dmaengine: driver for the ARM PL080/PL081 PrimeCells v5

This creates a DMAengine driver for the ARM PL080/PL081 PrimeCells
based on the implementation earlier submitted by Peter Pearse.
This is working like a charm for memcpy and slave DMA to the PL011
PrimeCell on the PB11MPCore.

This DMA controller is used in mostly unmodified form in the ARM
RealView and Versatile platforms, in the ST-Ericsson Nomadik, and
in the ST SPEAr platform.

It has been converted to use the header from the Samsung PL080
derivate instead of its own defintions. The Samsungs have a custom
driver in their mach-* folders though, atleast we can share the
register definitions.

Cc: Peter Pearse <peter.pearse@arm.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Alessandro Rubini <rubini@unipv.it>
Acked-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
[GFP_KERNEL to GFP_NOWAIT in pl08x_prep_dma_memcpy]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 2176 insertions, 0 deletions

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 9520cf02edc..f82ef10a836 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -49,6 +49,14 @@ config INTEL_MID_DMAC
 config ASYNC_TX_DISABLE_CHANNEL_SWITCH
 	bool
 
+config AMBA_PL08X
+	bool "ARM PrimeCell PL080 or PL081 support"
+	depends on ARM_AMBA && EXPERIMENTAL
+	select DMA_ENGINE
+	help
+	  Platform has a PL08x DMAC device
+	  which can provide DMA engine support
+
 config INTEL_IOATDMA
 	tristate "Intel I/OAT DMA support"
 	depends on PCI && X86
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index 72bd70384d8..0b690e7e438 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -25,3 +25,4 @@ obj-$(CONFIG_TIMB_DMA) += timb_dma.o
 obj-$(CONFIG_STE_DMA40) += ste_dma40.o ste_dma40_ll.o
 obj-$(CONFIG_PL330_DMA) += pl330.o
 obj-$(CONFIG_PCH_DMA) += pch_dma.o
+obj-$(CONFIG_AMBA_PL08X) += amba-pl08x.o
diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
new file mode 100644
index 00000000000..b605cc9ac3a
--- /dev/null
+++ b/drivers/dma/amba-pl08x.c
@@ -0,0 +1,2167 @@
+/*
+ * Copyright (c) 2006 ARM Ltd.
+ * Copyright (c) 2010 ST-Ericsson SA
+ *
+ * Author: Peter Pearse <peter.pearse@arm.com>
+ * Author: Linus Walleij <linus.walleij@stericsson.com>
+ *
+ * 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 program is distributed in the hope that 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, write to the Free Software Foundation, Inc., 59
+ * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ *
+ * The full GNU General Public License is iin this distribution in the
+ * file called COPYING.
+ *
+ * Documentation: ARM DDI 0196G == PL080
+ * Documentation: ARM DDI 0218E	== PL081
+ *
+ * PL080 & PL081 both have 16 sets of DMA signals that can be routed to
+ * any channel.
+ *
+ * The PL080 has 8 channels available for simultaneous use, and the PL081
+ * has only two channels. So on these DMA controllers the number of channels
+ * and the number of incoming DMA signals are two totally different things.
+ * It is usually not possible to theoretically handle all physical signals,
+ * so a multiplexing scheme with possible denial of use is necessary.
+ *
+ * The PL080 has a dual bus master, PL081 has a single master.
+ *
+ * Memory to peripheral transfer may be visualized as
+ *	Get data from memory to DMAC
+ *	Until no data left
+ *		On burst request from peripheral
+ *			Destination burst from DMAC to peripheral
+ *			Clear burst request
+ *	Raise terminal count interrupt
+ *
+ * For peripherals with a FIFO:
+ * Source      burst size == half the depth of the peripheral FIFO
+ * Destination burst size == the depth of the peripheral FIFO
+ *
+ * (Bursts are irrelevant for mem to mem transfers - there are no burst
+ * signals, the DMA controller will simply facilitate its AHB master.)
+ *
+ * ASSUMES default (little) endianness for DMA transfers
+ *
+ * Only DMAC flow control is implemented
+ *
+ * Global TODO:
+ * - Break out common code from arch/arm/mach-s3c64xx and share
+ */
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/dmapool.h>
+#include <linux/amba/bus.h>
+#include <linux/dmaengine.h>
+#include <linux/amba/pl08x.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+#include <asm/hardware/pl080.h>
+#include <asm/dma.h>
+#include <asm/mach/dma.h>
+#include <asm/atomic.h>
+#include <asm/processor.h>
+#include <asm/cacheflush.h>
+
+#define DRIVER_NAME	"pl08xdmac"
+
+/**
+ * struct vendor_data - vendor-specific config parameters
+ * for PL08x derivates
+ * @name: the name of this specific variant
+ * @channels: the number of channels available in this variant
+ * @dualmaster: whether this version supports dual AHB masters
+ * or not.
