linux-kernel - Re: [RFT PATCH 13/15] drm/imx/ipuv3: Call drm_atomic_helper

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Message-ID: <32186b941d6228a102b5e799aadf34206b58ac15.camel@pengutronix.de>
Date:   Mon, 04 Sep 2023 10:30:38 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Douglas Anderson <dianders@...omium.org>,
        dri-devel@...ts.freedesktop.org, Maxime Ripard <mripard@...nel.org>
Cc:     Sascha Hauer <s.hauer@...gutronix.de>, airlied@...il.com,
        daniel@...ll.ch, festevam@...il.com, kernel@...gutronix.de,
        linux-arm-kernel@...ts.infradead.org, linux-imx@....com,
        linux-kernel@...r.kernel.org, shawnguo@...nel.org
Subject: Re: [RFT PATCH 13/15] drm/imx/ipuv3: Call
 drm_atomic_helper_shutdown() at shutdown/unbind time

On Fr, 2023-09-01 at 16:41 -0700, Douglas Anderson wrote:
> Based on grepping through the source code this driver appears to be
> missing a call to drm_atomic_helper_shutdown() at system shutdown time
> and at driver unbind 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 and at driver remove (or unbind) time comes
> straight out of the kernel doc "driver instance overview" in
> drm_drv.c.
> 
> A few notes about this fix:
> - When adding drm_atomic_helper_shutdown() to the unbind path, I added
>   it after drm_kms_helper_poll_fini() since that's when other drivers
>   seemed to have it.
> - Technically with a previous patch, ("drm/atomic-helper:
>   drm_atomic_helper_shutdown(NULL) should be a noop"), we don't
>   actually need to check to see if our "drm" pointer is NULL before
>   calling drm_atomic_helper_shutdown(). We'll leave the "if" test in,
>   though, so that this patch can land without any dependencies. It
>   could potentially be removed later.
> - This patch also makes sure to set the drvdata to NULL in the case of
>   bind errors to make sure that shutdown can't access freed data.
> 
> Suggested-by: Maxime Ripard <mripard@...nel.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Thank you,
Tested-by: Philipp Zabel <p.zabel@...gutronix.de>

regards
Philipp