Merge branch 'topic/rcar' into for-linus

3 files changed, 1761 insertions, 1 deletions

diff --git a/drivers/dma/sh/Kconfig b/drivers/dma/sh/Kconfig
index 0349125a2e20..8190ad225a1b 100644
--- a/drivers/dma/sh/Kconfig
+++ b/drivers/dma/sh/Kconfig
@@ -2,6 +2,10 @@
 # DMA engine configuration for sh
 #
 
+config RENESAS_DMA
+	bool
+	select DMA_ENGINE
+
 #
 # DMA Engine Helpers
 #
@@ -12,7 +16,7 @@ config SH_DMAE_BASE
 	depends on !SUPERH || SH_DMA
 	depends on !SH_DMA_API
 	default y
-	select DMA_ENGINE
+	select RENESAS_DMA
 	help
 	  Enable support for the Renesas SuperH DMA controllers.
 
@@ -52,3 +56,11 @@ config RCAR_AUDMAC_PP
 	depends on SH_DMAE_BASE
 	help
 	  Enable support for the Renesas R-Car Audio DMAC Peripheral Peripheral controllers.
+
+config RCAR_DMAC
+	tristate "Renesas R-Car Gen2 DMA Controller"
+	depends on ARCH_SHMOBILE || COMPILE_TEST
+	select RENESAS_DMA
+	help
+	  This driver supports the general purpose DMA controller found in the
+	  Renesas R-Car second generation SoCs.
diff --git a/drivers/dma/sh/Makefile b/drivers/dma/sh/Makefile
index 0a5cfdb76e45..2852f9db61a4 100644
--- a/drivers/dma/sh/Makefile
+++ b/drivers/dma/sh/Makefile
@@ -16,3 +16,4 @@ obj-$(CONFIG_SH_DMAE) += shdma.o
 obj-$(CONFIG_SUDMAC) += sudmac.o
 obj-$(CONFIG_RCAR_HPB_DMAE) += rcar-hpbdma.o
 obj-$(CONFIG_RCAR_AUDMAC_PP) += rcar-audmapp.o
+obj-$(CONFIG_RCAR_DMAC) += rcar-dmac.o
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
new file mode 100644
index 000000000000..29dd09ad41ff
--- /dev/null
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -0,0 +1,1747 @@
+/*
+ * Renesas R-Car Gen2 DMA Controller Driver
+ *
+ * Copyright (C) 2014 Renesas Electronics Inc.
+ *
+ * Author: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_dma.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include "../dmaengine.h"
+
+/*
+ * struct rcar_dmac_xfer_chunk - Descriptor for a hardware transfer
+ * @node: entry in the parent's chunks list
+ * @src_addr: device source address
+ * @dst_addr: device destination address
+ * @size: transfer size in bytes
+ */
+struct rcar_dmac_xfer_chunk {
+	struct list_head node;
+
+	dma_addr_t src_addr;
+	dma_addr_t dst_addr;
+	u32 size;
+};
+
+/*
+ * struct rcar_dmac_hw_desc - Hardware descriptor for a transfer chunk
+ * @sar: value of the SAR register (source address)
+ * @dar: value of the DAR register (destination address)
+ * @tcr: value of the TCR register (transfer count)
+ */
+struct rcar_dmac_hw_desc {
+	u32 sar;
+	u32 dar;
+	u32 tcr;
+	u32 reserved;
+} __attribute__((__packed__));
+
+/*
+ * struct rcar_dmac_desc - R-Car Gen2 DMA Transfer Descriptor
+ * @async_tx: base DMA asynchronous transaction descriptor
+ * @direction: direction of the DMA transfer
+ * @xfer_shift: log2 of the transfer size
+ * @chcr: value of the channel configuration register for this transfer
+ * @node: entry in the channel's descriptors lists
+ * @chunks: list of transfer chunks for this transfer
+ * @running: the transfer chunk being currently processed
+ * @nchunks: number of transfer chunks for this transfer
+ * @hwdescs.use: whether the transfer descriptor uses hardware descriptors
+ * @hwdescs.mem: hardware descriptors memory for the transfer
+ * @hwdescs.dma: device address of the hardware descriptors memory
+ * @hwdescs.size: size of the hardware descriptors in bytes
+ * @size: transfer size in bytes
+ * @cyclic: when set indicates that the DMA transfer is cyclic
+ */
+struct rcar_dmac_desc {
+	struct dma_async_tx_descriptor async_tx;
+	enum dma_transfer_direction direction;
+	unsigned int xfer_shift;
+	u32 chcr;
+
+	struct list_head node;
+	struct list_head chunks;
+	struct rcar_dmac_xfer_chunk *running;
+	unsigned int nchunks;
+
+	struct {
+		bool use;
+		struct rcar_dmac_hw_desc *mem;
+		dma_addr_t dma;
+		size_t size;
+	} hwdescs;
+
+	unsigned int size;
+	bool cyclic;
+};
+
+#define to_rcar_dmac_desc(d)	container_of(d, struct rcar_dmac_desc, async_tx)
+
+/*
+ * struct rcar_dmac_desc_page - One page worth of descriptors
+ * @node: entry in the channel's pages list
+ * @descs: array of DMA descriptors
+ * @chunks: array of transfer chunk descriptors
+ */
+struct rcar_dmac_desc_page {
+	struct list_head node;
+
+	union {
+		struct rcar_dmac_desc descs[0];
+		struct rcar_dmac_xfer_chunk chunks[0];
+	};
+};
+
+#define RCAR_DMAC_DESCS_PER_PAGE					\
+	((PAGE_SIZE - offsetof(struct rcar_dmac_desc_page, descs)) /	\
+	sizeof(struct rcar_dmac_desc))
+#define RCAR_DMAC_XFER_CHUNKS_PER_PAGE					\
+	((PAGE_SIZE - offsetof(struct rcar_dmac_desc_page, chunks)) /	\
+	sizeof(struct rcar_dmac_xfer_chunk))
+
+/*
+ * struct rcar_dmac_chan - R-Car Gen2 DMA Controller Channel
+ * @chan: base DMA channel object
+ * @iomem: channel I/O memory base
+ * @index: index of this channel in the controller
+ * @src_xfer_size: size (in bytes) of hardware transfers on the source side
+ * @dst_xfer_size: size (in bytes) of hardware transfers on the destination side
+ * @src_slave_addr: slave source memory address
+ * @dst_slave_addr: slave destination memory address
+ * @mid_rid: hardware MID/RID for the DMA client using this channel
+ * @lock: protects the channel CHCR register and the desc members
+ * @desc.free: list of free descriptors
+ * @desc.pending: list of pending descriptors (submitted with tx_submit)
+ * @desc.active: list of active descriptors (activated with issue_pending)
+ * @desc.done: list of completed descriptors
+ * @desc.wait: list of descriptors waiting for an ack
+ * @desc.running: the descriptor being processed (a member of the active list)
+ * @desc.chunks_free: list of free transfer chunk descriptors
+ * @desc.pages: list of pages used by allocated descriptors
+ */
+struct rcar_dmac_chan {
+	struct dma_chan chan;
+	void __iomem *iomem;
+	unsigned int index;
+
+	unsigned int src_xfer_size;
+	unsigned int dst_xfer_size;
+	dma_addr_t src_slave_addr;
+	dma_addr_t dst_slave_addr;
+	int mid_rid;
+
+	spinlock_t lock;
+
