From 4998f1a30cf8e21c5bc0766fde4fa58e1adabd72 Mon Sep 17 00:00:00 2001 From: Sascha Hauer Date: Wed, 18 Nov 2009 15:21:44 +0100 Subject: [PATCH] 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 --- arch/arm/plat-mxc/dma-mx1-mx2.c | 3 ++- arch/arm/plat-mxc/include/mach/dma-mx1-mx2.h | 8 ++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) 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, -- 2.30.2