[PATCH] DMA: add a driver for AMBA AXI NBPF DMAC IP cores

* [PATCH] DMA: add a driver for AMBA AXI NBPF DMAC IP cores
@ 2014-04-12 17:39 Guennadi Liakhovetski
       [not found] ` <Pine.LNX.4.64.1404121932040.8725-0199iw4Nj15frtckUFj5Ag@public.gmane.org>
  0 siblings, 1 reply; 3+ messages in thread
From: Guennadi Liakhovetski @ 2014-04-12 17:39 UTC (permalink / raw)
  To: dmaengine-u79uwXL29TY76Z2rM5mHXA
  Cc: Koul, Vinod, devicetree-u79uwXL29TY76Z2rM5mHXA, Grant Likely,
	Rob Herring

This patch adds a driver for NBPF DMAC IP cores from Renesas, designed for
the AMBA AXI bus.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski-Mmb7MZpHnFY@public.gmane.org>
---

Tested on a Xilinx zc706-based board with an SD-host (driver will be 
submitted shortly) and a PL011 UART.

 Documentation/devicetree/bindings/dma/nbpfaxi.txt |   61 +
 drivers/dma/Kconfig                               |    6 +
 drivers/dma/Makefile                              |    1 +
 drivers/dma/nbpfaxi.c                             | 1554 +++++++++++++++++++++
 include/dt-bindings/dma/nbpfaxi.h                 |   20 +
 5 files changed, 1642 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/dma/nbpfaxi.txt
 create mode 100644 drivers/dma/nbpfaxi.c
 create mode 100644 include/dt-bindings/dma/nbpfaxi.h

diff --git a/Documentation/devicetree/bindings/dma/nbpfaxi.txt b/Documentation/devicetree/bindings/dma/nbpfaxi.txt
new file mode 100644
index 0000000..d5e2522
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/nbpfaxi.txt
@@ -0,0 +1,61 @@
+* Renesas "Type-AXI" NBPFAXI* DMA controllers
+
+* DMA controller
+
+Required properties
+
+- compatible:	must be one of
+		"renesas,nbpfaxi64dmac1b4"
+		"renesas,nbpfaxi64dmac1b8"
+		"renesas,nbpfaxi64dmac1b16"
+		"renesas,nbpfaxi64dmac4b4"
+		"renesas,nbpfaxi64dmac4b8"
+		"renesas,nbpfaxi64dmac4b16"
+		"renesas,nbpfaxi64dmac8b4"
+		"renesas,nbpfaxi64dmac8b8"
+		"renesas,nbpfaxi64dmac8b16"
+- #dma-cells:	must be 2: the first integer is a terminal number, to which this
+		slave is connected, the second one is flags. Flags is a bitmask
+		with the following bits defined:
+
+#define NBPF_SLAVE_RQ_HIGH	1
+#define NBPF_SLAVE_RQ_LOW	2
+#define NBPF_SLAVE_RQ_LEVEL	4
+
+Optional properties:
+
+You can use dma-channels and dma-requests as described in dma.txt, although they
+won't be used, this information is derived from the compatibility string.
+
+Example:
+
+	dma: dma-controller@48000000 {
+		compatible = "renesas,nbpfaxi64dmac8b4";
+		reg = <0x48000000 0x400>;
+		interrupts = <0 12 0x4
+			      0 13 0x4
+			      0 14 0x4
+			      0 15 0x4
+			      0 16 0x4
+			      0 17 0x4
+			      0 18 0x4
+			      0 19 0x4>;
+		#dma-cells = <2>;
+		dma-channels = <8>;
+		dma-requests = <8>;
+	};
+
+* DMA client
+
+Required properties:
+
+dmas and dma-names are required, as described in dma.txt.
+
+Example:
+
+#include <dt-bindings/dma/nbpfaxi.h>
+
+...
+		dmas = <&dma 0 (NBPF_SLAVE_RQ_HIGH | NBPF_SLAVE_RQ_LEVEL)
+			&dma 1 (NBPF_SLAVE_RQ_HIGH | NBPF_SLAVE_RQ_LEVEL)>;
+		dma-names = "rx", "tx";
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index ba06d1d..513207a 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -361,6 +361,12 @@ config FSL_EDMA
 	  multiplexing capability for DMA request sources(slot).
 	  This module can be found on Freescale Vybrid and LS-1 SoCs.
 
+config NBPFAXI_DMA
+	tristate "Renesas Type-AXI NBPF DMA support"
+	select DMA_ENGINE
+	help
+	  Support for "Type-AXI" NBPF DMA IPs from Renesas
+
 config DMA_ENGINE
 	bool
 
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index 5150c82..9589ebb 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -46,3 +46,4 @@ obj-$(CONFIG_K3_DMA) += k3dma.o
 obj-$(CONFIG_MOXART_DMA) += moxart-dma.o
 obj-$(CONFIG_FSL_EDMA) += fsl-edma.o
 obj-$(CONFIG_QCOM_BAM_DMA) += qcom_bam_dma.o
+obj-$(CONFIG_NBPFAXI_DMA) += nbpfaxi.o
diff --git a/drivers/dma/nbpfaxi.c b/drivers/dma/nbpfaxi.c
new file mode 100644
index 0000000..152bb13
--- /dev/null
+++ b/drivers/dma/nbpfaxi.c
@@ -0,0 +1,1554 @@
+/*
+ * Copyright (C) 2013-2014 Renesas Europe Ltd.
+ * Author: Guennadi Liakhovetski <g.liakhovetski-Mmb7MZpHnFY@public.gmane.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/log2.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_dma.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <dt-bindings/dma/nbpfaxi.h>
+
+#include "dmaengine.h"
+
+#define NBPF_REG_CHAN_OFFSET	0
+#define NBPF_REG_CHAN_SIZE	0x40
+
+/* Channel Current Transaction Byte register */
+#define NBPF_CHAN_CUR_TR_BYTE	0x20
+
+/* Channel Status register */
+#define NBPF_CHAN_STAT	0x24
+#define NBPF_CHAN_STAT_EN	1
+#define NBPF_CHAN_STAT_TACT	4
+#define NBPF_CHAN_STAT_ERR	0x10
+#define NBPF_CHAN_STAT_END	0x20
+#define NBPF_CHAN_STAT_TC	0x40
+#define NBPF_CHAN_STAT_DER	0x400
+
+/* Channel Control register */
+#define NBPF_CHAN_CTRL	0x28
+#define NBPF_CHAN_CTRL_SETEN	1
+#define NBPF_CHAN_CTRL_CLREN	2
+#define NBPF_CHAN_CTRL_STG	4
+#define NBPF_CHAN_CTRL_SWRST	8
+#define NBPF_CHAN_CTRL_CLRRQ	0x10
+#define NBPF_CHAN_CTRL_CLREND	0x20
+#define NBPF_CHAN_CTRL_CLRTC	0x40
+#define NBPF_CHAN_CTRL_SETSUS	0x100
+#define NBPF_CHAN_CTRL_CLRSUS	0x200
+
+/* Channel Configuration register */
+#define NBPF_CHAN_CFG	0x2c
+#define NBPF_CHAN_CFG_SEL	7		/* terminal SELect: 0..7 */
+#define NBPF_CHAN_CFG_REQD	8		/* REQuest Direction: DMAREQ is 0: input, 1: output */
+#define NBPF_CHAN_CFG_LOEN	0x10		/* LOw ENable: low DMA request line is: 0: inactive, 1: active */
+#define NBPF_CHAN_CFG_HIEN	0x20		/* HIgh ENable: high DMA request line is: 0: inactive, 1: active */
+#define NBPF_CHAN_CFG_LVL	0x40		/* LeVeL: DMA request line is sensed as 0: edge, 1: level */
+#define NBPF_CHAN_CFG_AM	0x700		/* ACK Mode: 0: Pulse mode, 1: Level mode, b'1x: Bus Cycle */
+#define NBPF_CHAN_CFG_SDS	0xf000		/* Source Data Size: 0: 8 bits,... , 7: 1024 bits */
+#define NBPF_CHAN_CFG_DDS	0xf0000		/* Destination Data Size: as above */
+#define NBPF_CHAN_CFG_SAD	0x100000	/* Source ADdress counting: 0: increment, 1: fixed */
+#define NBPF_CHAN_CFG_DAD	0x200000	/* Destination ADdress counting: 0: increment, 1: fixed */
+#define NBPF_CHAN_CFG_TM	0x400000	/* Transfer Mode: 0: single, 1: block TM */
+#define NBPF_CHAN_CFG_DEM	0x1000000	/* DMAEND interrupt Mask */
+#define NBPF_CHAN_CFG_TCM	0x2000000	/* DMATCO interrupt Mask */
+#define NBPF_CHAN_CFG_SBE	0x8000000	/* Sweep Buffer Enable */
