[alsa-devel] [RFC PATCH 17/40] soundwire: bus: use runtime_pm_get_sync/pm when enabled

[Pierre-Louis Bossart]

This thread became unreadable with interleaved top-posting, allow me 
restate the options and ask PM folks what they think

On 7/25/19 6:40 PM, Pierre-Louis Bossart wrote:
> Not all platforms support runtime_pm for now, let's use runtime_pm
> only when enabled.
> 
> Suggested-by: Srinivas Kandagatla <srinivas.kandagatla at linaro.org>
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> ---
>   drivers/soundwire/bus.c | 25 ++++++++++++++++---------
>   1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
> index 5ad4109dc72f..0a45dc5713df 100644
> --- a/drivers/soundwire/bus.c
> +++ b/drivers/soundwire/bus.c
> @@ -332,12 +332,16 @@ int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
>   	if (ret < 0)
>   		return ret;
>   
> -	ret = pm_runtime_get_sync(slave->bus->dev);
> -	if (ret < 0)
> -		return ret;
> +	if (pm_runtime_enabled(slave->bus->dev)) {
> +		ret = pm_runtime_get_sync(slave->bus->dev);
> +		if (ret < 0)
> +			return ret;
> +	}
>   
>   	ret = sdw_transfer(slave->bus, &msg);
> -	pm_runtime_put(slave->bus->dev);
> +
> +	if (pm_runtime_enabled(slave->bus->dev))
> +		pm_runtime_put(slave->bus->dev);

This is option1: we explicitly test if pm_runtime is enabled before 
calling _get_sync() and _put()

option2 (suggested by Jan Kotas): catch the -EACCESS error code

  	ret = pm_runtime_get_sync(slave->bus->dev);
-	if (ret < 0)
+	if (ret < 0 && ret != -EACCES)
  		return ret;

option3: ignore the return value as done in quite a few drivers

Are there any other options? I am personally surprised this is not 
handled in the pm_runtime core, not sure why users need to test for this?

Thanks
Pierre