;
        struct dma_async_tx_descriptor  *txd = &desc->txd;

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

        dwc->completed = txd->cookie;
        callback = txd->callback;
        param = txd->callback_param;

        dwc_sync_desc_for_cpu(dwc, desc);
        list_splice_init(&txd->tx_list, &dwc->free_list);
        list_move(&desc->desc_node, &dwc->free_list);

        /*
         * We use dma_unmap_page() regardless of how the buffers were
         * mapped before they were submitted...
         */
        if (!(txd->flags & DMA_COMPL_SKIP_DEST_UNMAP))
                dma_unmap_page(chan2parent(&dwc->chan), desc->lli.dar,
                               desc->len, DMA_FROM_DEVICE);
        if (!(txd->flags & DMA_COMPL_SKIP_SRC_UNMAP))
                dma_unmap_page(chan2parent(&dwc->chan), desc->lli.sar,
                               desc->len, DMA_TO_DEVICE);

        /*
         * 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);
}

static void dwc_complete_all(struct dw_dma *dw, struct dw_dma_chan *dwc)
{
        struct dw_desc *desc, *_desc;
        LIST_HEAD(list);

        if (dma_readl(dw, CH_EN) & dwc->mask) {
                dev_err(chan2dev(&dwc->chan),
                        "BUG: XFER bit set, but channel not idle!\n");

                /* Try to continue after resetting the channel... */
                channel_clear_bit(dw, CH_EN, dwc->mask);
                while (dma_readl(dw, CH_EN) & dwc->mask)
                        cpu_relax();
        }

        /*
         * Submit queued descriptors ASAP, i.e. before we go through
         * the completed ones.
         */
        if (!list_empty(&dwc->queue))
                dwc_dostart(dwc, dwc_first_queued(dwc));
        list_splice_init(&dwc->active_list, &list);
        list_splice_init(&dwc->queue, &dwc->active_list);

        list_for_each_entry_safe(desc, _desc, &list, desc_node)
                dwc_descriptor_complete(dwc, desc);
}

static void dwc_scan_descriptors(struct dw_dma *dw, struct dw_dma_chan *dwc)
{
        dma_addr_t llp;
        struct dw_desc *desc, *_desc;
        struct dw_desc *child;
        u32 status_xfer;

        /*
         * Clear block interrupt flag before scanning so that we don't
         * miss any, and read LLP before RAW_XFER to ensure it is
         * valid if we decide to scan the list.
         */
        dma_writel(dw, CLEAR.BLOCK, dwc->mask);
        llp = channel_readl(dwc, LLP);
        status_xfer = dma_readl(dw, RAW.XFER);

        if (status_xfer & dwc->mask) {
                /* Everything we've submitted is done */
                dma_writel(dw, CLEAR.XFER, dwc->mask);
                dwc_complete_all(dw, dwc);
                return;
        }

        dev_vdbg(chan2dev(&dwc->chan), "scan_descriptors: llp=0x%x\n", llp);

        list_for_each_entry_safe(desc, _desc, &dwc->active_list, desc_node) {
                if (desc->lli.llp == llp)
                        /* This one is currently in progress */
                        return;

                list_for_each_entry(child, &desc->txd.tx_list, desc_node)
                        if (child->lli.llp == llp)
                                /* Currently in progress */
                                return;

                /*
                 * No descriptors so far seem to be in progress, i.e.
                 * this one must be done.
                 */
                dwc_descriptor_complete(dwc, desc);
        }

        dev_err(chan2dev(&dwc->chan),
                "BUG: All descriptors done, but channel not idle!\n");

