Re: [RFT PATCH v2 09/12] drm/exynos: Call drm_atomic_helper_shutdown() at shutdown/unbind time

[Marek Szyprowski <m.szyprowski@samsung.com>]

On 21.09.2023 21:26, 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@kernel.org>
> Reviewed-by: Maxime Ripard <mripard@kernel.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Seems to be working fine on all my test Exynos-based boards with display.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
> This commit is only compile-time tested.
>
> (no changes since v1)
>
>   drivers/gpu/drm/exynos/exynos_drm_drv.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> index 8399256cb5c9..5380fb6c55ae 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_drv.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> @@ -300,6 +300,7 @@ static int exynos_drm_bind(struct device *dev)
>   	drm_mode_config_cleanup(drm);
>   	exynos_drm_cleanup_dma(drm);
>   	kfree(private);
> +	dev_set_drvdata(dev, NULL);
>   err_free_drm:
>   	drm_dev_put(drm);
>   
> @@ -313,6 +314,7 @@ static void exynos_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);
>   	drm_mode_config_cleanup(drm);
> @@ -350,9 +352,18 @@ static int exynos_drm_platform_remove(struct platform_device *pdev)
>   	return 0;
>   }
>   
> +static void exynos_drm_platform_shutdown(struct platform_device *pdev)
> +{
> +	struct drm_device *drm = platform_get_drvdata(pdev);
> +
> +	if (drm)
> +		drm_atomic_helper_shutdown(drm);
> +}
> +
>   static struct platform_driver exynos_drm_platform_driver = {
>   	.probe	= exynos_drm_platform_probe,
>   	.remove	= exynos_drm_platform_remove,
> +	.shutdown = exynos_drm_platform_shutdown,
>   	.driver	= {
>   		.name	= "exynos-drm",
>   		.pm	= &exynos_drm_pm_ops,

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland