dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller

This AHB DMA Controller (aka HDMA or DMAC on AT91 systems) is availlable on
at91sam9rl chip. It will be used on other products in the future.

This first release covers only the memory-to-memory tranfer type. This is the
only tranfer type supported by this chip.  On other products, it will be used
also for peripheral DMA transfer (slave API support to come).

I used dmatest client without problem in different configurations to test it.

Full documentation for this controller can be found in the SAM9RL datasheet:
http://www.atmel.com/dyn/products/product_card.asp?part_id=4243

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 1009 insertions, 0 deletions

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
new file mode 100644
index 000000000000..64dbf0ce128e
--- /dev/null
+++ b/drivers/dma/at_hdmac.c
@@ -0,0 +1,1009 @@
+/*
+ * Driver for the Atmel AHB DMA Controller (aka HDMA or DMAC on AT91 systems)
+ *
+ * Copyright (C) 2008 Atmel Corporation
+ *
+ * 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.
+ *
+ *
+ * This supports the Atmel AHB DMA Controller,
+ *
+ * The driver has currently been tested with the Atmel AT91SAM9RL
+ * and AT91SAM9G45 series.
+ */
+
+#include <linux/clk.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmapool.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include "at_hdmac_regs.h"
+
+/*
+ * Glossary
+ * --------
+ *
+ * at_hdmac		: Name of the ATmel AHB DMA Controller
+ * at_dma_ / atdma	: ATmel DMA controller entity related
+ * atc_	/ atchan	: ATmel DMA Channel entity related
+ */
+
+#define	ATC_DEFAULT_CFG		(ATC_FIFOCFG_HALFFIFO)
+#define	ATC_DEFAULT_CTRLA	(0)
+#define	ATC_DEFAULT_CTRLB	(ATC_SIF(0)	\
+				|ATC_DIF(1))
+
+/*
+ * Initial number of descriptors to allocate for each channel. This could
+ * be increased during dma usage.
+ */
+static unsigned int init_nr_desc_per_channel = 64;
+module_param(init_nr_desc_per_channel, uint, 0644);
+MODULE_PARM_DESC(init_nr_desc_per_channel,
+		 "initial descriptors per channel (default: 64)");
+
+
+/* prototypes */
+static dma_cookie_t atc_tx_submit(struct dma_async_tx_descriptor *tx);
+
+
+/*----------------------------------------------------------------------*/
+
+static struct at_desc *atc_first_active(struct at_dma_chan *atchan)
+{
+	return list_first_entry(&atchan->active_list,
+				struct at_desc, desc_node);
+}
+
+static struct at_desc *atc_first_queued(struct at_dma_chan *atchan)
+{
+	return list_first_entry(&atchan->queue,
+				struct at_desc, desc_node);
+}
+
+/**
+ * atc_alloc_descriptor - allocate and return an initilized descriptor
+ * @chan: the channel to allocate descriptors for
+ * @gfp_flags: GFP allocation flags
+ *
+ * Note: The ack-bit is positioned in the descriptor flag at creation time
+ *       to make initial allocation more convenient. This bit will be cleared
+ *       and control will be given to client at usage time (during
+ *       preparation functions).
+ */
+static struct at_desc *atc_alloc_descriptor(struct dma_chan *chan,
+					    gfp_t gfp_flags)
+{
+	struct at_desc	*desc = NULL;
+	struct at_dma	*atdma = to_at_dma(chan->device);
+	dma_addr_t phys;
+
+	desc = dma_pool_alloc(atdma->dma_desc_pool, gfp_flags, &phys);
+	if (desc) {
+		memset(desc, 0, sizeof(struct at_desc));
+		dma_async_tx_descriptor_init(&desc->txd, chan);
+		/* txd.flags will be overwritten in prep functions */
+		desc->txd.flags = DMA_CTRL_ACK;
+		desc->txd.tx_submit = atc_tx_submit;
+		desc->txd.phys = phys;
+	}
+
