dmaengine: Add driver for Altera / Intel mSGDMA IP core

This driver adds support for the Altera / Intel modular Scatter-Gather
Direct Memory Access (mSGDMA) intellectual property (IP) to the Linux
DMAengine subsystem. Currently it supports the following op modes:

- DMA_MEMCPY
- DMA_SG
- DMA_SLAVE

This implementation has been tested on an Altera Cyclone FPGA connected
via PCIe, both on an ARM and an x86 platform.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/Kconfig

@@ -56,6 +56,12 @@ config DMA_OF
 	select DMA_ENGINE
 
 #devices
+config ALTERA_MSGDMA
+	tristate "Altera / Intel mSGDMA Engine"
+	select DMA_ENGINE
+	help
+	  Enable support for Altera / Intel mSGDMA controller.
+
 config AMBA_PL08X
 	bool "ARM PrimeCell PL080 or PL081 support"
 	depends on ARM_AMBA

drivers/dma/Makefile

@@ -12,6 +12,7 @@ obj-$(CONFIG_DMA_OF) += of-dma.o
 obj-$(CONFIG_DMATEST) += dmatest.o
 
 #devices
+obj-$(CONFIG_ALTERA_MSGDMA) += altera-msgdma.o
 obj-$(CONFIG_AMBA_PL08X) += amba-pl08x.o
 obj-$(CONFIG_AMCC_PPC440SPE_ADMA) += ppc4xx/
 obj-$(CONFIG_AT_HDMAC) += at_hdmac.o

drivers/dma/altera-msgdma.c

@@ -0,0 +1,1031 @@
+/*
+ * DMA driver for Altera mSGDMA IP core
+ *
+ * Copyright (C) 2017 Stefan Roese <sr@denx.de>
+ *
+ * Based on drivers/dma/xilinx/zynqmp_dma.c, which is:
+ * Copyright (C) 2016 Xilinx, Inc. All rights reserved.
+ *
+ * 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.
+ */
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmapool.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include "dmaengine.h"
+
+#define MSGDMA_MAX_TRANS_LEN		U32_MAX
+#define MSGDMA_DESC_NUM			1024
+
+/**
+ * struct msgdma_extended_desc - implements an extended descriptor
+ * @read_addr_lo: data buffer source address low bits
+ * @write_addr_lo: data buffer destination address low bits
+ * @len: the number of bytes to transfer per descriptor
+ * @burst_seq_num: bit 31:24 write burst
+ *		   bit 23:16 read burst
+ *		   bit 15:00 sequence number
+ * @stride: bit 31:16 write stride
+ *	    bit 15:00 read stride
+ * @read_addr_hi: data buffer source address high bits
+ * @write_addr_hi: data buffer destination address high bits
+ * @control: characteristics of the transfer
+ */
+struct msgdma_extended_desc {
+	u32 read_addr_lo;
+	u32 write_addr_lo;
+	u32 len;
+	u32 burst_seq_num;
+	u32 stride;
+	u32 read_addr_hi;
+	u32 write_addr_hi;
+	u32 control;
+};
+
+/* mSGDMA descriptor control field bit definitions */
+#define MSGDMA_DESC_CTL_SET_CH(x)	((x) & 0xff)
+#define MSGDMA_DESC_CTL_GEN_SOP		BIT(8)
+#define MSGDMA_DESC_CTL_GEN_EOP		BIT(9)
+#define MSGDMA_DESC_CTL_PARK_READS	BIT(10)
+#define MSGDMA_DESC_CTL_PARK_WRITES	BIT(11)
+#define MSGDMA_DESC_CTL_END_ON_EOP	BIT(12)
+#define MSGDMA_DESC_CTL_END_ON_LEN	BIT(13)
+#define MSGDMA_DESC_CTL_TR_COMP_IRQ	BIT(14)
+#define MSGDMA_DESC_CTL_EARLY_IRQ	BIT(15)
+#define MSGDMA_DESC_CTL_TR_ERR_IRQ	GENMASK(23, 16)
+#define MSGDMA_DESC_CTL_EARLY_DONE	BIT(24)
+
+/*
+ * Writing "1" the "go" bit commits the entire descriptor into the
+ * descriptor FIFO(s)
+ */
+#define MSGDMA_DESC_CTL_GO		BIT(31)
+
+/* Tx buffer control flags */
+#define MSGDMA_DESC_CTL_TX_FIRST	(MSGDMA_DESC_CTL_GEN_SOP |	\
+					 MSGDMA_DESC_CTL_TR_ERR_IRQ |	\
+					 MSGDMA_DESC_CTL_GO)
+
+#define MSGDMA_DESC_CTL_TX_MIDDLE	(MSGDMA_DESC_CTL_TR_ERR_IRQ |	\
+					 MSGDMA_DESC_CTL_GO)
+
+#define MSGDMA_DESC_CTL_TX_LAST		(MSGDMA_DESC_CTL_GEN_EOP |	\
+					 MSGDMA_DESC_CTL_TR_COMP_IRQ |	\
+					 MSGDMA_DESC_CTL_TR_ERR_IRQ |	\
+					 MSGDMA_DESC_CTL_GO)
+
+#define MSGDMA_DESC_CTL_TX_SINGLE	(MSGDMA_DESC_CTL_GEN_SOP |	\
+					 MSGDMA_DESC_CTL_GEN_EOP |	\
+					 MSGDMA_DESC_CTL_TR_COMP_IRQ |	\
+					 MSGDMA_DESC_CTL_TR_ERR_IRQ |	\
+					 MSGDMA_DESC_CTL_GO)
