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authorSascha Hauer <s.hauer@pengutronix.de>2009-11-18 15:21:44 +0100
committerSascha Hauer <s.hauer@pengutronix.de>2009-11-24 08:40:14 +0100
commit4998f1a30cf8e21c5bc0766fde4fa58e1adabd72 (patch)
treec58feecc32d7fbe7d128094a72ff9e4471fcdd3d
parent74b2a70e34c69687f82b1319a358b21afeea497c (diff)
downloadlinux-4998f1a30cf8e21c5bc0766fde4fa58e1adabd72.tar.bz2
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>
-rw-r--r--arch/arm/plat-mxc/dma-mx1-mx2.c3
-rw-r--r--arch/arm/plat-mxc/include/mach/dma-mx1-mx2.h8
2 files changed, 10 insertions, 1 deletions
diff --git a/arch/arm/plat-mxc/dma-mx1-mx2.c b/arch/arm/plat-mxc/dma-mx1-mx2.c
index 77646436c00e..9c1b3f9c4f4d 100644
--- a/arch/arm/plat-mxc/dma-mx1-mx2.c
+++ b/arch/arm/plat-mxc/dma-mx1-mx2.c
@@ -156,7 +156,8 @@ static inline int imx_dma_sg_next(int channel, struct scatterlist *sg)
}
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 b3876cc238ca..07be8ad7ec37 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 @@ imx_dma_setup_single(int channel, dma_addr_t dma_address,
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,