+	return desc;
+}
+
+/**
+ * atc_desc_get - get a unsused descriptor from free_list
+ * @atchan: channel we want a new descriptor for
+ */
+static struct at_desc *atc_desc_get(struct at_dma_chan *atchan)
+{
+	struct at_desc *desc, *_desc;
+	struct at_desc *ret = NULL;
+	unsigned int i = 0;
+	LIST_HEAD(tmp_list);
+
+	spin_lock_bh(&atchan->lock);
+	list_for_each_entry_safe(desc, _desc, &atchan->free_list, desc_node) {
+		i++;
+		if (async_tx_test_ack(&desc->txd)) {
+			list_del(&desc->desc_node);
+			ret = desc;
+			break;
+		}
+		dev_dbg(chan2dev(&atchan->chan_common),
+				"desc %p not ACKed\n", desc);
+	}
+	spin_unlock_bh(&atchan->lock);
+	dev_vdbg(chan2dev(&atchan->chan_common),
+		"scanned %u descriptors on freelist\n", i);
+
+	/* no more descriptor available in initial pool: create one more */
+	if (!ret) {
+		ret = atc_alloc_descriptor(&atchan->chan_common, GFP_ATOMIC);
+		if (ret) {
+			spin_lock_bh(&atchan->lock);
+			atchan->descs_allocated++;
+			spin_unlock_bh(&atchan->lock);
+		} else {
+			dev_err(chan2dev(&atchan->chan_common),
+					"not enough descriptors available\n");
+		}
+	}
+
+	return ret;
+}
+
+/**
+ * atc_desc_put - move a descriptor, including any children, to the free list
+ * @atchan: channel we work on
+ * @desc: descriptor, at the head of a chain, to move to free list
+ */
+static void atc_desc_put(struct at_dma_chan *atchan, struct at_desc *desc)
+{
+	if (desc) {
+		struct at_desc *child;
+
+		spin_lock_bh(&atchan->lock);
+		list_for_each_entry(child, &desc->txd.tx_list, desc_node)
+			dev_vdbg(chan2dev(&atchan->chan_common),
+					"moving child desc %p to freelist\n",
+					child);
+		list_splice_init(&desc->txd.tx_list, &atchan->free_list);
+		dev_vdbg(chan2dev(&atchan->chan_common),
+			 "moving desc %p to freelist\n", desc);
+		list_add(&desc->desc_node, &atchan->free_list);
+		spin_unlock_bh(&atchan->lock);
+	}
+}
+
+/**
+ * atc_assign_cookie - compute and assign new cookie
+ * @atchan: channel we work on
+ * @desc: descriptor to asign cookie for
+ *
+ * Called with atchan->lock held and bh disabled
+ */
+static dma_cookie_t
+atc_assign_cookie(struct at_dma_chan *atchan, struct at_desc *desc)
+{
+	dma_cookie_t cookie = atchan->chan_common.cookie;
+
+	if (++cookie < 0)
+		cookie = 1;
+
+	atchan->chan_common.cookie = cookie;
+	desc->txd.cookie = cookie;
+
+	return cookie;
+}
+
+/**
+ * atc_dostart - starts the DMA engine for real
+ * @atchan: the channel we want to start
+ * @first: first descriptor in the list we want to begin with
+ *
+ * Called with atchan->lock held and bh disabled
+ */
+static void atc_dostart(struct at_dma_chan *atchan, struct at_desc *first)
+{
+	struct at_dma	*atdma = to_at_dma(atchan->chan_common.device);
+
+	/* ASSERT:  channel is idle */
+	if (atc_chan_is_enabled(atchan)) {
+		dev_err(chan2dev(&atchan->chan_common),
+			"BUG: Attempted to start non-idle channel\n");
+		dev_err(chan2dev(&atchan->chan_common),
+			"  channel: s0x%x d0x%x ctrl0x%x:0x%x l0x%x\n",
+			channel_readl(atchan, SADDR),
+			channel_readl(atchan, DADDR),
+			channel_readl(atchan, CTRLA),
+			channel_readl(atchan, CTRLB),
+			channel_readl(atchan, DSCR));
+
+		/* The tasklet will hopefully advance the queue... */
+		return;
+	}
+
+	vdbg_dump_regs(atchan);
+
+	/* clear any pending interrupt */
+	while (dma_readl(atdma, EBCISR))
+		cpu_relax();
+
+	channel_writel(atchan, SADDR, 0);
+	channel_writel(atchan, DADDR, 0);
+	channel_writel(atchan, CTRLA, 0);
+	channel_writel(atchan, CTRLB, 0);
+	channel_writel(atchan, DSCR, first->txd.phys);