+
+#define MSGDMA_DESC_CTL_RX_SINGLE	(MSGDMA_DESC_CTL_END_ON_EOP |	\
+					 MSGDMA_DESC_CTL_END_ON_LEN |	\
+					 MSGDMA_DESC_CTL_TR_COMP_IRQ |	\
+					 MSGDMA_DESC_CTL_EARLY_IRQ |	\
+					 MSGDMA_DESC_CTL_TR_ERR_IRQ |	\
+					 MSGDMA_DESC_CTL_GO)
+
+/* mSGDMA extended descriptor stride definitions */
+#define MSGDMA_DESC_STRIDE_RD		0x00000001
+#define MSGDMA_DESC_STRIDE_WR		0x00010000
+#define MSGDMA_DESC_STRIDE_RW		0x00010001
+
+/**
+ * struct msgdma_csr - mSGDMA dispatcher control and status register map
+ * @status: Read/Clear
+ * @control: Read/Write
+ * @rw_fill_level: bit 31:16 - write fill level
+ *		   bit 15:00 - read fill level
+ * @resp_fill_level: bit 15:00 - response FIFO fill level
+ * @rw_seq_num: bit 31:16 - write sequence number
+ *		bit 15:00 - read sequence number
+ * @pad: reserved
+ */
+struct msgdma_csr {
+	u32 status;
+	u32 control;
+	u32 rw_fill_level;
+	u32 resp_fill_level;
+	u32 rw_seq_num;
+	u32 pad[3];
+};
+
+/* mSGDMA CSR status register bit definitions */
+#define MSGDMA_CSR_STAT_BUSY			BIT(0)
+#define MSGDMA_CSR_STAT_DESC_BUF_EMPTY		BIT(1)
+#define MSGDMA_CSR_STAT_DESC_BUF_FULL		BIT(2)
+#define MSGDMA_CSR_STAT_RESP_BUF_EMPTY		BIT(3)
+#define MSGDMA_CSR_STAT_RESP_BUF_FULL		BIT(4)
+#define MSGDMA_CSR_STAT_STOPPED			BIT(5)
+#define MSGDMA_CSR_STAT_RESETTING		BIT(6)
+#define MSGDMA_CSR_STAT_STOPPED_ON_ERR		BIT(7)
+#define MSGDMA_CSR_STAT_STOPPED_ON_EARLY	BIT(8)
+#define MSGDMA_CSR_STAT_IRQ			BIT(9)
+#define MSGDMA_CSR_STAT_MASK			GENMASK(9, 0)
+#define MSGDMA_CSR_STAT_MASK_WITHOUT_IRQ	GENMASK(8, 0)
+
+#define DESC_EMPTY	(MSGDMA_CSR_STAT_DESC_BUF_EMPTY | \
+			 MSGDMA_CSR_STAT_RESP_BUF_EMPTY)
+
+/* mSGDMA CSR control register bit definitions */
+#define MSGDMA_CSR_CTL_STOP			BIT(0)
+#define MSGDMA_CSR_CTL_RESET			BIT(1)
+#define MSGDMA_CSR_CTL_STOP_ON_ERR		BIT(2)
+#define MSGDMA_CSR_CTL_STOP_ON_EARLY		BIT(3)
+#define MSGDMA_CSR_CTL_GLOBAL_INTR		BIT(4)
+#define MSGDMA_CSR_CTL_STOP_DESCS		BIT(5)
+
+/* mSGDMA CSR fill level bits */
+#define MSGDMA_CSR_WR_FILL_LEVEL_GET(v)		(((v) & 0xffff0000) >> 16)
+#define MSGDMA_CSR_RD_FILL_LEVEL_GET(v)		((v) & 0x0000ffff)
+#define MSGDMA_CSR_RESP_FILL_LEVEL_GET(v)	((v) & 0x0000ffff)
+
+#define MSGDMA_CSR_SEQ_NUM_GET(v)		(((v) & 0xffff0000) >> 16)
+
+/* mSGDMA response register map */
+struct msgdma_response {
+	u32 bytes_transferred;
+	u32 status;
+};
+
+/* mSGDMA response register bit definitions */
+#define MSGDMA_RESP_EARLY_TERM	BIT(8)
+#define MSGDMA_RESP_ERR_MASK	0xff
+
+/**
+ * struct msgdma_sw_desc - implements a sw descriptor
+ * @async_tx: support for the async_tx api
+ * @hw_desc: assosiated HW descriptor
+ * @free_list: node of the free SW descriprots list
+ */
+struct msgdma_sw_desc {
+	struct dma_async_tx_descriptor async_tx;
+	struct msgdma_extended_desc hw_desc;
+	struct list_head node;
+	struct list_head tx_list;
+};
+
+/**
+ * struct msgdma_device - DMA device structure
+ */
+struct msgdma_device {
+	spinlock_t lock;
+	struct device *dev;
+	struct tasklet_struct irq_tasklet;
+	struct list_head pending_list;
+	struct list_head free_list;
+	struct list_head active_list;
+	struct list_head done_list;
+	u32 desc_free_cnt;
+	bool idle;
+
+	struct dma_device dmadev;
+	struct dma_chan	dmachan;
+	dma_addr_t hw_desq;
+	struct msgdma_sw_desc *sw_desq;
+	unsigned int npendings;
+
+	struct dma_slave_config slave_cfg;
+
+	int irq;
+
+	/* mSGDMA controller */
+	struct msgdma_csr *csr;
+
+	/* mSGDMA descriptors */
+	struct msgdma_extended_desc *desc;
+
+	/* mSGDMA response */
+	struct msgdma_response *resp;
+};
+
+#define to_mdev(chan)	container_of(chan, struct msgdma_device, dmachan)
+#define tx_to_desc(tx)	container_of(tx, struct msgdma_sw_desc, async_tx)
+
+/**
+ * msgdma_get_descriptor - Get the sw descriptor from the pool
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ *
+ * Return: The sw descriptor
+ */
+static struct msgdma_sw_desc *msgdma_get_descriptor(struct msgdma_device *mdev)
+{
+	struct msgdma_sw_desc *desc;
+
+	spin_lock_bh(&mdev->lock);
+	desc = list_first_entry(&mdev->free_list, struct msgdma_sw_desc, node);
+	list_del(&desc->node);
+	spin_unlock_bh(&mdev->lock);
+
+	INIT_LIST_HEAD(&desc->tx_list);
+
+	return desc;
+}
+
+/**
+ * msgdma_free_descriptor - Issue pending transactions
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ * @desc: Transaction descriptor pointer
+ */
+static void msgdma_free_descriptor(struct msgdma_device *mdev,
+				   struct msgdma_sw_desc *desc)
+{
+	struct msgdma_sw_desc *child, *next;
+
+	mdev->desc_free_cnt++;
+	list_add_tail(&desc->node, &mdev->free_list);
+	list_for_each_entry_safe(child, next, &desc->tx_list, node) {
+		mdev->desc_free_cnt++;
+		list_move_tail(&child->node, &mdev->free_list);
+	}
+}
+
+/**
+ * msgdma_free_desc_list - Free descriptors list
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ * @list: List to parse and delete the descriptor
+ */
+static void msgdma_free_desc_list(struct msgdma_device *mdev,
+				  struct list_head *list)
+{
+	struct msgdma_sw_desc *desc, *next;
+
+	list_for_each_entry_safe(desc, next, list, node)
+		msgdma_free_descriptor(mdev, desc);
+}
+
+/**
+ * msgdma_desc_config - Configure the descriptor
+ * @desc: Hw descriptor pointer
+ * @dst: Destination buffer address
+ * @src: Source buffer address
+ * @len: Transfer length
+ */
+static void msgdma_desc_config(struct msgdma_extended_desc *desc,
+			       dma_addr_t dst, dma_addr_t src, size_t len,
+			       u32 stride)
+{
+	/* Set lower 32bits of src & dst addresses in the descriptor */
+	desc->read_addr_lo = lower_32_bits(src);
+	desc->write_addr_lo = lower_32_bits(dst);
+
+	/* Set upper 32bits of src & dst addresses in the descriptor */
+	desc->read_addr_hi = upper_32_bits(src);
+	desc->write_addr_hi = upper_32_bits(dst);
+
+	desc->len = len;
+	desc->stride = stride;
+	desc->burst_seq_num = 0;	/* 0 will result in max burst length */
+
+	/*
+	 * Don't set interrupt on xfer end yet, this will be done later
+	 * for the "last" descriptor
+	 */
+	desc->control = MSGDMA_DESC_CTL_TR_ERR_IRQ | MSGDMA_DESC_CTL_GO |
+		MSGDMA_DESC_CTL_END_ON_LEN;
+}
+
+/**
+ * msgdma_desc_config_eod - Mark the descriptor as end descriptor
+ * @desc: Hw descriptor pointer
+ */
+static void msgdma_desc_config_eod(struct msgdma_extended_desc *desc)
+{
+	desc->control |= MSGDMA_DESC_CTL_TR_COMP_IRQ;
+}
+
+/**
+ * msgdma_tx_submit - Submit DMA transaction
+ * @tx: Async transaction descriptor pointer
+ *
+ * Return: cookie value
+ */
+static dma_cookie_t msgdma_tx_submit(struct dma_async_tx_descriptor *tx)
+{
+	struct msgdma_device *mdev = to_mdev(tx->chan);
+	struct msgdma_sw_desc *new;
+	dma_cookie_t cookie;
+
+	new = tx_to_desc(tx);
+	spin_lock_bh(&mdev->lock);
+	cookie = dma_cookie_assign(tx);
+
+	list_add_tail(&new->node, &mdev->pending_list);
+	spin_unlock_bh(&mdev->lock);
+
+	return cookie;
+}
+
+/**
+ * msgdma_prep_memcpy - prepare descriptors for memcpy transaction
+ * @dchan: DMA channel
+ * @dma_dst: Destination buffer address
+ * @dma_src: Source buffer address
+ * @len: Transfer length
+ * @flags: transfer ack flags
+ *
+ * Return: Async transaction descriptor on success and NULL on failure
+ */
+static struct dma_async_tx_descriptor *
+msgdma_prep_memcpy(struct dma_chan *dchan, dma_addr_t dma_dst,
+		   dma_addr_t dma_src, size_t len, ulong flags)
+{
+	struct msgdma_device *mdev = to_mdev(dchan);
+	struct msgdma_sw_desc *new, *first = NULL;
