ralink: add dma engine support

Signed-off-by: John Crispin <blogic@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39013 3c298f89-4303-0410-b956-a3cf2f4a3e73

1 files changed, 670 insertions, 0 deletions

diff --git a/target/linux/ramips/patches-3.10/0300-DMA-add-rt2880-dma-engine.patch b/target/linux/ramips/patches-3.10/0300-DMA-add-rt2880-dma-engine.patch
new file mode 100644
index 0000000000..8c8ddb9aca
--- /dev/null
+++ b/target/linux/ramips/patches-3.10/0300-DMA-add-rt2880-dma-engine.patch
@@ -0,0 +1,670 @@
+From 776726ff626249276936a7e1f865103ea4e1b7e9 Mon Sep 17 00:00:00 2001
+From: John Crispin <blogic@openwrt.org>
+Date: Tue, 3 Dec 2013 17:05:05 +0100
+Subject: [PATCH] DMA: add rt2880 dma engine
+
+Signed-off-by: John Crispin <blogic@openwrt.org>
+---
+ drivers/dma/Kconfig       |    6 +
+ drivers/dma/Makefile      |    1 +
+ drivers/dma/ralink-gdma.c |  596 +++++++++++++++++++++++++++++++++++++++++++++
+ 3 files changed, 603 insertions(+)
+ create mode 100644 drivers/dma/ralink-gdma.c
+
+Index: linux-3.10.18/drivers/dma/Kconfig
+===================================================================
+--- linux-3.10.18.orig/drivers/dma/Kconfig	2013-11-04 13:31:29.000000000 +0100
++++ linux-3.10.18/drivers/dma/Kconfig	2013-12-04 17:52:32.852756567 +0100
+@@ -312,6 +312,12 @@
+ 	help
+ 	  Support the MMP PDMA engine for PXA and MMP platfrom.
+ 
++config DMA_RALINK
++	tristate "RALINK DMA support"
++	depends on RALINK && SOC_MT7620
++	select DMA_ENGINE
++	select DMA_VIRTUAL_CHANNELS
++
+ config DMA_ENGINE
+ 	bool
+ 
+Index: linux-3.10.18/drivers/dma/ralink-gdma.c
+===================================================================
+--- /dev/null	1970-01-01 00:00:00.000000000 +0000
++++ linux-3.10.18/drivers/dma/ralink-gdma.c	2013-12-05 21:17:22.245128605 +0100
+@@ -0,0 +1,577 @@
++/*
++ *  Copyright (C) 2013, Lars-Peter Clausen <lars@metafoo.de>
++ *  GDMA4740 DMAC support
++ *
++ *  This program is free software; you can redistribute it and/or modify it
++ *  under  the terms of the GNU General	 Public License as published by the
++ *  Free Software Foundation;  either version 2 of the License, or (at your
++ *  option) any later version.
++ *
++ *  You should have received a copy of the GNU General Public License along
++ *  with this program; if not, write to the Free Software Foundation, Inc.,
++ *  675 Mass Ave, Cambridge, MA 02139, USA.
