dmaengine: rcar-dmac: Add Renesas R-Car Gen2 DMA Controller (DMAC) driver

The DMAC is a general purpose multi-channel DMA controller that supports
both slave and memcpy transfers.

The driver currently supports the DMAC found in the r8a7790 and r8a7791
SoCs. Support for compatible DMA controllers (such as the audio DMAC)
will be added later.

Feature-wise, automatic hardware handling of descriptors chains isn't
supported yet. LPAE support is implemented.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

4 files changed, 1518 insertions, 2 deletions

diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index 2022b54..b290e6a 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -19,7 +19,7 @@ obj-$(CONFIG_AT_HDMAC) += at_hdmac.o
 obj-$(CONFIG_AT_XDMAC) += at_xdmac.o
 obj-$(CONFIG_MX3_IPU) += ipu/
 obj-$(CONFIG_TXX9_DMAC) += txx9dmac.o
-obj-$(CONFIG_SH_DMAE_BASE) += sh/
+obj-$(CONFIG_RENESAS_DMA) += sh/
 obj-$(CONFIG_COH901318) += coh901318.o coh901318_lli.o
 obj-$(CONFIG_AMCC_PPC440SPE_ADMA) += ppc4xx/
 obj-$(CONFIG_IMX_SDMA) += imx-sdma.o
diff --git a/drivers/dma/sh/Kconfig b/drivers/dma/sh/Kconfig
index 0349125..8190ad2 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 0a5cfdb..2852f9d 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 0000000..89d40f9
--- /dev/null
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -0,0 +1,1503 @@
+/*
+ * 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/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_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
+ * @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 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(n)		((n) << 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;
+	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);
+
+	WARN_ON_ONCE(rcar_dmac_chan_is_busy(chan));
+
+#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);
+
+	if (chan->mid_rid >= 0)
+		rcar_dmac_chan_write(chan, RCAR_DMARS, chan->mid_rid);
+
+	rcar_dmac_chan_write(chan, RCAR_DMATCR,
+			     chunk->size >> desc->xfer_shift);
+
+	rcar_dmac_chan_write(chan, RCAR_DMACHCR, desc->chcr | RCAR_DMACHCR_DE |
+			     RCAR_DMACHCR_IE);
+}
+
+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 chunk will be reinitialized to an
+ * empty list as a result.
+ *
+ * The descriptor must have been removed from the channel's done list before
+ * calling this function.
+ *
+ * Locking: Must be called with the channel lock held.
+ */
+static void rcar_dmac_desc_put(struct rcar_dmac_chan *chan,
+			       struct rcar_dmac_desc *desc)
+{
+	list_splice_tail_init(&desc->chunks, &chan->desc.chunks_free);
+	list_add_tail(&desc->node, &chan->desc.free);
+}
+
+static void rcar_dmac_desc_recycle_acked(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc, *_desc;
+
+	list_for_each_entry_safe(desc, _desc, &chan->desc.wait, node) {
+		if (async_tx_test_ack(&desc->async_tx)) {
+			list_del(&desc->node);
+			rcar_dmac_desc_put(chan, desc);
+		}
+	}
+}
+
+/*
+ * 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;
+
+	spin_lock_irq(&chan->lock);
+
+	/* Recycle acked descriptors before attempting allocation. */
+	rcar_dmac_desc_recycle_acked(chan);
+
+	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;
+}
+
+/* -----------------------------------------------------------------------------
+ * 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_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 max_chunk_size;
+	unsigned int full_size = 0;
+	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;
+#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);
+		}
+	}
+
+	desc->size = full_size;
+
+	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;
+
+	/* 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_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 *chunk;
+	unsigned int residue = 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;
+
+	/* Compute the size of all chunks still to be transferred. */
+	list_for_each_entry_reverse(chunk, &desc->chunks, node) {
+		if (chunk == desc->running)
+			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_transfer_end(struct rcar_dmac_chan *chan)
+{
+	struct rcar_dmac_desc *desc = chan->desc.running;
+	struct rcar_dmac_xfer_chunk *chunk;
+	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 ends. Warn and
+		 * return.
+		 */
+		return IRQ_NONE;
+	}
+
+	/*
+	 * 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.
+	 */
+	chunk = desc->running;
+	if (!list_is_last(&chunk->node, &desc->chunks)) {
+		desc->running = list_next_entry(chunk, 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)
+{
+	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);
+	rcar_dmac_chan_write(chan, RCAR_DMACHCR,
+			     chcr & ~(RCAR_DMACHCR_TE | RCAR_DMACHCR_DE));
+
+	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);
+	}
+
+	/* Recycle all acked descriptors. */
+	rcar_dmac_desc_recycle_acked(chan);
+
+	spin_unlock_irq(&chan->lock);
+
+	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");