+	struct {
+		struct list_head free;
+		struct list_head pending;
+		struct list_head active;
+		struct list_head done;
+		struct list_head wait;
+		struct rcar_dmac_desc *running;
+
+		struct list_head chunks_free;
+
+		struct list_head pages;
+	} desc;
+};
+
+#define to_rcar_dmac_chan(c)	container_of(c, struct rcar_dmac_chan, chan)
+
+/*
+ * struct rcar_dmac - R-Car Gen2 DMA Controller
+ * @engine: base DMA engine object
+ * @dev: the hardware device
+ * @iomem: remapped I/O memory base
+ * @n_channels: number of available channels
+ * @channels: array of DMAC channels
+ * @modules: bitmask of client modules in use
+ */
+struct rcar_dmac {
+	struct dma_device engine;
+	struct device *dev;
+	void __iomem *iomem;
+
+	unsigned int n_channels;
+	struct rcar_dmac_chan *channels;
+
+	unsigned long modules[256 / BITS_PER_LONG];
+};
+
+#define to_rcar_dmac(d)		container_of(d, struct rcar_dmac, engine)
+
+/* -----------------------------------------------------------------------------
+ * Registers
+ */
+
+#define RCAR_DMAC_CHAN_OFFSET(i)	(0x8000 + 0x80 * (i))
+
+#define RCAR_DMAISTA			0x0020
+#define RCAR_DMASEC			0x0030
+#define RCAR_DMAOR			0x0060
+#define RCAR_DMAOR_PRI_FIXED		(0 << 8)
+#define RCAR_DMAOR_PRI_ROUND_ROBIN	(3 << 8)
+#define RCAR_DMAOR_AE			(1 << 2)
+#define RCAR_DMAOR_DME			(1 << 0)
+#define RCAR_DMACHCLR			0x0080
+#define RCAR_DMADPSEC			0x00a0
+
+#define RCAR_DMASAR			0x0000
+#define RCAR_DMADAR			0x0004
+#define RCAR_DMATCR			0x0008
+#define RCAR_DMATCR_MASK		0x00ffffff
+#define RCAR_DMATSR			0x0028
+#define RCAR_DMACHCR			0x000c
+#define RCAR_DMACHCR_CAE		(1 << 31)
+#define RCAR_DMACHCR_CAIE		(1 << 30)
+#define RCAR_DMACHCR_DPM_DISABLED	(0 << 28)
+#define RCAR_DMACHCR_DPM_ENABLED	(1 << 28)
+#define RCAR_DMACHCR_DPM_REPEAT		(2 << 28)
+#define RCAR_DMACHCR_DPM_INFINITE	(3 << 28)
+#define RCAR_DMACHCR_RPT_SAR		(1 << 27)
+#define RCAR_DMACHCR_RPT_DAR		(1 << 26)
+#define RCAR_DMACHCR_RPT_TCR		(1 << 25)
+#define RCAR_DMACHCR_DPB		(1 << 22)
+#define RCAR_DMACHCR_DSE		(1 << 19)
+#define RCAR_DMACHCR_DSIE		(1 << 18)
+#define RCAR_DMACHCR_TS_1B		((0 << 20) | (0 << 3))
+#define RCAR_DMACHCR_TS_2B		((0 << 20) | (1 << 3))
+#define RCAR_DMACHCR_TS_4B		((0 << 20) | (2 << 3))
+#define RCAR_DMACHCR_TS_16B		((0 << 20) | (3 << 3))
+#define RCAR_DMACHCR_TS_32B		((1 << 20) | (0 << 3))
+#define RCAR_DMACHCR_TS_64B		((1 << 20) | (1 << 3))
+#define RCAR_DMACHCR_TS_8B		((1 << 20) | (3 << 3))
+#define RCAR_DMACHCR_DM_FIXED		(0 << 14)
+#define RCAR_DMACHCR_DM_INC		(1 << 14)
+#define RCAR_DMACHCR_DM_DEC		(2 << 14)
+#define RCAR_DMACHCR_SM_FIXED		(0 << 12)
+#define RCAR_DMACHCR_SM_INC		(1 << 12)
+#define RCAR_DMACHCR_SM_DEC		(2 << 12)
+#define RCAR_DMACHCR_RS_AUTO		(4 << 8)
+#define RCAR_DMACHCR_RS_DMARS		(8 << 8)
+#define RCAR_DMACHCR_IE			(1 << 2)
+#define RCAR_DMACHCR_TE			(1 << 1)
+#define RCAR_DMACHCR_DE			(1 << 0)
+#define RCAR_DMATCRB			0x0018
+#define RCAR_DMATSRB			0x0038
+#define RCAR_DMACHCRB			0x001c
+#define RCAR_DMACHCRB_DCNT(n)		((n) << 24)
+#define RCAR_DMACHCRB_DPTR_MASK		(0xff << 16)
+#define RCAR_DMACHCRB_DPTR_SHIFT	16
+#define RCAR_DMACHCRB_DRST		(1 << 15)
+#define RCAR_DMACHCRB_DTS		(1 << 8)
+#define RCAR_DMACHCRB_SLM_NORMAL	(0 << 4)
+#define RCAR_DMACHCRB_SLM_CLK(n)	((8 | (n)) << 4)
+#define RCAR_DMACHCRB_PRI(n)		((n) << 0)
+#define RCAR_DMARS			0x0040
+#define RCAR_DMABUFCR			0x0048
+#define RCAR_DMABUFCR_MBU(n)		((n) << 16)
+#define RCAR_DMABUFCR_ULB(n)		((n) << 0)
+#define RCAR_DMADPBASE			0x0050
+#define RCAR_DMADPBASE_MASK		0xfffffff0
+#define RCAR_DMADPBASE_SEL		(1 << 0)
+#define RCAR_DMADPCR			0x0054
+#define RCAR_DMADPCR_DIPT(n)		((n) << 24)
+#define RCAR_DMAFIXSAR			0x0010
+#define RCAR_DMAFIXDAR			0x0014
+#define RCAR_DMAFIXDPBASE		0x0060
+
+/* Hardcode the MEMCPY transfer size to 4 bytes. */
+#define RCAR_DMAC_MEMCPY_XFER_SIZE	4
+
+/* -----------------------------------------------------------------------------
+ * Device access
+ */
+
+static void rcar_dmac_write(struct rcar_dmac *dmac, u32 reg, u32 data)
+{
+	if (reg == RCAR_DMAOR)
+		writew(data, dmac->iomem + reg);
+	else
+		writel(data, dmac->iomem + reg);
+}
+
+static u32 rcar_dmac_read(struct rcar_dmac *dmac, u32 reg)
+{
+	if (reg == RCAR_DMAOR)
+		return readw(dmac->iomem + reg);
+	else
+		return readl(dmac->iomem + reg);
+}
+
+static u32 rcar_dmac_chan_read(struct rcar_dmac_chan *chan, u32 reg)
+{
+	if (reg == RCAR_DMARS)
+		return readw(chan->iomem + reg);
+	else
+		return readl(chan->iomem + reg);
+}
+
+static void rcar_dmac_chan_write(struct rcar_dmac_chan *chan, u32 reg, u32 data)
+{
+	if (reg == RCAR_DMARS)
+		writew(data, chan->iomem + reg);
+	else
+		writel(data, chan->iomem + reg);
+}
+
+/* -----------------------------------------------------------------------------
+ * Initialization and configuration
+ */
+
+static bool rcar_dmac_chan_is_busy(struct rcar_dmac_chan *chan)
+{
+	u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
+
+	return (chcr & (RCAR_DMACHCR_DE | RCAR_DMACHCR_TE)) == RCAR_DMACHCR_DE;
+}
+
+static void rcar_dmac_chan_start_xfer(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc = chan->desc.running;
+	u32 chcr = desc->chcr;
+
+	WARN_ON_ONCE(rcar_dmac_chan_is_busy(chan));
+
+	if (chan->mid_rid >= 0)
+		rcar_dmac_chan_write(chan, RCAR_DMARS, chan->mid_rid);
+
+	if (desc->hwdescs.use) {
+		dev_dbg(chan->chan.device->dev,
+			"chan%u: queue desc %p: %u@%pad\n",
+			chan->index, desc, desc->nchunks, &desc->hwdescs.dma);
+
+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+		rcar_dmac_chan_write(chan, RCAR_DMAFIXDPBASE,
+				     desc->hwdescs.dma >> 32);
+#endif
+		rcar_dmac_chan_write(chan, RCAR_DMADPBASE,
+				     (desc->hwdescs.dma & 0xfffffff0) |
+				     RCAR_DMADPBASE_SEL);
+		rcar_dmac_chan_write(chan, RCAR_DMACHCRB,
+				     RCAR_DMACHCRB_DCNT(desc->nchunks - 1) |
+				     RCAR_DMACHCRB_DRST);
+
+		/*
+		 * Program the descriptor stage interrupt to occur after the end
+		 * of the first stage.