+	dma_writel(atdma, CHER, atchan->mask);
+
+	vdbg_dump_regs(atchan);
+}
+
+/**
+ * atc_chain_complete - finish work for one transaction chain
+ * @atchan: channel we work on
+ * @desc: descriptor at the head of the chain we want do complete
+ *
+ * Called with atchan->lock held and bh disabled */
+static void
+atc_chain_complete(struct at_dma_chan *atchan, struct at_desc *desc)
+{
+	dma_async_tx_callback		callback;
+	void				*param;
+	struct dma_async_tx_descriptor	*txd = &desc->txd;
+
+	dev_vdbg(chan2dev(&atchan->chan_common),
+		"descriptor %u complete\n", txd->cookie);
+
+	atchan->completed_cookie = txd->cookie;
+	callback = txd->callback;
+	param = txd->callback_param;
+
+	/* move children to free_list */
+	list_splice_init(&txd->tx_list, &atchan->free_list);
+	/* move myself to free_list */
+	list_move(&desc->desc_node, &atchan->free_list);
+
+	/* unmap dma addresses */
+	if (!(txd->flags & DMA_COMPL_SKIP_DEST_UNMAP)) {
+		if (txd->flags & DMA_COMPL_DEST_UNMAP_SINGLE)
+			dma_unmap_single(chan2parent(&atchan->chan_common),
+					desc->lli.daddr,
+					desc->len, DMA_FROM_DEVICE);
+		else
+			dma_unmap_page(chan2parent(&atchan->chan_common),
+					desc->lli.daddr,
+					desc->len, DMA_FROM_DEVICE);
+	}
+	if (!(txd->flags & DMA_COMPL_SKIP_SRC_UNMAP)) {
+		if (txd->flags & DMA_COMPL_SRC_UNMAP_SINGLE)
+			dma_unmap_single(chan2parent(&atchan->chan_common),
+					desc->lli.saddr,
+					desc->len, DMA_TO_DEVICE);
+		else
+			dma_unmap_page(chan2parent(&atchan->chan_common),
+					desc->lli.saddr,
+					desc->len, DMA_TO_DEVICE);
+	}
+
+	/*
+	 * The API requires that no submissions are done from a
+	 * callback, so we don't need to drop the lock here
+	 */
+	if (callback)
+		callback(param);
+
+	dma_run_dependencies(txd);
+}
+
+/**
+ * atc_complete_all - finish work for all transactions
+ * @atchan: channel to complete transactions for
+ *
+ * Eventually submit queued descriptors if any
+ *
+ * Assume channel is idle while calling this function
+ * Called with atchan->lock held and bh disabled
+ */
+static void atc_complete_all(struct at_dma_chan *atchan)
+{
+	struct at_desc *desc, *_desc;
+	LIST_HEAD(list);
+
+	dev_vdbg(chan2dev(&atchan->chan_common), "complete all\n");
+
+	BUG_ON(atc_chan_is_enabled(atchan));
+
+	/*
+	 * Submit queued descriptors ASAP, i.e. before we go through
+	 * the completed ones.
+	 */
+	if (!list_empty(&atchan->queue))
+		atc_dostart(atchan, atc_first_queued(atchan));
+	/* empty active_list now it is completed */
+	list_splice_init(&atchan->active_list, &list);
+	/* empty queue list by moving descriptors (if any) to active_list */
+	list_splice_init(&atchan->queue, &atchan->active_list);
+
+	list_for_each_entry_safe(desc, _desc, &list, desc_node)
+		atc_chain_complete(atchan, desc);
+}
+
+/**
+ * atc_cleanup_descriptors - cleanup up finished descriptors in active_list
+ * @atchan: channel to be cleaned up
+ *
+ * Called with atchan->lock held and bh disabled
+ */
+static void atc_cleanup_descriptors(struct at_dma_chan *atchan)
+{
+	struct at_desc	*desc, *_desc;
+	struct at_desc	*child;
+
+	dev_vdbg(chan2dev(&atchan->chan_common), "cleanup descriptors\n");
+
+	list_for_each_entry_safe(desc, _desc, &atchan->active_list, desc_node) {
+		if (!(desc->lli.ctrla & ATC_DONE))
+			/* This one is currently in progress */
+			return;
+
+		list_for_each_entry(child, &desc->txd.tx_list, desc_node)
+			if (!(child->lli.ctrla & ATC_DONE))
+				/* Currently in progress */
+				return;
+
+		/*
+		 * No descriptors so far seem to be in progress, i.e.
+		 * this chain must be done.
