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Subject[PATCH v2 04/15] dmaengine: bcm2835: Support dma flags for multi-beat burst
Date
From: Dom Cobley <popcornmix@gmail.com>

Add a control bit to enable a multi-beat burst on a DMA.
This improves DMA performance and is required for HDMI audio.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
---
drivers/dma/bcm2835-dma.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 69a77caf78cc..d442f8728c05 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -137,6 +137,7 @@ struct bcm2835_desc {
#define BCM2835_DMA_S_DREQ BIT(10) /* enable SREQ for source */
#define BCM2835_DMA_S_IGNORE BIT(11) /* ignore source reads - read 0 */
#define BCM2835_DMA_BURST_LENGTH(x) (((x) & 15) << 12)
+#define BCM2835_DMA_GET_BURST_LENGTH(x) (((x) >> 12) & 15)
#define BCM2835_DMA_CS_FLAGS(x) ((x) & (BCM2835_DMA_PRIORITY(15) | \
BCM2835_DMA_PANIC_PRIORITY(15) | \
BCM2835_DMA_WAIT_FOR_WRITES | \
@@ -160,6 +161,11 @@ struct bcm2835_desc {
#define WIDE_DEST(x) (((x) & BCM2835_DMA_WIDE_DEST) ? \
BCM2835_DMA_D_WIDTH : 0)

+/* A fake bit to request that the driver requires multi-beat burst */
+#define BCM2835_DMA_BURST BIT(30)
+#define BURST_LENGTH(x) (((x) & BCM2835_DMA_BURST) ? \
+ BCM2835_DMA_BURST_LENGTH(3) : 0)
+
/* debug register bits */
#define BCM2835_DMA_DEBUG_LAST_NOT_SET_ERR BIT(0)
#define BCM2835_DMA_DEBUG_FIFO_ERR BIT(1)
@@ -637,7 +643,8 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_memcpy(
struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
struct bcm2835_desc *d;
u32 info = BCM2835_DMA_D_INC | BCM2835_DMA_S_INC |
- WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) | WIDE_DEST(c->dreq);
+ WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) |
+ WIDE_DEST(c->dreq) | BURST_LENGTH(c->dreq);
u32 extra = BCM2835_DMA_INT_EN;
size_t max_len = bcm2835_dma_max_frame_length(c);
size_t frames;
@@ -668,8 +675,8 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
struct bcm2835_desc *d;
dma_addr_t src = 0, dst = 0;
- u32 info = WAIT_RESP(c->dreq) |
- WIDE_SOURCE(c->dreq) | WIDE_DEST(c->dreq);
+ u32 info = WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) |
+ WIDE_DEST(c->dreq) | BURST_LENGTH(c->dreq);
u32 extra = BCM2835_DMA_INT_EN;
size_t frames;

@@ -721,7 +728,8 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
struct bcm2835_desc *d;
dma_addr_t src, dst;
- u32 info = WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) | WIDE_DEST(c->dreq);
+ u32 info = WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) |
+ WIDE_DEST(c->dreq) | BURST_LENGTH(c->dreq);
u32 extra = 0;
size_t max_len = bcm2835_dma_max_frame_length(c);
size_t frames;
--
2.35.3

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