+		 */
+		rcar_dmac_chan_write(chan, RCAR_DMADPCR, RCAR_DMADPCR_DIPT(1));
+
+		chcr |= RCAR_DMACHCR_RPT_SAR | RCAR_DMACHCR_RPT_DAR
+		     |  RCAR_DMACHCR_RPT_TCR | RCAR_DMACHCR_DPB;
+
+		/*
+		 * If the descriptor isn't cyclic enable normal descriptor mode
+		 * and the transfer completion interrupt.
+		 */
+		if (!desc->cyclic)
+			chcr |= RCAR_DMACHCR_DPM_ENABLED | RCAR_DMACHCR_IE;
+		/*
+		 * If the descriptor is cyclic and has a callback enable the
+		 * descriptor stage interrupt in infinite repeat mode.
+		 */
+		else if (desc->async_tx.callback)
+			chcr |= RCAR_DMACHCR_DPM_INFINITE | RCAR_DMACHCR_DSIE;
+		/*
+		 * Otherwise just select infinite repeat mode without any
+		 * interrupt.
+		 */
+		else
+			chcr |= RCAR_DMACHCR_DPM_INFINITE;
+	} else {
+		struct rcar_dmac_xfer_chunk *chunk = desc->running;
+
+		dev_dbg(chan->chan.device->dev,
+			"chan%u: queue chunk %p: %u@%pad -> %pad\n",
+			chan->index, chunk, chunk->size, &chunk->src_addr,
+			&chunk->dst_addr);
+
+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+		rcar_dmac_chan_write(chan, RCAR_DMAFIXSAR,
+				     chunk->src_addr >> 32);
+		rcar_dmac_chan_write(chan, RCAR_DMAFIXDAR,
+				     chunk->dst_addr >> 32);
+#endif
+		rcar_dmac_chan_write(chan, RCAR_DMASAR,
+				     chunk->src_addr & 0xffffffff);
+		rcar_dmac_chan_write(chan, RCAR_DMADAR,
+				     chunk->dst_addr & 0xffffffff);
+		rcar_dmac_chan_write(chan, RCAR_DMATCR,
+				     chunk->size >> desc->xfer_shift);
+
+		chcr |= RCAR_DMACHCR_DPM_DISABLED | RCAR_DMACHCR_IE;
+	}
+
+	rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr | RCAR_DMACHCR_DE);
+}
+
+static int rcar_dmac_init(struct rcar_dmac *dmac)
+{
+	u16 dmaor;
+
+	/* Clear all channels and enable the DMAC globally. */
+	rcar_dmac_write(dmac, RCAR_DMACHCLR, 0x7fff);
+	rcar_dmac_write(dmac, RCAR_DMAOR,
+			RCAR_DMAOR_PRI_FIXED | RCAR_DMAOR_DME);
+
+	dmaor = rcar_dmac_read(dmac, RCAR_DMAOR);
+	if ((dmaor & (RCAR_DMAOR_AE | RCAR_DMAOR_DME)) != RCAR_DMAOR_DME) {
+		dev_warn(dmac->dev, "DMAOR initialization failed.\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/* -----------------------------------------------------------------------------
+ * Descriptors submission
+ */
+
+static dma_cookie_t rcar_dmac_tx_submit(struct dma_async_tx_descriptor *tx)
+{
+	struct rcar_dmac_chan *chan = to_rcar_dmac_chan(tx->chan);
+	struct rcar_dmac_desc *desc = to_rcar_dmac_desc(tx);
+	unsigned long flags;
+	dma_cookie_t cookie;
+
+	spin_lock_irqsave(&chan->lock, flags);
+
+	cookie = dma_cookie_assign(tx);
+
+	dev_dbg(chan->chan.device->dev, "chan%u: submit #%d@%p\n",
+		chan->index, tx->cookie, desc);
+
+	list_add_tail(&desc->node, &chan->desc.pending);
+	desc->running = list_first_entry(&desc->chunks,
+					 struct rcar_dmac_xfer_chunk, node);
+
+	spin_unlock_irqrestore(&chan->lock, flags);
+
+	return cookie;
+}
+
+/* -----------------------------------------------------------------------------
+ * Descriptors allocation and free
+ */
+
+/*
+ * rcar_dmac_desc_alloc - Allocate a page worth of DMA descriptors
+ * @chan: the DMA channel
+ * @gfp: allocation flags
+ */
+static int rcar_dmac_desc_alloc(struct rcar_dmac_chan *chan, gfp_t gfp)
+{
+	struct rcar_dmac_desc_page *page;
+	LIST_HEAD(list);
+	unsigned int i;
+
+	page = (void *)get_zeroed_page(gfp);
+	if (!page)
+		return -ENOMEM;
+
+	for (i = 0; i < RCAR_DMAC_DESCS_PER_PAGE; ++i) {
+		struct rcar_dmac_desc *desc = &page->descs[i];
+
+		dma_async_tx_descriptor_init(&desc->async_tx, &chan->chan);
+		desc->async_tx.tx_submit = rcar_dmac_tx_submit;
+		INIT_LIST_HEAD(&desc->chunks);
+
+		list_add_tail(&desc->node, &list);
+	}
+
+	spin_lock_irq(&chan->lock);
+	list_splice_tail(&list, &chan->desc.free);
+	list_add_tail(&page->node, &chan->desc.pages);
+	spin_unlock_irq(&chan->lock);
+
+	return 0;
+}
+
+/*
+ * rcar_dmac_desc_put - Release a DMA transfer descriptor
+ * @chan: the DMA channel
+ * @desc: the descriptor
+ *
+ * Put the descriptor and its transfer chunk descriptors back in the channel's
+ * free descriptors lists. The descriptor's chunks list will be reinitialized to
+ * an empty list as a result.
+ *
+ * The descriptor must have been removed from the channel's lists before calling
+ * this function.
+ *
+ * Locking: Must be called in non-atomic context.
+ */
+static void rcar_dmac_desc_put(struct rcar_dmac_chan *chan,
+			       struct rcar_dmac_desc *desc)
+{
+	spin_lock_irq(&chan->lock);
+	list_splice_tail_init(&desc->chunks, &chan->desc.chunks_free);
+	list_add_tail(&desc->node, &chan->desc.free);
+	spin_unlock_irq(&chan->lock);
+}
+
+static void rcar_dmac_desc_recycle_acked(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc, *_desc;
+	LIST_HEAD(list);
+
+	/*
+	 * We have to temporarily move all descriptors from the wait list to a
+	 * local list as iterating over the wait list, even with
+	 * list_for_each_entry_safe, isn't safe if we release the channel lock
+	 * around the rcar_dmac_desc_put() call.
+	 */
+	spin_lock_irq(&chan->lock);
+	list_splice_init(&chan->desc.wait, &list);
+	spin_unlock_irq(&chan->lock);
+
+	list_for_each_entry_safe(desc, _desc, &list, node) {
+		if (async_tx_test_ack(&desc->async_tx)) {
+			list_del(&desc->node);
+			rcar_dmac_desc_put(chan, desc);
+		}
+	}
+
+	if (list_empty(&list))
+		return;
+
+	/* Put the remaining descriptors back in the wait list. */
+	spin_lock_irq(&chan->lock);
+	list_splice(&list, &chan->desc.wait);
+	spin_unlock_irq(&chan->lock);
+}
+
+/*
+ * rcar_dmac_desc_get - Allocate a descriptor for a DMA transfer
+ * @chan: the DMA channel
+ *
+ * Locking: This function must be called in a non-atomic context.
+ *
+ * Return: A pointer to the allocated descriptor or NULL if no descriptor can
+ * be allocated.
+ */
+static struct rcar_dmac_desc *rcar_dmac_desc_get(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc;
+	int ret;
+
+	/* Recycle acked descriptors before attempting allocation. */
+	rcar_dmac_desc_recycle_acked(chan);
+
+	spin_lock_irq(&chan->lock);
+
+	do {
+		if (list_empty(&chan->desc.free)) {
+			/*
+			 * No free descriptors, allocate a page worth of them
+			 * and try again, as someone else could race us to get
+			 * the newly allocated descriptors. If the allocation
+			 * fails return an error.
