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

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Message-ID: <CAD=FV=VvbkKo9i994-GGFBKte=f_d9Vzh3o1UkTpTPSqCCEdeQ@mail.gmail.com>
Date:   Wed, 13 Sep 2023 11:21:12 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     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, p.zabel@...gutronix.de,
        shawnguo@...nel.org
Subject: Re: [RFT PATCH 13/15] drm/imx/ipuv3: Call drm_atomic_helper_shutdown()
 at shutdown/unbind time

Hi,

On Fri, Sep 1, 2023 at 4:42 PM Douglas Anderson <dianders@...omium.org> 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>
> ---
> This commit is only compile-time tested.
>
>  drivers/gpu/drm/imx/ipuv3/imx-drm-core.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c b/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c
> index 4a866ac60fff..4c8bc49758a7 100644
> --- a/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c
> +++ b/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c
> @@ -257,6 +257,7 @@ static int imx_drm_bind(struct device *dev)
>         drm_kms_helper_poll_fini(drm);
>         component_unbind_all(drm->dev, drm);
>  err_kms:
> +       dev_set_drvdata(dev, NULL);
>         drm_dev_put(drm);
>
>         return ret;
> @@ -269,6 +270,7 @@ static void imx_drm_unbind(struct device *dev)
>         drm_dev_unregister(drm);
>
>         drm_kms_helper_poll_fini(drm);
> +       drm_atomic_helper_shutdown(drm);
>
>         component_unbind_all(drm->dev, drm);
>
> @@ -298,6 +300,14 @@ static int imx_drm_platform_remove(struct platform_device *pdev)
>         return 0;
>  }
>
> +static void imx_drm_platform_shutdown(struct platform_device *pdev)
> +{
> +       struct drm_device *drm = platform_get_drvdata(pdev);
> +
> +       if (drm)
> +               drm_atomic_helper_shutdown(platform_get_drvdata(pdev));

Since this is now landing through the drm-misc-next tree, I got rid of
the check for NULL when applying and landed this after the patch
("drm/atomic-helper: drm_atomic_helper_shutdown(NULL) should be a
noop").


> @@ -325,6 +335,7 @@ MODULE_DEVICE_TABLE(of, imx_drm_dt_ids);
>  static struct platform_driver imx_drm_pdrv = {
>         .probe          = imx_drm_platform_probe,
>         .remove         = imx_drm_platform_remove,
> +       .shutdown       = imx_drm_platform_shutdown,

There was a trivial context conflict with commit 3095f1122203
("drm/imx/ipuv3: Convert to platform remove callback returning void")
that I resolved while applying.

I've now pushed to drm-misc-next:

02680d71dea8 drm/imx/ipuv3: Call drm_atomic_helper_shutdown() at
shutdown/unbind time