[alsa-devel] [PATCH 1/5] ASoC: Hold runtime PM references to components of active DAIs

[Peter Ujfalusi]

On 12/05/2011 02:01 AM, Mark Brown wrote:
> Every device that implements runtime power management for DAIs is doing
> it in pretty much the same way: in the startup callback they take a
> runtime PM reference and then in the shutdown callback they release that
> reference, keeping the device active while the DAI is active. Given the
> frequency with which this is done and the obviousness of the need to keep
> the device active in this period factor the code out into the core, taking
> references on the device for each CPU DAI, CODEC DAI and DMA device in the
> core.
> 
> As runtime PM is reference counted this shouldn't interfere with any
> other reference holding by the drivers, and since (in common with the
> existing implementations) we don't check for errors on enabling it
> shouldn't matter if the device actually has runtime PM enabled or not.
> 
> Signed-off-by: Mark Brown <broonie at opensource.wolfsonmicro.com>
> ---
>  sound/soc/soc-pcm.c |   15 +++++++++++++++
>  1 files changed, 15 insertions(+), 0 deletions(-)
> 
> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
> index 49aa71e..8aa7cec 100644
> --- a/sound/soc/soc-pcm.c
> +++ b/sound/soc/soc-pcm.c
> @@ -19,6 +19,7 @@
>  #include <linux/kernel.h>
>  #include <linux/init.h>
>  #include <linux/delay.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/slab.h>
>  #include <linux/workqueue.h>
>  #include <sound/core.h>
> @@ -77,6 +78,10 @@ static int soc_pcm_open(struct snd_pcm_substream *substream)
>  	struct snd_soc_dai_driver *codec_dai_drv = codec_dai->driver;
>  	int ret = 0;
>  
> +	pm_runtime_get_sync(cpu_dai->dev);
> +	pm_runtime_get_sync(codec_dai->dev);
> +	pm_runtime_get_sync(platform->dev);
> +
>  	mutex_lock_nested(&rtd->pcm_mutex, rtd->pcm_subclass);

I think it is better to move the pm_runtime_get_sync calls after the
mutex_lock_nested() to be really safe (and to not change the way DAI
drivers were handling the pm_runtime).

-- 
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