+ */
+struct vendor_data {
+	char *name;
+	u8 channels;
+	bool dualmaster;
+};
+
+/*
+ * PL08X private data structures
+ * An LLI struct - see pl08x TRM
+ * Note that next uses bit[0] as a bus bit,
+ * start & end do not - their bus bit info
+ * is in cctl
+ */
+struct lli {
+	dma_addr_t src;
+	dma_addr_t dst;
+	dma_addr_t next;
+	u32 cctl;
+};
+
+/**
+ * struct pl08x_driver_data - the local state holder for the PL08x
+ * @slave: slave engine for this instance
+ * @memcpy: memcpy engine for this instance
+ * @base: virtual memory base (remapped) for the PL08x
+ * @adev: the corresponding AMBA (PrimeCell) bus entry
+ * @vd: vendor data for this PL08x variant
+ * @pd: platform data passed in from the platform/machine
+ * @phy_chans: array of data for the physical channels
+ * @pool: a pool for the LLI descriptors
+ * @pool_ctr: counter of LLIs in the pool
+ * @lock: a spinlock for this struct
+ */
+struct pl08x_driver_data {
+	struct dma_device slave;
+	struct dma_device memcpy;
+	void __iomem *base;
+	struct amba_device *adev;
+	struct vendor_data *vd;
+	struct pl08x_platform_data *pd;
+	struct pl08x_phy_chan *phy_chans;
+	struct dma_pool *pool;
+	int pool_ctr;
+	spinlock_t lock;
+};
+
+/*
+ * PL08X specific defines
+ */
+
+/*
+ * Memory boundaries: the manual for PL08x says that the controller
+ * cannot read past a 1KiB boundary, so these defines are used to
+ * create transfer LLIs that do not cross such boundaries.
+ */
+#define PL08X_BOUNDARY_SHIFT		(10)	/* 1KB 0x400 */
+#define PL08X_BOUNDARY_SIZE		(1 << PL08X_BOUNDARY_SHIFT)
+
+/* Minimum period between work queue runs */
+#define PL08X_WQ_PERIODMIN	20
+
+/* Size (bytes) of each LLI buffer allocated for one transfer */
+# define PL08X_LLI_TSFR_SIZE	0x2000
+
+/* Maximimum times we call dma_pool_alloc on this pool without freeing */
+#define PL08X_MAX_ALLOCS	0x40
+#define MAX_NUM_TSFR_LLIS	(PL08X_LLI_TSFR_SIZE/sizeof(struct lli))
+#define PL08X_ALIGN		8
+
+static inline struct pl08x_dma_chan *to_pl08x_chan(struct dma_chan *chan)
+{
+	return container_of(chan, struct pl08x_dma_chan, chan);
+}
+
+/*
+ * Physical channel handling
+ */
+
+/* Whether a certain channel is busy or not */
+static int pl08x_phy_channel_busy(struct pl08x_phy_chan *ch)
+{
+	unsigned int val;
+
+	val = readl(ch->base + PL080_CH_CONFIG);
+	return val & PL080_CONFIG_ACTIVE;
+}
+
+/*
+ * Set the initial DMA register values i.e. those for the first LLI
+ * The next lli pointer and the configuration interrupt bit have
+ * been set when the LLIs were constructed
+ */
+static void pl08x_set_cregs(struct pl08x_driver_data *pl08x,
+			    struct pl08x_phy_chan *ch)
+{
+	/* Wait for channel inactive */
+	while (pl08x_phy_channel_busy(ch))
+		;
+
+	dev_vdbg(&pl08x->adev->dev,
+		"WRITE channel %d: csrc=%08x, cdst=%08x, "
+		 "cctl=%08x, clli=%08x, ccfg=%08x\n",
+		ch->id,
+		ch->csrc,
+		ch->cdst,
+		ch->cctl,
+		ch->clli,
+		ch->ccfg);
+
+	writel(ch->csrc, ch->base + PL080_CH_SRC_ADDR);
+	writel(ch->cdst, ch->base + PL080_CH_DST_ADDR);
+	writel(ch->clli, ch->base + PL080_CH_LLI);
+	writel(ch->cctl, ch->base + PL080_CH_CONTROL);
+	writel(ch->ccfg, ch->base + PL080_CH_CONFIG);
+}
+
+static inline void pl08x_config_phychan_for_txd(struct pl08x_dma_chan *plchan)
+{
+	struct pl08x_channel_data *cd = plchan->cd;
+	struct pl08x_phy_chan *phychan = plchan->phychan;
+	struct pl08x_txd *txd = plchan->at;
+
+	/* Copy the basic control register calculated at transfer config */
+	phychan->csrc = txd->csrc;
+	phychan->cdst = txd->cdst;
+	phychan->clli = txd->clli;
+	phychan->cctl = txd->cctl;
+
+	/* Assign the signal to the proper control registers */
+	phychan->ccfg = cd->ccfg;
+	phychan->ccfg &= ~PL080_CONFIG_SRC_SEL_MASK;
+	phychan->ccfg &= ~PL080_CONFIG_DST_SEL_MASK;
+	/* If it wasn't set from AMBA, ignore it */
+	if (txd->direction == DMA_TO_DEVICE)
+		/* Select signal as destination */
+		phychan->ccfg |=
+			(phychan->signal << PL080_CONFIG_DST_SEL_SHIFT);
+	else if (txd->direction == DMA_FROM_DEVICE)
+		/* Select signal as source */
+		phychan->ccfg |=
+			(phychan->signal << PL080_CONFIG_SRC_SEL_SHIFT);
+	/* Always enable error interrupts */
+	phychan->ccfg |= PL080_CONFIG_ERR_IRQ_MASK;
+	/* Always enable terminal interrupts */
+	phychan->ccfg |= PL080_CONFIG_TC_IRQ_MASK;
+}
+
+/*
+ * Enable the DMA channel
+ * Assumes all other configuration bits have been set
+ * as desired before this code is called
+ */
+static void pl08x_enable_phy_chan(struct pl08x_driver_data *pl08x,
+				  struct pl08x_phy_chan *ch)
+{
+	u32 val;
+
+	/*
+	 * Do not access config register until channel shows as disabled
+	 */
+	while (readl(pl08x->base + PL080_EN_CHAN) & (1 << ch->id))
+		;
+
+	/*
+	 * Do not access config register until channel shows as inactive
+	 */
+	val = readl(ch->base + PL080_CH_CONFIG);
+	while ((val & PL080_CONFIG_ACTIVE) || (val & PL080_CONFIG_ENABLE))
+		val = readl(ch->base + PL080_CH_CONFIG);
+
+	writel(val | PL080_CONFIG_ENABLE, ch->base + PL080_CH_CONFIG);
+}
+
+/*
+ * Overall DMAC remains enabled always.
