[PATCH v1 4/5] dmaengine: Add driver for NVIDIA Tegra AHB DMA controller

From: Dmitry Osipenko <digetx@gmail.com>
To: Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Laxman Dewangan <ldewangan@nvidia.com>,
	Peter De Schrijver <pdeschrijver@nvidia.com>,
	Prashant Gaikwad <pgaikwad@nvidia.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Rob Herring <robh+dt@kernel.org>,
	Vinod Koul <vinod.koul@intel.com>
Cc: linux-tegra@vger.kernel.org, devicetree@vger.kernel.org,
	dmaengine@vger.kernel.org, linux-clk@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v1 4/5] dmaengine: Add driver for NVIDIA Tegra AHB DMA controller
Date: Tue, 26 Sep 2017 02:22:05 +0300	[thread overview]
Message-ID: <0a45e058baba72124b91c663ce1d908d275f4044.1506380746.git.digetx@gmail.com> (raw)
In-Reply-To: <cover.1506380746.git.digetx@gmail.com>
In-Reply-To: <cover.1506380746.git.digetx@gmail.com>

AHB DMA controller presents on Tegra20/30 SoC's, it supports transfers
memory <-> AHB bus peripherals as well as mem-to-mem transfers. Driver
doesn't yet implement transfers larger than 64K and scatter-gather
transfers that have NENT > 1, HW doesn't have native support for these
cases.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/dma/Kconfig           |   9 +
 drivers/dma/Makefile          |   1 +
 drivers/dma/tegra20-ahb-dma.c | 679 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 689 insertions(+)
 create mode 100644 drivers/dma/tegra20-ahb-dma.c

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index fadc4d8783bd..937c110a715b 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -503,6 +503,15 @@ config TXX9_DMAC
 	  Support the TXx9 SoC internal DMA controller.  This can be
 	  integrated in chips such as the Toshiba TX4927/38/39.
 
+config TEGRA20_AHB_DMA
+	tristate "NVIDIA Tegra20 AHB DMA support"
+	depends on ARCH_TEGRA
+	select DMA_ENGINE
+	help
+	  Enable support for the NVIDIA Tegra20 AHB DMA controller driver.
+	  This DMA controller transfers data from memory to AHB peripherals
+	  or vice versa, it supports memory to memory data transfer as well.
+
 config TEGRA20_APB_DMA
 	bool "NVIDIA Tegra20 APB DMA support"
 	depends on ARCH_TEGRA
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index f08f8de1b567..82d5d36b0379 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_STE_DMA40) += ste_dma40.o ste_dma40_ll.o
 obj-$(CONFIG_STM32_DMA) += stm32-dma.o
 obj-$(CONFIG_S3C24XX_DMAC) += s3c24xx-dma.o
 obj-$(CONFIG_TXX9_DMAC) += txx9dmac.o
+obj-$(CONFIG_TEGRA20_AHB_DMA) += tegra20-ahb-dma.o
 obj-$(CONFIG_TEGRA20_APB_DMA) += tegra20-apb-dma.o
 obj-$(CONFIG_TEGRA210_ADMA) += tegra210-adma.o
 obj-$(CONFIG_TIMB_DMA) += timb_dma.o
diff --git a/drivers/dma/tegra20-ahb-dma.c b/drivers/dma/tegra20-ahb-dma.c
new file mode 100644
index 000000000000..8316d64e35e1
--- /dev/null
+++ b/drivers/dma/tegra20-ahb-dma.c
@@ -0,0 +1,679 @@
+/*