+		 */
+		atc_chain_complete(atchan, desc);
+	}
+}
+
+/**
+ * atc_advance_work - at the end of a transaction, move forward
+ * @atchan: channel where the transaction ended
+ *
+ * Called with atchan->lock held and bh disabled
+ */
+static void atc_advance_work(struct at_dma_chan *atchan)
+{
+	dev_vdbg(chan2dev(&atchan->chan_common), "advance_work\n");
+
+	if (list_empty(&atchan->active_list) ||
+	    list_is_singular(&atchan->active_list)) {
+		atc_complete_all(atchan);
+	} else {
+		atc_chain_complete(atchan, atc_first_active(atchan));
+		/* advance work */
+		atc_dostart(atchan, atc_first_active(atchan));
+	}
+}
+
+
+/**
+ * atc_handle_error - handle errors reported by DMA controller
+ * @atchan: channel where error occurs
+ *
+ * Called with atchan->lock held and bh disabled
+ */
+static void atc_handle_error(struct at_dma_chan *atchan)
+{
+	struct at_desc *bad_desc;
+	struct at_desc *child;
+
+	/*
+	 * The descriptor currently at the head of the active list is
+	 * broked. Since we don't have any way to report errors, we'll
+	 * just have to scream loudly and try to carry on.
+	 */
+	bad_desc = atc_first_active(atchan);
+	list_del_init(&bad_desc->desc_node);
+
+	/* As we are stopped, take advantage to push queued descriptors
+	 * in active_list */
+	list_splice_init(&atchan->queue, atchan->active_list.prev);
+
+	/* Try to restart the controller */
+	if (!list_empty(&atchan->active_list))
+		atc_dostart(atchan, atc_first_active(atchan));
+
+	/*
+	 * KERN_CRITICAL may seem harsh, but since this only happens
+	 * when someone submits a bad physical address in a
+	 * descriptor, we should consider ourselves lucky that the
+	 * controller flagged an error instead of scribbling over
+	 * random memory locations.
+	 */
+	dev_crit(chan2dev(&atchan->chan_common),
+			"Bad descriptor submitted for DMA!\n");
+	dev_crit(chan2dev(&atchan->chan_common),
+			"  cookie: %d\n", bad_desc->txd.cookie);
+	atc_dump_lli(atchan, &bad_desc->lli);
+	list_for_each_entry(child, &bad_desc->txd.tx_list, desc_node)
+		atc_dump_lli(atchan, &child->lli);
+
+	/* Pretend the descriptor completed successfully */
+	atc_chain_complete(atchan, bad_desc);
+}
+
+
+/*--  IRQ & Tasklet  ---------------------------------------------------*/
+
+static void atc_tasklet(unsigned long data)
+{
+	struct at_dma_chan *atchan = (struct at_dma_chan *)data;
+
+	/* Channel cannot be enabled here */
+	if (atc_chan_is_enabled(atchan)) {
+		dev_err(chan2dev(&atchan->chan_common),
+			"BUG: channel enabled in tasklet\n");
+		return;
+	}
+
+	spin_lock(&atchan->lock);
+	if (test_and_clear_bit(0, &atchan->error_status))
+		atc_handle_error(atchan);
+	else
+		atc_advance_work(atchan);
+
+	spin_unlock(&atchan->lock);
+}
+
+static irqreturn_t at_dma_interrupt(int irq, void *dev_id)
+{
+	struct at_dma		*atdma = (struct at_dma *)dev_id;
+	struct at_dma_chan	*atchan;
+	int			i;
+	u32			status, pending, imr;
+	int			ret = IRQ_NONE;
+
+	do {
+		imr = dma_readl(atdma, EBCIMR);
+		status = dma_readl(atdma, EBCISR);
+		pending = status & imr;
+
+		if (!pending)
+			break;
+
+		dev_vdbg(atdma->dma_common.dev,
+			"interrupt: status = 0x%08x, 0x%08x, 0x%08x\n",
+			 status, imr, pending);
+
+		for (i = 0; i < atdma->dma_common.chancnt; i++) {
+			atchan = &atdma->chan[i];
+			if (pending & (AT_DMA_CBTC(i) | AT_DMA_ERR(i))) {
+				if (pending & AT_DMA_ERR(i)) {
+					/* Disable channel on AHB error */
+					dma_writel(atdma, CHDR, atchan->mask);
+					/* Give information to tasklet */
+					set_bit(0, &atchan->error_status);
+				}
+				tasklet_schedule(&atchan->tasklet);
+				ret = IRQ_HANDLED;
+			}
+		}
+
+	} while (pending);
+
+	return ret;
+}
+
+
+/*--  DMA Engine API  --------------------------------------------------*/
+
+/**
+ * atc_tx_submit - set the prepared descriptor(s) to be executed by the engine
+ * @desc: descriptor at the head of the transaction chain
+ *
