linux-kernel - Re: [RFT PATCH 03/15] drm/ingenic: Call drm_atomic_helper

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Message-ID: <ac04dbc27e4d5f0fd3ec458b1ad7d4d2f2b39092.camel@crapouillou.net>
Date:   Wed, 13 Sep 2023 20:00:39 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Doug Anderson <dianders@...omium.org>
Cc:     dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>, airlied@...il.com,
        daniel@...ll.ch, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org
Subject: Re: [RFT PATCH 03/15] drm/ingenic: Call
 drm_atomic_helper_shutdown() at shutdown time

Hi Doug,

Le mercredi 13 septembre 2023 à 09:25 -0700, Doug Anderson a écrit :
> Hi,
> 
> On Tue, Sep 5, 2023 at 1:16 PM Doug Anderson <dianders@...omium.org>
> wrote:
> > 
> > Paul,
> > 
> > On Mon, Sep 4, 2023 at 2:15 AM Paul Cercueil <paul@...pouillou.net>
> > wrote:
> > > 
> > > Hi Douglas,
> > > 
> > > Le vendredi 01 septembre 2023 à 16:41 -0700, Douglas Anderson a
> > > écrit :
> > > > Based on grepping through the source code this driver appears
> > > > to be
> > > > missing a call to drm_atomic_helper_shutdown() at system
> > > > shutdown
> > > > time. Among other things, this means that if a panel is in use
> > > > that
> > > > it
> > > > won't be cleanly powered off at system shutdown time.
> > > > 
> > > > The fact that we should call drm_atomic_helper_shutdown() in
> > > > the case
> > > > of OS shutdown/restart comes straight out of the kernel doc
> > > > "driver
> > > > instance overview" in drm_drv.c.
> > > > 
> > > > Since this driver uses the component model and shutdown happens
> > > > at
> > > > the
> > > > base driver, we communicate whether we have to call
> > > > drm_atomic_helper_shutdown() by seeing if drvdata is non-NULL.
> > > > 
> > > > Suggested-by: Maxime Ripard <mripard@...nel.org>
> > > > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > > 
> > > LGTM.
> > > Acked-by: Paul Cercueil <paul@...pouillou.net>
> > 
> > Thanks for the Ack! Would you expect this patch to land through
> > "drm-misc", or do you expect it to go through some other tree?
> > Running:
> > 
> > ./scripts/get_maintainer.pl --scm -f
> > drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> > 
> > ...does not show that this driver normally goes through drm-misc,
> > but
> > it also doesn't show that it goes through any other tree so maybe
> > it's
> > just an artifact of the way it's tagged in the MAINTAINERS file? If
> > it's fine for this to go through drm-misc, I'll probably land it
> > (with
> > your Ack and Maxime's Review) sooner rather than later just to make
> > this patch series less unwieldy.
> > 
> > 
> > > > ---
> > > > This commit is only compile-time tested.
> > > > 
> > > > NOTE: this patch touches a lot more than other similar patches
> > > > since
> > > > the bind() function is long and we want to make sure that we
> > > > unset
> > > > the
> > > > drvdata if bind() fails.
> > > > 
> > > > While making this patch, I noticed that the bind() function of
> > > > this
> > > > driver is using "devm" and thus assumes it doesn't need to do
> > > > much
> > > > explicit error handling. That's actually a bug. As per kernel
> > > > docs
> > > > [1]
> > > > "the lifetime of the aggregate driver does not align with any
> > > > of the
> > > > underlying struct device instances. Therefore devm cannot be
> > > > used and
> > > > all resources acquired or allocated in this callback must be
> > > > explicitly released in the unbind callback". Fixing that is
> > > > outside
> > > > the scope of this commit.
> > > > 
> > > > [1] https://docs.kernel.org/driver-api/component.html
> > > > 
> > > 
> > > Noted, thanks.
> > 
> > FWIW, I think that at least a few other DRM drivers handle this by
> > doing some of their resource allocation / acquiring in the probe()
> > function and then only doing things in the bind() that absolutely
> > need
> > to be in the bind. ;-)
> 
> I've been collecting patches that are ready to land in drm-misc but,
> right now, I'm not taking this patch since I didn't get any
> clarification of whether it should land through drm-misc or somewhere
> else.

Sorry, you can take it in drm-misc, yes.

Cheers,
-Paul