+	struct msgdma_extended_desc *desc;
+	size_t copy;
+	u32 desc_cnt;
+
+	desc_cnt = DIV_ROUND_UP(len, MSGDMA_MAX_TRANS_LEN);
+
+	spin_lock_bh(&mdev->lock);
+	if (desc_cnt > mdev->desc_free_cnt) {
+		spin_unlock_bh(&mdev->lock);
+		dev_dbg(mdev->dev, "mdev %p descs are not available\n", mdev);
+		return NULL;
+	}
+	mdev->desc_free_cnt -= desc_cnt;
+	spin_unlock_bh(&mdev->lock);
+
+	do {
+		/* Allocate and populate the descriptor */
+		new = msgdma_get_descriptor(mdev);
+
+		copy = min_t(size_t, len, MSGDMA_MAX_TRANS_LEN);
+		desc = &new->hw_desc;
+		msgdma_desc_config(desc, dma_dst, dma_src, copy,
+				   MSGDMA_DESC_STRIDE_RW);
+		len -= copy;
+		dma_src += copy;
+		dma_dst += copy;
+		if (!first)
+			first = new;
+		else
+			list_add_tail(&new->node, &first->tx_list);
+	} while (len);
+
+	msgdma_desc_config_eod(desc);
+	async_tx_ack(&first->async_tx);
+	first->async_tx.flags = flags;
+
+	return &first->async_tx;
+}
+
+/**
+ * msgdma_prep_sg - prepare descriptors for a memory sg transaction
+ * @dchan: DMA channel
+ * @dst_sg: Destination scatter list
+ * @dst_sg_len: Number of entries in destination scatter list
+ * @src_sg: Source scatter list
+ * @src_sg_len: Number of entries in source scatter list
+ * @flags: transfer ack flags
+ *
+ * Return: Async transaction descriptor on success and NULL on failure
+ */
+static struct dma_async_tx_descriptor *
+msgdma_prep_sg(struct dma_chan *dchan, struct scatterlist *dst_sg,
+	       unsigned int dst_sg_len, struct scatterlist *src_sg,
+	       unsigned int src_sg_len, unsigned long flags)
+{
+	struct msgdma_device *mdev = to_mdev(dchan);
+	struct msgdma_sw_desc *new, *first = NULL;
+	void *desc = NULL;
+	size_t len, dst_avail, src_avail;
+	dma_addr_t dma_dst, dma_src;
+	u32 desc_cnt = 0, i;
+	struct scatterlist *sg;
+
+	for_each_sg(src_sg, sg, src_sg_len, i)
+		desc_cnt += DIV_ROUND_UP(sg_dma_len(sg), MSGDMA_MAX_TRANS_LEN);
+
+	spin_lock_bh(&mdev->lock);
+	if (desc_cnt > mdev->desc_free_cnt) {
+		spin_unlock_bh(&mdev->lock);
+		dev_dbg(mdev->dev, "mdev %p descs are not available\n", mdev);
+		return NULL;
+	}
+	mdev->desc_free_cnt -= desc_cnt;
+	spin_unlock_bh(&mdev->lock);
+
+	dst_avail = sg_dma_len(dst_sg);
+	src_avail = sg_dma_len(src_sg);
+
+	/* Run until we are out of scatterlist entries */
+	while (true) {
+		/* Allocate and populate the descriptor */
+		new = msgdma_get_descriptor(mdev);
+
+		desc = &new->hw_desc;
+		len = min_t(size_t, src_avail, dst_avail);
+		len = min_t(size_t, len, MSGDMA_MAX_TRANS_LEN);
+		if (len == 0)
+			goto fetch;
+		dma_dst = sg_dma_address(dst_sg) + sg_dma_len(dst_sg) -
+			dst_avail;
+		dma_src = sg_dma_address(src_sg) + sg_dma_len(src_sg) -
+			src_avail;
+
+		msgdma_desc_config(desc, dma_dst, dma_src, len,
+				   MSGDMA_DESC_STRIDE_RW);
+		dst_avail -= len;
+		src_avail -= len;
+
+		if (!first)
+			first = new;
+		else
+			list_add_tail(&new->node, &first->tx_list);
+fetch:
+		/* Fetch the next dst scatterlist entry */
+		if (dst_avail == 0) {
+			if (dst_sg_len == 0)
+				break;
+			dst_sg = sg_next(dst_sg);
+			if (dst_sg == NULL)
+				break;
+			dst_sg_len--;
+			dst_avail = sg_dma_len(dst_sg);
+		}
+		/* Fetch the next src scatterlist entry */
+		if (src_avail == 0) {
+			if (src_sg_len == 0)
+				break;
+			src_sg = sg_next(src_sg);
+			if (src_sg == NULL)
+				break;
+			src_sg_len--;
+			src_avail = sg_dma_len(src_sg);
+		}
+	}
+
+	msgdma_desc_config_eod(desc);
+	first->async_tx.flags = flags;
+
+	return &first->async_tx;
+}
+
+/**
+ * msgdma_prep_slave_sg - prepare descriptors for a slave sg transaction
+ *
+ * @dchan: DMA channel
+ * @sgl: Destination scatter list
+ * @sg_len: Number of entries in destination scatter list
+ * @dir: DMA transfer direction
