dmaengine: Driver for the Synopsys DesignWare DMA controller

This adds a driver for the Synopsys DesignWare DMA controller (aka
DMACA on AVR32 systems.) This DMA controller can be found integrated
on the AT32AP7000 chip and is primarily meant for peripheral DMA
transfer, but can also be used for memory-to-memory transfers.

This patch is based on a driver from David Brownell which was based on
an older version of the DMA Engine framework. It also implements the
proposed extensions to the DMA Engine API for slave DMA operations.

The dmatest client shows no problems, but there may still be room for
improvement performance-wise. DMA slave transfer performance is
definitely "good enough"; reading 100 MiB from an SD card running at ~20
MHz yields ~7.2 MiB/s average transfer rate.

Full documentation for this controller can be found in the Synopsys
DW AHB DMAC Databook:

http://www.synopsys.com/designware/docs/iip/DW_ahb_dmac/latest/doc/dw_ahb_dmac_db.pdf

The controller has lots of implementation options, so it's usually a
good idea to check the data sheet of the chip it's intergrated on as
well. The AT32AP7000 data sheet can be found here:

http://www.atmel.com/dyn/products/datasheets.asp?family_id=682


Changes since v4:
  * Use client_count instead of dma_chan_is_in_use()
  * Add missing include
  * Unmap buffers unless client told us not to

Changes since v3:
  * Update to latest DMA engine and DMA slave APIs
  * Embed the hw descriptor into the sw descriptor
  * Clean up and update MODULE_DESCRIPTION, copyright date, etc.

Changes since v2:
  * Dequeue all pending transfers in terminate_all()
  * Rename dw_dmac.h -> dw_dmac_regs.h
  * Define and use controller-specific dma_slave data
  * Fix up a few outdated comments
  * Define hardware registers as structs (doesn't generate better
    code, unfortunately, but it looks nicer.)
  * Get number of channels from platform_data instead of hardcoding it
    based on CONFIG_WHATEVER_CPU.
  * Give slave clients exclusive access to the channel

Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>,
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 1122 insertions, 0 deletions

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
new file mode 100644
index 000000000000..94df91771243
--- /dev/null
+++ b/drivers/dma/dw_dmac.c
@@ -0,0 +1,1122 @@
+/*
+ * 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 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(&dwc->chan.dev, "desc %p not ACKed\n", desc);
+                i++;
+        }
+        spin_unlock_bh(&dwc->lock);
+
+        dev_vdbg(&dwc->chan.dev, "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(dwc->chan.dev.parent,
+                                child->txd.phys, sizeof(child->lli),
+                                DMA_TO_DEVICE);
+        dma_sync_single_for_cpu(dwc->chan.dev.parent,
+                        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(&dwc->chan.dev,
+                                        "moving child desc %p to freelist\n",
+                                        child);
+                list_splice_init(&desc->txd.tx_list, &dwc->free_list);
+                dev_vdbg(&dwc->chan.dev, "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(&dwc->chan.dev,
+                        "BUG: Attempted to start non-idle channel\n");
+                dev_err(&dwc->chan.dev,
+                        "  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(&dwc->chan.dev, "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(dwc->chan.dev.parent, desc->lli.dar, desc->len,
+                                DMA_FROM_DEVICE);
+        if (!(txd->flags & DMA_COMPL_SKIP_SRC_UNMAP))
+                dma_unmap_page(dwc->chan.dev.parent, 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(&dwc->chan.dev,
+                        "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(&dwc->chan.dev, "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(&dwc->chan.dev,
+                "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, &dwc->chan.dev,
+                        "  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, &dwc->chan.dev,
+                        "Bad descriptor submitted for DMA!\n");
+        dev_printk(KERN_CRIT, &dwc->chan.dev,
+                        "  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.BLOCK);
+        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(&tx->chan->dev, "tx_submit: started %u\n",
+                                desc->txd.cookie);
+                dwc_dostart(dwc, desc);
+                list_add_tail(&desc->desc_node, &dwc->active_list);
+        } else {
+                dev_vdbg(&tx->chan->dev, "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(&chan->dev, "prep_dma_memcpy d0x%x s0x%x l0x%zx f0x%lx\n",
+                        dest, src, len, flags);
+
+        if (unlikely(!len)) {
+                dev_dbg(&chan->dev, "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(chan->dev.parent,
+                                        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(chan->dev.parent,
+                        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 = dwc->dws;
+        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(&chan->dev, "prep_dma_slave\n");
+
+        if (unlikely(!dws || !sg_len))
+                return NULL;
+
+        reg_width = dws->slave.reg_width;
+        prev = first = NULL;
+
+        sg_len = dma_map_sg(chan->dev.parent, 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->slave.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(&chan->dev,
+                                        "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(chan->dev.parent,
+                                                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->slave.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(&chan->dev,
+                                        "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(chan->dev.parent,
+                                                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(chan->dev.parent,
+                        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 dma_client *client)
+{
+        struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
+        struct dw_dma           *dw = to_dw_dma(chan->device);
+        struct dw_desc          *desc;
+        struct dma_slave        *slave;
+        struct dw_dma_slave     *dws;
+        int                     i;
+        u32                     cfghi;
+        u32                     cfglo;
+
+        dev_vdbg(&chan->dev, "alloc_chan_resources\n");
+
+        /* Channels doing slave DMA can only handle one client. */
+        if (dwc->dws || client->slave) {
+                if (chan->client_count)
+                        return -EBUSY;
+        }
+
+        /* ASSERT:  channel is idle */
+        if (dma_readl(dw, CH_EN) & dwc->mask) {
+                dev_dbg(&chan->dev, "DMA channel not idle?\n");
+                return -EIO;
+        }
+
+        dwc->completed = chan->cookie = 1;
+
+        cfghi = DWC_CFGH_FIFO_MODE;
+        cfglo = 0;
+
+        slave = client->slave;
+        if (slave) {
+                /*
+                 * We need controller-specific data to set up slave
+                 * transfers.
+                 */
+                BUG_ON(!slave->dma_dev || slave->dma_dev != dw->dma.dev);
+
+                dws = container_of(slave, struct dw_dma_slave, slave);
+
+                dwc->dws = dws;
+                cfghi = dws->cfg_hi;
+                cfglo = dws->cfg_lo;
+        } else {
+                dwc->dws = NULL;
+        }
+
+        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(&chan->dev,
+                                "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(chan->dev.parent, &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(&chan->dev,
+                "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(&chan->dev, "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;
+        dwc->dws = NULL;
+
+        /* 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(&chan->dev, "  freeing descriptor %p\n", desc);
+                dma_unmap_single(chan->dev.parent, desc->txd.phys,
+                                sizeof(desc->lli), DMA_TO_DEVICE);
+                kfree(desc);
+        }
+
+        dev_vdbg(&chan->dev, "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",
+                        pdev->dev.bus_id, 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>");