From d19a0acbd44ad6cd7b6deb75c48f610bbbc44c94 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
Date: Thu, 9 Apr 2015 12:34:11 +0200
Subject: [PATCH] dmaengine: bcm2835: Add slave dma support
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Add slave transfer capability to BCM2835 dmaengine driver.
This patch is pulled from the bcm2708-dmaengine driver in the
Raspberry Pi repo. The work was done by Gellert Weisz.

Tested using the bcm2835-mmc driver from the same repo.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
 drivers/dma/bcm2835-dma.c | 206 ++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 192 insertions(+), 14 deletions(-)

--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -1,11 +1,10 @@
 /*
  * BCM2835 DMA engine support
  *
- * This driver only supports cyclic DMA transfers
- * as needed for the I2S module.
- *
  * Author:      Florian Meier <florian.meier@koalo.de>
  *              Copyright 2013
+ *              Gellert Weisz <gellert@raspberrypi.org>
+ *              Copyright 2013-2014
  *
  * Based on
  *	OMAP DMAengine support by Russell King
@@ -95,6 +94,8 @@ struct bcm2835_desc {
 	size_t size;
 };
 
+#define BCM2835_DMA_WAIT_CYCLES	0  /* Slow down DMA transfers: 0-31 */
+
 #define BCM2835_DMA_CS		0x00
 #define BCM2835_DMA_ADDR	0x04
 #define BCM2835_DMA_SOURCE_AD	0x0c
@@ -111,12 +112,16 @@ struct bcm2835_desc {
 #define BCM2835_DMA_RESET	BIT(31) /* WO, self clearing */
 
 #define BCM2835_DMA_INT_EN	BIT(0)
+#define BCM2835_DMA_WAIT_RESP	BIT(3)
 #define BCM2835_DMA_D_INC	BIT(4)
+#define BCM2835_DMA_D_WIDTH	BIT(5)
 #define BCM2835_DMA_D_DREQ	BIT(6)
 #define BCM2835_DMA_S_INC	BIT(8)
+#define BCM2835_DMA_S_WIDTH	BIT(9)
 #define BCM2835_DMA_S_DREQ	BIT(10)
 
 #define BCM2835_DMA_PER_MAP(x)	((x) << 16)
+#define BCM2835_DMA_WAITS(x)	(((x) & 0x1f) << 21)
 
 #define BCM2835_DMA_DATA_TYPE_S8	1
 #define BCM2835_DMA_DATA_TYPE_S16	2
@@ -130,6 +135,14 @@ struct bcm2835_desc {
 #define BCM2835_DMA_CHAN(n)	((n) << 8) /* Base address */
 #define BCM2835_DMA_CHANIO(base, n) ((base) + BCM2835_DMA_CHAN(n))
 
+#define MAX_NORMAL_TRANSFER	SZ_1G
+/*
+ * Max length on a Lite channel is 65535 bytes.
+ * DMA handles byte-enables on SDRAM reads and writes even on 128-bit accesses,
+ * but byte-enables don't exist on peripheral addresses, so align to 32-bit.
+ */
+#define MAX_LITE_TRANSFER	(SZ_64K - 4)
+
 static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
 {
 	return container_of(d, struct bcm2835_dmadev, ddev);
@@ -226,12 +239,18 @@ static irqreturn_t bcm2835_dma_callback(
 	d = c->desc;
 
 	if (d) {
-		/* TODO Only works for cyclic DMA */
-		vchan_cyclic_callback(&d->vd);
-	}
+		if (c->cyclic) {
+			vchan_cyclic_callback(&d->vd);
 
-	/* Keep the DMA engine running */
-	writel(BCM2835_DMA_ACTIVE, c->chan_base + BCM2835_DMA_CS);
+			/* Keep the DMA engine running */
+			writel(BCM2835_DMA_ACTIVE,
+			       c->chan_base + BCM2835_DMA_CS);
+
+		} else {
+			vchan_cookie_complete(&c->desc->vd);
+			bcm2835_dma_start_desc(c);
+		}
+	}
 
 	spin_unlock_irqrestore(&c->vc.lock, flags);
 
@@ -339,8 +358,6 @@ static void bcm2835_dma_issue_pending(st
 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
 	unsigned long flags;
 