+			 */
+			spin_unlock_irq(&chan->lock);
+			ret = rcar_dmac_desc_alloc(chan, GFP_NOWAIT);
+			if (ret < 0)
+				return NULL;
+			spin_lock_irq(&chan->lock);
+			continue;
+		}
+
+		desc = list_first_entry(&chan->desc.free, struct rcar_dmac_desc,
+					node);
+		list_del(&desc->node);
+	} while (!desc);
+
+	spin_unlock_irq(&chan->lock);
+
+	return desc;
+}
+
+/*
+ * rcar_dmac_xfer_chunk_alloc - Allocate a page worth of transfer chunks
+ * @chan: the DMA channel
+ * @gfp: allocation flags
+ */
+static int rcar_dmac_xfer_chunk_alloc(struct rcar_dmac_chan *chan, gfp_t gfp)
+{
+	struct rcar_dmac_desc_page *page;
+	LIST_HEAD(list);
+	unsigned int i;
+
+	page = (void *)get_zeroed_page(gfp);
+	if (!page)
+		return -ENOMEM;
+
+	for (i = 0; i < RCAR_DMAC_XFER_CHUNKS_PER_PAGE; ++i) {
+		struct rcar_dmac_xfer_chunk *chunk = &page->chunks[i];
+
+		list_add_tail(&chunk->node, &list);
+	}
+
+	spin_lock_irq(&chan->lock);
+	list_splice_tail(&list, &chan->desc.chunks_free);
+	list_add_tail(&page->node, &chan->desc.pages);
+	spin_unlock_irq(&chan->lock);
+
+	return 0;
+}
+
+/*
+ * rcar_dmac_xfer_chunk_get - Allocate a transfer chunk for a DMA transfer
+ * @chan: the DMA channel
+ *
+ * Locking: This function must be called in a non-atomic context.
+ *
+ * Return: A pointer to the allocated transfer chunk descriptor or NULL if no
+ * descriptor can be allocated.
+ */
+static struct rcar_dmac_xfer_chunk *
+rcar_dmac_xfer_chunk_get(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_xfer_chunk *chunk;
+	int ret;
+
+	spin_lock_irq(&chan->lock);
+
+	do {
+		if (list_empty(&chan->desc.chunks_free)) {
+			/*
+			 * No free descriptors, allocate a page worth of them
+			 * and try again, as someone else could race us to get
+			 * the newly allocated descriptors. If the allocation
+			 * fails return an error.
+			 */
+			spin_unlock_irq(&chan->lock);
+			ret = rcar_dmac_xfer_chunk_alloc(chan, GFP_NOWAIT);
+			if (ret < 0)
+				return NULL;
+			spin_lock_irq(&chan->lock);
+			continue;
+		}
+
+		chunk = list_first_entry(&chan->desc.chunks_free,
+					  struct rcar_dmac_xfer_chunk, node);
+		list_del(&chunk->node);
+	} while (!chunk);
+
+	spin_unlock_irq(&chan->lock);
+
+	return chunk;
+}
+
+static void rcar_dmac_realloc_hwdesc(struct rcar_dmac_chan *chan,
+				     struct rcar_dmac_desc *desc, size_t size)
+{
+	/*
+	 * dma_alloc_coherent() allocates memory in page size increments. To
+	 * avoid reallocating the hardware descriptors when the allocated size
+	 * wouldn't change align the requested size to a multiple of the page
+	 * size.
+	 */
+	size = PAGE_ALIGN(size);
+
+	if (desc->hwdescs.size == size)
+		return;
+
+	if (desc->hwdescs.mem) {
+		dma_free_coherent(NULL, desc->hwdescs.size, desc->hwdescs.mem,
+				   desc->hwdescs.dma);
+		desc->hwdescs.mem = NULL;
+		desc->hwdescs.size = 0;
+	}
+
+	if (!size)
+		return;
+
+	desc->hwdescs.mem = dma_alloc_coherent(NULL, size, &desc->hwdescs.dma,
+					       GFP_NOWAIT);
+	if (!desc->hwdescs.mem)
+		return;
+
+	desc->hwdescs.size = size;
+}
+
+static int rcar_dmac_fill_hwdesc(struct rcar_dmac_chan *chan,
+				 struct rcar_dmac_desc *desc)
+{
+	struct rcar_dmac_xfer_chunk *chunk;
+	struct rcar_dmac_hw_desc *hwdesc;
+
+	rcar_dmac_realloc_hwdesc(chan, desc, desc->nchunks * sizeof(*hwdesc));
+
+	hwdesc = desc->hwdescs.mem;
+	if (!hwdesc)
+		return -ENOMEM;
+
+	list_for_each_entry(chunk, &desc->chunks, node) {
+		hwdesc->sar = chunk->src_addr;
+		hwdesc->dar = chunk->dst_addr;
+		hwdesc->tcr = chunk->size >> desc->xfer_shift;
+		hwdesc++;
+	}
+
+	return 0;
+}
+
+/* -----------------------------------------------------------------------------
+ * Stop and reset
+ */
+
+static void rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)
+{
+	u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
+
+	chcr &= ~(RCAR_DMACHCR_DSE | RCAR_DMACHCR_DSIE | RCAR_DMACHCR_IE |
+		  RCAR_DMACHCR_TE | RCAR_DMACHCR_DE);
+	rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr);
+}
+
+static void rcar_dmac_chan_reinit(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc, *_desc;
+	unsigned long flags;
+	LIST_HEAD(descs);
+
+	spin_lock_irqsave(&chan->lock, flags);
+
+	/* Move all non-free descriptors to the local lists. */
+	list_splice_init(&chan->desc.pending, &descs);
+	list_splice_init(&chan->desc.active, &descs);
+	list_splice_init(&chan->desc.done, &descs);
+	list_splice_init(&chan->desc.wait, &descs);
+
+	chan->desc.running = NULL;
+
+	spin_unlock_irqrestore(&chan->lock, flags);
+
+	list_for_each_entry_safe(desc, _desc, &descs, node) {
+		list_del(&desc->node);
+		rcar_dmac_desc_put(chan, desc);
+	}
+}
+
+static void rcar_dmac_stop(struct rcar_dmac *dmac)
+{
+	rcar_dmac_write(dmac, RCAR_DMAOR, 0);
+}
+
+static void rcar_dmac_abort(struct rcar_dmac *dmac)
+{
+	unsigned int i;
+
+	/* Stop all channels. */
+	for (i = 0; i < dmac->n_channels; ++i) {
+		struct rcar_dmac_chan *chan = &dmac->channels[i];
+
+		/* Stop and reinitialize the channel. */
+		spin_lock(&chan->lock);
+		rcar_dmac_chan_halt(chan);
+		spin_unlock(&chan->lock);
+
+		rcar_dmac_chan_reinit(chan);
+	}
+}
+
+/* -----------------------------------------------------------------------------
+ * Descriptors preparation
+ */
+
+static void rcar_dmac_chan_configure_desc(struct rcar_dmac_chan *chan,
+					  struct rcar_dmac_desc *desc)
+{
+	static const u32 chcr_ts[] = {
+		RCAR_DMACHCR_TS_1B, RCAR_DMACHCR_TS_2B,
+		RCAR_DMACHCR_TS_4B, RCAR_DMACHCR_TS_8B,
+		RCAR_DMACHCR_TS_16B, RCAR_DMACHCR_TS_32B,
+		RCAR_DMACHCR_TS_64B,
+	};
+
+	unsigned int xfer_size;
+	u32 chcr;
+
+	switch (desc->direction) {
+	case DMA_DEV_TO_MEM:
+		chcr = RCAR_DMACHCR_DM_INC | RCAR_DMACHCR_SM_FIXED
+		     | RCAR_DMACHCR_RS_DMARS;
+		xfer_size = chan->src_xfer_size;
+		break;
+
+	case DMA_MEM_TO_DEV:
+		chcr = RCAR_DMACHCR_DM_FIXED | RCAR_DMACHCR_SM_INC
+		     | RCAR_DMACHCR_RS_DMARS;
+		xfer_size = chan->dst_xfer_size;
+		break;
+
+	case DMA_MEM_TO_MEM:
+	default:
+		chcr = RCAR_DMACHCR_DM_INC | RCAR_DMACHCR_SM_INC
+		     | RCAR_DMACHCR_RS_AUTO;
+		xfer_size = RCAR_DMAC_MEMCPY_XFER_SIZE;
+		break;
+	}
+
+	desc->xfer_shift = ilog2(xfer_size);
+	desc->chcr = chcr | chcr_ts[desc->xfer_shift];
+}
+
+/*
+ * rcar_dmac_chan_prep_sg - prepare transfer descriptors from an SG list
+ *
+ * Common routine for public (MEMCPY) and slave DMA. The MEMCPY case is also
+ * converted to scatter-gather to guarantee consistent locking and a correct
+ * list manipulation. For slave DMA direction carries the usual meaning, and,
+ * logically, the SG list is RAM and the addr variable contains slave address,
+ * e.g., the FIFO I/O register. For MEMCPY direction equals DMA_MEM_TO_MEM
+ * and the SG list contains only one element and points at the source buffer.