        /* Try to continue after resetting the channel... */
        channel_clear_bit(dw, CH_EN, dwc->mask);
        while (dma_readl(dw, CH_EN) & dwc->mask)
                cpu_relax();

        if (!list_empty(&dwc->queue)) {
                dwc_dostart(dwc, dwc_first_queued(dwc));
                list_splice_init(&dwc->queue, &dwc->active_list);
        }
}

static void dwc_dump_lli(struct dw_dma_chan *dwc, struct dw_lli *lli)
{
        dev_printk(KERN_CRIT, chan2dev(&dwc->chan),
                        "  desc: s0x%x d0x%x l0x%x c0x%x:%x\n",
                        lli->sar, lli->dar, lli->llp,
                        lli->ctlhi, lli->ctllo);
}

static void dwc_handle_error(struct dw_dma *dw, struct dw_dma_chan *dwc)
{
        struct dw_desc *bad_desc;
        struct dw_desc *child;

        dwc_scan_descriptors(dw, dwc);

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

        /* Clear the error flag and try to restart the controller */
        dma_writel(dw, CLEAR.ERROR, dwc->mask);
        if (!list_empty(&dwc->active_list))
                dwc_dostart(dwc, dwc_first_active(dwc));

        /*
         * 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_printk(KERN_CRIT, chan2dev(&dwc->chan),
                        "Bad descriptor submitted for DMA!\n");
        dev_printk(KERN_CRIT, chan2dev(&dwc->chan),
                        "  cookie: %d\n", bad_desc->txd.cookie);
        dwc_dump_lli(dwc, &bad_desc->lli);
        list_for_each_entry(child, &bad_desc->txd.tx_list, desc_node)
                dwc_dump_lli(dwc, &child->lli);

        /* Pretend the descriptor completed successfully */
        dwc_descriptor_complete(dwc, bad_desc);
}

static void dw_dma_tasklet(unsigned long data)
{
        struct dw_dma *dw = (struct dw_dma *)data;
        struct dw_dma_chan *dwc;
        u32 status_block;
        u32 status_xfer;
        u32 status_err;
        int i;

        status_block = dma_readl(dw, RAW.BLOCK);
        status_xfer = dma_readl(dw, RAW.XFER);
        status_err = dma_readl(dw, RAW.ERROR);

        dev_vdbg(dw->dma.dev, "tasklet: status_block=%x status_err=%x\n",
                        status_block, status_err);

        for (i = 0; i < dw->dma.chancnt; i++) {
                dwc = &dw->chan[i];
                spin_lock(&dwc->lock);
                if (status_err & (1 << i))
                        dwc_handle_error(dw, dwc);
                else if ((status_block | status_xfer) & (1 << i))
                        dwc_scan_descriptors(dw, dwc);
                spin_unlock(&dwc->lock);
        }

        /*
         * Re-enable interrupts. Block Complete interrupts are only
         * enabled if the INT_EN bit in the descriptor is set. This
         * will trigger a scan before the whole list is done.
         */
        channel_set_bit(dw, MASK.XFER, dw->all_chan_mask);
        channel_set_bit(dw, MASK.BLOCK, dw->all_chan_mask);
        channel_set_bit(dw, MASK.ERROR, dw->all_chan_mask);
}

static irqreturn_t dw_dma_interrupt(int irq, void *dev_id)
{
        struct dw_dma *dw = dev_id;
        u32 status;

        dev_vdbg(dw->dma.dev, "interrupt: status=0x%x\n",
                        dma_readl(dw, STATUS_INT));

        /*
         * Just disable the interrupts. We'll turn them back on in the
         * softirq handler.
         */
        channel_clear_bit(dw, MASK.XFER, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.BLOCK, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.ERROR, dw->all_chan_mask);

        status = dma_readl(dw, STATUS_INT);
        if (status) {
                dev_err(dw->dma.dev,
                        "BUG: Unexpected interrupts pending: 0x%x\n",
                        status);

