At Thu, 28 Jun 2012 13:09:36 +0200, Lars-Peter Clausen wrote:
On 06/28/2012 09:01 AM, Laxman Dewangan wrote:
The pcm mmap for the substream dma buffer is done using the dma_mmap_writecombine(). Some of the chip sound driver like Spear, Tegra, Davinci, ep93xx,snd_imx, snd_mxs, NUC900, OMAP, Samsung are doing this mapping locally. Add api in the snd dmaengine driver so that different client of snd dmaengine can use this rather than implementing locally.
This is not really related to the dmaengine pcm driver. It's more of a coincidence that all upstream drivers which use the dmaengine pcm driver also use write-combined memory. In my opinion it would be better to add this to the ALSA core. Now that there is a generic dma_mmap_writecombine it may make sense to integrate this with snd_pcm_lib_default_mmap.
Agreed.
Also, it must be portable. So far, only ARM has dma_mmap_writecombine(), thus the build on other arch would fail as is.
thanks,
Takashi
- Lars
Signed-off-by: Laxman Dewangan ldewangan@nvidia.com
include/sound/dmaengine_pcm.h | 2 ++ sound/soc/soc-dmaengine-pcm.c | 17 +++++++++++++++++ 2 files changed, 19 insertions(+), 0 deletions(-)
diff --git a/include/sound/dmaengine_pcm.h b/include/sound/dmaengine_pcm.h index b877334..15c0d3c 100644 --- a/include/sound/dmaengine_pcm.h +++ b/include/sound/dmaengine_pcm.h @@ -47,4 +47,6 @@ int snd_dmaengine_pcm_close(struct snd_pcm_substream *substream);
struct dma_chan *snd_dmaengine_pcm_get_chan(struct snd_pcm_substream *substream);
+int snd_dmaengine_pcm_mmap_writecombine(struct snd_pcm_substream *substream,
struct vm_area_struct *vma);#endif diff --git a/sound/soc/soc-dmaengine-pcm.c b/sound/soc/soc-dmaengine-pcm.c index 5df529e..6535eb3 100644 --- a/sound/soc/soc-dmaengine-pcm.c +++ b/sound/soc/soc-dmaengine-pcm.c @@ -21,6 +21,7 @@ #include <linux/module.h> #include <linux/init.h> #include <linux/dmaengine.h> +#include <linux/dma-mapping.h> #include <linux/slab.h> #include <sound/pcm.h> #include <sound/pcm_params.h> @@ -313,3 +314,19 @@ int snd_dmaengine_pcm_close(struct snd_pcm_substream *substream) return 0; } EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_close);
+/**
- snd_dmaengine_pcm_mmap_writecombine - mmap stream dma buffer using
- dma_mmap_writecombine().
- @substream: PCM substream
- @vma: VM area.
- */
+int snd_dmaengine_pcm_mmap_writecombine(struct snd_pcm_substream *substream,
struct vm_area_struct *vma)+{
- struct snd_pcm_runtime *runtime = substream->runtime;
- return dma_mmap_writecombine(substream->pcm->card->dev, vma,
runtime->dma_area, runtime->dma_addr, runtime->dma_bytes);+} +EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_mmap_writecombine);