++ *
++ */
++
++#include <linux/dmaengine.h>
++#include <linux/dma-mapping.h>
++#include <linux/err.h>
++#include <linux/init.h>
++#include <linux/list.h>
++#include <linux/module.h>
++#include <linux/platform_device.h>
++#include <linux/slab.h>
++#include <linux/spinlock.h>
++#include <linux/irq.h>
++#include <linux/of_dma.h>
++
++#include "virt-dma.h"
++
++#define GDMA_NR_CHANS			16
++
++#define GDMA_REG_SRC_ADDR(x)		(0x00 + (x) * 0x10)
++#define GDMA_REG_DST_ADDR(x)		(0x04 + (x) * 0x10)
++
++#define GDMA_REG_CTRL0(x)		(0x08 + (x) * 0x10)
++#define GDMA_REG_CTRL0_TX_MASK		0xffff
++#define GDMA_REG_CTRL0_TX_SHIFT		16
++#define GDMA_REG_CTRL0_CURR_MASK	0xff
++#define GDMA_REG_CTRL0_CURR_SHIFT	8
++#define	GDMA_REG_CTRL0_SRC_ADDR_FIXED	BIT(7)
++#define GDMA_REG_CTRL0_DST_ADDR_FIXED	BIT(6)
++#define GDMA_REG_CTRL0_BURST_MASK	0x7
++#define GDMA_REG_CTRL0_BURST_SHIFT	3
++#define	GDMA_REG_CTRL0_DONE_INT		BIT(2)
++#define	GDMA_REG_CTRL0_ENABLE		BIT(1)
++#define	GDMA_REG_CTRL0_HW_MODE		0
++
++#define GDMA_REG_CTRL1(x)		(0x0c + (x) * 0x10)
++#define GDMA_REG_CTRL1_SEG_MASK		0xf
++#define GDMA_REG_CTRL1_SEG_SHIFT	22
++#define GDMA_REG_CTRL1_REQ_MASK		0x3f
++#define GDMA_REG_CTRL1_SRC_REQ_SHIFT	16
++#define GDMA_REG_CTRL1_DST_REQ_SHIFT	8
++#define GDMA_REG_CTRL1_CONTINOUS	BIT(14)
++#define GDMA_REG_CTRL1_NEXT_MASK	0x1f
++#define GDMA_REG_CTRL1_NEXT_SHIFT	3
++#define GDMA_REG_CTRL1_COHERENT		BIT(2)
++#define GDMA_REG_CTRL1_FAIL		BIT(1)
++#define GDMA_REG_CTRL1_MASK		BIT(0)
++
++#define GDMA_REG_UNMASK_INT		0x200
++#define GDMA_REG_DONE_INT		0x204
++
++#define GDMA_REG_GCT			0x220
++#define GDMA_REG_GCT_CHAN_MASK		0x3
++#define GDMA_REG_GCT_CHAN_SHIFT		3
++#define GDMA_REG_GCT_VER_MASK		0x3
++#define GDMA_REG_GCT_VER_SHIFT		1
++#define GDMA_REG_GCT_ARBIT_RR		BIT(0)
++
++enum gdma_dma_transfer_size {
++	GDMA_TRANSFER_SIZE_4BYTE	= 0,
++	GDMA_TRANSFER_SIZE_8BYTE	= 1,
++	GDMA_TRANSFER_SIZE_16BYTE	= 2,
++	GDMA_TRANSFER_SIZE_32BYTE	= 3,
++};
++
++struct gdma_dma_sg {
++	dma_addr_t addr;
++	unsigned int len;
++};
++
++struct gdma_dma_desc {
++	struct virt_dma_desc vdesc;
++
++	enum dma_transfer_direction direction;
++	bool cyclic;
++
++	unsigned int num_sgs;
++	struct gdma_dma_sg sg[];
++};
++
++struct gdma_dmaengine_chan {
++	struct virt_dma_chan vchan;
++	unsigned int id;
++
++	dma_addr_t fifo_addr;
++	unsigned int transfer_shift;
++
++	struct gdma_dma_desc *desc;
++	unsigned int next_sg;
++};
++
++struct gdma_dma_dev {
++	struct dma_device ddev;
++	void __iomem *base;
++	struct clk *clk;
++
++	struct gdma_dmaengine_chan chan[GDMA_NR_CHANS];
++};
++
++static struct gdma_dma_dev *gdma_dma_chan_get_dev(
++	struct gdma_dmaengine_chan *chan)
++{
++	return container_of(chan->vchan.chan.device, struct gdma_dma_dev,
++		ddev);
++}
++
++static struct gdma_dmaengine_chan *to_gdma_dma_chan(struct dma_chan *c)
++{
++	return container_of(c, struct gdma_dmaengine_chan, vchan.chan);
++}
++
++static struct gdma_dma_desc *to_gdma_dma_desc(struct virt_dma_desc *vdesc)
++{
