Re: [PATCH] ALSA: ASoC: move dma_data from snd_soc_dai to snd_soc_pcm_stream

[Peter Ujfalusi <peter.ujfalusi@nokia.com>]

Hello,

On Thursday 18 March 2010 21:23:58 ext Daniel Mack wrote:
> This fixes a memory corruption when ASoC devices are used in
> full-duplex mode. Specifically for pxa-ssp code, where this pointer
> is dynamically allocated for each direction and destroyed upon each
> stream start.
> 
> All other platforms are fixed blindly, I couldn't even compile-test
> them. Sorry for any breakage I may have caused.

At least the OMAP code should not be affected by the bug, that you have with the 
pxa-ssp. I think the bug could be also fixed within the pxa code, since the 
whole thing goes down to inconsistent memory management within the pxa code.

Having said that, I do think having separate dma_data for each streams is a 
really good idea.
One thing that I can think of in OMAP case, where this could fix a nasty race 
condition is (have never seen it, but it is in theory possible):
Also in duplex case, when the second hw_param gets called after the first 
omap_mcbsp_hw_params, and before the omap_pcm_hw_params for the first stream.
The second omap_mcbsp_hw_params will override the dma_data, thus we would set 
bogus parameters for the first stream.

I do have comment however (down).

For the omap-mcbsp.c and omap-pcm.c changes:
Acked-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>

..

> b/sound/soc/atmel/atmel_ssc_dai.c index e588e63..0b59806 100644
> --- a/sound/soc/atmel/atmel_ssc_dai.c
> +++ b/sound/soc/atmel/atmel_ssc_dai.c
> @@ -363,12 +363,12 @@ static int atmel_ssc_hw_params(struct
> snd_pcm_substream *substream, ssc_p->dma_params[dir] = dma_params;
> 
>         /*
> -        * The cpu_dai->dma_data field is only used to communicate the
> -        * appropriate DMA parameters to the pcm driver hw_params()
> +        * The snd_soc_pcm_stream->dma_data field is only used to
> communicate +        * the appropriate DMA parameters to the pcm driver
> hw_params() * function.  It should not be used for other purposes
>          * as it is common to all substreams.
>          */
> -       rtd->dai->cpu_dai->dma_data = dma_params;
> +       snd_soc_dai_set_dma_data(rtd->dai->cpu_dai, substream, dma_params);
> 
>         channels = params_channels(params);
> 
> diff --git a/sound/soc/davinci/davinci-i2s.c
> b/sound/soc/davinci/davinci-i2s.c index 6362ca0..4aad7ec 100644
> --- a/sound/soc/davinci/davinci-i2s.c
> +++ b/sound/soc/davinci/davinci-i2s.c
> @@ -585,7 +585,8 @@ static int davinci_i2s_probe(struct platform_device
> *pdev) dev->dma_params[SNDRV_PCM_STREAM_CAPTURE].channel = res->start;
> 
>         davinci_i2s_dai.private_data = dev;
> -       davinci_i2s_dai.dma_data = dev->dma_params;
> +       davinci_i2s_dai.capture.dma_data = dev->dma_params;
> +       davinci_i2s_dai.playback.dma_data = dev->dma_params;

Would not be more consistent around the places to actually use the
		snd_soc_dai_set_dma_data(...);
function instead of direct assignment here, and there randomly?

>         ret = snd_soc_register_dai(&davinci_i2s_dai);
>         if (ret != 0)
>                 goto err_free_mem;

-- 
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