omap: dma: Support for prefetch in destination synchronizedtransfer

Omap DMA controller can prefetch data in advance in case of
destination synchronized data transfer. This may increase
performance when target HW block doesn't have fifo.
Data is waiting for transfer request in DMA fifo instead of read from memory.

Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/dma.c

@@ -290,7 +290,7 @@ void omap_set_dma_transfer_params(int lch, int data_type, int elem_count,
 		val = dma_read(CCR(lch));
 
 		/* DMA_SYNCHRO_CONTROL_UPPER depends on the channel number */
-		val &= ~((3 << 19) | 0x1f);
+		val &= ~((1 << 23) | (3 << 19) | 0x1f);
 		val |= (dma_trigger & ~0x1f) << 14;
 		val |= dma_trigger & 0x1f;
 
@@ -304,11 +304,14 @@ void omap_set_dma_transfer_params(int lch, int data_type, int elem_count,
 		else
 			val &= ~(1 << 18);
 
-		if (src_or_dst_synch)
-			val |= 1 << 24;		/* source synch */
-		else
+		if (src_or_dst_synch == OMAP_DMA_DST_SYNC_PREFETCH) {
 			val &= ~(1 << 24);	/* dest synch */
-
+			val |= (1 << 23);	/* Prefetch */
+		} else if (src_or_dst_synch) {
+			val |= 1 << 24;		/* source synch */
+		} else {
+			val &= ~(1 << 24);	/* dest synch */
+		}
 		dma_write(val, CCR(lch));
 	}
 

arch/arm/plat-omap/include/plat/dma.h

@@ -345,6 +345,7 @@
 #define OMAP_DMA_SYNC_BLOCK		0x02
 #define OMAP_DMA_SYNC_PACKET		0x03
 
+#define OMAP_DMA_DST_SYNC_PREFETCH	0x02
 #define OMAP_DMA_SRC_SYNC		0x01
 #define OMAP_DMA_DST_SYNC		0x00