                /* Try to recover */
                channel_clear_bit(dw, MASK.XFER, (1 << 8) - 1);
                channel_clear_bit(dw, MASK.BLOCK, (1 << 8) - 1);
                channel_clear_bit(dw, MASK.SRC_TRAN, (1 << 8) - 1);
                channel_clear_bit(dw, MASK.DST_TRAN, (1 << 8) - 1);
                channel_clear_bit(dw, MASK.ERROR, (1 << 8) - 1);
        }

        tasklet_schedule(&dw->tasklet);

        return IRQ_HANDLED;
}

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

static dma_cookie_t dwc_tx_submit(struct dma_async_tx_descriptor *tx)
{
        struct dw_desc          *desc = txd_to_dw_desc(tx);
        struct dw_dma_chan      *dwc = to_dw_dma_chan(tx->chan);
        dma_cookie_t            cookie;

        spin_lock_bh(&dwc->lock);
        cookie = dwc_assign_cookie(dwc, desc);

        /*
         * REVISIT: We should attempt to chain as many descriptors as
         * possible, perhaps even appending to those already submitted
         * for DMA. But this is hard to do in a race-free manner.
         */
        if (list_empty(&dwc->active_list)) {
                dev_vdbg(chan2dev(tx->chan), "tx_submit: started %u\n",
                                desc->txd.cookie);
                dwc_dostart(dwc, desc);
                list_add_tail(&desc->desc_node, &dwc->active_list);
        } else {
                dev_vdbg(chan2dev(tx->chan), "tx_submit: queued %u\n",
                                desc->txd.cookie);

                list_add_tail(&desc->desc_node, &dwc->queue);
        }

        spin_unlock_bh(&dwc->lock);

        return cookie;
}

static struct dma_async_tx_descriptor *
dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
                size_t len, unsigned long flags)
{
        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
        struct dw_desc          *desc;
        struct dw_desc          *first;
        struct dw_desc          *prev;
        size_t                  xfer_count;
        size_t                  offset;
        unsigned int            src_width;
        unsigned int            dst_width;
        u32                     ctllo;

        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;
        }

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

        ctllo = DWC_DEFAULT_CTLLO
                        | DWC_CTLL_DST_WIDTH(dst_width)
                        | DWC_CTLL_SRC_WIDTH(src_width)
                        | DWC_CTLL_DST_INC
                        | DWC_CTLL_SRC_INC
                        | DWC_CTLL_FC_M2M;
        prev = first = NULL;

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

                desc = dwc_desc_get(dwc);
                if (!desc)
                        goto err_desc_get;

                desc->lli.sar = src + offset;
                desc->lli.dar = dest + offset;
                desc->lli.ctllo = ctllo;
                desc->lli.ctlhi = xfer_count;

                if (!first) {
                        first = desc;
                } else {
                        prev->lli.llp = desc->txd.phys;
                        dma_sync_single_for_device(chan2parent(chan),
                                        prev->txd.phys, sizeof(prev->lli),
                                        DMA_TO_DEVICE);
                        list_add_tail(&desc->desc_node,
                                        &first->txd.tx_list);
                }
                prev = desc;
        }


        if (flags & DMA_PREP_INTERRUPT)
                /* Trigger interrupt after last block */
                prev->lli.ctllo |= DWC_CTLL_INT_EN;

        prev->lli.llp = 0;
        dma_sync_single_for_device(chan2parent(chan),
                        prev->txd.phys, sizeof(prev->lli),
                        DMA_TO_DEVICE);

        first->txd.flags = flags;
        first->len = len;

        return &first->txd;

err_desc_get:
        dwc_desc_put(dwc, first);
        return NULL;
}

static struct dma_async_tx_descriptor *
dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
                unsigned int sg_len, enum dma_data_direction direction,
                unsigned long flags)
{
        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
        struct dw_dma_slave     *dws = chan->private;
        struct dw_desc          *prev;
        struct dw_desc          *first;
        u32                     ctllo;
        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_dma_slave\n");

        if (unlikely(!dws || !sg_len))
                return NULL;

        reg_width = dws->reg_width;
        prev = first = NULL;

        sg_len = dma_map_sg(chan2parent(chan), sgl, sg_len, direction);

        switch (direction) {
        case DMA_TO_DEVICE:
                ctllo = (DWC_DEFAULT_CTLLO
                                | DWC_CTLL_DST_WIDTH(reg_width)
                                | DWC_CTLL_DST_FIX
                                | DWC_CTLL_SRC_INC
                                | DWC_CTLL_FC_M2P);
                reg = dws->tx_reg;
                for_each_sg(sgl, sg, sg_len, i) {
                        struct dw_desc  *desc;
                        u32             len;
                        u32             mem;