+ */
+static struct dma_async_tx_descriptor *
+rcar_dmac_chan_prep_sg(struct rcar_dmac_chan *chan, struct scatterlist *sgl,
+		       unsigned int sg_len, dma_addr_t dev_addr,
+		       enum dma_transfer_direction dir, unsigned long dma_flags,
+		       bool cyclic)
+{
+	struct rcar_dmac_xfer_chunk *chunk;
+	struct rcar_dmac_desc *desc;
+	struct scatterlist *sg;
+	unsigned int nchunks = 0;
+	unsigned int max_chunk_size;
+	unsigned int full_size = 0;
+	bool highmem = false;
+	unsigned int i;
+
+	desc = rcar_dmac_desc_get(chan);
+	if (!desc)
+		return NULL;
+
+	desc->async_tx.flags = dma_flags;
+	desc->async_tx.cookie = -EBUSY;
+
+	desc->cyclic = cyclic;
+	desc->direction = dir;
+
+	rcar_dmac_chan_configure_desc(chan, desc);
+
+	max_chunk_size = (RCAR_DMATCR_MASK + 1) << desc->xfer_shift;
+
+	/*
+	 * Allocate and fill the transfer chunk descriptors. We own the only
+	 * reference to the DMA descriptor, there's no need for locking.
+	 */
+	for_each_sg(sgl, sg, sg_len, i) {
+		dma_addr_t mem_addr = sg_dma_address(sg);
+		unsigned int len = sg_dma_len(sg);
+
+		full_size += len;
+
+		while (len) {
+			unsigned int size = min(len, max_chunk_size);
+
+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+			/*
+			 * Prevent individual transfers from crossing 4GB
+			 * boundaries.
+			 */
+			if (dev_addr >> 32 != (dev_addr + size - 1) >> 32)
+				size = ALIGN(dev_addr, 1ULL << 32) - dev_addr;
+			if (mem_addr >> 32 != (mem_addr + size - 1) >> 32)
+				size = ALIGN(mem_addr, 1ULL << 32) - mem_addr;
+
+			/*
+			 * Check if either of the source or destination address
+			 * can't be expressed in 32 bits. If so we can't use
+			 * hardware descriptor lists.
+			 */
+			if (dev_addr >> 32 || mem_addr >> 32)
+				highmem = true;
+#endif
+
+			chunk = rcar_dmac_xfer_chunk_get(chan);
+			if (!chunk) {
+				rcar_dmac_desc_put(chan, desc);
+				return NULL;
+			}
+
+			if (dir == DMA_DEV_TO_MEM) {
+				chunk->src_addr = dev_addr;
+				chunk->dst_addr = mem_addr;
+			} else {
+				chunk->src_addr = mem_addr;
+				chunk->dst_addr = dev_addr;
+			}
+
+			chunk->size = size;
+
+			dev_dbg(chan->chan.device->dev,
+				"chan%u: chunk %p/%p sgl %u@%p, %u/%u %pad -> %pad\n",
+				chan->index, chunk, desc, i, sg, size, len,
+				&chunk->src_addr, &chunk->dst_addr);
+
+			mem_addr += size;
+			if (dir == DMA_MEM_TO_MEM)
+				dev_addr += size;
+
+			len -= size;
+
+			list_add_tail(&chunk->node, &desc->chunks);
+			nchunks++;
+		}
+	}
+
+	desc->nchunks = nchunks;
+	desc->size = full_size;
+
+	/*
+	 * Use hardware descriptor lists if possible when more than one chunk
+	 * needs to be transferred (otherwise they don't make much sense).
+	 *
+	 * The highmem check currently covers the whole transfer. As an
+	 * optimization we could use descriptor lists for consecutive lowmem
+	 * chunks and direct manual mode for highmem chunks. Whether the
+	 * performance improvement would be significant enough compared to the
+	 * additional complexity remains to be investigated.
+	 */
+	desc->hwdescs.use = !highmem && nchunks > 1;
+	if (desc->hwdescs.use) {
+		if (rcar_dmac_fill_hwdesc(chan, desc) < 0)
+			desc->hwdescs.use = false;
+	}
+
+	return &desc->async_tx;
+}
+
+/* -----------------------------------------------------------------------------
+ * DMA engine operations
+ */
+
+static int rcar_dmac_alloc_chan_resources(struct dma_chan *chan)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	int ret;
+
+	INIT_LIST_HEAD(&rchan->desc.free);
+	INIT_LIST_HEAD(&rchan->desc.pending);
+	INIT_LIST_HEAD(&rchan->desc.active);
+	INIT_LIST_HEAD(&rchan->desc.done);
+	INIT_LIST_HEAD(&rchan->desc.wait);
+	INIT_LIST_HEAD(&rchan->desc.chunks_free);
+	INIT_LIST_HEAD(&rchan->desc.pages);
+
+	/* Preallocate descriptors. */
+	ret = rcar_dmac_xfer_chunk_alloc(rchan, GFP_KERNEL);
+	if (ret < 0)
+		return -ENOMEM;
+
+	ret = rcar_dmac_desc_alloc(rchan, GFP_KERNEL);
+	if (ret < 0)
+		return -ENOMEM;
+
+	return pm_runtime_get_sync(chan->device->dev);
+}
+
+static void rcar_dmac_free_chan_resources(struct dma_chan *chan)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	struct rcar_dmac *dmac = to_rcar_dmac(chan->device);
+	struct rcar_dmac_desc_page *page, *_page;
+	struct rcar_dmac_desc *desc;
+	LIST_HEAD(list);
+
+	/* Protect against ISR */
+	spin_lock_irq(&rchan->lock);
+	rcar_dmac_chan_halt(rchan);
+	spin_unlock_irq(&rchan->lock);
+
+	/* Now no new interrupts will occur */
+
+	if (rchan->mid_rid >= 0) {
+		/* The caller is holding dma_list_mutex */
+		clear_bit(rchan->mid_rid, dmac->modules);
+		rchan->mid_rid = -EINVAL;
+	}
+
+	list_splice(&rchan->desc.free, &list);
+	list_splice(&rchan->desc.pending, &list);
+	list_splice(&rchan->desc.active, &list);
+	list_splice(&rchan->desc.done, &list);
+	list_splice(&rchan->desc.wait, &list);
+
+	list_for_each_entry(desc, &list, node)
+		rcar_dmac_realloc_hwdesc(rchan, desc, 0);
+
+	list_for_each_entry_safe(page, _page, &rchan->desc.pages, node) {
+		list_del(&page->node);
+		free_page((unsigned long)page);
+	}
+
+	pm_runtime_put(chan->device->dev);
+}
+
+static struct dma_async_tx_descriptor *
+rcar_dmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dma_dest,
+			  dma_addr_t dma_src, size_t len, unsigned long flags)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	struct scatterlist sgl;
+
+	if (!len)
+		return NULL;
+
+	sg_init_table(&sgl, 1);
+	sg_set_page(&sgl, pfn_to_page(PFN_DOWN(dma_src)), len,
+		    offset_in_page(dma_src));
+	sg_dma_address(&sgl) = dma_src;
+	sg_dma_len(&sgl) = len;
+
+	return rcar_dmac_chan_prep_sg(rchan, &sgl, 1, dma_dest,
+				      DMA_MEM_TO_MEM, flags, false);
+}
+
+static struct dma_async_tx_descriptor *
+rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
+			unsigned int sg_len, enum dma_transfer_direction dir,
+			unsigned long flags, void *context)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	dma_addr_t dev_addr;
+
+	/* Someone calling slave DMA on a generic channel? */
+	if (rchan->mid_rid < 0 || !sg_len) {
+		dev_warn(chan->device->dev,
+			 "%s: bad parameter: len=%d, id=%d\n",
+			 __func__, sg_len, rchan->mid_rid);
+		return NULL;
+	}
+
+	dev_addr = dir == DMA_DEV_TO_MEM
+		 ? rchan->src_slave_addr : rchan->dst_slave_addr;
+	return rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
+				      dir, flags, false);
+}
+
+#define RCAR_DMAC_MAX_SG_LEN	32
+
+static struct dma_async_tx_descriptor *
+rcar_dmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
+			  size_t buf_len, size_t period_len,
+			  enum dma_transfer_direction dir, unsigned long flags)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	struct dma_async_tx_descriptor *desc;
+	struct scatterlist *sgl;
+	dma_addr_t dev_addr;
+	unsigned int sg_len;
+	unsigned int i;
+
+	/* Someone calling slave DMA on a generic channel? */
+	if (rchan->mid_rid < 0 || buf_len < period_len) {
+		dev_warn(chan->device->dev,
+			"%s: bad parameter: buf_len=%zu, period_len=%zu, id=%d\n",
+			__func__, buf_len, period_len, rchan->mid_rid);
+		return NULL;
+	}
+
+	sg_len = buf_len / period_len;
+	if (sg_len > RCAR_DMAC_MAX_SG_LEN) {
+		dev_err(chan->device->dev,
+			"chan%u: sg length %d exceds limit %d",
+			rchan->index, sg_len, RCAR_DMAC_MAX_SG_LEN);
+		return NULL;
+	}
+
+	/*
+	 * Allocate the sg list dynamically as it would consume too much stack
+	 * space.
