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

[Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>]

Hi Jan,

On Fri, Jul 26, 2019 at 07:47:04AM +0000, Jan Kotas wrote:
> Hello,
> 
> I while back I proposed a patch for this, but it went nowhere.
> 
> https://patchwork.kernel.org/patch/10887405/
> Maybe something similar can be implemented?

Yes, I was thinking about checkint -EACCESS too, but then I noticed this code
in rpm_resume():

	else if (dev->power.disable_depth == 1 && dev->power.is_suspended
	    && dev->power.runtime_status == RPM_ACTIVE)
		retval = 1;

i.e. if RT-PM is disabled on the device (but only exactly once?..) and it's
active and the device is suspended for a system suspend, the function will
return 1. I don't understand the logic of this code, but it seems to me it
could break the -EACCESS check?

Thanks
Guennadi

> Jan
> 
> > On 26 Jul 2019, at 09:39, Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com> wrote:
> > 
> > EXTERNAL MAIL
> > 
> > 
> > Hi Pierre,
> > 
> > I might be wrong but this doesn't seem right to me. (Supposedly) all RT-PM
> > functions check for "enabled" internally. The only thing that can happen is
> > that if RT-PM isn't enabled some of those functions will return an error.
> > So, in those cases where the return value of RT-PM functions isn't checked,
> > I don't think you need to do anything. Where it is checked maybe do
> > 
> > +	if (ret < 0 && pm_runtime_enabled(slave->bus->dev))
> > 
> > Thanks
> > Guennadi
> > 
> > On Thu, Jul 25, 2019 at 06:40:09PM -0500, 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);
> >> 
> >> 	return ret;
> >> }
> >> @@ -359,13 +363,16 @@ int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
> >> 			   slave->dev_num, SDW_MSG_FLAG_WRITE, 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);
> >> 
> >> 	return ret;
> >> }
> >> -- 
> >> 2.20.1
> >> 
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