+ * Copyright 2017 Dmitry Osipenko <digetx@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of_dma.h>
+#include <linux/platform_device.h>
+#include <linux/reset.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include "dmaengine.h"
+
+#define TEGRA_AHBDMA_CMD			0x0
+#define TEGRA_AHBDMA_CMD_ENABLE			BIT(31)
+
+#define TEGRA_AHBDMA_IRQ_ENB_MASK		0x20
+#define TEGRA_AHBDMA_IRQ_ENB_CH(ch)		BIT(ch)
+
+#define TEGRA_AHBDMA_CHANNEL_BASE(ch)		(0x1000 + (ch) * 0x20)
+
+#define TEGRA_AHBDMA_CHANNEL_CSR		0x0
+#define TEGRA_AHBDMA_CHANNEL_ADDR_WRAP		BIT(18)
+#define TEGRA_AHBDMA_CHANNEL_FLOW		BIT(24)
+#define TEGRA_AHBDMA_CHANNEL_ONCE		BIT(26)
+#define TEGRA_AHBDMA_CHANNEL_DIR_TO_XMB		BIT(27)
+#define TEGRA_AHBDMA_CHANNEL_IE_EOC		BIT(30)
+#define TEGRA_AHBDMA_CHANNEL_ENABLE		BIT(31)
+#define TEGRA_AHBDMA_CHANNEL_REQ_SEL_SHIFT	16
+#define TEGRA_AHBDMA_CHANNEL_WCOUNT_MASK	0xFFFC
+
+#define TEGRA_AHBDMA_CHANNEL_STA		0x4
+#define TEGRA_AHBDMA_CHANNEL_IS_EOC		BIT(30)
+
+#define TEGRA_AHBDMA_CHANNEL_AHB_PTR		0x10
+
+#define TEGRA_AHBDMA_CHANNEL_AHB_SEQ		0x14
+#define TEGRA_AHBDMA_CHANNEL_INTR_ENB		BIT(31)
+#define TEGRA_AHBDMA_CHANNEL_AHB_BURST_SHIFT	24
+#define TEGRA_AHBDMA_CHANNEL_AHB_BURST_1	2
+#define TEGRA_AHBDMA_CHANNEL_AHB_BURST_4	3
+#define TEGRA_AHBDMA_CHANNEL_AHB_BURST_8	4
+
+#define TEGRA_AHBDMA_CHANNEL_XMB_PTR		0x18
+
+#define TEGRA_AHBDMA_BUS_WIDTH			BIT(DMA_SLAVE_BUSWIDTH_4_BYTES)
+
+#define TEGRA_AHBDMA_DIRECTIONS			BIT(DMA_DEV_TO_MEM) | \
+						BIT(DMA_MEM_TO_DEV)
+
+struct tegra_ahbdma_tx_desc {
+	struct dma_async_tx_descriptor desc;
+	struct tasklet_struct tasklet;
+	struct list_head node;
+	enum dma_transfer_direction dir;
+	dma_addr_t mem_paddr;
+	unsigned long flags;
+	size_t size;
+	bool in_fly;
+	bool cyclic;
+};
+
+struct tegra_ahbdma_chan {
+	struct dma_chan dma_chan;
+	struct list_head active_list;
+	struct list_head pending_list;
+	struct completion idling;
+	void __iomem *regs;
+	spinlock_t lock;
+	unsigned int id;
+};
+
+struct tegra_ahbdma {
+	struct tegra_ahbdma_chan channels[4];
+	struct dma_device dma_dev;
+	struct reset_control *rst;
+	struct clk *clk;
+	void __iomem *regs;
+};
+
+static inline struct tegra_ahbdma *to_ahbdma(struct dma_device *dev)
+{
+	return container_of(dev, struct tegra_ahbdma, dma_dev);
+}
+
+static inline struct tegra_ahbdma_chan *to_ahbdma_chan(struct dma_chan *chan)
+{
+	return container_of(chan, struct tegra_ahbdma_chan, dma_chan);
+}
+
+static inline struct tegra_ahbdma_tx_desc *to_ahbdma_tx_desc(
+				struct dma_async_tx_descriptor *tx)
+{
+	return container_of(tx, struct tegra_ahbdma_tx_desc, desc);
+}
+
+static void tegra_ahbdma_submit_tx(struct tegra_ahbdma_chan *chan,
+				   struct tegra_ahbdma_tx_desc *tx)
+{
+	u32 csr;
+
+	writel_relaxed(tx->mem_paddr,
+		       chan->regs + TEGRA_AHBDMA_CHANNEL_XMB_PTR);
+
+	csr = readl_relaxed(chan->regs + TEGRA_AHBDMA_CHANNEL_CSR);