+#define NBPF_CHAN_CFG_RSEL	0x10000000	/* RM: Register Set sELect */
+#define NBPF_CHAN_CFG_RSW	0x20000000	/* RM: Register Select sWitch */
+#define NBPF_CHAN_CFG_REN	0x40000000	/* RM: Register Set Enable */
+#define NBPF_CHAN_CFG_DMS	0x80000000	/* 0: register mode (RM), 1: link mode (LM) */
+
+#define NBPF_CHAN_NXLA	0x38
+#define NBPF_CHAN_CRLA	0x3c
+
+/* Link Header field */
+#define NBPF_HEADER_LV	1
+#define NBPF_HEADER_LE	2
+#define NBPF_HEADER_WBD	4
+#define NBPF_HEADER_DIM	8
+
+#define NBPF_CTRL	0x300
+#define NBPF_CTRL_PR	1		/* 0: fixed priority, 1: round robin */
+#define NBPF_CTRL_LVINT	2		/* DMAEND and DMAERR signalling: 0: pulse, 1: level */
+
+#define NBPF_DSTAT_ER	0x314
+#define NBPF_DSTAT_END	0x318
+
+#define NBPF_DMA_BUSWIDTHS \
+	(BIT(DMA_SLAVE_BUSWIDTH_UNDEFINED) | \
+	 BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) | \
+	 BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) | \
+	 BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) | \
+	 BIT(DMA_SLAVE_BUSWIDTH_8_BYTES))
+
+struct nbpf_config {
+	int num_channels;
+	int buffer_size;
+};
+
+/*
+ * We've got 3 types of objects, used to describe DMA transfers:
+ * 1. high-level descriptor, containing a struct dma_async_tx_descriptor object
+ *	in it, used to communicate with the user
+ * 2. hardware DMA link descriptors, that we pass to DMAC for DMA transfer
+ *	queuing, these must be DMAable, using either the streaming DMA API or
+ *	allocated from coherent memory - one per SG segment
+ * 3. one per SG segment descriptors, used to manage HW link descriptors from
+ *	(2). They do not have to be DMAable. They can either be (a) allocated
+ *	together with link descriptors as mixed (DMA / CPU) objects, or (b)
+ *	separately. Even if allocated separately it would be best to link them
+ *	to link descriptors once during channel resource allocation and always
+ *	use them as a single object.
+ * Therefore for both cases (a) and (b) at run-time objects (2) and (3) shall be
+ * treated as a single SG segment descriptor.
+ */
+
+struct nbpf_link_reg {
+	u32	header;
+	u32	src_addr;
+	u32	dst_addr;
+	u32	transaction_size;
+	u32	config;
+	u32	interval;
+	u32	extension;
+	u32	next;
+} __packed;
+
+struct nbpf_device;
+struct nbpf_channel;
+struct nbpf_desc;
+
+struct nbpf_link_desc {
+	struct nbpf_link_reg *hwdesc;
+	dma_addr_t hwdesc_dma_addr;
+	struct nbpf_desc *desc;
+	struct list_head node;
+};
+
+/**
+ * @sg:		list of hardware descriptors, represented by struct nbpf_link_desc
+ * @node:	member in channel descriptor lists
+ */
+struct nbpf_desc {
+	struct dma_async_tx_descriptor async_tx;
+	bool user_wait;
+	struct nbpf_channel *chan;
+	struct list_head sg;
+	struct list_head node;
+};
+
+/* Take a wild guess: allocate 4 segments per descriptor */
+#define NBPF_SEGMENTS_PER_DESC 4
+#define NBPF_DESCS_PER_PAGE ((PAGE_SIZE - sizeof(struct list_head)) /	\
+	(sizeof(struct nbpf_desc) +					\
+	 NBPF_SEGMENTS_PER_DESC *					\
+	 (sizeof(struct nbpf_link_desc) + sizeof(struct nbpf_link_reg))))
+#define NBPF_SEGMENTS_PER_PAGE (NBPF_SEGMENTS_PER_DESC * NBPF_DESCS_PER_PAGE)
+
+struct nbpf_desc_page {
+	struct list_head node;
+	struct nbpf_desc desc[NBPF_DESCS_PER_PAGE];
+	struct nbpf_link_desc ldesc[NBPF_SEGMENTS_PER_PAGE];
+	struct nbpf_link_reg hwdesc[NBPF_SEGMENTS_PER_PAGE];
+};
+
+#define NBPF_STATUS_SHIFT 7
+#define NBPF_STATUS_KEEP BIT(NBPF_STATUS_SHIFT)
+#define NBPF_STATUS_MASK (NBPF_STATUS_KEEP - 1)
+
+/**
+ * struct nbpf_channel - one DMAC channel
+ * @dma_chan:	standard dmaengine channel object
+ * @base:	register address base
+ * @nbpf:	DMAC
+ * @name:	IRQ name
+ * @irq:	IRQ number
+ * @slave_addr:	address for slave DMA
+ * @slave_width:slave data size in bytes
+ * @slave_burst:maximum slave burst size in bytes
+ * @terminal:	DMA terminal, assigned to this channel
+ * @dmarq_cfg:	DMA request line configuration - high / low, edge / level for NBPF_CHAN_CFG
+ * @flags:	configuration flags from DT
+ * @lock:	protect descriptor lists
+ * @free_links:	list of free link descriptors
+ * @free:	list of free descriptors
+ * @queued:	list of queued descriptors
+ * @active:	list of descriptors, scheduled for processing
+ * @done:	list of completed descriptors, waiting post-processing
+ * @desc_page:	list of additionally allocated descriptor pages - if any
+ */
+struct nbpf_channel {
+	struct dma_chan dma_chan;
+	void __iomem *base;
+	struct nbpf_device *nbpf;
+	char name[16];
+	int irq;
+	dma_addr_t slave_addr;
+	u32 slave_width;
+	u32 slave_burst;
+	unsigned int terminal;
+	u32 dmarq_cfg;
+	unsigned long flags;
+	spinlock_t lock;
+	struct list_head free_links;
+	struct list_head free;
+	struct list_head queued;
+	struct list_head active;
+	struct list_head done;
+	struct list_head desc_page;
+	struct nbpf_desc *running;
+	dma_cookie_t cookie_forgotten;
+	DECLARE_BITMAP(status, NBPF_STATUS_KEEP);
+	bool paused;
+};
+
+struct nbpf_device {
+	struct dma_device dma_dev;
+	void __iomem *base;
+	struct clk *clk;
+	const struct nbpf_config *config;
+	struct nbpf_channel chan[];
+};
+
+enum nbpf_model {
+	NBPF1B4,
+	NBPF1B8,
+	NBPF1B16,
+	NBPF4B4,
+	NBPF4B8,
+	NBPF4B16,
+	NBPF8B4,
+	NBPF8B8,
+	NBPF8B16,
+};
+
+static struct nbpf_config nbpf_cfg[] = {
+	[NBPF1B4] = {
+		.num_channels = 1,
+		.buffer_size = 4,
+	},
+	[NBPF1B8] = {
+		.num_channels = 1,
+		.buffer_size = 8,
+	},
+	[NBPF1B16] = {
+		.num_channels = 1,
+		.buffer_size = 16,
+	},
+	[NBPF4B4] = {
+		.num_channels = 4,
+		.buffer_size = 4,
+	},
+	[NBPF4B8] = {
+		.num_channels = 4,
+		.buffer_size = 8,
+	},
+	[NBPF4B16] = {
+		.num_channels = 4,
+		.buffer_size = 16,
+	},
+	[NBPF8B4] = {
+		.num_channels = 8,
+		.buffer_size = 4,
+	},
+	[NBPF8B8] = {
+		.num_channels = 8,
+		.buffer_size = 8,
+	},
+	[NBPF8B16] = {
+		.num_channels = 8,
+		.buffer_size = 16,
+	},
+};
+
+#define nbpf_to_chan(d) container_of(d, struct nbpf_channel, dma_chan)
+
+/*
+ * dmaengine drivers seem to have a lot in common and instead of sharing more
+ * code, they reimplement those common algorithms independently. In this driver
+ * we try to separate the hardware-specific part from the (largely) generic
+ * part. This improves code readability and makes it possible in the future to
+ * reuse the generic code in form of a helper library. That generic code should
+ * be suitable for various DMA controllers, using transfer descriptors in RAM
+ * and pushing one SG list at a time to the DMA controller.
