linux-kernel - Re: [PATCH 25/25] media: i2c: ccs-core: fix pm_runtime_get

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Date:   Wed, 5 May 2021 17:36:10 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
CC:     Sakari Ailus <sakari.ailus@...ux.intel.com>, <linuxarm@...wei.com>,
        <mauro.chehab@...wei.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>
Subject: Re: [PATCH 25/25] media: i2c: ccs-core: fix pm_runtime_get_sync()
 usage count

On Wed, 5 May 2021 16:06:45 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> wrote:

> Hi Jonathan,
> 
> Em Wed, 5 May 2021 13:35:48 +0100
> Jonathan Cameron <Jonathan.Cameron@...wei.com> escreveu:
> 
> > > > [PATCH] media: i2c: ccs-core: fix pm_runtime_get_sync() usage count
> > > > 
> > > > The pm_runtime_get_sync() internally increments the
> > > > dev->power.usage_count without decrementing it, even on errors.
> > > > 
> > > > There is a bug at ccs_pm_get_init(): when this function returns
> > > > an error, the stream is not started, and RPM usage_count
> > > > should not be incremented. However, if the calls to
> > > > v4l2_ctrl_handler_setup() return errors, it will be kept
> > > > incremented.
> > > > 
> > > > At ccs_suspend() the best is to replace it by the new
> > > > pm_runtime_resume_and_get(), introduced by:
> > > > commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> > > > in order to properly decrement the usage counter automatically,
> > > > in the case of errors.
> > > > 
> > > > Fixes: 96e3a6b92f23 ("media: smiapp: Avoid maintaining power state information")
> > > > Cc: stable@...r.kernel.org
> > > > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>    
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>  
> 
> Per Sakari's request (for practical reasons on backporting and
> c/c stable), this was split into two separate patches, one
> fixing the issues, and a separate trivial one with just the
> pm_runtime_resume_and_get(). I'm adding your RB on both.
Makes sense.

Jonathan

> 
> Thanks,
> Mauro