+
+	csr &= ~TEGRA_AHBDMA_CHANNEL_WCOUNT_MASK;
+	csr &= ~TEGRA_AHBDMA_CHANNEL_DIR_TO_XMB;
+	csr |= TEGRA_AHBDMA_CHANNEL_ENABLE;
+	csr |= TEGRA_AHBDMA_CHANNEL_IE_EOC;
+	csr |= tx->size - sizeof(u32);
+
+	if (tx->dir == DMA_DEV_TO_MEM)
+		csr |= TEGRA_AHBDMA_CHANNEL_DIR_TO_XMB;
+
+	if (!tx->cyclic)
+		csr |= TEGRA_AHBDMA_CHANNEL_ONCE;
+
+	writel_relaxed(csr, chan->regs + TEGRA_AHBDMA_CHANNEL_CSR);
+
+	tx->in_fly = true;
+}
+
+static void tegra_ahbdma_tasklet(unsigned long data)
+{
+	struct tegra_ahbdma_tx_desc *tx = (struct tegra_ahbdma_tx_desc *)data;
+	struct dma_async_tx_descriptor *desc = &tx->desc;
+
+	dmaengine_desc_get_callback_invoke(desc, NULL);
+
+	if (!tx->cyclic && !dmaengine_desc_test_reuse(desc))
+		kfree(tx);
+}
+
+static bool tegra_ahbdma_tx_completed(struct tegra_ahbdma_chan *chan,
+				      struct tegra_ahbdma_tx_desc *tx)
+{
+	struct dma_async_tx_descriptor *desc = &tx->desc;
+	bool reuse = dmaengine_desc_test_reuse(desc);
+	bool interrupt = tx->flags & DMA_PREP_INTERRUPT;
+	bool completed = !tx->cyclic;
+
+	if (completed)
+		dma_cookie_complete(desc);
+
+	if (interrupt)
+		tasklet_schedule(&tx->tasklet);
+
+	if (completed) {
+		list_del(&tx->node);
+
+		if (reuse)
+			tx->in_fly = false;
+
+		if (!interrupt && !reuse)
+			kfree(tx);
+	}
+
+	return completed;
+}
+
+static bool tegra_ahbdma_next_tx_issued(struct tegra_ahbdma_chan *chan)
+{
+	struct tegra_ahbdma_tx_desc *tx;
+
+	tx = list_first_entry_or_null(&chan->active_list,
+				      struct tegra_ahbdma_tx_desc,
+				      node);
+	if (tx)
+		tegra_ahbdma_submit_tx(chan, tx);
+
+	return !!tx;
+}
+
+static void tegra_ahbdma_handle_channel(struct tegra_ahbdma_chan *chan)
+{
+	struct tegra_ahbdma_tx_desc *tx;
+	unsigned long flags;
+	u32 status;
+
+	status = readl_relaxed(chan->regs + TEGRA_AHBDMA_CHANNEL_STA);
+	if (!(status & TEGRA_AHBDMA_CHANNEL_IS_EOC))
+		return;
+
+	writel_relaxed(TEGRA_AHBDMA_CHANNEL_IS_EOC,
+		       chan->regs + TEGRA_AHBDMA_CHANNEL_STA);
+
+	spin_lock_irqsave(&chan->lock, flags);
+
+	if (!completion_done(&chan->idling)) {
+		tx = list_first_entry(&chan->active_list,
+				      struct tegra_ahbdma_tx_desc,
+				      node);
+
+		if (tegra_ahbdma_tx_completed(chan, tx) &&
+		    !tegra_ahbdma_next_tx_issued(chan))
+			complete_all(&chan->idling);
+	}
+
+	spin_unlock_irqrestore(&chan->lock, flags);
+}
+
+static irqreturn_t tegra_ahbdma_isr(int irq, void *dev_id)
+{
+	struct tegra_ahbdma *tdma = dev_id;
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(tdma->channels); i++)
+		tegra_ahbdma_handle_channel(&tdma->channels[i]);
+
+	return IRQ_HANDLED;
+}
+
+static dma_cookie_t tegra_ahbdma_tx_submit(struct dma_async_tx_descriptor *desc)
+{
+	struct tegra_ahbdma_tx_desc *tx = to_ahbdma_tx_desc(desc);
+	struct tegra_ahbdma_chan *chan = to_ahbdma_chan(desc->chan);
+	dma_cookie_t cookie;
+
+	cookie = dma_cookie_assign(desc);
+