+	 */
+	sgl = kcalloc(sg_len, sizeof(*sgl), GFP_NOWAIT);
+	if (!sgl)
+		return NULL;
+
+	sg_init_table(sgl, sg_len);
+
+	for (i = 0; i < sg_len; ++i) {
+		dma_addr_t src = buf_addr + (period_len * i);
+
+		sg_set_page(&sgl[i], pfn_to_page(PFN_DOWN(src)), period_len,
+			    offset_in_page(src));
+		sg_dma_address(&sgl[i]) = src;
+		sg_dma_len(&sgl[i]) = period_len;
+	}
+
+	dev_addr = dir == DMA_DEV_TO_MEM
+		 ? rchan->src_slave_addr : rchan->dst_slave_addr;
+	desc = rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
+				      dir, flags, true);
+
+	kfree(sgl);
+	return desc;
+}
+
+static int rcar_dmac_device_config(struct dma_chan *chan,
+				   struct dma_slave_config *cfg)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+
+	/*
+	 * We could lock this, but you shouldn't be configuring the
+	 * channel, while using it...
+	 */
+	rchan->src_slave_addr = cfg->src_addr;
+	rchan->dst_slave_addr = cfg->dst_addr;
+	rchan->src_xfer_size = cfg->src_addr_width;
+	rchan->dst_xfer_size = cfg->dst_addr_width;
+
+	return 0;
+}
+
+static int rcar_dmac_chan_terminate_all(struct dma_chan *chan)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	unsigned long flags;
+
+	spin_lock_irqsave(&rchan->lock, flags);
+	rcar_dmac_chan_halt(rchan);
+	spin_unlock_irqrestore(&rchan->lock, flags);
+
+	/*
+	 * FIXME: No new interrupt can occur now, but the IRQ thread might still
+	 * be running.
+	 */
+
+	rcar_dmac_chan_reinit(rchan);
+
+	return 0;
+}
+
+static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
+					       dma_cookie_t cookie)
+{
+	struct rcar_dmac_desc *desc = chan->desc.running;
+	struct rcar_dmac_xfer_chunk *running = NULL;
+	struct rcar_dmac_xfer_chunk *chunk;
+	unsigned int residue = 0;
+	unsigned int dptr = 0;
+
+	if (!desc)
+		return 0;
+
+	/*
+	 * If the cookie doesn't correspond to the currently running transfer
+	 * then the descriptor hasn't been processed yet, and the residue is
+	 * equal to the full descriptor size.
+	 */
+	if (cookie != desc->async_tx.cookie)
+		return desc->size;
+
+	/*
+	 * In descriptor mode the descriptor running pointer is not maintained
+	 * by the interrupt handler, find the running descriptor from the
+	 * descriptor pointer field in the CHCRB register. In non-descriptor
+	 * mode just use the running descriptor pointer.
+	 */
+	if (desc->hwdescs.use) {
+		dptr = (rcar_dmac_chan_read(chan, RCAR_DMACHCRB) &
+			RCAR_DMACHCRB_DPTR_MASK) >> RCAR_DMACHCRB_DPTR_SHIFT;
+		WARN_ON(dptr >= desc->nchunks);
+	} else {
+		running = desc->running;
+	}
+
+	/* Compute the size of all chunks still to be transferred. */
+	list_for_each_entry_reverse(chunk, &desc->chunks, node) {
+		if (chunk == running || ++dptr == desc->nchunks)
+			break;
+
+		residue += chunk->size;
+	}
+
+	/* Add the residue for the current chunk. */
+	residue += rcar_dmac_chan_read(chan, RCAR_DMATCR) << desc->xfer_shift;
+
+	return residue;
+}
+
+static enum dma_status rcar_dmac_tx_status(struct dma_chan *chan,
+					   dma_cookie_t cookie,
+					   struct dma_tx_state *txstate)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	enum dma_status status;
+	unsigned long flags;
+	unsigned int residue;
+
+	status = dma_cookie_status(chan, cookie, txstate);
+	if (status == DMA_COMPLETE || !txstate)
+		return status;
+
+	spin_lock_irqsave(&rchan->lock, flags);
+	residue = rcar_dmac_chan_get_residue(rchan, cookie);
+	spin_unlock_irqrestore(&rchan->lock, flags);
+
+	dma_set_residue(txstate, residue);
+
+	return status;
+}
+
+static void rcar_dmac_issue_pending(struct dma_chan *chan)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	unsigned long flags;
+
+	spin_lock_irqsave(&rchan->lock, flags);
+
+	if (list_empty(&rchan->desc.pending))
+		goto done;
+
+	/* Append the pending list to the active list. */
+	list_splice_tail_init(&rchan->desc.pending, &rchan->desc.active);
+
+	/*
+	 * If no transfer is running pick the first descriptor from the active
+	 * list and start the transfer.
+	 */
+	if (!rchan->desc.running) {
+		struct rcar_dmac_desc *desc;
+
+		desc = list_first_entry(&rchan->desc.active,
+					struct rcar_dmac_desc, node);
+		rchan->desc.running = desc;
+
+		rcar_dmac_chan_start_xfer(rchan);
+	}
+
+done:
+	spin_unlock_irqrestore(&rchan->lock, flags);
+}
+
+/* -----------------------------------------------------------------------------
+ * IRQ handling
+ */
+
+static irqreturn_t rcar_dmac_isr_desc_stage_end(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc = chan->desc.running;
+	unsigned int stage;
+
+	if (WARN_ON(!desc || !desc->cyclic)) {
+		/*
+		 * This should never happen, there should always be a running
+		 * cyclic descriptor when a descriptor stage end interrupt is
+		 * triggered. Warn and return.
+		 */
+		return IRQ_NONE;
+	}
+
+	/* Program the interrupt pointer to the next stage. */
+	stage = (rcar_dmac_chan_read(chan, RCAR_DMACHCRB) &
+		 RCAR_DMACHCRB_DPTR_MASK) >> RCAR_DMACHCRB_DPTR_SHIFT;
+	rcar_dmac_chan_write(chan, RCAR_DMADPCR, RCAR_DMADPCR_DIPT(stage));
+
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t rcar_dmac_isr_transfer_end(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc = chan->desc.running;
+	irqreturn_t ret = IRQ_WAKE_THREAD;
+
+	if (WARN_ON_ONCE(!desc)) {
+		/*
+		 * This should never happen, there should always be a running
+		 * descriptor when a transfer end interrupt is triggered. Warn
+		 * and return.
