[PATCH v2 04/15] dmaengine: bcm2835: Support dma flags for multi-beat burst

[Andrea della Porta]

From: Dom Cobley <popcornmix@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Andrea della Porta <andrea.porta@xxxxxxxx>
---
 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