+ *
+ * Disabling individual channels could lose data.
+ *
+ * Disable the peripheral DMA after disabling the DMAC
+ * in order to allow the DMAC FIFO to drain, and
+ * hence allow the channel to show inactive
+ *
+ */
+static void pl08x_pause_phy_chan(struct pl08x_phy_chan *ch)
+{
+	u32 val;
+
+	/* Set the HALT bit and wait for the FIFO to drain */
+	val = readl(ch->base + PL080_CH_CONFIG);
+	val |= PL080_CONFIG_HALT;
+	writel(val, ch->base + PL080_CH_CONFIG);
+
+	/* Wait for channel inactive */
+	while (pl08x_phy_channel_busy(ch))
+		;
+}
+
+static void pl08x_resume_phy_chan(struct pl08x_phy_chan *ch)
+{
+	u32 val;
+
+	/* Clear the HALT bit */
+	val = readl(ch->base + PL080_CH_CONFIG);
+	val &= ~PL080_CONFIG_HALT;
+	writel(val, ch->base + PL080_CH_CONFIG);
+}
+
+
+/* Stops the channel */
+static void pl08x_stop_phy_chan(struct pl08x_phy_chan *ch)
+{
+	u32 val;
+
+	pl08x_pause_phy_chan(ch);
+
+	/* Disable channel */
+	val = readl(ch->base + PL080_CH_CONFIG);
+	val &= ~PL080_CONFIG_ENABLE;
+	val &= ~PL080_CONFIG_ERR_IRQ_MASK;
+	val &= ~PL080_CONFIG_TC_IRQ_MASK;
+	writel(val, ch->base + PL080_CH_CONFIG);
+}
+
+static inline u32 get_bytes_in_cctl(u32 cctl)
+{
+	/* The source width defines the number of bytes */
+	u32 bytes = cctl & PL080_CONTROL_TRANSFER_SIZE_MASK;
+
+	switch (cctl >> PL080_CONTROL_SWIDTH_SHIFT) {
+	case PL080_WIDTH_8BIT:
+		break;
+	case PL080_WIDTH_16BIT:
+		bytes *= 2;
+		break;
+	case PL080_WIDTH_32BIT:
+		bytes *= 4;
+		break;
+	}
+	return bytes;
+}
+
+/* The channel should be paused when calling this */
+static u32 pl08x_getbytes_chan(struct pl08x_dma_chan *plchan)
+{
+	struct pl08x_phy_chan *ch;
+	struct pl08x_txd *txdi = NULL;
+	struct pl08x_txd *txd;
+	unsigned long flags;
+	u32 bytes = 0;
+
+	spin_lock_irqsave(&plchan->lock, flags);
+
+	ch = plchan->phychan;
+	txd = plchan->at;
+
+	/*
+	 * Next follow the LLIs to get the number of pending bytes in the
+	 * currently active transaction.