+ */
+
+/*		Hardware-specific part		*/
+
+static inline u32 nbpf_chan_read(struct nbpf_channel *chan,
+				 unsigned int offset)
+{
+	u32 data = ioread32(chan->base + offset);
+	pr_debug("%s(0x%p + 0x%x) = 0x%x\n", __func__, chan->base, offset, data);
+	return data;
+}
+
+static inline void nbpf_chan_write(struct nbpf_channel *chan,
+				   unsigned int offset, u32 data)
+{
+	iowrite32(data, chan->base + offset);
+	pr_debug("%s(0x%p + 0x%x) = 0x%x\n", __func__, chan->base, offset, data);
+}
+
+static inline u32 nbpf_read(struct nbpf_device *nbpf,
+			    unsigned int offset)
+{
+	u32 data = ioread32(nbpf->base + offset);
+	pr_debug("%s(0x%p + 0x%x) = 0x%x\n", __func__, nbpf->base, offset, data);
+	return data;
+}
+
+static inline void nbpf_write(struct nbpf_device *nbpf,
+			      unsigned int offset, u32 data)
+{
+	iowrite32(data, nbpf->base + offset);
+	pr_debug("%s(0x%p + 0x%x) = 0x%x\n", __func__, nbpf->base, offset, data);
+}
+
+static void nbpf_chan_halt(struct nbpf_channel *chan)
+{
+	nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_CLREN);
+}
+
+static bool nbpf_status_get(struct nbpf_channel *chan)
+{
+	u32 status = nbpf_read(chan->nbpf, NBPF_DSTAT_END);
+
+	return status & BIT(chan - chan->nbpf->chan);
+}
+
+static void nbpf_status_ack(struct nbpf_channel *chan)
+{
+	nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_CLREND);
+}
+
+static u32 nbpf_error_get(struct nbpf_device *nbpf)
+{
+	return nbpf_read(nbpf, NBPF_DSTAT_ER);
+}
+
+struct nbpf_channel *nbpf_error_get_channel(struct nbpf_device *nbpf, u32 error)
+{
+	return nbpf->chan + __ffs(error);
+}
+
+static void nbpf_error_clear(struct nbpf_channel *chan)
+{
+	u32 status;
+	int i;
+
+	/* stop the channel, make sure DMA has been aborted */
+	nbpf_chan_halt(chan);
+
+	for (i = 0; i < 1000; i++) {
+		status = nbpf_chan_read(chan, NBPF_CHAN_STAT);
+		if (!(status & NBPF_CHAN_STAT_TACT))
+			break;
+		cpu_relax();
+	}
+
+	if (i == 1000)
+		dev_err(chan->dma_chan.device->dev, "%s() abort timeout\n", __func__);
+
+	nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_SWRST);
+}
+
+static int nbpf_start(struct nbpf_desc *desc)
+{
+	struct nbpf_channel *chan = desc->chan;
+	struct nbpf_link_desc *ldesc = list_first_entry(&desc->sg, struct nbpf_link_desc, node);
+
+	nbpf_chan_write(chan, NBPF_CHAN_NXLA, ldesc->hwdesc_dma_addr);
+	nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_SETEN | NBPF_CHAN_CTRL_CLRSUS);
+	chan->paused = false;
+
+	/* Software trigger MEMCPY - only MEMCPY uses the block mode */
+	if (ldesc->hwdesc->config & NBPF_CHAN_CFG_TM)
+		nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_STG);
+
+	dev_dbg(chan->nbpf->dma_dev.dev, "%s(): next 0x%x, cur 0x%x\n", __func__,
+		nbpf_chan_read(chan, NBPF_CHAN_NXLA), nbpf_chan_read(chan, NBPF_CHAN_CRLA));
+
+	return 0;
+}
+
+static void nbpf_chan_prepare(struct nbpf_channel *chan)
+{
+	chan->dmarq_cfg = (chan->flags & NBPF_SLAVE_RQ_HIGH ? NBPF_CHAN_CFG_HIEN : 0) |
+		(chan->flags & NBPF_SLAVE_RQ_LOW ? NBPF_CHAN_CFG_LOEN : 0) |
+		(chan->flags & NBPF_SLAVE_RQ_LEVEL ?
+		 NBPF_CHAN_CFG_LVL | (NBPF_CHAN_CFG_AM & 0x200) : 0) |
+		chan->terminal;
+}
+
+static void nbpf_chan_prepare_default(struct nbpf_channel *chan)
+{
+	/* Don't output DMAACK */
+	chan->dmarq_cfg = NBPF_CHAN_CFG_AM & 0x400;
+	chan->terminal = 0;
+	chan->flags = 0;
+}
+
+static void nbpf_chan_configure(struct nbpf_channel *chan)
+{
+	/*
+	 * We assume, that only the link mode and DMA request line configuration
+	 * have to be set in the configuration register manually. Dynamic
+	 * per-transfer configuration will be loaded from transfer descriptors.
+	 */
+	nbpf_chan_write(chan, NBPF_CHAN_CFG, NBPF_CHAN_CFG_DMS | chan->dmarq_cfg);
+}
+
+static u32 nbpf_xfer_ds(struct nbpf_device *nbpf, size_t size)
+{
+	/* Maximum supported bursts depend on the buffer size */
+	return min_t(int, __ffs(size), ilog2(nbpf->config->buffer_size * 8));
+}
+
+static u32 nbpf_xfer_size(struct nbpf_device *nbpf,
+			  enum dma_slave_buswidth width, u32 burst)
+{
+	size_t size;
+
+	if (!burst)
+		burst = 1;
+
+	switch (width) {
+	case DMA_SLAVE_BUSWIDTH_8_BYTES:
+		size = 8 * burst;
+		break;
+	case DMA_SLAVE_BUSWIDTH_4_BYTES:
+		size = 4 * burst;
+		break;
+	case DMA_SLAVE_BUSWIDTH_2_BYTES:
+		size = 2 * burst;
+		break;
+	default:
+		pr_warn("%s(): invalid bus width %u\n", __func__, width);
+	case DMA_SLAVE_BUSWIDTH_1_BYTE:
+		size = burst;
+	}
+
+	return nbpf_xfer_ds(nbpf, size);
+}
+
+/*
+ * We need a way to recognise slaves, whose data is sent "raw" over the bus,
+ * i.e. it isn't known in advance how many bytes will be received. Therefore
+ * the slave driver has to provide a "large enough" buffer and either read the
+ * buffer, when it is full, or detect, that some data has arrived, then wait for
+ * a timeout, if no more data arrives - receive what's already there. We want to
+ * handle such slaves in a special way to allow an optimised mode for other
+ * users, for whom the amount of data is known in advance. So far there's no way
+ * to recognise such slaves. We use a data-width check to distinguish between
+ * the SD host and the PL011 UART.
+ */
+#define nbpf_slave_can_burst(chan) (chan->slave_width >= 3)
+
+static int nbpf_prep_one(struct nbpf_link_desc *ldesc,
+			 enum dma_transfer_direction direction,
+			 dma_addr_t src, dma_addr_t dst, size_t size, bool last)
+{
+	struct nbpf_link_reg *hwdesc = ldesc->hwdesc;
+	struct nbpf_desc *desc = ldesc->desc;
+	struct nbpf_channel *chan = desc->chan;
+	struct device *dev = chan->dma_chan.device->dev;
+	size_t mem_xfer, slave_xfer;
+
+	hwdesc->header = NBPF_HEADER_WBD | NBPF_HEADER_LV |
+		(last ? NBPF_HEADER_LE : 0);
+
+	hwdesc->src_addr = src;
+	hwdesc->dst_addr = dst;
+	hwdesc->transaction_size = size;
+
+	/*
+	 * set config: SAD, DAD, DDS, SDS, etc.