++	return container_of(vdesc, struct gdma_dma_desc, vdesc);
++}
++
++static inline uint32_t gdma_dma_read(struct gdma_dma_dev *dma_dev,
++	unsigned int reg)
++{
++	return readl(dma_dev->base + reg);
++}
++
++static inline void gdma_dma_write(struct gdma_dma_dev *dma_dev,
++	unsigned reg, uint32_t val)
++{
++	//printk("gdma --> %p = 0x%08X\n", dma_dev->base + reg, val);
++	writel(val, dma_dev->base + reg);
++}
++
++static inline void gdma_dma_write_mask(struct gdma_dma_dev *dma_dev,
++	unsigned int reg, uint32_t val, uint32_t mask)
++{
++	uint32_t tmp;
++
++	tmp = gdma_dma_read(dma_dev, reg);
++	tmp &= ~mask;
++	tmp |= val;
++	gdma_dma_write(dma_dev, reg, tmp);
++}
++
++static struct gdma_dma_desc *gdma_dma_alloc_desc(unsigned int num_sgs)
++{
++	return kzalloc(sizeof(struct gdma_dma_desc) +
++		sizeof(struct gdma_dma_sg) * num_sgs, GFP_ATOMIC);
++}
++
++static enum gdma_dma_transfer_size gdma_dma_maxburst(u32 maxburst)
++{
++	if (maxburst <= 7)
++		return GDMA_TRANSFER_SIZE_4BYTE;
++	else if (maxburst <= 15)
++		return GDMA_TRANSFER_SIZE_8BYTE;
++	else if (maxburst <= 31)
++		return GDMA_TRANSFER_SIZE_16BYTE;
++
++	return GDMA_TRANSFER_SIZE_32BYTE;
++}
++
++static int gdma_dma_slave_config(struct dma_chan *c,
++	const struct dma_slave_config *config)
++{
++	struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
++	struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
++	enum gdma_dma_transfer_size transfer_size;
++	uint32_t flags;
++	uint32_t ctrl0, ctrl1;
++
++	switch (config->direction) {
++	case DMA_MEM_TO_DEV:
++		ctrl1 = 32 << GDMA_REG_CTRL1_SRC_REQ_SHIFT;
++		ctrl1 |= config->slave_id << GDMA_REG_CTRL1_DST_REQ_SHIFT;
++		flags = GDMA_REG_CTRL0_DST_ADDR_FIXED;
++		transfer_size = gdma_dma_maxburst(config->dst_maxburst);
++		chan->fifo_addr = config->dst_addr;
++		break;
++
++	case DMA_DEV_TO_MEM:
++		ctrl1 = config->slave_id << GDMA_REG_CTRL1_SRC_REQ_SHIFT;
++		ctrl1 |= 32 << GDMA_REG_CTRL1_DST_REQ_SHIFT;
++		flags = GDMA_REG_CTRL0_SRC_ADDR_FIXED;
++		transfer_size = gdma_dma_maxburst(config->src_maxburst);
++		chan->fifo_addr = config->src_addr;
++		break;
++
++	default:
++		return -EINVAL;
++	}
++
++	chan->transfer_shift = 1 + transfer_size;
++
++	ctrl0 = flags | GDMA_REG_CTRL0_HW_MODE;
++	ctrl0 |= GDMA_REG_CTRL0_DONE_INT;
++
++	ctrl1 &= ~(GDMA_REG_CTRL1_NEXT_MASK << GDMA_REG_CTRL1_NEXT_SHIFT);
++	ctrl1 |= chan->id << GDMA_REG_CTRL1_NEXT_SHIFT;
++	ctrl1 |= GDMA_REG_CTRL1_FAIL;
++	ctrl1 &= ~GDMA_REG_CTRL1_CONTINOUS;
++	gdma_dma_write(dma_dev, GDMA_REG_CTRL0(chan->id), ctrl0);
++	gdma_dma_write(dma_dev, GDMA_REG_CTRL1(chan->id), ctrl1);
++
++	return 0;
++}
++
++static int gdma_dma_terminate_all(struct dma_chan *c)
++{
++	struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
++	struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
++	unsigned long flags;
++	LIST_HEAD(head);
++
++	spin_lock_irqsave(&chan->vchan.lock, flags);
++	gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL0(chan->id), 0,
++			GDMA_REG_CTRL0_ENABLE);
++	chan->desc = NULL;
++	vchan_get_all_descriptors(&chan->vchan, &head);