+	 */
+	if (ch && txd) {
+		struct lli *llis_va = txd->llis_va;
+		struct lli *llis_bus = (struct lli *) txd->llis_bus;
+		u32 clli = readl(ch->base + PL080_CH_LLI);
+
+		/* First get the bytes in the current active LLI */
+		bytes = get_bytes_in_cctl(readl(ch->base + PL080_CH_CONTROL));
+
+		if (clli) {
+			int i = 0;
+
+			/* Forward to the LLI pointed to by clli */
+			while ((clli != (u32) &(llis_bus[i])) &&
+			       (i < MAX_NUM_TSFR_LLIS))
+				i++;
+
+			while (clli) {
+				bytes += get_bytes_in_cctl(llis_va[i].cctl);
+				/*
+				 * A clli of 0x00000000 will terminate the
+				 * LLI list
+				 */
+				clli = llis_va[i].next;
+				i++;
+			}
+		}
+	}
+
+	/* Sum up all queued transactions */
+	if (!list_empty(&plchan->desc_list)) {
+		list_for_each_entry(txdi, &plchan->desc_list, node) {
+			bytes += txdi->len;
+		}
+
+	}
+
+	spin_unlock_irqrestore(&plchan->lock, flags);
+
+	return bytes;
+}
+
+/*
+ * Allocate a physical channel for a virtual channel
+ */
+static struct pl08x_phy_chan *
+pl08x_get_phy_channel(struct pl08x_driver_data *pl08x,
+		      struct pl08x_dma_chan *virt_chan)
+{
+	struct pl08x_phy_chan *ch = NULL;
+	unsigned long flags;
+	int i;
+
+	/*
+	 * Try to locate a physical channel to be used for
+	 * this transfer. If all are taken return NULL and
+	 * the requester will have to cope by using some fallback
+	 * PIO mode or retrying later.
+	 */
+	for (i = 0; i < pl08x->vd->channels; i++) {
+		ch = &pl08x->phy_chans[i];
+
+		spin_lock_irqsave(&ch->lock, flags);
+
+		if (!ch->serving) {
+			ch->serving = virt_chan;
+			ch->signal = -1;
+			spin_unlock_irqrestore(&ch->lock, flags);
+			break;
+		}
+
+		spin_unlock_irqrestore(&ch->lock, flags);
+	}
+
+	if (i == pl08x->vd->channels) {
+		/* No physical channel available, cope with it */
+		return NULL;
+	}
+
+	return ch;
+}
+
+static inline void pl08x_put_phy_channel(struct pl08x_driver_data *pl08x,
+					 struct pl08x_phy_chan *ch)
+{
+	unsigned long flags;
+
+	/* Stop the channel and clear its interrupts */
+	pl08x_stop_phy_chan(ch);
+	writel((1 << ch->id), pl08x->base + PL080_ERR_CLEAR);
+	writel((1 << ch->id), pl08x->base + PL080_TC_CLEAR);
+
+	/* Mark it as free */
+	spin_lock_irqsave(&ch->lock, flags);
+	ch->serving = NULL;
+	spin_unlock_irqrestore(&ch->lock, flags);
+}
+
+/*
+ * LLI handling
+ */
+
+static inline unsigned int pl08x_get_bytes_for_cctl(unsigned int coded)
+{
+	switch (coded) {
+	case PL080_WIDTH_8BIT:
+		return 1;
+	case PL080_WIDTH_16BIT:
+		return 2;
+	case PL080_WIDTH_32BIT:
+		return 4;
+	default:
+		break;
+	}
+	BUG();
+	return 0;
+}
+
+static inline u32 pl08x_cctl_bits(u32 cctl, u8 srcwidth, u8 dstwidth,
+				  u32 tsize)
+{
+	u32 retbits = cctl;
+
+	/* Remove all src, dst and transfersize bits */
+	retbits &= ~PL080_CONTROL_DWIDTH_MASK;
+	retbits &= ~PL080_CONTROL_SWIDTH_MASK;
+	retbits &= ~PL080_CONTROL_TRANSFER_SIZE_MASK;
+
+	/* Then set the bits according to the parameters */
+	switch (srcwidth) {
+	case 1:
+		retbits |= PL080_WIDTH_8BIT << PL080_CONTROL_SWIDTH_SHIFT;
+		break;
+	case 2:
+		retbits |= PL080_WIDTH_16BIT << PL080_CONTROL_SWIDTH_SHIFT;
+		break;
+	case 4:
+		retbits |= PL080_WIDTH_32BIT << PL080_CONTROL_SWIDTH_SHIFT;
+		break;
+	default:
+		BUG();
+		break;
+	}
+
+	switch (dstwidth) {
+	case 1:
+		retbits |= PL080_WIDTH_8BIT << PL080_CONTROL_DWIDTH_SHIFT;
+		break;
+	case 2:
+		retbits |= PL080_WIDTH_16BIT << PL080_CONTROL_DWIDTH_SHIFT;
+		break;
+	case 4:
+		retbits |= PL080_WIDTH_32BIT << PL080_CONTROL_DWIDTH_SHIFT;
+		break;
+	default:
+		BUG();
+		break;
+	}
+
+	retbits |= tsize << PL080_CONTROL_TRANSFER_SIZE_SHIFT;
+	return retbits;
+}
+
+/*
+ * Autoselect a master bus to use for the transfer
