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Date:   Fri, 26 Jul 2019 10:42:40 +0200
From:   Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>
To:     Jan Kotas <jank@...ence.com>
Cc:     "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "tiwai@...e.de" <tiwai@...e.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Vinod Koul <vkoul@...nel.org>, Mark Brown <broonie@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        "slawomir.blauciak@...el.com" <slawomir.blauciak@...el.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [alsa-devel] [RFC PATCH 17/40] soundwire: bus: use
 runtime_pm_get_sync/pm when enabled

On Fri, Jul 26, 2019 at 08:33:35AM +0000, Jan Kotas wrote:
> 
> 
> > On 26 Jul 2019, at 10:22, Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com> wrote:
> > 
> > EXTERNAL MAIL
> > 
> > 
> > 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://urldefense.proofpoint.com/v2/url?u=https-3A__patchwork.kernel.org_patch_10887405_&d=DwIBAg&c=aUq983L2pue2FqKFoP6PGHMJQyoJ7kl3s3GZ-_haXqY&r=g7GAQENVXx_RQdyXHInPMg&m=i_0S359hFIVqNgv3fR5_MNzDOHP99trdXszZ-FMiQEE&s=ddktFZYlePh-bC7kXeoKWt4QomupzHATK4FLY4oSWKA&e= 
> >> 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?
> > 
> 
> Hi,
> 
> In such case ret < 0 will not be true, which I think is fine,
> if I’m understanding you correctly.

Yes, if we just have to distinguish a single case "RT-PM is enabled and it failed."
Which is indeed the case here, it seems. However if we want to check whether RT-PM
is disabled after a call to, say, pm_runtime_get_sync(), then just checking
-EACCESS isn't always enough - there can be cases when RT-PM is disabled and the
return code is 1. But yes, just for checking for failures, like here, it should be
fine.

Thanks
Guennadi

> >> Jan
> >> 
> >>> On 26 Jul 2019, at 09:39, Guennadi Liakhovetski <guennadi.liakhovetski@...ux.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@...aro.org>
> >>>> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.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
> >>>> 
> >>>> _______________________________________________
> >>>> Alsa-devel mailing list
> >>>> Alsa-devel@...a-project.org
> >>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__mailman.alsa-2Dproject.org_mailman_listinfo_alsa-2Ddevel&d=DwIBAg&c=aUq983L2pue2FqKFoP6PGHMJQyoJ7kl3s3GZ-_haXqY&r=g7GAQENVXx_RQdyXHInPMg&m=vETGQLSPeGb7K_ZsXv4Tl3VFfdXzyummTDga97ozJcg&s=LiW4SToh5U0zhnkox54oRhJ1u3vFNbBB9nmzRDuCDjI&e=
> >> 
> >> _______________________________________________
> >> Alsa-devel mailing list
> >> Alsa-devel@...a-project.org
> >> https://urldefense.proofpoint.com/v2/url?u=https-3A__mailman.alsa-2Dproject.org_mailman_listinfo_alsa-2Ddevel&d=DwIBAg&c=aUq983L2pue2FqKFoP6PGHMJQyoJ7kl3s3GZ-_haXqY&r=g7GAQENVXx_RQdyXHInPMg&m=i_0S359hFIVqNgv3fR5_MNzDOHP99trdXszZ-FMiQEE&s=RxPHxKfI3v6Fkh7qzKjq8sNi-5QMoY8XfyMDSquA38o&e= 
> 
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