+ * @flags: transfer ack flags
+ * @context: transfer context (unused)
+ */
+static struct dma_async_tx_descriptor *
+msgdma_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
+		     unsigned int sg_len, enum dma_transfer_direction dir,
+		     unsigned long flags, void *context)
+
+{
+	struct msgdma_device *mdev = to_mdev(dchan);
+	struct dma_slave_config *cfg = &mdev->slave_cfg;
+	struct msgdma_sw_desc *new, *first = NULL;
+	void *desc = NULL;
+	size_t len, avail;
+	dma_addr_t dma_dst, dma_src;
+	u32 desc_cnt = 0, i;
+	struct scatterlist *sg;
+	u32 stride;
+
+	for_each_sg(sgl, sg, sg_len, i)
+		desc_cnt += DIV_ROUND_UP(sg_dma_len(sg), MSGDMA_MAX_TRANS_LEN);
+
+	spin_lock_bh(&mdev->lock);
+	if (desc_cnt > mdev->desc_free_cnt) {
+		spin_unlock_bh(&mdev->lock);
+		dev_dbg(mdev->dev, "mdev %p descs are not available\n", mdev);
+		return NULL;
+	}
+	mdev->desc_free_cnt -= desc_cnt;
+	spin_unlock_bh(&mdev->lock);
+
+	avail = sg_dma_len(sgl);
+
+	/* Run until we are out of scatterlist entries */
+	while (true) {
+		/* Allocate and populate the descriptor */
+		new = msgdma_get_descriptor(mdev);
+
+		desc = &new->hw_desc;
+		len = min_t(size_t, avail, MSGDMA_MAX_TRANS_LEN);
+
+		if (dir == DMA_MEM_TO_DEV) {
+			dma_src = sg_dma_address(sgl) + sg_dma_len(sgl) - avail;
+			dma_dst = cfg->dst_addr;
+			stride = MSGDMA_DESC_STRIDE_RD;
+		} else {
+			dma_src = cfg->src_addr;
+			dma_dst = sg_dma_address(sgl) + sg_dma_len(sgl) - avail;
+			stride = MSGDMA_DESC_STRIDE_WR;
+		}
+		msgdma_desc_config(desc, dma_dst, dma_src, len, stride);
+		avail -= len;
+
+		if (!first)
+			first = new;
+		else
+			list_add_tail(&new->node, &first->tx_list);
+
+		/* Fetch the next scatterlist entry */
+		if (avail == 0) {
+			if (sg_len == 0)
+				break;
+			sgl = sg_next(sgl);
+			if (sgl == NULL)
+				break;
+			sg_len--;
+			avail = sg_dma_len(sgl);
+		}
+	}
+
+	msgdma_desc_config_eod(desc);
+	first->async_tx.flags = flags;
+
+	return &first->async_tx;
+}
+
+static int msgdma_dma_config(struct dma_chan *dchan,
+			     struct dma_slave_config *config)
+{
+	struct msgdma_device *mdev = to_mdev(dchan);
+
+	memcpy(&mdev->slave_cfg, config, sizeof(*config));
+
+	return 0;
+}
+
+static void msgdma_reset(struct msgdma_device *mdev)
+{
+	u32 val;
+	int ret;
+
+	/* Reset mSGDMA */
+	iowrite32(MSGDMA_CSR_STAT_MASK, &mdev->csr->status);
+	iowrite32(MSGDMA_CSR_CTL_RESET, &mdev->csr->control);
+
+	ret = readl_poll_timeout(&mdev->csr->status, val,
+				 (val & MSGDMA_CSR_STAT_RESETTING) == 0,
+				 1, 10000);
+	if (ret)
+		dev_err(mdev->dev, "DMA channel did not reset\n");
+
+	/* Clear all status bits */
+	iowrite32(MSGDMA_CSR_STAT_MASK, &mdev->csr->status);
+
+	/* Enable the DMA controller including interrupts */
+	iowrite32(MSGDMA_CSR_CTL_STOP_ON_ERR | MSGDMA_CSR_CTL_STOP_ON_EARLY |
+		  MSGDMA_CSR_CTL_GLOBAL_INTR, &mdev->csr->control);
+
+	mdev->idle = true;
+};
+
+static void msgdma_copy_one(struct msgdma_device *mdev,
+			    struct msgdma_sw_desc *desc)
+{
+	struct msgdma_extended_desc *hw_desc = mdev->desc;
+
+	/*
+	 * Check if the DESC FIFO it not full. If its full, we need to wait
+	 * for at least one entry to become free again
+	 */
+	while (ioread32(&mdev->csr->status) & MSGDMA_CSR_STAT_DESC_BUF_FULL)
+		mdelay(1);
+
+	/*
+	 * The descriptor needs to get copied into the descriptor FIFO
+	 * of the DMA controller. The descriptor will get flushed to the
+	 * FIFO, once the last word (control word) is written. Since we
+	 * are not 100% sure that memcpy() writes all word in the "correct"
+	 * oder (address from low to high) on all architectures, we make
+	 * sure this control word is written last by single coding it and
+	 * adding some write-barriers here.
+	 */
+	memcpy(hw_desc, &desc->hw_desc, sizeof(desc->hw_desc) - sizeof(u32));
+
+	/* Write control word last to flush this descriptor into the FIFO */
+	mdev->idle = false;
+	wmb();
+	iowrite32(desc->hw_desc.control, &hw_desc->control);
+	wmb();
+}
+
+/**
+ * msgdma_copy_desc_to_fifo - copy descriptor(s) into controller FIFO
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ * @desc: Transaction descriptor pointer
+ */
+static void msgdma_copy_desc_to_fifo(struct msgdma_device *mdev,
+				     struct msgdma_sw_desc *desc)
+{
+	struct msgdma_sw_desc *sdesc, *next;
+
+	msgdma_copy_one(mdev, desc);
+
+	list_for_each_entry_safe(sdesc, next, &desc->tx_list, node)
+		msgdma_copy_one(mdev, sdesc);
+}
+
+/**
+ * msgdma_start_transfer - Initiate the new transfer
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ */
+static void msgdma_start_transfer(struct msgdma_device *mdev)
+{
+	struct msgdma_sw_desc *desc;
+
+	if (!mdev->idle)
+		return;
+
+	desc = list_first_entry_or_null(&mdev->pending_list,
+					struct msgdma_sw_desc, node);
+	if (!desc)
+		return;
+
+	list_splice_tail_init(&mdev->pending_list, &mdev->active_list);
+	msgdma_copy_desc_to_fifo(mdev, desc);
+}
+
+/**
+ * msgdma_issue_pending - Issue pending transactions
+ * @chan: DMA channel pointer
+ */
+static void msgdma_issue_pending(struct dma_chan *chan)
+{
+	struct msgdma_device *mdev = to_mdev(chan);
+
+	spin_lock_bh(&mdev->lock);
+	msgdma_start_transfer(mdev);
+	spin_unlock_bh(&mdev->lock);
+}
+
+/**
+ * msgdma_chan_desc_cleanup - Cleanup the completed descriptors
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ */
+static void msgdma_chan_desc_cleanup(struct msgdma_device *mdev)
+{
+	struct msgdma_sw_desc *desc, *next;
+
+	list_for_each_entry_safe(desc, next, &mdev->done_list, node) {
+		dma_async_tx_callback callback;
+		void *callback_param;
+
+		list_del(&desc->node);
+
+		callback = desc->async_tx.callback;
+		callback_param = desc->async_tx.callback_param;
+		if (callback) {
+			spin_unlock(&mdev->lock);
+			callback(callback_param);
+			spin_lock(&mdev->lock);
+		}
+
+		/* Run any dependencies, then free the descriptor */
+		msgdma_free_descriptor(mdev, desc);
+	}
+}
+
+/**
+ * msgdma_complete_descriptor - Mark the active descriptor as complete
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ */
+static void msgdma_complete_descriptor(struct msgdma_device *mdev)
+{
+	struct msgdma_sw_desc *desc;
+
+	desc = list_first_entry_or_null(&mdev->active_list,
+					struct msgdma_sw_desc, node);
+	if (!desc)
+		return;
+	list_del(&desc->node);
+	dma_cookie_complete(&desc->async_tx);
+	list_add_tail(&desc->node, &mdev->done_list);
+}
+
+/**
+ * msgdma_free_descriptors - Free channel descriptors
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ */
+static void msgdma_free_descriptors(struct msgdma_device *mdev)
+{
+	msgdma_free_desc_list(mdev, &mdev->active_list);
+	msgdma_free_desc_list(mdev, &mdev->pending_list);
+	msgdma_free_desc_list(mdev, &mdev->done_list);
+}
+
+/**
+ * msgdma_free_chan_resources - Free channel resources
+ * @dchan: DMA channel pointer
+ */
+static void msgdma_free_chan_resources(struct dma_chan *dchan)
+{
+	struct msgdma_device *mdev = to_mdev(dchan);
+
+	spin_lock_bh(&mdev->lock);
+	msgdma_free_descriptors(mdev);
+	spin_unlock_bh(&mdev->lock);
+	kfree(mdev->sw_desq);
+}
+
+/**
+ * msgdma_alloc_chan_resources - Allocate channel resources
+ * @dchan: DMA channel
+ *
+ * Return: Number of descriptors on success and failure value on error
+ */
+static int msgdma_alloc_chan_resources(struct dma_chan *dchan)
+{
+	struct msgdma_device *mdev = to_mdev(dchan);