+	 * Note on transfer sizes: the DMAC can perform unaligned DMA transfers,
+	 * but it is important to have transaction size a multiple of both
+	 * receiver and transmitter transfer sizes. It is also possible to use
+	 * different RAM and device transfer sizes, and it does work well with
+	 * some devices, e.g. with V08R07S01E SD host controllers, which can use
+	 * 128 byte transfers. But this doesn't work with other devices,
+	 * especially when the transaction size is unknown. This is the case,
+	 * e.g. with serial drivers like amba-pl011.c. For reception it sets up
+	 * the transaction size of 4K and if fewer bytes are received, it
+	 * pauses DMA and reads out data received via DMA as well as those left
+	 * in the Rx FIFO. For this to work with the RAM side using burst
+	 * transfers we enable the SBE bit and terminate the transfer in our
+	 * DMA_PAUSE handler.
+	 */
+	mem_xfer = nbpf_xfer_ds(chan->nbpf, size);
+	slave_xfer = min(mem_xfer, nbpf_slave_can_burst(chan) ?
+			 chan->slave_burst : chan->slave_width);
+
+	switch (direction) {
+	case DMA_DEV_TO_MEM:
+		/*
+		 * Is the slave narrower than 64 bits, i.e. isn't using the full
+		 * bus width and cannot use bursts?
+		 */
+		if (mem_xfer > chan->slave_burst && !nbpf_slave_can_burst(chan))
+			mem_xfer = chan->slave_burst;
+		/* Device-to-RAM DMA is unreliable without REQD set */
+		hwdesc->config = NBPF_CHAN_CFG_SAD | (NBPF_CHAN_CFG_DDS & (mem_xfer << 16)) |
+			(NBPF_CHAN_CFG_SDS & (slave_xfer << 12)) | NBPF_CHAN_CFG_REQD |
+			NBPF_CHAN_CFG_SBE;
+		break;
+	case DMA_MEM_TO_DEV:
+		hwdesc->config = NBPF_CHAN_CFG_DAD | (NBPF_CHAN_CFG_SDS & (mem_xfer << 12)) |
+			(NBPF_CHAN_CFG_DDS & (slave_xfer << 16)) | NBPF_CHAN_CFG_REQD;
+		break;
+	case DMA_MEM_TO_MEM:
+		hwdesc->config = NBPF_CHAN_CFG_TCM | NBPF_CHAN_CFG_TM |
+			(NBPF_CHAN_CFG_SDS & (mem_xfer << 12)) |
+			(NBPF_CHAN_CFG_DDS & (mem_xfer << 16));
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	hwdesc->config |= chan->dmarq_cfg | (last ? 0 : NBPF_CHAN_CFG_DEM) |
+		NBPF_CHAN_CFG_DMS;
+
+	dev_dbg(dev, "%s(): desc @ 0x%x: hdr 0x%x, cfg 0x%x, %u @ 0x%x -> 0x%x\n",
+		__func__, ldesc->hwdesc_dma_addr, hwdesc->header,
+		hwdesc->config, size, src, dst);
+
+	dma_sync_single_for_device(dev, ldesc->hwdesc_dma_addr, sizeof(*hwdesc),
+				   DMA_TO_DEVICE);
+
+	return 0;
+}
+
+static size_t nbpf_bytes_left(struct nbpf_channel *chan)
+{
+	return nbpf_chan_read(chan, NBPF_CHAN_CUR_TR_BYTE);
+}
+
+static void nbpf_configure(struct nbpf_device *nbpf)
+{
+	nbpf_write(nbpf, NBPF_CTRL, NBPF_CTRL_LVINT);
+}
+
+static void nbpf_pause(struct nbpf_channel *chan)
+{
+	nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_SETSUS);
+	/* See comment in nbpf_prep_one() */
+	nbpf_chan_write(chan, NBPF_CHAN_CTRL, NBPF_CHAN_CTRL_CLREN);
+}
+
+/*		Generic part			*/
+
+/* DMA ENGINE functions */
+static void nbpf_issue_pending(struct dma_chan *dchan)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+	unsigned long flags;
+
+	dev_dbg(dchan->device->dev, "Entry %s()\n", __func__);
+
+	spin_lock_irqsave(&chan->lock, flags);
+	if (list_empty(&chan->queued))
+		goto unlock;
+
+	list_splice_tail_init(&chan->queued, &chan->active);
+
+	if (!chan->running) {
+		struct nbpf_desc *desc = list_first_entry(&chan->active,
+						struct nbpf_desc, node);
+		if (!nbpf_start(desc))
+			chan->running = desc;
+	}
+
+unlock:
+	spin_unlock_irqrestore(&chan->lock, flags);
+}
+
+/*
+ * cookies are numbered 1...DMA_MAX_COOKIE=INT_MAX
+ */
+static void nbpf_cookie_update(struct nbpf_channel *chan, dma_cookie_t cookie)
+{
+	dma_cookie_t forgotten = cookie - NBPF_STATUS_KEEP;
+
+	if (cookie < NBPF_STATUS_KEEP && !chan->cookie_forgotten)
+		/* Not forgetting yet */
+		return;
+
+	if (forgotten < DMA_MIN_COOKIE)
+		/* Wrapped */
+		forgotten = (DMA_MAX_COOKIE & ~NBPF_STATUS_MASK) + cookie;
+	chan->cookie_forgotten = forgotten;
+}
+
+static bool nbpf_cookie_in_cache(struct nbpf_channel *chan,
+		dma_cookie_t cookie, struct dma_tx_state *state)
+{
+	if (cookie > chan->cookie_forgotten)
+		return true;
+
+	/*
+	 * We still remember the cookie, if it has wrapped beyond INT_MAX:
+	 * (1) forgotten is almost INT_MAX
+	 * cookie_forgotten >> NBPF_STATUS_SHIFT == DMA_MAX_COOKIE >> NBPF_STATUS_SHIFT
+	 * and enquired is small
+	 * (2)
+	 * cookie & ~NBPF_STATUS_MASK == 0
+	 */
+
+	return chan->cookie_forgotten >> NBPF_STATUS_SHIFT ==
+		DMA_MAX_COOKIE >> NBPF_STATUS_SHIFT &&
+		!(cookie < ~NBPF_STATUS_MASK);
+}
+
+static void nbpf_cookie_success(struct nbpf_channel *chan, dma_cookie_t cookie)
+{
+	nbpf_cookie_update(chan, cookie);
+	clear_bit(cookie & NBPF_STATUS_MASK, chan->status);
+}
+
+static void nbpf_cookie_fail(struct nbpf_channel *chan, dma_cookie_t cookie)
+{
+	nbpf_cookie_update(chan, cookie);
+	set_bit(cookie & NBPF_STATUS_MASK, chan->status);
+}
+
+static enum dma_status nbpf_cookie_cached(struct nbpf_channel *chan,
+		dma_cookie_t cookie, struct dma_tx_state *state)
+{
+	return test_bit(cookie & NBPF_STATUS_MASK, chan->status) ?