                        desc = dwc_desc_get(dwc);
                        if (!desc) {
                                dev_err(chan2dev(chan),
                                        "not enough descriptors available\n");
                                goto err_desc_get;
                        }

                        mem = sg_phys(sg);
                        len = sg_dma_len(sg);
                        mem_width = 2;
                        if (unlikely(mem & 3 || len & 3))
                                mem_width = 0;

                        desc->lli.sar = mem;
                        desc->lli.dar = reg;
                        desc->lli.ctllo = ctllo | DWC_CTLL_SRC_WIDTH(mem_width);
                        desc->lli.ctlhi = len >> mem_width;

                        if (!first) {
                                first = desc;
                        } else {
                                prev->lli.llp = desc->txd.phys;
                                dma_sync_single_for_device(chan2parent(chan),
                                                prev->txd.phys,
                                                sizeof(prev->lli),
                                                DMA_TO_DEVICE);
                                list_add_tail(&desc->desc_node,
                                                &first->txd.tx_list);
                        }
                        prev = desc;
                        total_len += len;
                }
                break;
        case DMA_FROM_DEVICE:
                ctllo = (DWC_DEFAULT_CTLLO
                                | DWC_CTLL_SRC_WIDTH(reg_width)
                                | DWC_CTLL_DST_INC
                                | DWC_CTLL_SRC_FIX
                                | DWC_CTLL_FC_P2M);

                reg = dws->rx_reg;
                for_each_sg(sgl, sg, sg_len, i) {
                        struct dw_desc  *desc;
                        u32             len;
                        u32             mem;

                        desc = dwc_desc_get(dwc);
                        if (!desc) {
                                dev_err(chan2dev(chan),
                                        "not enough descriptors available\n");
                                goto err_desc_get;
                        }

                        mem = sg_phys(sg);
                        len = sg_dma_len(sg);
                        mem_width = 2;
                        if (unlikely(mem & 3 || len & 3))
                                mem_width = 0;

                        desc->lli.sar = reg;
                        desc->lli.dar = mem;
                        desc->lli.ctllo = ctllo | DWC_CTLL_DST_WIDTH(mem_width);
                        desc->lli.ctlhi = len >> reg_width;

                        if (!first) {
                                first = desc;
                        } else {
                                prev->lli.llp = desc->txd.phys;
                                dma_sync_single_for_device(chan2parent(chan),
                                                prev->txd.phys,
                                                sizeof(prev->lli),
                                                DMA_TO_DEVICE);
                                list_add_tail(&desc->desc_node,
                                                &first->txd.tx_list);
                        }
                        prev = desc;
                        total_len += len;
                }
                break;
        default:
                return NULL;
        }

        if (flags & DMA_PREP_INTERRUPT)
                /* Trigger interrupt after last block */
                prev->lli.ctllo |= DWC_CTLL_INT_EN;

        prev->lli.llp = 0;
        dma_sync_single_for_device(chan2parent(chan),
                        prev->txd.phys, sizeof(prev->lli),
                        DMA_TO_DEVICE);

        first->len = total_len;

        return &first->txd;

err_desc_get:
        dwc_desc_put(dwc, first);
        return NULL;
}

static void dwc_terminate_all(struct dma_chan *chan)
{
        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
        struct dw_dma           *dw = to_dw_dma(chan->device);
        struct dw_desc          *desc, *_desc;
        LIST_HEAD(list);

