linux-kernel - Re: [RFT PATCH 2/6] drm: Call drm_atomic_helper_shutdown() at shutdown time for misc drivers

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Message-ID: <06ac6d3b-e82e-dd25-ab21-90db76f3a5fd@ideasonboard.com>
Date:   Tue, 19 Sep 2023 10:31:05 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Douglas Anderson <dianders@...omium.org>,
        dri-devel@...ts.freedesktop.org, Maxime Ripard <mripard@...nel.org>
Cc:     airlied@...il.com, airlied@...hat.com, alain.volmat@...s.st.com,
        alexander.deucher@....com, alexandre.belloni@...tlin.com,
        alison.wang@....com, bbrezillon@...nel.org,
        christian.koenig@....com, claudiu.beznea@...rochip.com,
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        linus.walleij@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...ts.linux.dev, liviu.dudau@....com,
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        sam@...nborg.org, samuel@...lland.org,
        spice-devel@...ts.freedesktop.org, stefan@...er.ch,
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        tiantao6@...ilicon.com, tzimmermann@...e.de,
        virtualization@...ts.linux-foundation.org, wens@...e.org,
        xinliang.liu@...aro.org, yongqin.liu@...aro.org, zackr@...are.com
Subject: Re: [RFT PATCH 2/6] drm: Call drm_atomic_helper_shutdown() at
 shutdown time for misc drivers

On 02/09/2023 02:39, Douglas Anderson wrote:
> Based on grepping through the source code these drivers appear 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.
> 
> All of the drivers in this patch were fairly straightforward to fix
> since they already had a call to drm_atomic_helper_shutdown() at
> remove/unbind time but were just lacking one at system shutdown. The
> only hitch is that some of these drivers use the component model to
> register/unregister their DRM devices. The shutdown callback is part
> of the original device. The typical solution here, based on how other
> DRM drivers do this, is to keep track of whether the device is bound
> based on drvdata. In most cases the drvdata is the drm_device, so we
> can just make sure it is NULL when the device is not bound. In some
> drivers, this required minor code changes. To make things simpler,
> drm_atomic_helper_shutdown() has been modified to consider a NULL
> drm_device as a noop in the patch ("drm/atomic-helper:
> drm_atomic_helper_shutdown(NULL) should be a noop").
> 
> Suggested-by: Maxime Ripard <mripard@...nel.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

For omapdrm:

Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Tested-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>

  Tomi