+		DMA_ERROR : DMA_COMPLETE;
+}
+
+static enum dma_status nbpf_tx_status(struct dma_chan *dchan,
+		dma_cookie_t cookie, struct dma_tx_state *state)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+	enum dma_status status = dma_cookie_status(dchan, cookie, state);
+	dma_cookie_t running = chan->running ? chan->running->async_tx.cookie : -EINVAL;
+
+	if (chan->paused)
+		status = DMA_PAUSED;
+
+	/* Note: we cannot return residues for old cookies */
+	if (state && cookie == running) {
+		state->residue = nbpf_bytes_left(chan);
+		dev_dbg(dchan->device->dev, "%s(): residue %u\n", __func__,
+			state->residue);
+	}
+
+	if (status == DMA_IN_PROGRESS || status == DMA_PAUSED)
+		return status;
+
+	if (nbpf_cookie_in_cache(chan, cookie, state))
+		return nbpf_cookie_cached(chan, cookie, state);
+
+	return status;
+}
+
+static dma_cookie_t nbpf_tx_submit(struct dma_async_tx_descriptor *tx)
+{
+	struct nbpf_desc *desc = container_of(tx, struct nbpf_desc, async_tx);
+	struct nbpf_channel *chan = desc->chan;
+	unsigned long flags;
+	dma_cookie_t cookie;
+
+	spin_lock_irqsave(&chan->lock, flags);
+	cookie = dma_cookie_assign(tx);
+	list_add_tail(&desc->node, &chan->queued);
+	spin_unlock_irqrestore(&chan->lock, flags);
+
+	dev_dbg(chan->dma_chan.device->dev, "Entry %s(%d)\n", __func__, cookie);
+
+	return cookie;
+}
+
+static int nbpf_desc_page_alloc(struct nbpf_channel *chan)
+{
+	struct dma_chan *dchan = &chan->dma_chan;
+	struct nbpf_desc_page *dpage = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+	struct nbpf_link_desc *ldesc;
+	struct nbpf_link_reg *hwdesc;
+	struct nbpf_desc *desc;
+	LIST_HEAD(head);
+	LIST_HEAD(lhead);
+	int i;
+	struct device *dev = dchan->device->dev;
+
+	if (!dpage)
+		return -ENOMEM;
+
+	dev_dbg(dev, "%s(): alloc %lu descriptors, %lu segments, total alloc %u\n",
+		__func__, NBPF_DESCS_PER_PAGE, NBPF_SEGMENTS_PER_PAGE, sizeof(*dpage));
+
+	for (i = 0, ldesc = dpage->ldesc, hwdesc = dpage->hwdesc;
+	     i < ARRAY_SIZE(dpage->ldesc);
+	     i++, ldesc++, hwdesc++) {
+		ldesc->hwdesc = hwdesc;
+		list_add_tail(&ldesc->node, &lhead);
+		ldesc->hwdesc_dma_addr = dma_map_single(dchan->device->dev,
+					hwdesc, sizeof(*hwdesc), DMA_TO_DEVICE);
+
+		dev_dbg(dev, "%s(): mapped %p to %u\n", __func__,
+			hwdesc, ldesc->hwdesc_dma_addr);
+	}
+
+	for (i = 0, desc = dpage->desc;
+	     i < ARRAY_SIZE(dpage->desc);
+	     i++, desc++) {
+		dma_async_tx_descriptor_init(&desc->async_tx, dchan);
+		desc->async_tx.tx_submit = nbpf_tx_submit;
+		desc->chan = chan;
+		INIT_LIST_HEAD(&desc->sg);
+		list_add_tail(&desc->node, &head);
+	}
+
+	/*
+	 * This function cannot be called from interrupt context, so, no need to
+	 * save flags
+	 */
+	spin_lock_irq(&chan->lock);
+	list_splice_tail(&lhead, &chan->free_links);
+	list_splice_tail(&head, &chan->free);
+	list_add(&dpage->node, &chan->desc_page);
+	spin_unlock_irq(&chan->lock);
+
+	return ARRAY_SIZE(dpage->desc);
+}
+
+static void nbpf_desc_put(struct nbpf_desc *desc)
+{
+	struct nbpf_channel *chan = desc->chan;
+	struct nbpf_link_desc *ldesc, *tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&chan->lock, flags);
+	list_for_each_entry_safe(ldesc, tmp, &desc->sg, node)
+		list_move(&ldesc->node, &chan->free_links);
+
+	list_add(&desc->node, &chan->free);
+	spin_unlock_irqrestore(&chan->lock, flags);
+}
+
+static void nbpf_scan_acked(struct nbpf_channel *chan)
+{
+	struct nbpf_desc *desc, *tmp;
+	unsigned long flags;
+	LIST_HEAD(head);
+
+	spin_lock_irqsave(&chan->lock, flags);
+	list_for_each_entry_safe(desc, tmp, &chan->done, node)
+		if (async_tx_test_ack(&desc->async_tx) && desc->user_wait) {
+			list_move(&desc->node, &head);
+			desc->user_wait = false;
+		}
+	spin_unlock_irqrestore(&chan->lock, flags);
+
+	list_for_each_entry_safe(desc, tmp, &head, node) {
+		list_del(&desc->node);
+		nbpf_desc_put(desc);
+	}
+}
+
+/*
+ * We have to allocate descriptors with the channel lock dropped. This means,
+ * before we re-acquire the lock buffers can be taken already, so we have to
+ * re-check after re-acquiring the lock and possibly retry, if buffers are gone
+ * again.
+ */
+static struct nbpf_desc *nbpf_desc_get(struct nbpf_channel *chan, size_t len)
+{
+	struct nbpf_desc *desc = NULL;
+	struct nbpf_link_desc *ldesc, *prev = NULL;
+
+	nbpf_scan_acked(chan);
+
+	spin_lock_irq(&chan->lock);
+
+	do {
+		int i = 0, ret;
+
+		if (list_empty(&chan->free)) {
+			/* No more free descriptors */
+			spin_unlock_irq(&chan->lock);
+			ret = nbpf_desc_page_alloc(chan);
+			if (ret < 0)
+				return NULL;
+			spin_lock_irq(&chan->lock);
+			continue;
+		}
+		desc = list_first_entry(&chan->free, struct nbpf_desc, node);
+		list_del(&desc->node);
+
+		do {
+			if (list_empty(&chan->free_links)) {
+				/* No more free link descriptors */
+				spin_unlock_irq(&chan->lock);
+				ret = nbpf_desc_page_alloc(chan);
+				if (ret < 0) {
+					nbpf_desc_put(desc);
+					return NULL;
+				}
+				spin_lock_irq(&chan->lock);
+				continue;
+			}
+
+			ldesc = list_first_entry(&chan->free_links,
+						 struct nbpf_link_desc, node);
+			ldesc->desc = desc;
+			if (prev)
+				prev->hwdesc->next = ldesc->hwdesc_dma_addr;
+
+			prev = ldesc;
+			list_move_tail(&ldesc->node, &desc->sg);
+
+			i++;
+		} while (i < len);
+	} while (!desc);
+
+	prev->hwdesc->next = 0;
+
+	spin_unlock_irq(&chan->lock);
+
+	return desc;
+}
+
+static void nbpf_chan_idle(struct nbpf_channel *chan)
+{
+	struct nbpf_desc *desc, *tmp;
+	unsigned long flags;
+	LIST_HEAD(head);
+
+	spin_lock_irqsave(&chan->lock, flags);
+
+	list_splice_init(&chan->done, &head);
+	list_splice_init(&chan->active, &head);
+	list_splice_init(&chan->queued, &head);
+
+	chan->running = NULL;
+
+	spin_unlock_irqrestore(&chan->lock, flags);
+
+	list_for_each_entry_safe(desc, tmp, &head, node) {
+		dev_dbg(chan->nbpf->dma_dev.dev, "%s(): force-free desc %p cookie %d\n",
+			__func__, desc, desc->async_tx.cookie);
+		list_del(&desc->node);
+		nbpf_cookie_fail(chan, desc->async_tx.cookie);
+		nbpf_desc_put(desc);
+	}
+}
+
+static int nbpf_control(struct dma_chan *dchan, enum dma_ctrl_cmd cmd,
+			unsigned long arg)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+	struct dma_slave_config *config;
+
+	dev_dbg(dchan->device->dev, "Entry %s(%d)\n", __func__, cmd);
+
+	switch (cmd) {
+	case DMA_TERMINATE_ALL:
+		dev_dbg(dchan->device->dev, "Terminating\n");
+		nbpf_chan_halt(chan);
+		nbpf_chan_idle(chan);
+		break;
+	case DMA_SLAVE_CONFIG:
+		if (!arg)
+			return -EINVAL;
+		config = (struct dma_slave_config *)arg;
+
+		/*
+		 * We could check config->slave_id to match chan->terminal here,
+		 * but with DT they would be coming from the same source, so
+		 * such a check would be superflous
+		 */
+
+		switch (config->direction) {
+		case DMA_MEM_TO_DEV:
+			chan->slave_addr = config->dst_addr;
+			chan->slave_width = nbpf_xfer_size(chan->nbpf,
+							config->dst_addr_width, 1);
+			chan->slave_burst = nbpf_xfer_size(chan->nbpf,
+							config->dst_addr_width,
+							config->dst_maxburst);
+			break;
+		case DMA_DEV_TO_MEM:
+			chan->slave_addr = config->src_addr;
+			chan->slave_width = nbpf_xfer_size(chan->nbpf,
+							config->src_addr_width, 1);
+			chan->slave_burst = nbpf_xfer_size(chan->nbpf,
+							config->src_addr_width,
+							config->src_maxburst);
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case DMA_PAUSE:
+		chan->paused = true;
+		nbpf_pause(chan);
+		break;
+	case DMA_RESUME:
+		/* Leave unimplemented until we get a use case. */
+	default:
+		return -ENXIO;
+	}
+
+	return 0;
+}
+
+static struct dma_async_tx_descriptor *nbpf_prep_sg(struct nbpf_channel *chan,
+		struct scatterlist *src_sg, struct scatterlist *dst_sg,
+		size_t len, enum dma_transfer_direction direction,
+		unsigned long flags)
+{
+	struct nbpf_link_desc *ldesc;
+	struct scatterlist *mem_sg;
+	struct nbpf_desc *desc;
+	bool inc_src, inc_dst;
+	int i = 0;
+
+	switch (direction) {
+	case DMA_DEV_TO_MEM:
+		mem_sg = dst_sg;
+		inc_src = false;
+		inc_dst = true;
+		break;
+	case DMA_MEM_TO_DEV:
+		mem_sg = src_sg;
+		inc_src = true;
+		inc_dst = false;
+		break;
+	default:
+	case DMA_MEM_TO_MEM:
+		mem_sg = src_sg;
+		inc_src = true;
+		inc_dst = true;
+	}
+
+	desc = nbpf_desc_get(chan, len);
+	if (!desc)
+		return NULL;
+
+	desc->async_tx.flags = flags;
+	desc->async_tx.cookie = -EBUSY;
+	desc->user_wait = false;
+
+	/*
+	 * this is a private descriptor list, and we own the descriptor. No need
+	 * to lock.
+	 */
+	list_for_each_entry(ldesc, &desc->sg, node) {
+		int ret = nbpf_prep_one(ldesc, direction,
+					sg_dma_address(src_sg),
+					sg_dma_address(dst_sg),
+					sg_dma_len(mem_sg),
+					i == len - 1);
+		if (ret < 0) {
+			nbpf_desc_put(desc);
+			return NULL;
+		}
+		if (inc_src)
+			src_sg = sg_next(src_sg);
+		if (inc_dst)
+			dst_sg = sg_next(dst_sg);
+		mem_sg = direction == DMA_DEV_TO_MEM ? dst_sg : src_sg;
+		i++;
+	}
+
+	/* The user has to return the descriptor to us ASAP via .tx_submit() */
+	return &desc->async_tx;
+}
+
+static struct dma_async_tx_descriptor *nbpf_prep_memcpy(
+	struct dma_chan *dchan, dma_addr_t dst, dma_addr_t src,
+	size_t len, unsigned long flags)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+	struct scatterlist dst_sg;
+	struct scatterlist src_sg;
+
+	sg_init_table(&dst_sg, 1);
+	sg_init_table(&src_sg, 1);
+
+	sg_dma_address(&dst_sg) = dst;
+	sg_dma_address(&src_sg) = src;
+
+	sg_dma_len(&dst_sg) = len;
+	sg_dma_len(&src_sg) = len;
+
+	dev_dbg(dchan->device->dev, "%s(): %u @ 0x%x -> 0x%x\n",
+		__func__, len, src, dst);
+
+	return nbpf_prep_sg(chan, &src_sg, &dst_sg, 1,
+			    DMA_MEM_TO_MEM, flags);
+}
+
+static struct dma_async_tx_descriptor *nbpf_prep_memcpy_sg(
+	struct dma_chan *dchan,
+	struct scatterlist *dst_sg, unsigned int dst_nents,
+	struct scatterlist *src_sg, unsigned int src_nents,
+	unsigned long flags)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+
+	if (dst_nents != src_nents)
+		return NULL;
+
+	return nbpf_prep_sg(chan, src_sg, dst_sg, src_nents,
+			    DMA_MEM_TO_MEM, flags);
+}
+
+static struct dma_async_tx_descriptor *nbpf_prep_slave_sg(
+	struct dma_chan *dchan, struct scatterlist *sgl, unsigned int sg_len,
+	enum dma_transfer_direction direction, unsigned long flags, void *context)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+	struct scatterlist slave_sg;
+
+	dev_dbg(dchan->device->dev, "Entry %s()\n", __func__);
+
+	sg_init_table(&slave_sg, 1);
+	sg_dma_address(&slave_sg) = chan->slave_addr;
+
+	switch (direction) {
+	case DMA_MEM_TO_DEV:
+		return nbpf_prep_sg(chan, sgl, &slave_sg, sg_len,
+				    direction, flags);
+	case DMA_DEV_TO_MEM:
+		return nbpf_prep_sg(chan, &slave_sg, sgl, sg_len,
+				    direction, flags);
+	default:
+		return NULL;
+	}
+}
+
+static int nbpf_alloc_chan_resources(struct dma_chan *dchan)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+	int ret;
+
+	INIT_LIST_HEAD(&chan->free);
+	INIT_LIST_HEAD(&chan->free_links);
+	INIT_LIST_HEAD(&chan->queued);
+	INIT_LIST_HEAD(&chan->active);
+	INIT_LIST_HEAD(&chan->done);
+
+	memset(chan->status, 0, sizeof(chan->status));
+
+	ret = nbpf_desc_page_alloc(chan);
+	if (ret < 0)
+		return ret;
+
+	dev_dbg(dchan->device->dev, "Entry %s(): terminal %u\n", __func__,
+		chan->terminal);
+
+	nbpf_chan_configure(chan);
+
+	return ret;
+}
+
+static void nbpf_free_chan_resources(struct dma_chan *dchan)
+{
+	struct nbpf_channel *chan = nbpf_to_chan(dchan);
+	struct nbpf_desc_page *dpage, *tmp;
+
+	dev_dbg(dchan->device->dev, "Entry %s()\n", __func__);
+
+	nbpf_chan_halt(chan);
+	/* Clean up for if a channel is re-used for MEMCPY after slave DMA */
+	nbpf_chan_prepare_default(chan);
+
+	list_for_each_entry_safe(dpage, tmp, &chan->desc_page, node) {
+		struct nbpf_link_desc *ldesc;
+		int i;
+		list_del(&dpage->node);
+		for (i = 0, ldesc = dpage->ldesc;
+		     i < ARRAY_SIZE(dpage->ldesc);
+		     i++, ldesc++)
+			dma_unmap_single(dchan->device->dev, ldesc->hwdesc_dma_addr,
+					 sizeof(*ldesc->hwdesc), DMA_TO_DEVICE);
+		free_page((unsigned long)dpage);
+	}
+}
+
+static int nbpf_slave_caps(struct dma_chan *dchan,
+			   struct dma_slave_caps *caps)
+{
+	caps->src_addr_widths = NBPF_DMA_BUSWIDTHS;
+	caps->dstn_addr_widths = NBPF_DMA_BUSWIDTHS;
+	caps->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
+	caps->cmd_pause = false;
+	caps->cmd_terminate = true;
+
+	return 0;
+}
+
+static bool nbpf_dma_filter(struct dma_chan *chan, void *param)
+{
+	return param == chan->device->dev->of_node;
+}
+
+static struct dma_chan *nbpf_of_xlate(struct of_phandle_args *dma_spec,
+				      struct of_dma *ofdma)
+{
+	dma_cap_mask_t mask;
+	struct dma_chan *dchan;
+	struct nbpf_channel *chan;
+
+	if (dma_spec->args_count != 2)
+		return NULL;
+
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_SLAVE, mask);
+
+	dchan = dma_request_channel(mask, nbpf_dma_filter, ofdma->of_node);
+	if (!dchan)
+		return NULL;
+
+	dev_dbg(dchan->device->dev, "Entry %s(%s)\n", __func__,
+		dma_spec->np->name);
+
+	chan = nbpf_to_chan(dchan);
+
+	chan->terminal = dma_spec->args[0];
+	chan->flags = dma_spec->args[1];
+
+	nbpf_chan_prepare(chan);
+	nbpf_chan_configure(chan);
+
+	return dchan;
+}
+
+static irqreturn_t nbpf_chan_irqt(int irq, void *dev)
+{
+	struct nbpf_channel *chan = dev;
+	struct nbpf_desc *desc, *tmp;
+	dma_async_tx_callback callback;
+	void *param;
+
+	while (!list_empty(&chan->done)) {
+		bool found = false, must_put, recycling = false;
+
+		spin_lock_irq(&chan->lock);
+
+		list_for_each_entry_safe(desc, tmp, &chan->done, node) {
+			if (!desc->user_wait) {
+				/* Newly completed descriptor, have to process */
+				found = true;
+				break;
+			} else if (async_tx_test_ack(&desc->async_tx)) {
+				/*
+				 * This descriptor was waiting for a user ACK,
+				 * it can be recycled now.