+ * this prefers the destination bus if both available
+ * if fixed address on one bus the other will be chosen
+ */
+void pl08x_choose_master_bus(struct pl08x_bus_data *src_bus,
+	struct pl08x_bus_data *dst_bus, struct pl08x_bus_data **mbus,
+	struct pl08x_bus_data **sbus, u32 cctl)
+{
+	if (!(cctl & PL080_CONTROL_DST_INCR)) {
+		*mbus = src_bus;
+		*sbus = dst_bus;
+	} else if (!(cctl & PL080_CONTROL_SRC_INCR)) {
+		*mbus = dst_bus;
+		*sbus = src_bus;
+	} else {
+		if (dst_bus->buswidth == 4) {
+			*mbus = dst_bus;
+			*sbus = src_bus;
+		} else if (src_bus->buswidth == 4) {
+			*mbus = src_bus;
+			*sbus = dst_bus;
+		} else if (dst_bus->buswidth == 2) {
+			*mbus = dst_bus;
+			*sbus = src_bus;
+		} else if (src_bus->buswidth == 2) {
+			*mbus = src_bus;
+			*sbus = dst_bus;
+		} else {
+			/* src_bus->buswidth == 1 */
+			*mbus = dst_bus;
+			*sbus = src_bus;
+		}
+	}
+}
+
+/*
+ * Fills in one LLI for a certain transfer descriptor
+ * and advance the counter
+ */
+int pl08x_fill_lli_for_desc(struct pl08x_driver_data *pl08x,
+			    struct pl08x_txd *txd, int num_llis, int len,
+			    u32 cctl, u32 *remainder)
+{
+	struct lli *llis_va = txd->llis_va;
+	struct lli *llis_bus = (struct lli *) txd->llis_bus;
+
+	BUG_ON(num_llis >= MAX_NUM_TSFR_LLIS);
+
+	llis_va[num_llis].cctl		= cctl;
+	llis_va[num_llis].src		= txd->srcbus.addr;
+	llis_va[num_llis].dst		= txd->dstbus.addr;
+
+	/*
+	 * On versions with dual masters, you can optionally AND on
+	 * PL080_LLI_LM_AHB2 to the LLI to tell the hardware to read
+	 * in new LLIs with that controller, but we always try to
+	 * choose AHB1 to point into memory. The idea is to have AHB2
+	 * fixed on the peripheral and AHB1 messing around in the
+	 * memory. So we don't manipulate this bit currently.
+	 */
+
+	llis_va[num_llis].next =
+		(dma_addr_t)((u32) &(llis_bus[num_llis + 1]));
+
+	if (cctl & PL080_CONTROL_SRC_INCR)
+		txd->srcbus.addr += len;
+	if (cctl & PL080_CONTROL_DST_INCR)
+		txd->dstbus.addr += len;
+
+	*remainder -= len;
+
+	return num_llis + 1;
+}
+
+/*
+ * Return number of bytes to fill to boundary, or len
+ */
+static inline u32 pl08x_pre_boundary(u32 addr, u32 len)
+{
+	u32 boundary;
+
+	boundary = ((addr >> PL08X_BOUNDARY_SHIFT) + 1)
+		<< PL08X_BOUNDARY_SHIFT;
+
+	if (boundary < addr + len)
+		return boundary - addr;
+	else
+		return len;
+}
+
+/*
+ * This fills in the table of LLIs for the transfer descriptor
+ * Note that we assume we never have to change the burst sizes
+ * Return 0 for error
+ */
+static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x,
+			      struct pl08x_txd *txd)
+{
+	struct pl08x_channel_data *cd = txd->cd;
+	struct pl08x_bus_data *mbus, *sbus;
+	u32 remainder;
+	int num_llis = 0;
+	u32 cctl;
+	int max_bytes_per_lli;
+	int total_bytes = 0;
+	struct lli *llis_va;
+	struct lli *llis_bus;
+
+	if (!txd) {
+		dev_err(&pl08x->adev->dev, "%s no descriptor\n", __func__);
+		return 0;
+	}
+
+	txd->llis_va = dma_pool_alloc(pl08x->pool, GFP_NOWAIT,
+				      &txd->llis_bus);
+	if (!txd->llis_va) {
+		dev_err(&pl08x->adev->dev, "%s no memory for llis\n", __func__);
+		return 0;
+	}
+
+	pl08x->pool_ctr++;
+
+	/*
+	 * Initialize bus values for this transfer
+	 * from the passed optimal values
+	 */
+	if (!cd) {
+		dev_err(&pl08x->adev->dev, "%s no channel data\n", __func__);
+		return 0;
+	}
+
+	/* Get the default CCTL from the platform data */
+	cctl = cd->cctl;
+
+	/*
+	 * On the PL080 we have two bus masters and we
+	 * should select one for source and one for
+	 * destination. We try to use AHB2 for the
+	 * bus which does not increment (typically the
+	 * peripheral) else we just choose something.