+ * Queue chain if DMA engine is working already
+ *
+ * Cookie increment and adding to active_list or queue must be atomic
+ */
+static dma_cookie_t atc_tx_submit(struct dma_async_tx_descriptor *tx)
+{
+	struct at_desc		*desc = txd_to_at_desc(tx);
+	struct at_dma_chan	*atchan = to_at_dma_chan(tx->chan);
+	dma_cookie_t		cookie;
+
+	spin_lock_bh(&atchan->lock);
+	cookie = atc_assign_cookie(atchan, desc);
+
+	if (list_empty(&atchan->active_list)) {
+		dev_vdbg(chan2dev(tx->chan), "tx_submit: started %u\n",
+				desc->txd.cookie);
+		atc_dostart(atchan, desc);
+		list_add_tail(&desc->desc_node, &atchan->active_list);
+	} else {
+		dev_vdbg(chan2dev(tx->chan), "tx_submit: queued %u\n",
+				desc->txd.cookie);
+		list_add_tail(&desc->desc_node, &atchan->queue);
+	}
+
+	spin_unlock_bh(&atchan->lock);
+
+	return cookie;
+}
+
+/**
+ * atc_prep_dma_memcpy - prepare a memcpy operation
+ * @chan: the channel to prepare operation on
+ * @dest: operation virtual destination address
+ * @src: operation virtual source address
+ * @len: operation length
+ * @flags: tx descriptor status flags
+ */
+static struct dma_async_tx_descriptor *
+atc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
+		size_t len, unsigned long flags)
+{
+	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
+	struct at_desc		*desc = NULL;
+	struct at_desc		*first = NULL;
+	struct at_desc		*prev = NULL;
+	size_t			xfer_count;
+	size_t			offset;
+	unsigned int		src_width;
+	unsigned int		dst_width;
+	u32			ctrla;
+	u32			ctrlb;
+
+	dev_vdbg(chan2dev(chan), "prep_dma_memcpy: d0x%x s0x%x l0x%zx f0x%lx\n",
+			dest, src, len, flags);
+
+	if (unlikely(!len)) {
+		dev_dbg(chan2dev(chan), "prep_dma_memcpy: length is zero!\n");
+		return NULL;
+	}
+
+	ctrla =   ATC_DEFAULT_CTRLA;
+	ctrlb =   ATC_DEFAULT_CTRLB
+		| ATC_SRC_ADDR_MODE_INCR
+		| ATC_DST_ADDR_MODE_INCR
+		| ATC_FC_MEM2MEM;
+
+	/*
+	 * We can be a lot more clever here, but this should take care
+	 * of the most common optimization.
+	 */
+	if (!((src | dest  | len) & 3)) {
+		ctrla |= ATC_SRC_WIDTH_WORD | ATC_DST_WIDTH_WORD;
+		src_width = dst_width = 2;
+	} else if (!((src | dest | len) & 1)) {
+		ctrla |= ATC_SRC_WIDTH_HALFWORD | ATC_DST_WIDTH_HALFWORD;
+		src_width = dst_width = 1;
+	} else {
+		ctrla |= ATC_SRC_WIDTH_BYTE | ATC_DST_WIDTH_BYTE;
+		src_width = dst_width = 0;
+	}
+
+	for (offset = 0; offset < len; offset += xfer_count << src_width) {
+		xfer_count = min_t(size_t, (len - offset) >> src_width,
+				ATC_BTSIZE_MAX);
+
+		desc = atc_desc_get(atchan);
+		if (!desc)
+			goto err_desc_get;
+
+		desc->lli.saddr = src + offset;
+		desc->lli.daddr = dest + offset;
+		desc->lli.ctrla = ctrla | xfer_count;
+		desc->lli.ctrlb = ctrlb;
+
+		desc->txd.cookie = 0;
+		async_tx_ack(&desc->txd);
+
+		if (!first) {
+			first = desc;
+		} else {
+			/* inform the HW lli about chaining */
+			prev->lli.dscr = desc->txd.phys;
+			/* insert the link descriptor to the LD ring */
+			list_add_tail(&desc->desc_node,
+					&first->txd.tx_list);
+		}
+		prev = desc;
+	}
+
+	/* First descriptor of the chain embedds additional information */
+	first->txd.cookie = -EBUSY;
+	first->len = len;
+
+	/* set end-of-link to the last link descriptor of list*/
+	set_desc_eol(desc);
+
+	desc->txd.flags = flags; /* client is in control of this ack */
+
+	return &first->txd;
+
+err_desc_get:
+	atc_desc_put(atchan, first);
+	return NULL;
+}
+
+/**
+ * atc_is_tx_complete - poll for transaction completion
+ * @chan: DMA channel
+ * @cookie: transaction identifier to check status of
+ * @done: if not %NULL, updated with last completed transaction
+ * @used: if not %NULL, updated with last used transaction
+ *
+ * If @done and @used are passed in, upon return they reflect the driver
+ * internal state and can be used with dma_async_is_complete() to check
+ * the status of multiple cookies without re-checking hardware state.
