linux-kernel - Re: [PATCH] driver core: Call pm_runtime_put_sync() only after device

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Message-ID: <20230511103923.hvibdyo5ges4bab2@pengutronix.de>
Date:   Thu, 11 May 2023 12:39:23 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH] driver core: Call pm_runtime_put_sync() only after
 device_remove()

On Thu, May 11, 2023 at 12:18:09PM +0200, Rafael J. Wysocki wrote:
> On Thu, May 11, 2023 at 9:34 AM Uwe Kleine-König
> <u.kleine-koenig@...gutronix.de> wrote:
> >
> > Many drivers that use runtime PM call pm_runtime_get_sync() or one of
> > its variants in their remove callback. So calling pm_runtime_put_sync()
> > directly before calling the remove callback results (under some
> > conditions) in the driver's suspend routine being called just to resume
> > it again afterwards.
> >
> > So delay the pm_runtime_put_sync() call until after device_remove().
> >
> > Confirmed on a stm32mp157a that doing
> >
> >         echo 4400e000.can > /sys/bus/platform/drivers/m_can_platform/unbind
> >
> > (starting with a runtime-pm suspended 4400e000.can) results in one call
> > less of m_can_runtime_resume() and m_can_runtime_suspend() each after
> > this change was applied.
> >
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> 
> I'm not against this change, although I kind of expect it to trigger
> some fallout that will need to be addressed.  So caveat emtor.
> 
> Anyway
> 
> Reviewed-by: Rafael J. Wysocki <rafael@...nel.org>

Thanks for your review tag. I wondered if there will be some fallout,
and don't know what to expect yet. Sounds like getting it into next soon
is a good idea?!

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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