+	spin_lock_irq(&chan->lock);
+	list_add_tail(&tx->node, &chan->pending_list);
+	spin_unlock_irq(&chan->lock);
+
+	return cookie;
+}
+
+static int tegra_ahbdma_tx_desc_free(struct dma_async_tx_descriptor *desc)
+{
+	kfree(to_ahbdma_tx_desc(desc));
+
+	return 0;
+}
+
+static struct dma_async_tx_descriptor *tegra_ahbdma_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 tegra_ahbdma_tx_desc *tx;
+
+	/* unimplemented */
+	if (sg_len != 1 || sg_dma_len(sgl) > SZ_64K)
+		return NULL;
+
+	tx = kzalloc(sizeof(*tx), GFP_KERNEL);
+	if (!tx)
+		return NULL;
+
+	dma_async_tx_descriptor_init(&tx->desc, chan);
+
+	tx->desc.tx_submit	= tegra_ahbdma_tx_submit;
+	tx->desc.desc_free	= tegra_ahbdma_tx_desc_free;
+	tx->mem_paddr		= sg_dma_address(sgl);
+	tx->size		= sg_dma_len(sgl);
+	tx->flags		= flags;
+	tx->dir			= dir;
+
+	tasklet_init(&tx->tasklet, tegra_ahbdma_tasklet, (unsigned long)tx);
+
+	return &tx->desc;
+}
+
+static struct dma_async_tx_descriptor *tegra_ahbdma_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 tegra_ahbdma_tx_desc *tx;
+
+	/* unimplemented */
+	if (buf_len != period_len || buf_len > SZ_64K)
+		return NULL;
+
+	tx = kzalloc(sizeof(*tx), GFP_KERNEL);
+	if (!tx)
+		return NULL;
+
+	dma_async_tx_descriptor_init(&tx->desc, chan);
+
+	tx->desc.tx_submit	= tegra_ahbdma_tx_submit;
+	tx->mem_paddr		= buf_addr;
+	tx->size		= buf_len;
+	tx->flags		= flags;
+	tx->cyclic		= true;
+	tx->dir			= dir;
+
+	tasklet_init(&tx->tasklet, tegra_ahbdma_tasklet, (unsigned long)tx);
+
+	return &tx->desc;
+}
+
+static void tegra_ahbdma_issue_pending(struct dma_chan *chan)
+{
+	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
+	struct tegra_ahbdma_tx_desc *tx;
+	struct list_head *entry, *tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ahbdma_chan->lock, flags);
+
+	list_for_each_safe(entry, tmp, &ahbdma_chan->pending_list)
+		list_move_tail(entry, &ahbdma_chan->active_list);
+
+	if (completion_done(&ahbdma_chan->idling)) {
+		tx = list_first_entry_or_null(&ahbdma_chan->active_list,
+					      struct tegra_ahbdma_tx_desc,
+					      node);
+		if (tx) {
+			tegra_ahbdma_submit_tx(ahbdma_chan, tx);
+			reinit_completion(&ahbdma_chan->idling);
+		}
+	}
+
+	spin_unlock_irqrestore(&ahbdma_chan->lock, flags);
+}
+
+static enum dma_status tegra_ahbdma_tx_status(struct dma_chan *chan,
+					      dma_cookie_t cookie,
+					      struct dma_tx_state *state)
+{
+	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
+	struct tegra_ahbdma_tx_desc *tx;
+	enum dma_status cookie_status;
+	unsigned long flags;
+	size_t residual;
+	u32 status;
+
+	spin_lock_irqsave(&ahbdma_chan->lock, flags);
+
+	cookie_status = dma_cookie_status(chan, cookie, state);
+	if (cookie_status != DMA_COMPLETE) {
+		list_for_each_entry(tx, &ahbdma_chan->active_list, node) {
+			if (tx->desc.cookie == cookie)
+				goto found;
+		}
+	}
+
+	goto unlock;
+
+found:
+	if (tx->in_fly) {
+		status = readl_relaxed(
+			ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_STA);
+		status  &= TEGRA_AHBDMA_CHANNEL_WCOUNT_MASK;
+
+		residual = status;
+	} else
+		residual = tx->size;
+
+	dma_set_residue(state, residual);
+
+unlock:
+	spin_unlock_irqrestore(&ahbdma_chan->lock, flags);
+
+	return cookie_status;
+}
+
+static int tegra_ahbdma_terminate_all(struct dma_chan *chan)
+{
+	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
+	struct tegra_ahbdma_tx_desc *tx;
+	struct list_head *entry, *tmp;
+	u32 csr;
+
+	spin_lock_irq(&ahbdma_chan->lock);
+
+	csr = readl_relaxed(ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_CSR);
+	csr &= ~TEGRA_AHBDMA_CHANNEL_ENABLE;
+
+	writel_relaxed(csr, ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_CSR);
+
+	list_for_each_safe(entry, tmp, &ahbdma_chan->active_list) {
+		tx = list_entry(entry, struct tegra_ahbdma_tx_desc, node);
+		list_del(entry);
+		kfree(tx);
+	}
+
+	list_for_each_safe(entry, tmp, &ahbdma_chan->pending_list) {
+		tx = list_entry(entry, struct tegra_ahbdma_tx_desc, node);
+		list_del(entry);
+		kfree(tx);
+	}
+
+	complete_all(&ahbdma_chan->idling);
+
+	spin_unlock_irq(&ahbdma_chan->lock);
+
+	return 0;
+}
+
+static int tegra_ahbdma_config(struct dma_chan *chan,
+			       struct dma_slave_config *sconfig)
+{
+	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
+	enum dma_transfer_direction dir = sconfig->direction;
+	u32 burst, ahb_seq, ahb_addr;
+
+	if (sconfig->src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES ||
+	    sconfig->dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
+		return -EINVAL;
+
+	if (dir == DMA_DEV_TO_MEM) {
+		burst    = sconfig->src_maxburst;
+		ahb_addr = sconfig->src_addr;
+	} else {
+		burst    = sconfig->dst_maxburst;
+		ahb_addr = sconfig->dst_addr;
+	}
+
+	switch (burst) {
+	case 1: burst = TEGRA_AHBDMA_CHANNEL_AHB_BURST_1; break;
+	case 4: burst = TEGRA_AHBDMA_CHANNEL_AHB_BURST_4; break;
+	case 8: burst = TEGRA_AHBDMA_CHANNEL_AHB_BURST_8; break;
+	default:
+		return -EINVAL;
+	}
+
+	ahb_seq  = burst << TEGRA_AHBDMA_CHANNEL_AHB_BURST_SHIFT;
+	ahb_seq |= TEGRA_AHBDMA_CHANNEL_ADDR_WRAP;
+	ahb_seq |= TEGRA_AHBDMA_CHANNEL_INTR_ENB;
+
+	writel_relaxed(ahb_seq,
+		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_SEQ);
+
+	writel_relaxed(ahb_addr,
+		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_PTR);
+
+	return 0;
+}
+
+static void tegra_ahbdma_synchronize(struct dma_chan *chan)
+{
+	wait_for_completion(&to_ahbdma_chan(chan)->idling);
+}
+
+static void tegra_ahbdma_free_chan_resources(struct dma_chan *chan)
+{
+	struct tegra_ahbdma_chan *ahbdma_chan = to_ahbdma_chan(chan);
+	struct tegra_ahbdma_tx_desc *tx;
+	struct list_head *entry, *tmp;
+
+	list_for_each_safe(entry, tmp, &ahbdma_chan->pending_list) {
+		tx = list_entry(entry, struct tegra_ahbdma_tx_desc, node);
+		list_del(entry);
+		kfree(tx);
+	}
+}
+
+static void tegra_ahbdma_init_channel(struct tegra_ahbdma *tdma,
+				      unsigned int chan_id)
+{
+	struct tegra_ahbdma_chan *ahbdma_chan = &tdma->channels[chan_id];
+	struct dma_chan *dma_chan = &ahbdma_chan->dma_chan;
+	struct dma_device *dma_dev = &tdma->dma_dev;
+
+	INIT_LIST_HEAD(&ahbdma_chan->active_list);
+	INIT_LIST_HEAD(&ahbdma_chan->pending_list);
+	init_completion(&ahbdma_chan->idling);
+	spin_lock_init(&ahbdma_chan->lock);
+	complete(&ahbdma_chan->idling);
+
+	ahbdma_chan->regs = tdma->regs + TEGRA_AHBDMA_CHANNEL_BASE(chan_id);
+	ahbdma_chan->id = chan_id;
+
+	dma_cookie_init(dma_chan);
+	dma_chan->device = dma_dev;
+
+	list_add_tail(&dma_chan->device_node, &dma_dev->channels);
+}
+
+static struct dma_chan *tegra_ahbdma_of_xlate(struct of_phandle_args *dma_spec,
+					      struct of_dma *ofdma)
+{
+	struct tegra_ahbdma *tdma = ofdma->of_dma_data;
+	struct dma_chan *chan;
+	u32 csr;
+
+	chan = dma_get_any_slave_channel(&tdma->dma_dev);
+	if (!chan)
+		return NULL;
+
+	/* enable channels flow control */
+	if (dma_spec->args_count == 1) {
+		csr  = TEGRA_AHBDMA_CHANNEL_FLOW;
+		csr |= dma_spec->args[0] << TEGRA_AHBDMA_CHANNEL_REQ_SEL_SHIFT;
+
+		writel_relaxed(csr,
+			to_ahbdma_chan(chan)->regs + TEGRA_AHBDMA_CHANNEL_CSR);
+	}
+
+	return chan;
+}
+
+static int tegra_ahbdma_init_hw(struct tegra_ahbdma *tdma, struct device *dev)
+{
+	int err;
+
+	err = reset_control_assert(tdma->rst);
+	if (err) {
+		dev_err(dev, "Failed to assert reset: %d\n", err);
+		return err;
+	}
+
+	err = clk_prepare_enable(tdma->clk);
+	if (err) {
+		dev_err(dev, "Failed to enable clock: %d\n", err);
+		return err;
+	}
+
+	usleep_range(1000, 2000);
+
+	err = reset_control_deassert(tdma->rst);
+	if (err) {
+		dev_err(dev, "Failed to deassert reset: %d\n", err);
+		return err;
+	}
+
+	writel_relaxed(TEGRA_AHBDMA_CMD_ENABLE, tdma->regs + TEGRA_AHBDMA_CMD);
+
+	writel_relaxed(TEGRA_AHBDMA_IRQ_ENB_CH(0) |
+		       TEGRA_AHBDMA_IRQ_ENB_CH(1) |
+		       TEGRA_AHBDMA_IRQ_ENB_CH(2) |
+		       TEGRA_AHBDMA_IRQ_ENB_CH(3),
+		       tdma->regs + TEGRA_AHBDMA_IRQ_ENB_MASK);
+
+	return 0;
+}
+
+static int tegra_ahbdma_probe(struct platform_device *pdev)
+{
+	struct dma_device *dma_dev;
+	struct tegra_ahbdma *tdma;
+	struct resource *res_regs;
+	unsigned int i;
+	int irq;
+	int err;
+
+	tdma = devm_kzalloc(&pdev->dev, sizeof(*tdma), GFP_KERNEL);
+	if (!tdma)
+		return -ENOMEM;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "Failed to get IRQ\n");
+		return irq;
+	}
+
+	err = devm_request_irq(&pdev->dev, irq, tegra_ahbdma_isr, 0,
+			       dev_name(&pdev->dev), tdma);
+	if (err) {
+		dev_err(&pdev->dev, "Failed to request IRQ\n");
+		return -ENODEV;
+	}
+
+	res_regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res_regs)
+		return -ENODEV;
+
+	tdma->regs = devm_ioremap_resource(&pdev->dev, res_regs);
