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mxc: mx1/mx2 DMA: add a possibility to create an endless DMA transfer

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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>
This commit is contained in:
Sascha Hauer 2009-11-18 15:21:44 +01:00
parent 74b2a70e34
commit 4998f1a30c
2 changed files with 10 additions and 1 deletions
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3
arch/arm/plat-mxc/dma-mx1-mx2.c
View File

@ -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));

8
arch/arm/plat-mxc/include/mach/dma-mx1-mx2.h
View File

@ -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,