+		 */
+		return IRQ_NONE;
+	}
+
+	/*
+	 * The transfer end interrupt isn't generated for each chunk when using
+	 * descriptor mode. Only update the running chunk pointer in
+	 * non-descriptor mode.
+	 */
+	if (!desc->hwdescs.use) {
+		/*
+		 * If we haven't completed the last transfer chunk simply move
+		 * to the next one. Only wake the IRQ thread if the transfer is
+		 * cyclic.
+		 */
+		if (!list_is_last(&desc->running->node, &desc->chunks)) {
+			desc->running = list_next_entry(desc->running, node);
+			if (!desc->cyclic)
+				ret = IRQ_HANDLED;
+			goto done;
+		}
+
+		/*
+		 * We've completed the last transfer chunk. If the transfer is
+		 * cyclic, move back to the first one.
+		 */
+		if (desc->cyclic) {
+			desc->running =
+				list_first_entry(&desc->chunks,
+						 struct rcar_dmac_xfer_chunk,
+						 node);
+			goto done;
+		}
+	}
+
+	/* The descriptor is complete, move it to the done list. */
+	list_move_tail(&desc->node, &chan->desc.done);
+
+	/* Queue the next descriptor, if any. */
+	if (!list_empty(&chan->desc.active))
+		chan->desc.running = list_first_entry(&chan->desc.active,
+						      struct rcar_dmac_desc,
+						      node);
+	else
+		chan->desc.running = NULL;
+
+done:
+	if (chan->desc.running)
+		rcar_dmac_chan_start_xfer(chan);
+
+	return ret;
+}
+
+static irqreturn_t rcar_dmac_isr_channel(int irq, void *dev)
+{
+	u32 mask = RCAR_DMACHCR_DSE | RCAR_DMACHCR_TE;
+	struct rcar_dmac_chan *chan = dev;
+	irqreturn_t ret = IRQ_NONE;
+	u32 chcr;
+
+	spin_lock(&chan->lock);
+
+	chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
+	if (chcr & RCAR_DMACHCR_TE)
+		mask |= RCAR_DMACHCR_DE;
+	rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr & ~mask);
+
+	if (chcr & RCAR_DMACHCR_DSE)
+		ret |= rcar_dmac_isr_desc_stage_end(chan);
+
+	if (chcr & RCAR_DMACHCR_TE)
+		ret |= rcar_dmac_isr_transfer_end(chan);
+
+	spin_unlock(&chan->lock);
+
+	return ret;
+}
+
+static irqreturn_t rcar_dmac_isr_channel_thread(int irq, void *dev)
+{
+	struct rcar_dmac_chan *chan = dev;
+	struct rcar_dmac_desc *desc;
+
+	spin_lock_irq(&chan->lock);
+
+	/* For cyclic transfers notify the user after every chunk. */
+	if (chan->desc.running && chan->desc.running->cyclic) {
+		dma_async_tx_callback callback;
+		void *callback_param;
+
+		desc = chan->desc.running;
+		callback = desc->async_tx.callback;
+		callback_param = desc->async_tx.callback_param;
+
+		if (callback) {
+			spin_unlock_irq(&chan->lock);
+			callback(callback_param);
+			spin_lock_irq(&chan->lock);
+		}
+	}
+
+	/*
+	 * Call the callback function for all descriptors on the done list and
+	 * move them to the ack wait list.
+	 */
+	while (!list_empty(&chan->desc.done)) {
+		desc = list_first_entry(&chan->desc.done, struct rcar_dmac_desc,
+					node);
+		dma_cookie_complete(&desc->async_tx);
+		list_del(&desc->node);
+
+		if (desc->async_tx.callback) {
+			spin_unlock_irq(&chan->lock);
+			/*
+			 * We own the only reference to this descriptor, we can
+			 * safely dereference it without holding the channel
+			 * lock.
+			 */
+			desc->async_tx.callback(desc->async_tx.callback_param);
+			spin_lock_irq(&chan->lock);
+		}
+
+		list_add_tail(&desc->node, &chan->desc.wait);
+	}
+
+	spin_unlock_irq(&chan->lock);
+
+	/* Recycle all acked descriptors. */
+	rcar_dmac_desc_recycle_acked(chan);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t rcar_dmac_isr_error(int irq, void *data)
+{
+	struct rcar_dmac *dmac = data;
+
+	if (!(rcar_dmac_read(dmac, RCAR_DMAOR) & RCAR_DMAOR_AE))
+		return IRQ_NONE;
+
+	/*
+	 * An unrecoverable error occurred on an unknown channel. Halt the DMAC,
+	 * abort transfers on all channels, and reinitialize the DMAC.
+	 */
+	rcar_dmac_stop(dmac);
+	rcar_dmac_abort(dmac);
+	rcar_dmac_init(dmac);
+
+	return IRQ_HANDLED;
+}
+
+/* -----------------------------------------------------------------------------
+ * OF xlate and channel filter
+ */
+
+static bool rcar_dmac_chan_filter(struct dma_chan *chan, void *arg)
+{
+	struct rcar_dmac *dmac = to_rcar_dmac(chan->device);
+	struct of_phandle_args *dma_spec = arg;
+
+	/*
+	 * FIXME: Using a filter on OF platforms is a nonsense. The OF xlate
+	 * function knows from which device it wants to allocate a channel from,
+	 * and would be perfectly capable of selecting the channel it wants.
+	 * Forcing it to call dma_request_channel() and iterate through all
+	 * channels from all controllers is just pointless.
+	 */
+	if (chan->device->device_config != rcar_dmac_device_config ||
+	    dma_spec->np != chan->device->dev->of_node)
+		return false;
+
+	return !test_and_set_bit(dma_spec->args[0], dmac->modules);
+}
+
+static struct dma_chan *rcar_dmac_of_xlate(struct of_phandle_args *dma_spec,
+					   struct of_dma *ofdma)
+{
+	struct rcar_dmac_chan *rchan;
+	struct dma_chan *chan;
+	dma_cap_mask_t mask;
+
+	if (dma_spec->args_count != 1)
+		return NULL;
+
+	/* Only slave DMA channels can be allocated via DT */
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_SLAVE, mask);
+
+	chan = dma_request_channel(mask, rcar_dmac_chan_filter, dma_spec);
+	if (!chan)
+		return NULL;
+
+	rchan = to_rcar_dmac_chan(chan);
+	rchan->mid_rid = dma_spec->args[0];
+
+	return chan;
+}
+
+/* -----------------------------------------------------------------------------
+ * Power management
+ */
+
+#ifdef CONFIG_PM_SLEEP
+static int rcar_dmac_sleep_suspend(struct device *dev)
+{
+	/*
+	 * TODO: Wait for the current transfer to complete and stop the device.