        /*
         * 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_bh(&dwc->lock);

        channel_clear_bit(dw, CH_EN, dwc->mask);

        while (dma_readl(dw, CH_EN) & dwc->mask)
                cpu_relax();

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

        spin_unlock_bh(&dwc->lock);

        /* Flush all pending and queued descriptors */
        list_for_each_entry_safe(desc, _desc, &list, desc_node)
                dwc_descriptor_complete(dwc, desc);
}

static enum dma_status
dwc_is_tx_complete(struct dma_chan *chan,
                dma_cookie_t cookie,
                dma_cookie_t *done, dma_cookie_t *used)
{
        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
        dma_cookie_t            last_used;
        dma_cookie_t            last_complete;
        int                     ret;

        last_complete = dwc->completed;
        last_used = chan->cookie;

        ret = dma_async_is_complete(cookie, last_complete, last_used);
        if (ret != DMA_SUCCESS) {
                dwc_scan_descriptors(to_dw_dma(chan->device), dwc);

                last_complete = dwc->completed;
                last_used = chan->cookie;

                ret = dma_async_is_complete(cookie, last_complete, last_used);
        }

        if (done)
                *done = last_complete;
        if (used)
                *used = last_used;

        return ret;
}

static void dwc_issue_pending(struct dma_chan *chan)
{
        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);

        spin_lock_bh(&dwc->lock);
        if (!list_empty(&dwc->queue))
                dwc_scan_descriptors(to_dw_dma(chan->device), dwc);
        spin_unlock_bh(&dwc->lock);
}

static int dwc_alloc_chan_resources(struct dma_chan *chan)
{
        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
        struct dw_dma           *dw = to_dw_dma(chan->device);
        struct dw_desc          *desc;
        struct dw_dma_slave     *dws;
        int                     i;
        u32                     cfghi;
        u32                     cfglo;

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

        /* ASSERT:  channel is idle */
        if (dma_readl(dw, CH_EN) & dwc->mask) {
                dev_dbg(chan2dev(chan), "DMA channel not idle?\n");
                return -EIO;
        }

        dwc->completed = chan->cookie = 1;

        cfghi = DWC_CFGH_FIFO_MODE;
        cfglo = 0;

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

                cfghi = dws->cfg_hi;
                cfglo = dws->cfg_lo;
        }
        channel_writel(dwc, CFG_LO, cfglo);
        channel_writel(dwc, CFG_HI, cfghi);

        /*
         * NOTE: some controllers may have additional features that we
         * need to initialize here, like "scatter-gather" (which
         * doesn't mean what you think it means), and status writeback.
         */

        spin_lock_bh(&dwc->lock);
        i = dwc->descs_allocated;
        while (dwc->descs_allocated < NR_DESCS_PER_CHANNEL) {
                spin_unlock_bh(&dwc->lock);

                desc = kzalloc(sizeof(struct dw_desc), GFP_KERNEL);
                if (!desc) {
                        dev_info(chan2dev(chan),
                                "only allocated %d descriptors\n", i);
                        spin_lock_bh(&dwc->lock);
                        break;
                }

                dma_async_tx_descriptor_init(&desc->txd, chan);
                desc->txd.tx_submit = dwc_tx_submit;
                desc->txd.flags = DMA_CTRL_ACK;
                INIT_LIST_HEAD(&desc->txd.tx_list);
                desc->txd.phys = dma_map_single(chan2parent(chan), &desc->lli,
                                sizeof(desc->lli), DMA_TO_DEVICE);
                dwc_desc_put(dwc, desc);

                spin_lock_bh(&dwc->lock);
                i = ++dwc->descs_allocated;
        }

        /* Enable interrupts */
        channel_set_bit(dw, MASK.XFER, dwc->mask);
        channel_set_bit(dw, MASK.BLOCK, dwc->mask);
        channel_set_bit(dw, MASK.ERROR, dwc->mask);

        spin_unlock_bh(&dwc->lock);

        dev_dbg(chan2dev(chan),
                "alloc_chan_resources allocated %d descriptors\n", i);

        return i;
}

static void dwc_free_chan_resources(struct dma_chan *chan)
{
        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
        struct dw_dma           *dw = to_dw_dma(chan->device);
        struct dw_desc          *desc, *_desc;
        LIST_HEAD(list);