+	if (IS_ERR(tdma->regs))
+		return PTR_ERR(tdma->regs);
+
+	tdma->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(tdma->clk)) {
+		dev_err(&pdev->dev, "Failed to get AHB-DMA clock\n");
+		return PTR_ERR(tdma->clk);
+	}
+
+	tdma->rst = devm_reset_control_get(&pdev->dev, NULL);
+	if (IS_ERR(tdma->rst)) {
+		dev_err(&pdev->dev, "Failed to get AHB-DMA reset\n");
+		return PTR_ERR(tdma->rst);
+	}
+
+	err = tegra_ahbdma_init_hw(tdma, &pdev->dev);
+	if (err)
+		return err;
+
+	dma_dev = &tdma->dma_dev;
+
+	INIT_LIST_HEAD(&dma_dev->channels);
+
+	for (i = 0; i < ARRAY_SIZE(tdma->channels); i++)
+		tegra_ahbdma_init_channel(tdma, i);
+
+	dma_cap_set(DMA_PRIVATE, dma_dev->cap_mask);
+	dma_cap_set(DMA_CYCLIC, dma_dev->cap_mask);
+	dma_cap_set(DMA_SLAVE, dma_dev->cap_mask);
+
+	dma_dev->max_burst		= 8;
+	dma_dev->directions		= TEGRA_AHBDMA_DIRECTIONS;
+	dma_dev->src_addr_widths	= TEGRA_AHBDMA_BUS_WIDTH;
+	dma_dev->dst_addr_widths	= TEGRA_AHBDMA_BUS_WIDTH;
+	dma_dev->descriptor_reuse	= true;
+	dma_dev->residue_granularity	= DMA_RESIDUE_GRANULARITY_BURST;
+	dma_dev->device_free_chan_resources = tegra_ahbdma_free_chan_resources;
+	dma_dev->device_prep_slave_sg	= tegra_ahbdma_prep_slave_sg;
+	dma_dev->device_prep_dma_cyclic	= tegra_ahbdma_prep_dma_cyclic;
+	dma_dev->device_terminate_all	= tegra_ahbdma_terminate_all;
+	dma_dev->device_issue_pending	= tegra_ahbdma_issue_pending;
+	dma_dev->device_tx_status	= tegra_ahbdma_tx_status;
+	dma_dev->device_config		= tegra_ahbdma_config;
+	dma_dev->device_synchronize	= tegra_ahbdma_synchronize;
+	dma_dev->dev			= &pdev->dev;
+
+	err = dma_async_device_register(dma_dev);
+	if (err) {
+		dev_err(&pdev->dev, "Device registration failed %d\n", err);
+		return err;
+	}
+
+	err = of_dma_controller_register(pdev->dev.of_node,
+					 tegra_ahbdma_of_xlate, tdma);
+	if (err) {
+		dev_err(&pdev->dev, "OF registration failed %d\n", err);
+		dma_async_device_unregister(dma_dev);
+		return err;
+	}
+
+	platform_set_drvdata(pdev, tdma);
+
+	return 0;
+}
+
+static int tegra_ahbdma_remove(struct platform_device *pdev)
+{
+	struct tegra_ahbdma *tdma = platform_get_drvdata(pdev);
+
+	of_dma_controller_free(pdev->dev.of_node);
+	dma_async_device_unregister(&tdma->dma_dev);
+	clk_disable_unprepare(tdma->clk);
+
+	return 0;
+}
+
+static const struct of_device_id tegra_ahbdma_of_match[] = {
+	{ .compatible = "nvidia,tegra20-ahbdma" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, tegra_ahbdma_of_match);
+
+static struct platform_driver tegra_ahbdma_driver = {
+	.driver = {
+		.name	= "tegra-ahbdma",
+		.of_match_table = tegra_ahbdma_of_match,
+	},
+	.probe	= tegra_ahbdma_probe,
+	.remove	= tegra_ahbdma_remove,
+};
+module_platform_driver(tegra_ahbdma_driver);
+
+MODULE_DESCRIPTION("NVIDIA Tegra AHB DMA Controller driver");
+MODULE_AUTHOR("Dmitry Osipenko <digetx@gmail.com>");
+MODULE_LICENSE("GPL");
-- 
2.14.1