++	spin_unlock_irqrestore(&chan->vchan.lock, flags);
++
++	vchan_dma_desc_free_list(&chan->vchan, &head);
++
++	return 0;
++}
++
++static int gdma_dma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
++	unsigned long arg)
++{
++	struct dma_slave_config *config = (struct dma_slave_config *)arg;
++
++	switch (cmd) {
++	case DMA_SLAVE_CONFIG:
++		return gdma_dma_slave_config(chan, config);
++	case DMA_TERMINATE_ALL:
++		return gdma_dma_terminate_all(chan);
++	default:
++		return -ENOSYS;
++	}
++}
++
++static int gdma_dma_start_transfer(struct gdma_dmaengine_chan *chan)
++{
++	struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
++	dma_addr_t src_addr, dst_addr;
++	struct virt_dma_desc *vdesc;
++	struct gdma_dma_sg *sg;
++
++	gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL0(chan->id), 0,
++			GDMA_REG_CTRL0_ENABLE);
++
++	if (!chan->desc) {
++		vdesc = vchan_next_desc(&chan->vchan);
++		if (!vdesc)
++			return 0;
++		chan->desc = to_gdma_dma_desc(vdesc);
++		chan->next_sg = 0;
++	}
++
++	if (chan->next_sg == chan->desc->num_sgs)
++		chan->next_sg = 0;
++
++	sg = &chan->desc->sg[chan->next_sg];
++
++	if (chan->desc->direction == DMA_MEM_TO_DEV) {
++		src_addr = sg->addr;
++		dst_addr = chan->fifo_addr;
++	} else {
++		src_addr = chan->fifo_addr;
++		dst_addr = sg->addr;
++	}
++	gdma_dma_write(dma_dev, GDMA_REG_SRC_ADDR(chan->id), src_addr);
++	gdma_dma_write(dma_dev, GDMA_REG_DST_ADDR(chan->id), dst_addr);
++	gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL0(chan->id),
++			(sg->len << GDMA_REG_CTRL0_TX_SHIFT) | GDMA_REG_CTRL0_ENABLE,
++			GDMA_REG_CTRL0_TX_MASK << GDMA_REG_CTRL0_TX_SHIFT);
++	chan->next_sg++;
++	gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL1(chan->id), 0, GDMA_REG_CTRL1_MASK);
++
++	return 0;
++}
++
++static void gdma_dma_chan_irq(struct gdma_dmaengine_chan *chan)
++{
++	spin_lock(&chan->vchan.lock);
++	if (chan->desc) {
++		if (chan->desc && chan->desc->cyclic) {
++			vchan_cyclic_callback(&chan->desc->vdesc);
++		} else {
++			if (chan->next_sg == chan->desc->num_sgs) {
++				chan->desc = NULL;
++				vchan_cookie_complete(&chan->desc->vdesc);
++			}
++		}
++	}
++	gdma_dma_start_transfer(chan);
++	spin_unlock(&chan->vchan.lock);
++}
++
++static irqreturn_t gdma_dma_irq(int irq, void *devid)
++{
++	struct gdma_dma_dev *dma_dev = devid;
++	uint32_t unmask, done;
++	unsigned int i;
++
++	unmask = gdma_dma_read(dma_dev, GDMA_REG_UNMASK_INT);
++	gdma_dma_write(dma_dev, GDMA_REG_UNMASK_INT, unmask);
++	done = gdma_dma_read(dma_dev, GDMA_REG_DONE_INT);
++
++	for (i = 0; i < GDMA_NR_CHANS; ++i)
++		if (done & BIT(i))
++			gdma_dma_chan_irq(&dma_dev->chan[i]);
++	gdma_dma_write(dma_dev, GDMA_REG_DONE_INT, done);
++
++	return IRQ_HANDLED;
++}
++
++static void gdma_dma_issue_pending(struct dma_chan *c)
++{
++	struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
++	unsigned long flags;
++
++	spin_lock_irqsave(&chan->vchan.lock, flags);
++	if (vchan_issue_pending(&chan->vchan) && !chan->desc)
