Re: [RFC PATCH 17/40] soundwire: bus: use runtime_pm_get_sync/pm when enabled

Pierre-Louis Bossart
2019-07-26T18:09:01Z

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@linaro.org>
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@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