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

        /* ASSERT:  channel is idle */
        BUG_ON(!list_empty(&dwc->active_list));
        BUG_ON(!list_empty(&dwc->queue));
        BUG_ON(dma_readl(to_dw_dma(chan->device), CH_EN) & dwc->mask);

        spin_lock_bh(&dwc->lock);
        list_splice_init(&dwc->free_list, &list);
        dwc->descs_allocated = 0;

        /* Disable interrupts */
        channel_clear_bit(dw, MASK.XFER, dwc->mask);
        channel_clear_bit(dw, MASK.BLOCK, dwc->mask);
        channel_clear_bit(dw, MASK.ERROR, dwc->mask);

        spin_unlock_bh(&dwc->lock);

        list_for_each_entry_safe(desc, _desc, &list, desc_node) {
                dev_vdbg(chan2dev(chan), "  freeing descriptor %p\n", desc);
                dma_unmap_single(chan2parent(chan), desc->txd.phys,
                                sizeof(desc->lli), DMA_TO_DEVICE);
                kfree(desc);
        }

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

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

static void dw_dma_off(struct dw_dma *dw)
{
        dma_writel(dw, CFG, 0);

        channel_clear_bit(dw, MASK.XFER, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.BLOCK, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.SRC_TRAN, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.DST_TRAN, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.ERROR, dw->all_chan_mask);

        while (dma_readl(dw, CFG) & DW_CFG_DMA_EN)
                cpu_relax();
}

static int __init dw_probe(struct platform_device *pdev)
{
        struct dw_dma_platform_data *pdata;
        struct resource         *io;
        struct dw_dma           *dw;
        size_t                  size;
        int                     irq;
        int                     err;
        int                     i;

        pdata = pdev->dev.platform_data;
        if (!pdata || pdata->nr_channels > DW_DMA_MAX_NR_CHANNELS)
                return -EINVAL;

        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 dw_dma);
        size += pdata->nr_channels * sizeof(struct dw_dma_chan);
        dw = kzalloc(size, GFP_KERNEL);
        if (!dw)
                return -ENOMEM;

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

        memset(dw, 0, sizeof *dw);

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

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

        /* force dma off, just in case */
        dw_dma_off(dw);

        err = request_irq(irq, dw_dma_interrupt, 0, "dw_dmac", dw);
        if (err)
                goto err_irq;

        platform_set_drvdata(pdev, dw);

        tasklet_init(&dw->tasklet, dw_dma_tasklet, (unsigned long)dw);

        dw->all_chan_mask = (1 << pdata->nr_channels) - 1;

        INIT_LIST_HEAD(&dw->dma.channels);
        for (i = 0; i < pdata->nr_channels; i++, dw->dma.chancnt++) {
                struct dw_dma_chan      *dwc = &dw->chan[i];

                dwc->chan.device = &dw->dma;
                dwc->chan.cookie = dwc->completed = 1;
                dwc->chan.chan_id = i;
                list_add_tail(&dwc->chan.device_node, &dw->dma.channels);

                dwc->ch_regs = &__dw_regs(dw)->CHAN[i];
                spin_lock_init(&dwc->lock);
                dwc->mask = 1 << i;

