mxc: mx1/mx2 DMA: add a possibility to create an endless DMA transfer
This is useful for audio where we do not want to setup a new scatterlist
after playing 4GB of audio data. This would cause skips in the playback.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/arch/arm/plat-mxc/dma-mx1-mx2.c b/arch/arm/plat-mxc/dma-mx1-mx2.c
index 7764643..9c1b3f9 100644
--- a/arch/arm/plat-mxc/dma-mx1-mx2.c
+++ b/arch/arm/plat-mxc/dma-mx1-mx2.c
@@ -156,7 +156,8 @@
}
now = min(imxdma->resbytes, sg->length);
- imxdma->resbytes -= now;
+ if (imxdma->resbytes != IMX_DMA_LENGTH_LOOP)
+ imxdma->resbytes -= now;
if ((imxdma->dma_mode & DMA_MODE_MASK) == DMA_MODE_READ)
__raw_writel(sg->dma_address, DMA_BASE + DMA_DAR(channel));
diff --git a/arch/arm/plat-mxc/include/mach/dma-mx1-mx2.h b/arch/arm/plat-mxc/include/mach/dma-mx1-mx2.h
index b3876cc..07be8ad 100644
--- a/arch/arm/plat-mxc/include/mach/dma-mx1-mx2.h
+++ b/arch/arm/plat-mxc/include/mach/dma-mx1-mx2.h
@@ -58,6 +58,14 @@
unsigned int dma_length, unsigned int dev_addr,
unsigned int dmamode);
+
+/*
+ * Use this flag as the dma_length argument to imx_dma_setup_sg()
+ * to create an endless running dma loop. The end of the scatterlist
+ * must be linked to the beginning for this to work.
+ */
+#define IMX_DMA_LENGTH_LOOP ((unsigned int)-1)
+
int
imx_dma_setup_sg(int channel, struct scatterlist *sg,
unsigned int sgcount, unsigned int dma_length,