-	c->cyclic = true; /* Nothing else is implemented */
-
 	spin_lock_irqsave(&c->vc.lock, flags);
 	if (vchan_issue_pending(&c->vc) && !c->desc)
 		bcm2835_dma_start_desc(c);
@@ -358,7 +375,7 @@ static struct dma_async_tx_descriptor *b
 	struct bcm2835_desc *d;
 	dma_addr_t dev_addr;
 	unsigned int es, sync_type;
-	unsigned int frame;
+	unsigned int frame, max_size;
 	int i;
 
 	/* Grab configuration */
@@ -393,7 +410,12 @@ static struct dma_async_tx_descriptor *b
 
 	d->c = c;
 	d->dir = direction;
-	d->frames = buf_len / period_len;
+	if (c->ch >= 8) /* LITE channel */
+		max_size = MAX_LITE_TRANSFER;
+	else
+		max_size = MAX_NORMAL_TRANSFER;
+	period_len = min(period_len, max_size);
+	d->frames = (buf_len - 1) / (period_len + 1);
 
 	d->cb_list = kcalloc(d->frames, sizeof(*d->cb_list), GFP_KERNEL);
 	if (!d->cb_list) {
@@ -441,17 +463,171 @@ static struct dma_async_tx_descriptor *b
 				BCM2835_DMA_PER_MAP(c->dreq);
 
 		/* Length of a frame */
-		control_block->length = period_len;
+		if (frame != d->frames - 1)
+			control_block->length = period_len;
+		else
+			control_block->length = buf_len - (d->frames - 1) *
+						period_len;
 		d->size += control_block->length;
 
 		/*
 		 * Next block is the next frame.
-		 * This DMA engine driver currently only supports cyclic DMA.
+		 * This function is called on cyclic DMA transfers.
 		 * Therefore, wrap around at number of frames.
 		 */
 		control_block->next = d->cb_list[((frame + 1) % d->frames)].paddr;
 	}
 