+	 */
+	cctl &= ~(PL080_CONTROL_DST_AHB2 | PL080_CONTROL_SRC_AHB2);
+	if (pl08x->vd->dualmaster) {
+		if (cctl & PL080_CONTROL_SRC_INCR)
+			/* Source increments, use AHB2 for destination */
+			cctl |= PL080_CONTROL_DST_AHB2;
+		else if (cctl & PL080_CONTROL_DST_INCR)
+			/* Destination increments, use AHB2 for source */
+			cctl |= PL080_CONTROL_SRC_AHB2;
+		else
+			/* Just pick something, source AHB1 dest AHB2 */
+			cctl |= PL080_CONTROL_DST_AHB2;
+	}
+
+	/* Find maximum width of the source bus */
+	txd->srcbus.maxwidth =
+		pl08x_get_bytes_for_cctl((cctl & PL080_CONTROL_SWIDTH_MASK) >>
+				       PL080_CONTROL_SWIDTH_SHIFT);
+
+	/* Find maximum width of the destination bus */
+	txd->dstbus.maxwidth =
+		pl08x_get_bytes_for_cctl((cctl & PL080_CONTROL_DWIDTH_MASK) >>
+				       PL080_CONTROL_DWIDTH_SHIFT);
+
+	/* Set up the bus widths to the maximum */
+	txd->srcbus.buswidth = txd->srcbus.maxwidth;
+	txd->dstbus.buswidth = txd->dstbus.maxwidth;
+	dev_vdbg(&pl08x->adev->dev,
+		 "%s source bus is %d bytes wide, dest bus is %d bytes wide\n",
+		 __func__, txd->srcbus.buswidth, txd->dstbus.buswidth);
+
+
+	/*
+	 * Bytes transferred == tsize * MIN(buswidths), not max(buswidths)
+	 */
+	max_bytes_per_lli = min(txd->srcbus.buswidth, txd->dstbus.buswidth) *
+		PL080_CONTROL_TRANSFER_SIZE_MASK;
+	dev_vdbg(&pl08x->adev->dev,
+		 "%s max bytes per lli = %d\n",
+		 __func__, max_bytes_per_lli);
+
+	/* We need to count this down to zero */
+	remainder = txd->len;
+	dev_vdbg(&pl08x->adev->dev,
+		 "%s remainder = %d\n",
+		 __func__, remainder);
+
+	/*
+	 * Choose bus to align to
+	 * - prefers destination bus if both available
+	 * - if fixed address on one bus chooses other
+	 * - modifies cctl to choose an apropriate master
+	 */
+	pl08x_choose_master_bus(&txd->srcbus, &txd->dstbus,
+				&mbus, &sbus, cctl);
+
+
+	/*
+	 * The lowest bit of the LLI register
+	 * is also used to indicate which master to
+	 * use for reading the LLIs.
+	 */
+
+	if (txd->len < mbus->buswidth) {
+		/*
+		 * Less than a bus width available
+		 * - send as single bytes
+		 */
+		while (remainder) {
+			dev_vdbg(&pl08x->adev->dev,
+				 "%s single byte LLIs for a transfer of "
+				 "less than a bus width (remain %08x)\n",
+				 __func__, remainder);
+			cctl = pl08x_cctl_bits(cctl, 1, 1, 1);
+			num_llis =
+				pl08x_fill_lli_for_desc(pl08x, txd, num_llis, 1,
+					cctl, &remainder);
+			total_bytes++;
+		}
+	} else {
+		/*
+		 *  Make one byte LLIs until master bus is aligned
+		 *  - slave will then be aligned also
+		 */
+		while ((mbus->addr) % (mbus->buswidth)) {
+			dev_vdbg(&pl08x->adev->dev,
+				"%s adjustment lli for less than bus width "
+				 "(remain %08x)\n",
+				 __func__, remainder);
+			cctl = pl08x_cctl_bits(cctl, 1, 1, 1);
+			num_llis = pl08x_fill_lli_for_desc
+				(pl08x, txd, num_llis, 1, cctl, &remainder);
+			total_bytes++;
+		}
+
+		/*
+		 *  Master now aligned
+		 * - if slave is not then we must set its width down
+		 */
+		if (sbus->addr % sbus->buswidth) {
+			dev_dbg(&pl08x->adev->dev,
+				"%s set down bus width to one byte\n",
+				 __func__);
+
+			sbus->buswidth = 1;
+		}
+
+		/*
+		 * Make largest possible LLIs until less than one bus
+		 * width left
+		 */
+		while (remainder > (mbus->buswidth - 1)) {
+			int lli_len, target_len;
+			int tsize;
+			int odd_bytes;
+
+			/*
+			 * If enough left try to send max possible,
+			 * otherwise try to send the remainder
+			 */
+			target_len = remainder;
+			if (remainder > max_bytes_per_lli)
+				target_len = max_bytes_per_lli;
+
+			/*
+			 * Set bus lengths for incrementing busses
+			 * to number of bytes which fill to next memory
+			 * boundary
+			 */
+			if (cctl & PL080_CONTROL_SRC_INCR)
+				txd->srcbus.fill_bytes =
+					pl08x_pre_boundary(
+						txd->srcbus.addr,
+						remainder);
+			else
+				txd->srcbus.fill_bytes =
+					max_bytes_per_lli;
+
+			if (cctl & PL080_CONTROL_DST_INCR)
+				txd->dstbus.fill_bytes =
+					pl08x_pre_boundary(