++		gdma_dma_start_transfer(chan);
++	spin_unlock_irqrestore(&chan->vchan.lock, flags);
++}
++
++static struct dma_async_tx_descriptor *gdma_dma_prep_slave_sg(
++	struct dma_chan *c, struct scatterlist *sgl,
++	unsigned int sg_len, enum dma_transfer_direction direction,
++	unsigned long flags, void *context)
++{
++	struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
++	struct gdma_dma_desc *desc;
++	struct scatterlist *sg;
++	unsigned int i;
++
++	desc = gdma_dma_alloc_desc(sg_len);
++	if (!desc)
++		return NULL;
++
++	for_each_sg(sgl, sg, sg_len, i) {
++		desc->sg[i].addr = sg_dma_address(sg);
++		desc->sg[i].len = sg_dma_len(sg);
++	}
++
++	desc->num_sgs = sg_len;
++	desc->direction = direction;
++	desc->cyclic = false;
++
++	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
++}
++
++static struct dma_async_tx_descriptor *gdma_dma_prep_dma_cyclic(
++	struct dma_chan *c, dma_addr_t buf_addr, size_t buf_len,
++	size_t period_len, enum dma_transfer_direction direction,
++	unsigned long flags, void *context)
++{
++	struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
++	struct gdma_dma_desc *desc;
++	unsigned int num_periods, i;
++
++	if (buf_len % period_len)
++		return NULL;
++
++	num_periods = buf_len / period_len;
++
++	desc = gdma_dma_alloc_desc(num_periods);
++	if (!desc)
++		return NULL;
++
++	for (i = 0; i < num_periods; i++) {
++		desc->sg[i].addr = buf_addr;
++		desc->sg[i].len = period_len;
++		buf_addr += period_len;
++	}
++
++	desc->num_sgs = num_periods;
++	desc->direction = direction;
++	desc->cyclic = true;
++
++	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
++}
++
++static size_t gdma_dma_desc_residue(struct gdma_dmaengine_chan *chan,
++	struct gdma_dma_desc *desc, unsigned int next_sg)
++{
++	struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
++	unsigned int residue, count;
++	unsigned int i;
++
++	residue = 0;
++
++	for (i = next_sg; i < desc->num_sgs; i++)
++		residue += desc->sg[i].len;
++
++	if (next_sg != 0) {
++		count = gdma_dma_read(dma_dev, GDMA_REG_CTRL0(chan->id));
++		count >>= GDMA_REG_CTRL0_CURR_SHIFT;
++		count &= GDMA_REG_CTRL0_CURR_MASK;
++		residue += count << chan->transfer_shift;
++	}
++
++	return residue;
++}
++
++static enum dma_status gdma_dma_tx_status(struct dma_chan *c,
++	dma_cookie_t cookie, struct dma_tx_state *state)
++{
++	struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
++	struct virt_dma_desc *vdesc;
++	enum dma_status status;
++	unsigned long flags;
++
++	status = dma_cookie_status(c, cookie, state);
++	if (status == DMA_SUCCESS || !state)
++		return status;
++
++	spin_lock_irqsave(&chan->vchan.lock, flags);
++	vdesc = vchan_find_desc(&chan->vchan, cookie);
++	if (cookie == chan->desc->vdesc.tx.cookie) {
++		state->residue = gdma_dma_desc_residue(chan, chan->desc,
++				chan->next_sg);
++	} else if (vdesc) {
++		state->residue = gdma_dma_desc_residue(chan,
++				to_gdma_dma_desc(vdesc), 0);
++	} else {
++		state->residue = 0;
++	}
++	spin_unlock_irqrestore(&chan->vchan.lock, flags);