+	struct msgdma_sw_desc *desc;
+	int i;
+
+	mdev->sw_desq = kcalloc(MSGDMA_DESC_NUM, sizeof(*desc), GFP_NOWAIT);
+	if (!mdev->sw_desq)
+		return -ENOMEM;
+
+	mdev->idle = true;
+	mdev->desc_free_cnt = MSGDMA_DESC_NUM;
+
+	INIT_LIST_HEAD(&mdev->free_list);
+
+	for (i = 0; i < MSGDMA_DESC_NUM; i++) {
+		desc = mdev->sw_desq + i;
+		dma_async_tx_descriptor_init(&desc->async_tx, &mdev->dmachan);
+		desc->async_tx.tx_submit = msgdma_tx_submit;
+		list_add_tail(&desc->node, &mdev->free_list);
+	}
+
+	return MSGDMA_DESC_NUM;
+}
+
+/**
+ * msgdma_tasklet - Schedule completion tasklet
+ * @data: Pointer to the Altera sSGDMA channel structure
+ */
+static void msgdma_tasklet(unsigned long data)
+{
+	struct msgdma_device *mdev = (struct msgdma_device *)data;
+	u32 count;
+	u32 size;
+	u32 status;
+
+	spin_lock(&mdev->lock);
+
+	/* Read number of responses that are available */
+	count = ioread32(&mdev->csr->resp_fill_level);
+	dev_dbg(mdev->dev, "%s (%d): response count=%d\n",
+		__func__, __LINE__, count);
+
+	while (count--) {
+		/*
+		 * Read both longwords to purge this response from the FIFO
+		 * On Avalon-MM implementations, size and status do not
+		 * have any real values, like transferred bytes or error
+		 * bits. So we need to just drop these values.
+		 */
+		size = ioread32(&mdev->resp->bytes_transferred);
+		status = ioread32(&mdev->resp->status);
+
+		msgdma_complete_descriptor(mdev);
+		msgdma_chan_desc_cleanup(mdev);
+	}
+
+	spin_unlock(&mdev->lock);
+}
+
+/**
+ * msgdma_irq_handler - Altera mSGDMA Interrupt handler
+ * @irq: IRQ number
+ * @data: Pointer to the Altera mSGDMA device structure
+ *
+ * Return: IRQ_HANDLED/IRQ_NONE
+ */
+static irqreturn_t msgdma_irq_handler(int irq, void *data)
+{
+	struct msgdma_device *mdev = data;
+	u32 status;
+
+	status = ioread32(&mdev->csr->status);
+	if ((status & MSGDMA_CSR_STAT_BUSY) == 0) {
+		/* Start next transfer if the DMA controller is idle */
+		spin_lock(&mdev->lock);
+		mdev->idle = true;
+		msgdma_start_transfer(mdev);
+		spin_unlock(&mdev->lock);
+	}
+
+	tasklet_schedule(&mdev->irq_tasklet);
+
+	/* Clear interrupt in mSGDMA controller */
+	iowrite32(MSGDMA_CSR_STAT_IRQ, &mdev->csr->status);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * msgdma_chan_remove - Channel remove function
+ * @mdev: Pointer to the Altera mSGDMA device structure
+ */
+static void msgdma_dev_remove(struct msgdma_device *mdev)
+{
+	if (!mdev)
+		return;
+
+	devm_free_irq(mdev->dev, mdev->irq, mdev);
+	tasklet_kill(&mdev->irq_tasklet);
+	list_del(&mdev->dmachan.device_node);
+}
+
+static int request_and_map(struct platform_device *pdev, const char *name,
+			   struct resource **res, void __iomem **ptr)
+{
+	struct resource *region;
+	struct device *device = &pdev->dev;
+
+	*res = platform_get_resource_byname(pdev, IORESOURCE_MEM, name);
+	if (*res == NULL) {
+		dev_err(device, "resource %s not defined\n", name);
+		return -ENODEV;
+	}
+
+	region = devm_request_mem_region(device, (*res)->start,
+					 resource_size(*res), dev_name(device));
+	if (region == NULL) {
+		dev_err(device, "unable to request %s\n", name);
+		return -EBUSY;
+	}
+
+	*ptr = devm_ioremap_nocache(device, region->start,
+				    resource_size(region));
+	if (*ptr == NULL) {
+		dev_err(device, "ioremap_nocache of %s failed!", name);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+/**
+ * msgdma_probe - Driver probe function
+ * @pdev: Pointer to the platform_device structure
+ *
+ * Return: '0' on success and failure value on error
+ */
+static int msgdma_probe(struct platform_device *pdev)
+{
+	struct msgdma_device *mdev;
+	struct dma_device *dma_dev;
