linux-kernel - Re: [alsa-devel] [RFC PATCH 17/40] soundwire: bus: use runtime_pm_get

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Message-ID: <20190730155809.GS23480@smile.fi.intel.com>
Date:   Tue, 30 Jul 2019 18:58:09 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-pm@...r.kernel.org,
        tiwai@...e.de, gregkh@...uxfoundation.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, vkoul@...nel.org, broonie@...nel.org,
        srinivas.kandagatla@...aro.org, jank@...ence.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 Tue, Jul 30, 2019 at 07:57:46AM -0500, Pierre-Louis Bossart wrote:
> On 7/30/19 6:21 AM, Andy Shevchenko wrote:
> > On Mon, Jul 29, 2019 at 05:07:39PM -0500, Pierre-Louis Bossart wrote:
> > > On 7/26/19 2:08 PM, Andy Shevchenko wrote:
> > > > On Fri, Jul 26, 2019 at 01:08:57PM -0500, Pierre-Louis Bossart wrote:
> > 
> > > > > -	if (ret < 0)
> > > > > +	if (ret < 0 && ret != -EACCES)
> > > > 
> > > > ...and here, the pm_runtime_put_noidle() call is missed.
> > > 
> > > yes but in the example you provided, they actually do more work than just
> > > decrement the device usage counter:
> > 
> > In their case they would like to do that. You decide what is appropriate call
> > in your case.
> > 
> > My point is, that reference counter in case of error handling should be
> > returned back to its value.
> 
> Agree on the reference count.
> I am however not clear on the next step and 'what is appropriate'.
> 
> If pm_runtime_get_sync() failed, then technically the device was not resumed

Not so straight. It depends on reference count. It might be true (most cases
I think), or not true, if device had been resumed previously by other call.

> so marking it as last_busy+autosuspend, or using a plain vanilla put() will
> not result in any action. I must be missing something here.

put_noidle(). Because if it failed on the first call and was resumed, put()
will try to shut it down (since reference count goes to no-user base).

-- 
With Best Regards,
Andy Shevchenko