+				 */
+				list_del(&desc->node);
+				spin_unlock_irq(&chan->lock);
+				nbpf_desc_put(desc);
+				recycling = true;
+				break;
+			}
+		}
+
+		if (recycling)
+			continue;
+
+		if (!found) {
+			/* This can happen if TERMINATE_ALL has been called */
+			spin_unlock_irq(&chan->lock);
+			break;
+		}
+
+		dev_dbg(chan->dma_chan.device->dev,
+			"%s(): chan %p #%d: cookie %d complete\n",
+			__func__, &chan->dma_chan, chan - chan->nbpf->chan,
+			desc->async_tx.cookie);
+		dma_cookie_complete(&desc->async_tx);
+
+		/*
+		 * With released lock we cannot dereference desc, maybe it's
+		 * still on the "done" list
+		 */
+		if (async_tx_test_ack(&desc->async_tx)) {
+			list_del(&desc->node);
+			must_put = true;
+		} else {
+			desc->user_wait = true;
+			must_put = false;
+		}
+
+		callback = desc->async_tx.callback;
+		param = desc->async_tx.callback_param;
+
+		nbpf_cookie_success(chan, desc->async_tx.cookie);
+
+		/* ack and callback completed descriptor */
+		spin_unlock_irq(&chan->lock);
+
+		if (callback)
+			callback(param);
+
+		if (must_put)
+			nbpf_desc_put(desc);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t nbpf_chan_irq(int irq, void *dev)
+{
+	struct nbpf_channel *chan = dev;
+	bool done = nbpf_status_get(chan);
+	struct nbpf_desc *desc;
+	irqreturn_t ret;
+
+	if (!done)
+		return IRQ_NONE;
+
+	nbpf_status_ack(chan);
+
+	dev_dbg(&chan->dma_chan.dev->device, "%s()\n", __func__);
+
+	spin_lock(&chan->lock);
+	desc = chan->running;
+	if (WARN_ON(!desc)) {
+		ret = IRQ_NONE;
+		goto unlock;
+	} else {
+		ret = IRQ_WAKE_THREAD;
+	}
+
+	list_move_tail(&desc->node, &chan->done);
+	chan->running = NULL;
+
+	if (!list_empty(&chan->active)) {
+		desc = list_first_entry(&chan->active,
+					struct nbpf_desc, node);
+		if (!nbpf_start(desc))
+			chan->running = desc;
+	}
+
+unlock:
+	spin_unlock(&chan->lock);
+
+	return ret;
+}
+
+static irqreturn_t nbpf_err_irq(int irq, void *dev)
+{
+	struct nbpf_device *nbpf = dev;
+	u32 error = nbpf_error_get(nbpf);
+
+	dev_warn(nbpf->dma_dev.dev, "DMA error IRQ %u\n", irq);
+
+	if (!error)
+		return IRQ_NONE;
+
+	do {
+		struct nbpf_channel *chan = nbpf_error_get_channel(nbpf, error);
+		/* On error: abort all queued transfers, no callback */
+		nbpf_error_clear(chan);
+		nbpf_chan_idle(chan);
+		error = nbpf_error_get(nbpf);
+	} while (error);
+
+	return IRQ_HANDLED;
+}
+
+static int nbpf_chan_probe(struct nbpf_device *nbpf, int n)
+{
+	struct dma_device *dma_dev = &nbpf->dma_dev;
+	int pdev_id = to_platform_device(dma_dev->dev)->id;
+	struct nbpf_channel *chan = nbpf->chan + n;
+	int ret;
+
+	chan->nbpf = nbpf;
+	chan->base = nbpf->base + NBPF_REG_CHAN_OFFSET + NBPF_REG_CHAN_SIZE * n;
+	INIT_LIST_HEAD(&chan->desc_page);
+	spin_lock_init(&chan->lock);
+	chan->dma_chan.device = dma_dev;
+	dma_cookie_init(&chan->dma_chan);
+	nbpf_chan_prepare_default(chan);
+
+	dev_dbg(dma_dev->dev, "%s(): channel %d: -> %p\n", __func__, n, chan->base);
+
+	if (pdev_id >= 0)
+		snprintf(chan->name, sizeof(chan->name),
+			 "nbpf %d.%d", pdev_id, n);
+	else
+		snprintf(chan->name, sizeof(chan->name),
+			 "nbpf %d", n);
+
+	ret = devm_request_threaded_irq(dma_dev->dev, chan->irq,
+			nbpf_chan_irq, nbpf_chan_irqt, IRQF_SHARED,
+			chan->name, chan);
+	if (ret < 0)
+		return ret;
+
+	/* Add the channel to DMA device channel list */
+	list_add_tail(&chan->dma_chan.device_node,
+		      &dma_dev->channels);
+
+	return 0;
+}
+
+static const struct of_device_id nbpf_match[] = {
+	{.compatible = "renesas,nbpfaxi64dmac1b4",	.data = &nbpf_cfg[NBPF1B4]},
+	{.compatible = "renesas,nbpfaxi64dmac1b8",	.data = &nbpf_cfg[NBPF1B8]},
+	{.compatible = "renesas,nbpfaxi64dmac1b16",	.data = &nbpf_cfg[NBPF1B16]},
+	{.compatible = "renesas,nbpfaxi64dmac4b4",	.data = &nbpf_cfg[NBPF4B4]},
+	{.compatible = "renesas,nbpfaxi64dmac4b8",	.data = &nbpf_cfg[NBPF4B8]},
+	{.compatible = "renesas,nbpfaxi64dmac4b16",	.data = &nbpf_cfg[NBPF4B16]},
+	{.compatible = "renesas,nbpfaxi64dmac8b4",	.data = &nbpf_cfg[NBPF8B4]},
+	{.compatible = "renesas,nbpfaxi64dmac8b8",	.data = &nbpf_cfg[NBPF8B8]},
+	{.compatible = "renesas,nbpfaxi64dmac8b16",	.data = &nbpf_cfg[NBPF8B16]},
+	{}
+};
+MODULE_DEVICE_TABLE(of, nbpf_match);
+
+static int nbpf_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct of_device_id *of_id = of_match_device(nbpf_match, dev);
+	struct device_node *np = dev->of_node;
+	struct nbpf_device *nbpf;
+	struct dma_device *dma_dev;
+	struct resource *iomem, *irq_res;
+	const struct nbpf_config *cfg;
+	int num_channels;
+	int ret, irq, eirq, i;
+	int irqbuf[9] /* maximum 8 channels + error IRQ */;
+	unsigned int irqs = 0;
+
+	BUILD_BUG_ON(sizeof(struct nbpf_desc_page) > PAGE_SIZE);
+
+	/* DT only */
+	if (!np || !of_id || !of_id->data)
+		return -ENODEV;
+
+	cfg = of_id->data;
+	num_channels = cfg->num_channels;
+
+	nbpf = devm_kzalloc(dev, sizeof(*nbpf) + num_channels *
+			    sizeof(nbpf->chan[0]), GFP_KERNEL);
+	if (!nbpf) {
+		dev_err(dev, "Memory allocation failed\n");
+		return -ENOMEM;
+	}
+	dma_dev = &nbpf->dma_dev;
+	dma_dev->dev = dev;
+
+	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	nbpf->base = devm_ioremap_resource(dev, iomem);
+	if (IS_ERR(nbpf->base))
+		return PTR_ERR(nbpf->base);
+
+	nbpf->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(nbpf->clk))
+		return PTR_ERR(nbpf->clk);
+
+	nbpf->config = cfg;
+
+	for (i = 0; irqs < ARRAY_SIZE(irqbuf); i++) {
+		irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, i);
+		if (!irq_res)
+			break;
+