+	c->cyclic = true;
+
+	return vchan_tx_prep(&c->vc, &d->vd, flags);
+}
+
+static struct dma_async_tx_descriptor *
+bcm2835_dma_prep_slave_sg(struct dma_chan *chan,
+			  struct scatterlist *sgl,
+			  unsigned int sg_len,
+			  enum dma_transfer_direction direction,
+			  unsigned long flags, void *context)
+{
+	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
+	enum dma_slave_buswidth dev_width;
+	struct bcm2835_desc *d;
+	dma_addr_t dev_addr;
+	struct scatterlist *sgent;
+	unsigned int i, sync_type, split_cnt, max_size;
+
+	if (!is_slave_direction(direction)) {
+		dev_err(chan->device->dev, "direction not supported\n");
+		return NULL;
+	}
+
+	if (direction == DMA_DEV_TO_MEM) {
+		dev_addr = c->cfg.src_addr;
+		dev_width = c->cfg.src_addr_width;
+		sync_type = BCM2835_DMA_S_DREQ;
+	} else {
+		dev_addr = c->cfg.dst_addr;
+		dev_width = c->cfg.dst_addr_width;
+		sync_type = BCM2835_DMA_D_DREQ;
+	}
+
+	/* Bus width translates to the element size (ES) */
+	switch (dev_width) {
+	case DMA_SLAVE_BUSWIDTH_4_BYTES:
+		break;
+	default:
+		dev_err(chan->device->dev, "buswidth not supported: %i\n",
+			dev_width);
+		return NULL;
+	}
+
+	/* Allocate and setup the descriptor. */
+	d = kzalloc(sizeof(*d), GFP_NOWAIT);
+	if (!d)
+		return NULL;
+
+	d->dir = direction;
+
+	if (c->ch >= 8) /* LITE channel */
+		max_size = MAX_LITE_TRANSFER;
+	else
+		max_size = MAX_NORMAL_TRANSFER;
+
+	/*
+	 * Store the length of the SG list in d->frames
+	 * taking care to account for splitting up transfers
+	 * too large for a LITE channel
+	 */
+	d->frames = 0;
+	for_each_sg(sgl, sgent, sg_len, i) {
+		unsigned int len = sg_dma_len(sgent);
+
+		d->frames += len / max_size + 1;
+	}
+
+	/* Allocate memory for control blocks */
+	d->control_block_size = d->frames * sizeof(struct bcm2835_dma_cb);
+	d->control_block_base = dma_zalloc_coherent(chan->device->dev,
+			d->control_block_size, &d->control_block_base_phys,
+			GFP_NOWAIT);
+	if (!d->control_block_base) {
+		kfree(d);
+		return NULL;
+	}
+
+	/*
+	 * Iterate over all SG entries, create a control block
+	 * for each frame and link them together.
+	 * Count the number of times an SG entry had to be split
+	 * as a result of using a LITE channel
+	 */
+	split_cnt = 0;
+
+	for_each_sg(sgl, sgent, sg_len, i) {
+		unsigned int j;
+		dma_addr_t addr = sg_dma_address(sgent);
+		unsigned int len = sg_dma_len(sgent);
+
+		for (j = 0; j < len; j += max_size) {
+			struct bcm2835_dma_cb *control_block =
+				&d->control_block_base[i + split_cnt];
+
+			/* Setup addresses */
+			if (d->dir == DMA_DEV_TO_MEM) {
+				control_block->info = BCM2835_DMA_D_INC |
+						      BCM2835_DMA_D_WIDTH |
+						      BCM2835_DMA_S_DREQ;
+				control_block->src = dev_addr;
+				control_block->dst = addr + (dma_addr_t)j;
+			} else {
+				control_block->info = BCM2835_DMA_S_INC |
+						      BCM2835_DMA_S_WIDTH |
+						      BCM2835_DMA_D_DREQ;
+				control_block->src = addr + (dma_addr_t)j;
+				control_block->dst = dev_addr;
+			}
+
+			/* Common part */
+			control_block->info |=
+				BCM2835_DMA_WAITS(BCM2835_DMA_WAIT_CYCLES);
+			control_block->info |= BCM2835_DMA_WAIT_RESP;
+
+			/* Enable */
+			if (i == sg_len - 1 && len - j <= max_size)
+				control_block->info |= BCM2835_DMA_INT_EN;
+
+			/* Setup synchronization */
+			if (sync_type)
+				control_block->info |= sync_type;
+
+			/* Setup DREQ channel */
+			if (c->dreq)
+				control_block->info |=
+					BCM2835_DMA_PER_MAP(c->dreq);
+
+			/* Length of a frame */
+			control_block->length = min(len - j, max_size);
+			d->size += control_block->length;
+
+			if (i < sg_len - 1 || len - j > max_size) {
+				/* Next block is the next frame. */
+				control_block->next =
+					d->control_block_base_phys +
+					sizeof(struct bcm2835_dma_cb) *
+					(i + split_cnt + 1);
+			} else {
+				/* Next block is empty. */
+				control_block->next = 0;
+			}
+
+			if (len - j > max_size)
+				split_cnt++;
+		}
+	}
+
+	c->cyclic = false;
+
 	return vchan_tx_prep(&c->vc, &d->vd, flags);
 error_cb:
 	i--;
@@ -620,6 +796,7 @@ static int bcm2835_dma_probe(struct plat
 	od->ddev.device_tx_status = bcm2835_dma_tx_status;
 	od->ddev.device_issue_pending = bcm2835_dma_issue_pending;
 	od->ddev.device_prep_dma_cyclic = bcm2835_dma_prep_dma_cyclic;
+	od->ddev.device_prep_slave_sg = bcm2835_dma_prep_slave_sg;
 	od->ddev.device_config = bcm2835_dma_slave_config;
 	od->ddev.device_terminate_all = bcm2835_dma_terminate_all;
 	od->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
@@ -708,4 +885,5 @@ module_platform_driver(bcm2835_dma_drive
 MODULE_ALIAS("platform:bcm2835-dma");
 MODULE_DESCRIPTION("BCM2835 DMA engine driver");
 MODULE_AUTHOR("Florian Meier <florian.meier@koalo.de>");
+MODULE_AUTHOR("Gellert Weisz <gellert@raspberrypi.org>");
 MODULE_LICENSE("GPL v2");