+ */
+static enum dma_status
+atc_is_tx_complete(struct dma_chan *chan,
+		dma_cookie_t cookie,
+		dma_cookie_t *done, dma_cookie_t *used)
+{
+	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
+	dma_cookie_t		last_used;
+	dma_cookie_t		last_complete;
+	enum dma_status		ret;
+
+	dev_vdbg(chan2dev(chan), "is_tx_complete: %d (d%d, u%d)\n",
+			cookie, done ? *done : 0, used ? *used : 0);
+
+	spin_lock_bh(atchan->lock);
+
+	last_complete = atchan->completed_cookie;
+	last_used = chan->cookie;
+
+	ret = dma_async_is_complete(cookie, last_complete, last_used);
+	if (ret != DMA_SUCCESS) {
+		atc_cleanup_descriptors(atchan);
+
+		last_complete = atchan->completed_cookie;
+		last_used = chan->cookie;
+
+		ret = dma_async_is_complete(cookie, last_complete, last_used);
+	}
+
+	spin_unlock_bh(atchan->lock);
+
+	if (done)
+		*done = last_complete;
+	if (used)
+		*used = last_used;
+
+	return ret;
+}
+
+/**
+ * atc_issue_pending - try to finish work
+ * @chan: target DMA channel
+ */
+static void atc_issue_pending(struct dma_chan *chan)
+{
+	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
+
+	dev_vdbg(chan2dev(chan), "issue_pending\n");
+
+	if (!atc_chan_is_enabled(atchan)) {
+		spin_lock_bh(&atchan->lock);
+		atc_advance_work(atchan);
+		spin_unlock_bh(&atchan->lock);
+	}
+}
+
+/**
+ * atc_alloc_chan_resources - allocate resources for DMA channel
+ * @chan: allocate descriptor resources for this channel
+ * @client: current client requesting the channel be ready for requests
+ *
+ * return - the number of allocated descriptors
+ */
+static int atc_alloc_chan_resources(struct dma_chan *chan)
+{
+	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
+	struct at_dma		*atdma = to_at_dma(chan->device);
+	struct at_desc		*desc;
+	int			i;
+	LIST_HEAD(tmp_list);
+
+	dev_vdbg(chan2dev(chan), "alloc_chan_resources\n");
+
+	/* ASSERT:  channel is idle */
+	if (atc_chan_is_enabled(atchan)) {
+		dev_dbg(chan2dev(chan), "DMA channel not idle ?\n");
+		return -EIO;
+	}
+
+	/* have we already been set up? */
+	if (!list_empty(&atchan->free_list))
+		return atchan->descs_allocated;
+
+	/* Allocate initial pool of descriptors */
+	for (i = 0; i < init_nr_desc_per_channel; i++) {
+		desc = atc_alloc_descriptor(chan, GFP_KERNEL);
+		if (!desc) {
+			dev_err(atdma->dma_common.dev,
+				"Only %d initial descriptors\n", i);
+			break;
+		}
+		list_add_tail(&desc->desc_node, &tmp_list);
+	}
+
+	spin_lock_bh(&atchan->lock);
+	atchan->descs_allocated = i;
+	list_splice(&tmp_list, &atchan->free_list);
+	atchan->completed_cookie = chan->cookie = 1;
+	spin_unlock_bh(&atchan->lock);
+
+	/* channel parameters */
+	channel_writel(atchan, CFG, ATC_DEFAULT_CFG);
+
+	dev_dbg(chan2dev(chan),
+		"alloc_chan_resources: allocated %d descriptors\n",
+		atchan->descs_allocated);
+
+	return atchan->descs_allocated;
+}
+
+/**
+ * atc_free_chan_resources - free all channel resources
+ * @chan: DMA channel
+ */
+static void atc_free_chan_resources(struct dma_chan *chan)
+{
+	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
+	struct at_dma		*atdma = to_at_dma(chan->device);
+	struct at_desc		*desc, *_desc;
+	LIST_HEAD(list);
+
+	dev_dbg(chan2dev(chan), "free_chan_resources: (descs allocated=%u)\n",
+		atchan->descs_allocated);
+
+	/* ASSERT:  channel is idle */
+	BUG_ON(!list_empty(&atchan->active_list));
+	BUG_ON(!list_empty(&atchan->queue));
+	BUG_ON(atc_chan_is_enabled(atchan));
+
+	list_for_each_entry_safe(desc, _desc, &atchan->free_list, desc_node) {