+		for (irq = irq_res->start; irq <= irq_res->end;
+		     irq++, irqs++)
+			irqbuf[irqs] = irq;
+	}
+
+	dev_dbg(dev, "%s(): mapped %x -> %p\n", __func__, iomem->start, nbpf->base);
+
+	/*
+	 * 3 IRQ resource schemes are supported:
+	 * 1. 1 shared IRQ for error and all channels
+	 * 2. 2 IRQs: one for error and one shared for all channels
+	 * 3. 1 IRQ for error and an own IRQ for each channel
+	 */
+	if (irqs != 1 && irqs != 2 && irqs != num_channels + 1)
+		return -ENXIO;
+
+	if (irqs == 1) {
+		eirq = irqbuf[0];
+
+		for (i = 0; i <= num_channels; i++)
+			nbpf->chan[i].irq = irqbuf[0];
+	} else {
+		eirq = platform_get_irq_byname(pdev, "error");
+		if (eirq < 0)
+			return eirq;
+
+		if (irqs == num_channels + 1) {
+			struct nbpf_channel *chan;
+
+			for (i = 0, chan = nbpf->chan; i <= num_channels;
+			     i++, chan++) {
+				/* Skip the error IRQ */
+				if (irqbuf[i] == eirq)
+					i++;
+				chan->irq = irqbuf[i];
+			}
+
+			if (chan != nbpf->chan + num_channels)
+				return -EINVAL;
+		} else {
+			/* 2 IRQs and more than one channel */
+			if (irqbuf[0] == eirq)
+				irq = irqbuf[1];
+			else
+				irq = irqbuf[0];
+
+			for (i = 0; i <= num_channels; i++)
+				nbpf->chan[i].irq = irq;
+		}
+	}
+
+	ret = devm_request_threaded_irq(dev, eirq, nbpf_err_irq, NULL,
+					IRQF_SHARED, "dma error", nbpf);
+	if (ret < 0)
+		return ret;
+
+	INIT_LIST_HEAD(&dma_dev->channels);
+
+	/* Create DMA Channel */
+	for (i = 0; i < num_channels; i++) {
+		ret = nbpf_chan_probe(nbpf, i);
+		if (ret < 0)
+			return ret;
+	}
+
+	dma_cap_set(DMA_MEMCPY, dma_dev->cap_mask);
+	dma_cap_set(DMA_SLAVE, dma_dev->cap_mask);
+	dma_cap_set(DMA_SG, dma_dev->cap_mask);
+
+	/* Common and MEMCPY operations */
+	dma_dev->device_alloc_chan_resources
+		= nbpf_alloc_chan_resources;
+	dma_dev->device_free_chan_resources = nbpf_free_chan_resources;
+	dma_dev->device_prep_dma_sg = nbpf_prep_memcpy_sg;
+	dma_dev->device_prep_dma_memcpy = nbpf_prep_memcpy;
+	dma_dev->device_tx_status = nbpf_tx_status;
+	dma_dev->device_issue_pending = nbpf_issue_pending;
+	dma_dev->device_slave_caps = nbpf_slave_caps;
+
+	/*
+	 * If we drop support for unaligned MEMCPY buffer addresses and / or
+	 * lengths by setting
+	 * dma_dev->copy_align = 4;
+	 * then we can set transfer length to 4 bytes in nbpf_prep_one() for
+	 * DMA_MEM_TO_MEM
+	 */
+
+	/* Compulsory for DMA_SLAVE fields */
+	dma_dev->device_prep_slave_sg = nbpf_prep_slave_sg;
+	dma_dev->device_control = nbpf_control;
+
+	if (np) {
+		ret = of_dma_controller_register(np, nbpf_of_xlate, pdev);
+		if (ret < 0)
+			return ret;
+	}
+
+	platform_set_drvdata(pdev, nbpf);
+
+	ret = clk_prepare_enable(nbpf->clk);
+	if (ret < 0)
+		goto e_of_unreg;
+
+	nbpf_configure(nbpf);
+
+	ret = dma_async_device_register(dma_dev);
+	if (ret < 0)
+		goto e_clk_off;
+
+	return 0;
+
+e_clk_off:
+	clk_disable_unprepare(nbpf->clk);
+e_of_unreg:
+	of_dma_controller_free(np);
+
+	return ret;
+}
+
+static int nbpf_remove(struct platform_device *pdev)
+{
+	struct nbpf_device *nbpf = platform_get_drvdata(pdev);
+
+	dma_async_device_unregister(&nbpf->dma_dev);
+	clk_disable_unprepare(nbpf->clk);
+	of_dma_controller_free(pdev->dev.of_node);
+
+	return 0;
+}
+
+static struct platform_device_id nbpf_ids[] = {
+	{"nbpfaxi64dmac1b4",	(kernel_ulong_t)&nbpf_cfg[NBPF1B4]},
+	{"nbpfaxi64dmac1b8",	(kernel_ulong_t)&nbpf_cfg[NBPF1B8]},
+	{"nbpfaxi64dmac1b16",	(kernel_ulong_t)&nbpf_cfg[NBPF1B16]},
+	{"nbpfaxi64dmac4b4",	(kernel_ulong_t)&nbpf_cfg[NBPF4B4]},
+	{"nbpfaxi64dmac4b8",	(kernel_ulong_t)&nbpf_cfg[NBPF4B8]},
+	{"nbpfaxi64dmac4b16",	(kernel_ulong_t)&nbpf_cfg[NBPF4B16]},
+	{"nbpfaxi64dmac8b4",	(kernel_ulong_t)&nbpf_cfg[NBPF8B4]},
+	{"nbpfaxi64dmac8b8",	(kernel_ulong_t)&nbpf_cfg[NBPF8B8]},
+	{"nbpfaxi64dmac8b16",	(kernel_ulong_t)&nbpf_cfg[NBPF8B16]},
+	{},
+};
+MODULE_DEVICE_TABLE(platform, nbpf_ids);
+
+#ifdef CONFIG_PM_RUNTIME
+static int nbpf_runtime_suspend(struct device *dev)
+{
+	struct nbpf_device *nbpf = platform_get_drvdata(to_platform_device(dev));
+	clk_disable_unprepare(nbpf->clk);
+	return 0;
+}
+
+static int nbpf_runtime_resume(struct device *dev)
+{
+	struct nbpf_device *nbpf = platform_get_drvdata(to_platform_device(dev));
+	return clk_prepare_enable(nbpf->clk);
+}
+#endif
+
+static const struct dev_pm_ops nbpf_pm_ops = {
+	SET_RUNTIME_PM_OPS(nbpf_runtime_suspend, nbpf_runtime_resume, NULL)
+};
+
+static struct platform_driver nbpf_driver = {
+	.driver = {
+		.owner = THIS_MODULE,
+		.name = "dma-nbpf",
+		.of_match_table = nbpf_match,
+		.pm = &nbpf_pm_ops,
+	},
+	.id_table = nbpf_ids,
+	.probe = nbpf_probe,
+	.remove = nbpf_remove,
+};
+
+module_platform_driver(nbpf_driver);
+
+MODULE_AUTHOR("Guennadi Liakhovetski <g.liakhovetski-Mmb7MZpHnFY@public.gmane.org>");
+MODULE_DESCRIPTION("dmaengine driver for NBPFAXI64* DMACs");
+MODULE_LICENSE("GPL v2");
diff --git a/include/dt-bindings/dma/nbpfaxi.h b/include/dt-bindings/dma/nbpfaxi.h
new file mode 100644
index 0000000..74f2054
--- /dev/null
+++ b/include/dt-bindings/dma/nbpfaxi.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2013 Renesas Europe Ltd.
+ * Author: Guennadi Liakhovetski <g.liakhovetski-Mmb7MZpHnFY@public.gmane.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef DT_BINDINGS_NBPFAXI_H
+#define DT_BINDINGS_NBPFAXI_H
+
+/**
+ * Use "#dma-cells = <2>;" with the second integer defining slave DMA flags:
+ */
+#define NBPF_SLAVE_RQ_HIGH	1
+#define NBPF_SLAVE_RQ_LOW	2
+#define NBPF_SLAVE_RQ_LEVEL	4
+
+#endif
-- 
1.9.1

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