path: root/drivers/dma/dw_dmac.c

/*
 * Driver for the Synopsys DesignWare DMA Controller (aka DMACA on
 * AVR32 systems.)
 *
 * Copyright (C) 2007-2008 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#include "dw_dmac_regs.h"

/*
 * This supports the Synopsys "DesignWare AHB Central DMA Controller",
 * (DW_ahb_dmac) which is used with various AMBA 2.0 systems (not all
 * of which use ARM any more).  See the "Databook" from Synopsys for
 * information beyond what licensees probably provide.
 *
 * The driver has currently been tested only with the Atmel AT32AP7000,
 * which does not support descriptor writeback.
 */

/* NOTE:  DMS+SMS is system-specific. We should get this information
 * from the platform code somehow.
 */
#define DWC_DEFAULT_CTLLO	(DWC_CTLL_DST_MSIZE(0)		\
				| DWC_CTLL_SRC_MSIZE(0)		\
				| DWC_CTLL_DMS(0)		\
				| DWC_CTLL_SMS(1)		\
				| DWC_CTLL_LLP_D_EN		\
				| DWC_CTLL_LLP_S_EN)

/*
 * This is configuration-dependent and usually a funny size like 4095.
 * Let's round it down to the nearest power of two.
 *
 * Note that this is a transfer count, i.e. if we transfer 32-bit
 * words, we can do 8192 bytes per descriptor.
 *
 * This parameter is also system-specific.
 */
#define DWC_MAX_COUNT	2048U

/*
 * Number of descriptors to allocate for each channel. This should be
 * made configurable somehow; preferably, the clients (at least the
 * ones using slave transfers) should be able to give us a hint.
 */
#define NR_DESCS_PER_CHANNEL	64

/*----------------------------------------------------------------------*/

/*
 * Because we're not relying on writeback from the controller (it may not
 * even be configured into the core!) we don't need to use dma_pool.  These
 * descriptors -- and associated data -- are cacheable.  We do need to make
 * sure their dcache entries are written back before handing them off to
 * the controller, though.
 */

static struct dw_desc *dwc_first_active(struct dw_dma_chan *dwc)
{
	return list_entry(dwc->active_list.next, struct dw_desc, desc_node);
}

static struct dw_desc *dwc_first_queued(struct dw_dma_chan *dwc)
{
	return list_entry(dwc->queue.next, struct dw_desc, desc_node);
}

static struct dw_desc *dwc_desc_get(struct dw_dma_chan *dwc)
{
	struct dw_desc *desc, *_desc;
	struct dw_desc *ret = NULL;
	unsigned int i = 0;

	spin_lock_bh(&dwc->lock);
	list_for_each_entry_safe(desc, _desc, &dwc->free_list, desc_node) {
		if (async_tx_test_ack(&desc->txd)) {
			list_del(&desc->desc_node);
			ret = desc;
			break;
		}
		dev_dbg(&dwc->chan.dev, "desc %p not ACKed\n", desc);
		i++;
	}
	spin_unlock_bh(&dwc->lock);

	dev_vdbg(&dwc->chan.dev, "scanned %u descriptors on freelist\n", i);

	return ret;
}

static void dwc_sync_desc_for_cpu(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
	struct dw_desc	*child;

	list_for_each_entry(child, &desc->txd.tx_list, desc_node)
		dma_sync_single_for_cpu(dwc->chan.dev.parent,
				child->txd.phys, sizeof(child->lli),
				DMA_TO_DEVICE);
	dma_sync_single_for_cpu(dwc->chan.dev.parent,
			desc->txd.phys, sizeof(desc->lli),
			DMA_TO_DEVICE);
}

/*
 * Move a descriptor, including any children, to the free list.
 * `desc' must not be on any lists.
 */
static void dwc_desc_put(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
	if (desc) {
		struct dw_desc *child;

		dwc_sync_desc_for_cpu(dwc, desc);

		spin_lock_bh(&dwc->lock);
		list_for_each_entry(child, &desc->txd.tx_list, desc_node)
			dev_vdbg(&dwc->chan.dev,
					"moving child desc %p to freelist\n",
					child);
		list_splice_init(&desc->txd.tx_list, &dwc->free_list);
		dev_vdbg(&dwc->chan.dev, "moving desc %p to freelist\n", desc);
		list_add(&desc->desc_node, &dwc->free_list);
		spin_unlock_bh(&dwc->lock);
	}
}

/* Called with dwc->lock held and bh disabled */
static dma_cookie_t
dwc_assign_cookie(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
	dma_cookie_t