+		dev_vdbg(chan2dev(chan), "  freeing descriptor %p\n", desc);
+		list_del(&desc->desc_node);
+		/* free link descriptor */
+		dma_pool_free(atdma->dma_desc_pool, desc, desc->txd.phys);
+	}
+	list_splice_init(&atchan->free_list, &list);
+	atchan->descs_allocated = 0;
+
+	dev_vdbg(chan2dev(chan), "free_chan_resources: done\n");
+}
+
+
+/*--  Module Management  -----------------------------------------------*/
+
+/**
+ * at_dma_off - disable DMA controller
+ * @atdma: the Atmel HDAMC device
+ */
+static void at_dma_off(struct at_dma *atdma)
+{
+	dma_writel(atdma, EN, 0);
+
+	/* disable all interrupts */
+	dma_writel(atdma, EBCIDR, -1L);
+
+	/* confirm that all channels are disabled */
+	while (dma_readl(atdma, CHSR) & atdma->all_chan_mask)
+		cpu_relax();
+}
+
+static int __init at_dma_probe(struct platform_device *pdev)
+{
+	struct at_dma_platform_data *pdata;
+	struct resource		*io;
+	struct at_dma		*atdma;
+	size_t			size;
+	int			irq;
+	int			err;
+	int			i;
+
+	/* get DMA Controller parameters from platform */
+	pdata = pdev->dev.platform_data;
+	if (!pdata || pdata->nr_channels > AT_DMA_MAX_NR_CHANNELS)
+		return -EINVAL;
+
+	io = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!io)
+		return -EINVAL;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	size = sizeof(struct at_dma);
+	size += pdata->nr_channels * sizeof(struct at_dma_chan);
+	atdma = kzalloc(size, GFP_KERNEL);
+	if (!atdma)
+		return -ENOMEM;
+
+	/* discover transaction capabilites from the platform data */
+	atdma->dma_common.cap_mask = pdata->cap_mask;
+	atdma->all_chan_mask = (1 << pdata->nr_channels) - 1;
+
+	size = io->end - io->start + 1;
+	if (!request_mem_region(io->start, size, pdev->dev.driver->name)) {
+		err = -EBUSY;
+		goto err_kfree;
+	}
+
+	atdma->regs = ioremap(io->start, size);
+	if (!atdma->regs) {
+		err = -ENOMEM;
+		goto err_release_r;
+	}
+
+	atdma->clk = clk_get(&pdev->dev, "dma_clk");
+	if (IS_ERR(atdma->clk)) {
+		err = PTR_ERR(atdma->clk);
+		goto err_clk;
+	}
+	clk_enable(atdma->clk);
+
+	/* force dma off, just in case */
+	at_dma_off(atdma);
+
+	err = request_irq(irq, at_dma_interrupt, 0, "at_hdmac", atdma);
+	if (err)
+		goto err_irq;
+
+	platform_set_drvdata(pdev, atdma);
+
+	/* create a pool of consistent memory blocks for hardware descriptors */
+	atdma->dma_desc_pool = dma_pool_create("at_hdmac_desc_pool",
+			&pdev->dev, sizeof(struct at_desc),
+			4 /* word alignment */, 0);
+	if (!atdma->dma_desc_pool) {
+		dev_err(&pdev->dev, "No memory for descriptors dma pool\n");
+		err = -ENOMEM;
+		goto err_pool_create;
+	}
+
+	/* clear any pending interrupt */
+	while (dma_readl(atdma, EBCISR))
+		cpu_relax();
+
+	/* initialize channels related values */
+	INIT_LIST_HEAD(&atdma->dma_common.channels);
+	for (i = 0; i < pdata->nr_channels; i++, atdma->dma_common.chancnt++) {
+		struct at_dma_chan	*atchan = &atdma->chan[i];
+
+		atchan->chan_common.device = &atdma->dma_common;
+		atchan->chan_common.cookie = atchan->completed_cookie = 1;
+		atchan->chan_common.chan_id = i;
+		list_add_tail(&atchan->chan_common.device_node,
+				&atdma->dma_common.channels);
+
+		atchan->ch_regs = atdma->regs + ch_regs(i);
+		spin_lock_init(&atchan->lock);
+		atchan->mask = 1 << i;
+
+		INIT_LIST_HEAD(&atchan->active_list);
+		INIT_LIST_HEAD(&atchan->queue);
+		INIT_LIST_HEAD(&atchan->free_list);
+
+		tasklet_init(&atchan->tasklet, atc_tasklet,
+				(unsigned long)atchan);