++
++	return status;
++}
++
++static int gdma_dma_alloc_chan_resources(struct dma_chan *c)
++{
++	return 0;
++}
++
++static void gdma_dma_free_chan_resources(struct dma_chan *c)
++{
++	vchan_free_chan_resources(to_virt_chan(c));
++}
++
++static void gdma_dma_desc_free(struct virt_dma_desc *vdesc)
++{
++	kfree(container_of(vdesc, struct gdma_dma_desc, vdesc));
++}
++
++static struct dma_chan *
++of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
++			struct of_dma *ofdma)
++{
++	struct gdma_dma_dev *dma_dev = ofdma->of_dma_data;
++	unsigned int request = dma_spec->args[0];
++
++	if (request >= GDMA_NR_CHANS)
++		return NULL;
++
++	return dma_get_slave_channel(&(dma_dev->chan[request].vchan.chan));
++}
++
++static int gdma_dma_probe(struct platform_device *pdev)
++{
++	struct gdma_dmaengine_chan *chan;
++	struct gdma_dma_dev *dma_dev;
++	struct dma_device *dd;
++	unsigned int i;
++	struct resource *res;
++	uint32_t gct;
++	int ret;
++	int irq;
++
++
++	dma_dev = devm_kzalloc(&pdev->dev, sizeof(*dma_dev), GFP_KERNEL);
++	if (!dma_dev)
++		return -EINVAL;
++
++	dd = &dma_dev->ddev;
++
++	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
++	dma_dev->base = devm_ioremap_resource(&pdev->dev, res);
++	if (IS_ERR(dma_dev->base))
++		return PTR_ERR(dma_dev->base);
++
++	dma_cap_set(DMA_SLAVE, dd->cap_mask);
++	dma_cap_set(DMA_CYCLIC, dd->cap_mask);
++	dd->device_alloc_chan_resources = gdma_dma_alloc_chan_resources;
++	dd->device_free_chan_resources = gdma_dma_free_chan_resources;
++	dd->device_tx_status = gdma_dma_tx_status;
++	dd->device_issue_pending = gdma_dma_issue_pending;
++	dd->device_prep_slave_sg = gdma_dma_prep_slave_sg;
++	dd->device_prep_dma_cyclic = gdma_dma_prep_dma_cyclic;
++	dd->device_control = gdma_dma_control;
++	dd->dev = &pdev->dev;
++	dd->chancnt = GDMA_NR_CHANS;
++	INIT_LIST_HEAD(&dd->channels);
++
++	for (i = 0; i < dd->chancnt; i++) {
++		chan = &dma_dev->chan[i];
++		chan->id = i;
++		chan->vchan.desc_free = gdma_dma_desc_free;
++		vchan_init(&chan->vchan, dd);
++	}
++
++	ret = dma_async_device_register(dd);
++	if (ret)
++		return ret;
++
++	ret = of_dma_controller_register(pdev->dev.of_node,
++		of_dma_xlate_by_chan_id, dma_dev);
++	if (ret)
++		goto err_unregister;
++
++	irq = platform_get_irq(pdev, 0);
++	ret = request_irq(irq, gdma_dma_irq, 0, dev_name(&pdev->dev), dma_dev);
++	if (ret)
++		goto err_unregister;
++
++	gdma_dma_write(dma_dev, GDMA_REG_UNMASK_INT, 0);
++	gdma_dma_write(dma_dev, GDMA_REG_DONE_INT, BIT(dd->chancnt) - 1);
++
++	gct = gdma_dma_read(dma_dev, GDMA_REG_GCT);
++	dev_info(&pdev->dev, "revision: %d, channels: %d\n",
++		(gct >> GDMA_REG_GCT_VER_SHIFT) & GDMA_REG_GCT_VER_MASK,
++		8 << ((gct >> GDMA_REG_GCT_CHAN_SHIFT) & GDMA_REG_GCT_CHAN_MASK));
++	platform_set_drvdata(pdev, dma_dev);
++
++	gdma_dma_write(dma_dev, GDMA_REG_GCT, GDMA_REG_GCT_ARBIT_RR);
++
++	return 0;
++
++err_unregister:
++	dma_async_device_unregister(dd);
++	return ret;
++}
++
++static int gdma_dma_remove(struct platform_device *pdev)
++{