+						txd->dstbus.addr,
+						remainder);
+			else
+				txd->dstbus.fill_bytes =
+						max_bytes_per_lli;
+
+			/*
+			 *  Find the nearest
+			 */
+			lli_len	= min(txd->srcbus.fill_bytes,
+				txd->dstbus.fill_bytes);
+
+			BUG_ON(lli_len > remainder);
+
+			if (lli_len <= 0) {
+				dev_err(&pl08x->adev->dev,
+					"%s lli_len is %d, <= 0\n",
+						__func__, lli_len);
+				return 0;
+			}
+
+			if (lli_len == target_len) {
+				/*
+				 * Can send what we wanted
+				 */
+				/*
+				 *  Maintain alignment
+				 */
+				lli_len	= (lli_len/mbus->buswidth) *
+							mbus->buswidth;
+				odd_bytes = 0;
+			} else {
+				/*
+				 * So now we know how many bytes to transfer
+				 * to get to the nearest boundary
+				 * The next lli will past the boundary
+				 * - however we may be working to a boundary
+				 *   on the slave bus
+				 *   We need to ensure the master stays aligned
+				 */
+				odd_bytes = lli_len % mbus->buswidth;
+				/*
+				 * - and that we are working in multiples
+				 *   of the bus widths
+				 */
+				lli_len -= odd_bytes;
+
+			}
+
+			if (lli_len) {
+				/*
+				 * Check against minimum bus alignment:
+				 * Calculate actual transfer size in relation
+				 * to bus width an get a maximum remainder of
+				 * the smallest bus width - 1
+				 */
+				/* FIXME: use round_down()? */
+				tsize = lli_len / min(mbus->buswidth,
+						      sbus->buswidth);
+				lli_len	= tsize * min(mbus->buswidth,
+						      sbus->buswidth);
+
+				if (target_len != lli_len) {
+					dev_vdbg(&pl08x->adev->dev,
+					"%s can't send what we want. Desired %08x, lli of %08x bytes in txd of %08x\n",
+					__func__, target_len, lli_len, txd->len);
+				}
+
+				cctl = pl08x_cctl_bits(cctl,
+						       txd->srcbus.buswidth,
+						       txd->dstbus.buswidth,
+						       tsize);
+
+				dev_vdbg(&pl08x->adev->dev,
+					"%s fill lli with single lli chunk of size %08x (remainder %08x)\n",
+					__func__, lli_len, remainder);
+				num_llis = pl08x_fill_lli_for_desc(pl08x, txd,
+						num_llis, lli_len, cctl,
+						&remainder);
+				total_bytes += lli_len;
+			}
+
+
+			if (odd_bytes) {
+				/*
+				 * Creep past the boundary,
+				 * maintaining master alignment
+				 */
+				int j;
+				for (j = 0; (j < mbus->buswidth)
+						&& (remainder); j++) {
+					cctl = pl08x_cctl_bits(cctl, 1, 1, 1);
+					dev_vdbg(&pl08x->adev->dev,
+						"%s align with boundardy, single byte (remain %08x)\n",
+						__func__, remainder);
+					num_llis =
+						pl08x_fill_lli_for_desc(pl08x,
+							txd, num_llis, 1,
+							cctl, &remainder);
+					total_bytes++;
+				}
+			}
+		}
+
+		/*
+		 * Send any odd bytes
+		 */
+		if (remainder < 0) {
+			dev_err(&pl08x->adev->dev, "%s remainder not fitted 0x%08x bytes\n",
+					__func__, remainder);
+			return 0;
+		}
+
+		while (remainder) {
+			cctl = pl08x_cctl_bits(cctl, 1, 1, 1);
+			dev_vdbg(&pl08x->adev->dev,
+				"%s align with boundardy, single odd byte (remain %d)\n",
+				__func__, remainder);
+			num_llis = pl08x_fill_lli_for_desc(pl08x, txd, num_llis,
+					1, cctl, &remainder);
+			total_bytes++;
+		}
+	}
+	if (total_bytes != txd->len) {
+		dev_err(&pl08x->adev->dev,
+			"%s size of encoded lli:s don't match total txd, transferred 0x%08x from size 0x%08x\n",
+			__func__, total_bytes, txd->len);
+		return 0;
+	}
+
+	if (num_llis >= MAX_NUM_TSFR_LLIS) {
+		dev_err(&pl08x->adev->dev,
+			"%s need to increase MAX_NUM_TSFR_LLIS from 0x%08x\n",
+			__func__, (u32) MAX_NUM_TSFR_LLIS);
+		return 0;
+	}
+	/*
+	 * Decide whether this is a loop or a terminated transfer
+	 */
+	llis_va = txd->llis_va;
+	llis_bus = (struct lli *) txd->llis_bus;
+
+	if (cd->circular_buffer) {
+		/*
+		 * Loop the circular buffer so that the next element
+		 * points back to the beginning of the LLI.
+		 */
+		llis_va[num_llis - 1].next =
+			(dma_addr_t)((unsigned int)&(llis_bus[0]));
+	} else {
+		/*
+		 * On non-circular buffers, the final LLI terminates
+		 * the LLI.