+	struct resource *dma_res;
+	int ret;
+
+	mdev = devm_kzalloc(&pdev->dev, sizeof(*mdev), GFP_NOWAIT);
+	if (!mdev)
+		return -ENOMEM;
+
+	mdev->dev = &pdev->dev;
+
+	/* Map CSR space */
+	ret = request_and_map(pdev, "csr", &dma_res, (void **)&mdev->csr);
+	if (ret)
+		return ret;
+
+	/* Map (extended) descriptor space */
+	ret = request_and_map(pdev, "desc", &dma_res, (void **)&mdev->desc);
+	if (ret)
+		return ret;
+
+	/* Map response space */
+	ret = request_and_map(pdev, "resp", &dma_res, (void **)&mdev->resp);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, mdev);
+
+	/* Get interrupt nr from platform data */
+	mdev->irq = platform_get_irq(pdev, 0);
+	if (mdev->irq < 0)
+		return -ENXIO;
+
+	ret = devm_request_irq(&pdev->dev, mdev->irq, msgdma_irq_handler,
+			       0, dev_name(&pdev->dev), mdev);
+	if (ret)
+		return ret;
+
+	tasklet_init(&mdev->irq_tasklet, msgdma_tasklet, (unsigned long)mdev);
+
+	dma_cookie_init(&mdev->dmachan);
+
+	spin_lock_init(&mdev->lock);
+
+	INIT_LIST_HEAD(&mdev->active_list);
+	INIT_LIST_HEAD(&mdev->pending_list);
+	INIT_LIST_HEAD(&mdev->done_list);
+	INIT_LIST_HEAD(&mdev->free_list);
+
+	dma_dev = &mdev->dmadev;
+
+	/* Set DMA capabilities */
+	dma_cap_zero(dma_dev->cap_mask);
+	dma_cap_set(DMA_MEMCPY, dma_dev->cap_mask);
+	dma_cap_set(DMA_SG, dma_dev->cap_mask);
+	dma_cap_set(DMA_SLAVE, dma_dev->cap_mask);
+
+	dma_dev->src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
+	dma_dev->dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
+	dma_dev->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM) |
+		BIT(DMA_MEM_TO_MEM);
+	dma_dev->residue_granularity = DMA_RESIDUE_GRANULARITY_DESCRIPTOR;
+
+	/* Init DMA link list */
+	INIT_LIST_HEAD(&dma_dev->channels);
+
+	/* Set base routines */
+	dma_dev->device_tx_status = dma_cookie_status;
+	dma_dev->device_issue_pending = msgdma_issue_pending;
+	dma_dev->dev = &pdev->dev;
+
+	dma_dev->copy_align = DMAENGINE_ALIGN_4_BYTES;
+	dma_dev->device_prep_dma_memcpy = msgdma_prep_memcpy;
+	dma_dev->device_prep_dma_sg = msgdma_prep_sg;
+	dma_dev->device_prep_slave_sg = msgdma_prep_slave_sg;
+	dma_dev->device_config = msgdma_dma_config;
+
+	dma_dev->device_alloc_chan_resources = msgdma_alloc_chan_resources;
+	dma_dev->device_free_chan_resources = msgdma_free_chan_resources;
+
+	mdev->dmachan.device = dma_dev;
+	list_add_tail(&mdev->dmachan.device_node, &dma_dev->channels);
+
+	/* Set DMA mask to 64 bits */
+	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+	if (ret) {
+		dev_warn(&pdev->dev, "unable to set coherent mask to 64");
+		ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+		if (ret)
+			goto fail;
+	}
+
+	msgdma_reset(mdev);
+
+	ret = dma_async_device_register(dma_dev);
+	if (ret)
+		goto fail;
+
+	dev_notice(&pdev->dev, "Altera mSGDMA driver probe success\n");
+
+	return 0;
+
+fail:
+	msgdma_dev_remove(mdev);
+
+	return ret;
+}
+
+/**
+ * msgdma_dma_remove - Driver remove function
+ * @pdev: Pointer to the platform_device structure
+ *
+ * Return: Always '0'
+ */
+static int msgdma_remove(struct platform_device *pdev)
+{
+	struct msgdma_device *mdev = platform_get_drvdata(pdev);
+
+	dma_async_device_unregister(&mdev->dmadev);
+	msgdma_dev_remove(mdev);
+
+	dev_notice(&pdev->dev, "Altera mSGDMA driver removed\n");
+
+	return 0;
+}
+
+static struct platform_driver msgdma_driver = {
+	.driver = {
+		.name = "altera-msgdma",
+	},
+	.probe = msgdma_probe,
+	.remove = msgdma_remove,
+};
+
+module_platform_driver(msgdma_driver);
+
+MODULE_ALIAS("platform:altera-msgdma");
+MODULE_DESCRIPTION("Altera mSGDMA driver");
+MODULE_AUTHOR("Stefan Roese <sr@denx.de>");
+MODULE_LICENSE("GPL");