++	struct gdma_dma_dev *dma_dev = platform_get_drvdata(pdev);
++	int irq = platform_get_irq(pdev, 0);
++
++	free_irq(irq, dma_dev);
++        of_dma_controller_free(pdev->dev.of_node);
++	dma_async_device_unregister(&dma_dev->ddev);
++
++	return 0;
++}
++
++static const struct of_device_id gdma_of_match_table[] = {
++	{ .compatible = "ralink,rt2880-gdma" },
++	{ },
++};
++
++static struct platform_driver gdma_dma_driver = {
++	.probe = gdma_dma_probe,
++	.remove = gdma_dma_remove,
++	.driver = {
++		.name = "gdma-rt2880",
++		.owner = THIS_MODULE,
++		.of_match_table = gdma_of_match_table,
++	},
++};
++module_platform_driver(gdma_dma_driver);
++
++MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
++MODULE_DESCRIPTION("GDMA4740 DMA driver");
++MODULE_LICENSE("GPLv2");
+Index: linux-3.10.18/drivers/dma/dmaengine.c
+===================================================================
+--- linux-3.10.18.orig/drivers/dma/dmaengine.c	2013-11-04 13:31:29.000000000 +0100
++++ linux-3.10.18/drivers/dma/dmaengine.c	2013-12-04 17:52:32.856756568 +0100
+@@ -504,6 +504,32 @@
+ }
+ 
+ /**
++ * dma_request_slave_channel - try to get specific channel exclusively
++ * @chan: target channel
++ */
++struct dma_chan *dma_get_slave_channel(struct dma_chan *chan)
++{
++	int err = -EBUSY;
++
++	/* lock against __dma_request_channel */
++	mutex_lock(&dma_list_mutex);
++
++	if (chan->client_count == 0) {
++		err = dma_chan_get(chan);
++		if (err)
++			pr_debug("%s: failed to get %s: (%d)\n",
++				__func__, dma_chan_name(chan), err);
++	} else
++		chan = NULL;
++
++	mutex_unlock(&dma_list_mutex);
++
++	return chan;
++}
++EXPORT_SYMBOL_GPL(dma_get_slave_channel);
++
++
++/**
+  * dma_request_channel - try to allocate an exclusive channel
+  * @mask: capabilities that the channel must satisfy
+  * @fn: optional callback to disposition available channels
+Index: linux-3.10.18/include/linux/dmaengine.h
+===================================================================
+--- linux-3.10.18.orig/include/linux/dmaengine.h	2013-11-04 13:31:29.000000000 +0100
++++ linux-3.10.18/include/linux/dmaengine.h	2013-12-04 17:52:32.856756568 +0100
+@@ -999,6 +999,7 @@
+ int dma_async_device_register(struct dma_device *device);
+ void dma_async_device_unregister(struct dma_device *device);
+ void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
++struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
+ struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
+ struct dma_chan *net_dma_find_channel(void);
+ #define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
+Index: linux-3.10.18/drivers/dma/Makefile
+===================================================================
+--- linux-3.10.18.orig/drivers/dma/Makefile	2013-11-04 13:31:29.000000000 +0100
++++ linux-3.10.18/drivers/dma/Makefile	2013-12-04 17:52:32.856756568 +0100
+@@ -38,3 +38,4 @@
+ obj-$(CONFIG_MMP_TDMA) += mmp_tdma.o
+ obj-$(CONFIG_DMA_OMAP) += omap-dma.o
+ obj-$(CONFIG_MMP_PDMA) += mmp_pdma.o
++obj-$(CONFIG_DMA_RALINK) += ralink-gdma.o