+		 */
+		llis_va[num_llis - 1].next = 0;
+		/*
+		 * The final LLI element shall also fire an interrupt
+		 */
+		llis_va[num_llis - 1].cctl |= PL080_CONTROL_TC_IRQ_EN;
+	}
+
+	/* Now store the channel register values */
+	txd->csrc = llis_va[0].src;
+	txd->cdst = llis_va[0].dst;
+	if (num_llis > 1)
+		txd->clli = llis_va[0].next;
+	else
+		txd->clli = 0;
+
+	txd->cctl = llis_va[0].cctl;
+	/* ccfg will be set at physical channel allocation time */
+
+#ifdef VERBOSE_DEBUG
+	{
+		int i;
+
+		for (i = 0; i < num_llis; i++) {
+			dev_vdbg(&pl08x->adev->dev,
+				 "lli %d @%p: csrc=%08x, cdst=%08x, cctl=%08x, clli=%08x\n",
+				 i,
+				 &llis_va[i],
+				 llis_va[i].src,
+				 llis_va[i].dst,
+				 llis_va[i].cctl,
+				 llis_va[i].next
+				);
+		}
+	}
+#endif
+
+	return num_llis;
+}
+
+/* You should call this with the struct pl08x lock held */
+static void pl08x_free_txd(struct pl08x_driver_data *pl08x,
+			   struct pl08x_txd *txd)
+{
+	if (!txd)
+		dev_err(&pl08x->adev->dev,
+			"%s no descriptor to free\n",
+			__func__);
+
+	/* Free the LLI */
+	dma_pool_free(pl08x->pool, txd->llis_va,
+		      txd->llis_bus);
+
+	pl08x->pool_ctr--;
+
+	kfree(txd);
+}
+
+static void pl08x_free_txd_list(struct pl08x_driver_data *pl08x,
+				struct pl08x_dma_chan *plchan)
+{
+	struct pl08x_txd *txdi = NULL;
+	struct pl08x_txd *next;
+
+	if (!list_empty(&plchan->desc_list)) {
+		list_for_each_entry_safe(txdi,
+					 next, &plchan->desc_list, node) {
+			list_del(&txdi->node);
+			pl08x_free_txd(pl08x, txdi);
+		}
+
+	}
+}
+
+/*
+ * The DMA ENGINE API
+ */
+static int pl08x_alloc_chan_resources(struct dma_chan *chan)
+{
+	return 0;
+}
+
+static void pl08x_free_chan_resources(struct dma_chan *chan)
+{
+}
+
+/*
+ * This should be called with the channel plchan->lock held
+ */
+static int prep_phy_channel(struct pl08x_dma_chan *plchan,
+			    struct pl08x_txd *txd)
+{
+	struct pl08x_driver_data *pl08x = plchan->host;
+	struct pl08x_phy_chan *ch;
+	int ret;
+
+	/* Check if we already have a channel */
+	if (plchan->phychan)
+		return 0;
+
+	ch = pl08x_get_phy_channel(pl08x, plchan);
+	if (!ch) {
+		/* No physical channel available, cope with it */
+		dev_dbg(&pl08x->adev->dev, "no physical channel available for xfer on %s\n", plchan->name);
+		return -EBUSY;
+	}
+
+	/*
+	 * OK we have a physical channel: for memcpy() this is all we
+	 * need, but for slaves the physical signals may be muxed!
+	 * Can the platform allow us to use this channel?
+	 */
+	if (plchan->slave &&
+	    ch->signal < 0 &&
+	    pl08x->pd->get_signal) {
+		ret = pl08x->pd->get_signal(plchan);
+		if (ret < 0) {
+			dev_dbg(&pl08x->adev->dev,
+				"unable to use physical channel %d for transfer on %s due to platform restrictions\n",
+				ch->id, plchan->name);
+			/* Release physical channel & return */
+			pl08x_put_phy_channel(pl08x, ch);
+			return -EBUSY;
+		}
+		ch->signal = ret;
+	}
+
+	dev_dbg(&pl08x->adev->dev, "allocated physical channel %d and signal %d for xfer on %s\n",
+		 ch->id,
+		 ch->signal,
+		 plchan->name);
+
+	plchan->phychan = ch;
+
+	return 0;
+}
+
+static dma_cookie_t pl08x_tx_submit(struct dma_async_tx_descriptor *tx)
+{
+	struct pl08x_dma_chan *plchan = to_pl08x_chan(tx->chan);
+
+	atomic_inc(&plchan->last_issued);
+	tx->cookie = atomic_read(&plchan->last_issued);
+	/* This unlock follows the lock in the prep() function */
+	spin_unlock_irqrestore(&plchan->lock, plchan->lockflags);
+
+	return tx->cookie;
+}
+
+static struct dma_async_tx_descriptor *pl08x_prep_dma_interrupt(
+		struct dma_chan *chan, unsigned long flags)
+{
+	struct dma_async_tx_descriptor *retval = NULL;
+
+	return retval;
+}
+
+/*
+ * Code accessing dma_async_is_complete() in a tight loop
+ * may give problems - could schedule where indicated.
+ * If slaves are relying on interrupts to signal completion this
+ * function must not be called with interrupts disabled
+ */
+static enum dma_status
+pl08x_dma_tx_status(stru