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

                channel_clear_bit(dw, CH_EN, dwc->mask);
        }

        /* Clear/disable all interrupts on all channels. */
        dma_writel(dw, CLEAR.XFER, dw->all_chan_mask);
        dma_writel(dw, CLEAR.BLOCK, dw->all_chan_mask);
        dma_writel(dw, CLEAR.SRC_TRAN, dw->all_chan_mask);
        dma_writel(dw, CLEAR.DST_TRAN, dw->all_chan_mask);
        dma_writel(dw, CLEAR.ERROR, dw->all_chan_mask);

        channel_clear_bit(dw, MASK.XFER, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.BLOCK, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.SRC_TRAN, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.DST_TRAN, dw->all_chan_mask);
        channel_clear_bit(dw, MASK.ERROR, dw->all_chan_mask);

        dma_cap_set(DMA_MEMCPY, dw->dma.cap_mask);
        dma_cap_set(DMA_SLAVE, dw->dma.cap_mask);
        dw->dma.dev = &pdev->dev;
        dw->dma.device_alloc_chan_resources = dwc_alloc_chan_resources;
        dw->dma.device_free_chan_resources = dwc_free_chan_resources;

        dw->dma.device_prep_dma_memcpy = dwc_prep_dma_memcpy;

        dw->dma.device_prep_slave_sg = dwc_prep_slave_sg;
        dw->dma.device_terminate_all = dwc_terminate_all;

        dw->dma.device_is_tx_complete = dwc_is_tx_complete;
        dw->dma.device_issue_pending = dwc_issue_pending;

        dma_writel(dw, CFG, DW_CFG_DMA_EN);

        printk(KERN_INFO "%s: DesignWare DMA Controller, %d channels\n",
                        dev_name(&pdev->dev), dw->dma.chancnt);

        dma_async_device_register(&dw->dma);

        return 0;

err_irq:
        clk_disable(dw->clk);
        clk_put(dw->clk);
err_clk:
        iounmap(dw->regs);
        dw->regs = NULL;
err_release_r:
        release_resource(io);
err_kfree:
        kfree(dw);
        return err;
}

static int __exit dw_remove(struct platform_device *pdev)
{
        struct dw_dma           *dw = platform_get_drvdata(pdev);
        struct dw_dma_chan      *dwc, *_dwc;
        struct resource         *io;

        dw_dma_off(dw);
        dma_async_device_unregister(&dw->dma);

        free_irq(platform_get_irq(pdev, 0), dw);
        tasklet_kill(&dw->tasklet);

        list_for_each_entry_safe(dwc, _dwc, &dw->dma.channels,
                        chan.device_node) {
                list_del(&dwc->chan.device_node);
                channel_clear_bit(dw, CH_EN, dwc->mask);
        }

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

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

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

        kfree(dw);

        return 0;
}

static void dw_shutdown(struct platform_device *pdev)
{
        struct dw_dma   *dw = platform_get_drvdata(pdev);

        dw_dma_off(platform_get_drvdata(pdev));
        clk_disable(dw->clk);
}

static int dw_suspend_late(struct platform_device *pdev, pm_message_t mesg)
{
        struct dw_dma   *dw = platform_get_drvdata(pdev);

        dw_dma_off(platform_get_drvdata(pdev));
        clk_disable(dw->clk);
        return 0;
}

static int dw_resume_early(struct platform_device *pdev)
{
        struct dw_dma   *dw = platform_get_drvdata(pdev);

        clk_enable(dw->clk);
        dma_writel(dw, CFG, DW_CFG_DMA_EN);
        return 0;

}

static struct platform_driver dw_driver = {
        .remove         = __exit_p(dw_remove),
        .shutdown       = dw_shutdown,
        .suspend_late   = dw_suspend_late,
        .resume_early   = dw_resume_early,
        .driver = {
                .name   = "dw_dmac",
        },
};

static int __init dw_init(void)
{
        return platform_driver_probe(&dw_driver, dw_probe);
}
module_init(dw_init);

static void __exit dw_exit(void)
{
        platform_driver_unregister(&dw_driver);
}
module_exit(dw_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Synopsys DesignWare DMA Controller driver");
MODULE_AUTHOR("Haavard Skinnemoen <haavard.skinnemoen@atmel.com>");