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Subject[PATCH] dmaengine: bcm2835: Add slave dma support
Date
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 with the bcm2835-mmc driver from the same repo.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---

Gellert Weisz has ended his internship with Raspberry Pi Trading and
was not available to sign off this patch.

Changes from original code:
Remove slave_id use.
SDHCI_BCM_DMA_WAITS changed to BCM2835_DMA_WAIT_CYCLES.
Use SZ_* macros instead of decimal values.
Change MAX_LITE_TRANSFER from 32k to 64K - 1.
Fix several whitespace issues.

Lee Jones' comments in previous email to Piotr Król:
Remove __func__ from dev_err message.
Cleanup comments.


Quick testing:
Enable CONFIG_DMA_BCM2835
Apply patch: https://gist.github.com/notro/0c9184df1b43a793f006


drivers/dma/bcm2835-dma.c | 200 ++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 186 insertions(+), 14 deletions(-)

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index c92d6a7..4230aac 100644
--- 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
@@ -89,6 +88,8 @@ 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
@@ -105,12 +106,16 @@ 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
@@ -124,6 +129,9 @@ 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_LITE_TRANSFER (SZ_64K - 1)
+#define MAX_NORMAL_TRANSFER SZ_1G
+
static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
{
return container_of(d, struct bcm2835_dmadev, ddev);
@@ -217,12 +225,18 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data)
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);

@@ -323,8 +337,6 @@ static void bcm2835_dma_issue_pending(struct dma_chan *chan)
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);
@@ -342,7 +354,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
struct bcm2835_desc *d;
dma_addr_t dev_addr;
unsigned int es, sync_type;
- unsigned int frame;
+ unsigned int frame, max_size;

/* Grab configuration */
if (!is_slave_direction(direction)) {
@@ -375,7 +387,12 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
return NULL;

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);

/* Allocate memory for control blocks */
d->control_block_size = d->frames * sizeof(struct bcm2835_dma_cb);
@@ -420,12 +437,16 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
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->control_block_base_phys +
@@ -433,6 +454,155 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
* ((frame + 1) % d->frames);
}

+ 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 es, sync_type;
+ unsigned int i, j, splitct, 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:
+ es = BCM2835_DMA_DATA_TYPE_S32;
+ break;
+ default:
+ 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 += 1 + len / max_size;
+ }
+
+ /* 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
+ */
+ splitct = 0;
+
+ for_each_sg(sgl, sgent, sg_len, i) {
+ 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 + splitct];
+
+ /* 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 != 0)
+ 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 + splitct + 1);
+ } else {
+ /* Next block is empty. */
+ control_block->next = 0;
+ }
+
+ if (len - j > max_size)
+ splitct++;
+ }
+ }
+
+ c->cyclic = false;
+
return vchan_tx_prep(&c->vc, &d->vd, flags);
}

@@ -590,6 +760,7 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
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);
@@ -678,4 +849,5 @@ module_platform_driver(bcm2835_dma_driver);
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");
--
2.2.2


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