+		atc_enable_irq(atchan);
+	}
+
+	/* set base routines */
+	atdma->dma_common.device_alloc_chan_resources = atc_alloc_chan_resources;
+	atdma->dma_common.device_free_chan_resources = atc_free_chan_resources;
+	atdma->dma_common.device_is_tx_complete = atc_is_tx_complete;
+	atdma->dma_common.device_issue_pending = atc_issue_pending;
+	atdma->dma_common.dev = &pdev->dev;
+
+	/* set prep routines based on capability */
+	if (dma_has_cap(DMA_MEMCPY, atdma->dma_common.cap_mask))
+		atdma->dma_common.device_prep_dma_memcpy = atc_prep_dma_memcpy;
+
+	dma_writel(atdma, EN, AT_DMA_ENABLE);
+
+	dev_info(&pdev->dev, "Atmel AHB DMA Controller ( %s%s), %d channels\n",
+	  dma_has_cap(DMA_MEMCPY, atdma->dma_common.cap_mask) ? "cpy " : "",
+	  dma_has_cap(DMA_SLAVE, atdma->dma_common.cap_mask)  ? "slave " : "",
+	  atdma->dma_common.chancnt);
+
+	dma_async_device_register(&atdma->dma_common);
+
+	return 0;
+
+err_pool_create:
+	platform_set_drvdata(pdev, NULL);
+	free_irq(platform_get_irq(pdev, 0), atdma);
+err_irq:
+	clk_disable(atdma->clk);
+	clk_put(atdma->clk);
+err_clk:
+	iounmap(atdma->regs);
+	atdma->regs = NULL;
+err_release_r:
+	release_mem_region(io->start, size);
+err_kfree:
+	kfree(atdma);
+	return err;
+}
+
+static int __exit at_dma_remove(struct platform_device *pdev)
+{
+	struct at_dma		*atdma = platform_get_drvdata(pdev);
+	struct dma_chan		*chan, *_chan;
+	struct resource		*io;
+
+	at_dma_off(atdma);
+	dma_async_device_unregister(&atdma->dma_common);
+
+	dma_pool_destroy(atdma->dma_desc_pool);
+	platform_set_drvdata(pdev, NULL);
+	free_irq(platform_get_irq(pdev, 0), atdma);
+
+	list_for_each_entry_safe(chan, _chan, &atdma->dma_common.channels,
+			device_node) {
+		struct at_dma_chan	*atchan = to_at_dma_chan(chan);
+
+		/* Disable interrupts */
+		atc_disable_irq(atchan);
+		tasklet_disable(&atchan->tasklet);
+
+		tasklet_kill(&atchan->tasklet);
+		list_del(&chan->device_node);
+	}
+
+	clk_disable(atdma->clk);
+	clk_put(atdma->clk);
+
+	iounmap(atdma->regs);
+	atdma->regs = NULL;
+
+	io = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	release_mem_region(io->start, io->end - io->start + 1);
+
+	kfree(atdma);
+
+	return 0;
+}
+
+static void at_dma_shutdown(struct platform_device *pdev)
+{
+	struct at_dma	*atdma = platform_get_drvdata(pdev);
+
+	at_dma_off(platform_get_drvdata(pdev));
+	clk_disable(atdma->clk);
+}
+
+static int at_dma_suspend_late(struct platform_device *pdev, pm_message_t mesg)
+{
+	struct at_dma	*atdma = platform_get_drvdata(pdev);
+
+	at_dma_off(platform_get_drvdata(pdev));
+	clk_disable(atdma->clk);
+	return 0;
+}
+
+static int at_dma_resume_early(struct platform_device *pdev)
+{
+	struct at_dma	*atdma = platform_get_drvdata(pdev);
+
+	clk_enable(atdma->clk);
+	dma_writel(atdma, EN, AT_DMA_ENABLE);
+	return 0;
+
+}
+
+static struct platform_driver at_dma_driver = {
+	.remove		= __exit_p(at_dma_remove),
+	.shutdown	= at_dma_shutdown,
+	.suspend_late	= at_dma_suspend_late,
+	.resume_early	= at_dma_resume_early,
+	.driver = {
+		.name	= "at_hdmac",
+	},
+};
+
+static int __init at_dma_init(void)
+{
+	return platform_driver_probe(&at_dma_driver, at_dma_probe);
+}
+module_init(at_dma_init);
+
+static void __exit at_dma_exit(void)
+{
+	platform_driver_unregister(&at_dma_driver);
+}
+module_exit(at_dma_exit);
+
+MODULE_DESCRIPTION("Atmel AHB DMA Controller driver");
+MODULE_AUTHOR("Nicolas Ferre <nicolas.ferre@atmel.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:at_hdmac");