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

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Message-ID: <20230517-amigo-depth-00436cd21520-mkl@pengutronix.de>
Date:   Wed, 17 May 2023 11:55:27 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Johan Hovold <johan@...nel.org>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] driver core: Call pm_runtime_put_sync() only after
 device_remove()

On 17.05.2023 10:28:01, Johan Hovold wrote:
> Right, but we do have drivers that have CONFIG_PM as an explicit
> dependency.
> 
> > In the end something like 72362dcdf654 ("can: mcp251xfd:
> > mcp251xfd_unregister(): simplify runtime PM handling") might be an
> > approach. But IMHO it's more complicated than it should be and honestly
> > I'm not sure if it's safe and correct this way.
> 
> Yeah, unfortunately runtime PM is fairly underspecified so we end up
> with this multitude of implementations, many of which are broken in
> various ways. A smaller API with documented best-practices may have
> helped, but that's not where we are right now.
> 
> Looks like 72362dcdf654 ("can: mcp251xfd: mcp251xfd_unregister():
> simplify runtime PM handling") introduces yet another way to do things,
> and which will break if anyone enables (or tries to use this pattern in
> another driver with) autosuspend...

ACK - I think in that driver it works, as the runtime PM is resumed
during interface up and suspended in interface down. IMHO autosuspend
would not bring any benefits here...

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
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