+	 */
+	return 0;
+}
+
+static int rcar_dmac_sleep_resume(struct device *dev)
+{
+	/* TODO: Resume transfers, if any. */
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_PM
+static int rcar_dmac_runtime_suspend(struct device *dev)
+{
+	return 0;
+}
+
+static int rcar_dmac_runtime_resume(struct device *dev)
+{
+	struct rcar_dmac *dmac = dev_get_drvdata(dev);
+
+	return rcar_dmac_init(dmac);
+}
+#endif
+
+static const struct dev_pm_ops rcar_dmac_pm = {
+	SET_SYSTEM_SLEEP_PM_OPS(rcar_dmac_sleep_suspend, rcar_dmac_sleep_resume)
+	SET_RUNTIME_PM_OPS(rcar_dmac_runtime_suspend, rcar_dmac_runtime_resume,
+			   NULL)
+};
+
+/* -----------------------------------------------------------------------------
+ * Probe and remove
+ */
+
+static int rcar_dmac_chan_probe(struct rcar_dmac *dmac,
+				struct rcar_dmac_chan *rchan,
+				unsigned int index)
+{
+	struct platform_device *pdev = to_platform_device(dmac->dev);
+	struct dma_chan *chan = &rchan->chan;
+	char pdev_irqname[5];
+	char *irqname;
+	int irq;
+	int ret;
+
+	rchan->index = index;
+	rchan->iomem = dmac->iomem + RCAR_DMAC_CHAN_OFFSET(index);
+	rchan->mid_rid = -EINVAL;
+
+	spin_lock_init(&rchan->lock);
+
+	/* Request the channel interrupt. */
+	sprintf(pdev_irqname, "ch%u", index);
+	irq = platform_get_irq_byname(pdev, pdev_irqname);
+	if (irq < 0) {
+		dev_err(dmac->dev, "no IRQ specified for channel %u\n", index);
+		return -ENODEV;
+	}
+
+	irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
+				 dev_name(dmac->dev), index);
+	if (!irqname)
+		return -ENOMEM;
+
+	ret = devm_request_threaded_irq(dmac->dev, irq, rcar_dmac_isr_channel,
+					rcar_dmac_isr_channel_thread, 0,
+					irqname, rchan);
+	if (ret) {
+		dev_err(dmac->dev, "failed to request IRQ %u (%d)\n", irq, ret);
+		return ret;
+	}
+
+	/*
+	 * Initialize the DMA engine channel and add it to the DMA engine
+	 * channels list.
+	 */
+	chan->device = &dmac->engine;
+	dma_cookie_init(chan);
+
+	list_add_tail(&chan->device_node, &dmac->engine.channels);
+
+	return 0;
+}
+
+static int rcar_dmac_parse_of(struct device *dev, struct rcar_dmac *dmac)
+{
+	struct device_node *np = dev->of_node;
+	int ret;
+
+	ret = of_property_read_u32(np, "dma-channels", &dmac->n_channels);
+	if (ret < 0) {
+		dev_err(dev, "unable to read dma-channels property\n");
+		return ret;
+	}
+
+	if (dmac->n_channels <= 0 || dmac->n_channels >= 100) {
+		dev_err(dev, "invalid number of channels %u\n",
+			dmac->n_channels);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int rcar_dmac_probe(struct platform_device *pdev)
+{
+	const enum dma_slave_buswidth widths = DMA_SLAVE_BUSWIDTH_1_BYTE |
+		DMA_SLAVE_BUSWIDTH_2_BYTES | DMA_SLAVE_BUSWIDTH_4_BYTES |
+		DMA_SLAVE_BUSWIDTH_8_BYTES | DMA_SLAVE_BUSWIDTH_16_BYTES |
+		DMA_SLAVE_BUSWIDTH_32_BYTES | DMA_SLAVE_BUSWIDTH_64_BYTES;
+	struct dma_device *engine;
+	struct rcar_dmac *dmac;
+	struct resource *mem;
+	unsigned int i;
+	char *irqname;
+	int irq;
+	int ret;
+
+	dmac = devm_kzalloc(&pdev->dev, sizeof(*dmac), GFP_KERNEL);
+	if (!dmac)
+		return -ENOMEM;
+
+	dmac->dev = &pdev->dev;
+	platform_set_drvdata(pdev, dmac);
+
+	ret = rcar_dmac_parse_of(&pdev->dev, dmac);
+	if (ret < 0)
+		return ret;
+
+	dmac->channels = devm_kcalloc(&pdev->dev, dmac->n_channels,
+				      sizeof(*dmac->channels), GFP_KERNEL);
+	if (!dmac->channels)
+		return -ENOMEM;
+
+	/* Request resources. */
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	dmac->iomem = devm_ioremap_resource(&pdev->dev, mem);
+	if (IS_ERR(dmac->iomem))
+		return PTR_ERR(dmac->iomem);
+
+	irq = platform_get_irq_byname(pdev, "error");
+	if (irq < 0) {
+		dev_err(&pdev->dev, "no error IRQ specified\n");
+		return -ENODEV;
+	}
+
+	irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:error",
+				 dev_name(dmac->dev));
+	if (!irqname)
+		return -ENOMEM;
+
+	ret = devm_request_irq(&pdev->dev, irq, rcar_dmac_isr_error, 0,
+			       irqname, dmac);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to request IRQ %u (%d)\n",
+			irq, ret);
+		return ret;
+	}
+
+	/* Enable runtime PM and initialize the device. */
+	pm_runtime_enable(&pdev->dev);
+	ret = pm_runtime_get_sync(&pdev->dev);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "runtime PM get sync failed (%d)\n", ret);
+		return ret;
+	}
+
+	ret = rcar_dmac_init(dmac);
+	pm_runtime_put(&pdev->dev);
+
+	if (ret) {
+		dev_err(&pdev->dev, "failed to reset device\n");
+		goto error;
+	}
+
+	/* Initialize the channels. */
+	INIT_LIST_HEAD(&dmac->engine.channels);
+
+	for (i = 0; i < dmac->n_channels; ++i) {
+		ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i], i);
+		if (ret < 0)
+			goto error;
+	}
+
+	/* Register the DMAC as a DMA provider for DT. */
+	ret = of_dma_controller_register(pdev->dev.of_node, rcar_dmac_of_xlate,
+					 NULL);
+	if (ret < 0)
+		goto error;
+
+	/*
+	 * Register the DMA engine device.
+	 *
+	 * Default transfer size of 32 bytes requires 32-byte alignment.
+	 */
+	engine = &dmac->engine;
+	dma_cap_set(DMA_MEMCPY, engine->cap_mask);
+	dma_cap_set(DMA_SLAVE, engine->cap_mask);
+
+	engine->dev = &pdev->dev;
+	engine->copy_align = ilog2(RCAR_DMAC_MEMCPY_XFER_SIZE);
+
+	engine->src_addr_widths = widths;
+	engine->dst_addr_widths = widths;
+	engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
+	engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
+
+	engine->device_alloc_chan_resources = rcar_dmac_alloc_chan_resources;
+	engine->device_free_chan_resources = rcar_dmac_free_chan_resources;
+	engine->device_prep_dma_memcpy = rcar_dmac_prep_dma_memcpy;
+	engine->device_prep_slave_sg = rcar_dmac_prep_slave_sg;
+	engine->device_prep_dma_cyclic = rcar_dmac_prep_dma_cyclic;
+	engine->device_config = rcar_dmac_device_config;
+	engine->device_terminate_all = rcar_dmac_chan_terminate_all;
+	engine->device_tx_status = rcar_dmac_tx_status;
+	engine->device_issue_pending = rcar_dmac_issue_pending;
+
+	ret = dma_async_device_register(engine);
+	if (ret < 0)
+		goto error;
+
+	return 0;
+
+error:
+	of_dma_controller_free(pdev->dev.of_node);
+	pm_runtime_disable(&pdev->dev);
+	return ret;
+}
+
+static int rcar_dmac_remove(struct platform_device *pdev)
+{
+	struct rcar_dmac *dmac = platform_get_drvdata(pdev);
+
+	of_dma_controller_free(pdev->dev.of_node);
+	dma_async_device_unregister(&dmac->engine);
+
+	pm_runtime_disable(&pdev->dev);
+
+	return 0;
+}
+
+static void rcar_dmac_shutdown(struct platform_device *pdev)
+{
+	struct rcar_dmac *dmac = platform_get_drvdata(pdev);
+
+	rcar_dmac_stop(dmac);
+}
+
+static const struct of_device_id rcar_dmac_of_ids[] = {
+	{ .compatible = "renesas,rcar-dmac", },
+	{ /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rcar_dmac_of_ids);
+
+static struct platform_driver rcar_dmac_driver = {
+	.driver		= {
+		.pm	= &rcar_dmac_pm,
+		.name	= "rcar-dmac",
+		.of_match_table = rcar_dmac_of_ids,
+	},
+	.probe		= rcar_dmac_probe,
+	.remove		= rcar_dmac_remove,
+	.shutdown	= rcar_dmac_shutdown,
+};
+
+module_platform_driver(rcar_dmac_driver);
+
+MODULE_DESCRIPTION("R-Car Gen2 DMA Controller Driver");
+MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
+MODULE_LICENSE("GPL v2");