[RFT PATCH 05/15] drm/mediatek: Call drm_atomic_helper_shutdown() at shutdown time

[Douglas Anderson]

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.

This driver users the component model and shutdown happens in the base
driver. The "drvdata" for this driver will always be valid if
shutdown() is called and we know that if the "drm" pointer in our
private data is non-NULL then we need to call
drm_atomic_helper_shutdown(). 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.

Suggested-by: Maxime Ripard <mripard at kernel.org>
Signed-off-by: Douglas Anderson <dianders at chromium.org>
---
This commit is only compile-time tested.

 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 961715dd5b11..8b1c9c992ca8 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -921,6 +921,14 @@ static int mtk_drm_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static void mtk_drm_shutdown(struct platform_device *pdev)
+{
+	struct mtk_drm_private *private = platform_get_drvdata(pdev);
+
+	if (private->drm)
+		drm_atomic_helper_shutdown(private->drm);
+}
+
 static int mtk_drm_sys_prepare(struct device *dev)
 {
 	struct mtk_drm_private *private = dev_get_drvdata(dev);
@@ -952,6 +960,7 @@ static const struct dev_pm_ops mtk_drm_pm_ops = {
 static struct platform_driver mtk_drm_platform_driver = {
 	.probe	= mtk_drm_probe,
 	.remove	= mtk_drm_remove,
+	.shutdown = mtk_drm_shutdown,
 	.driver	= {
 		.name	= "mediatek-drm",
 		.pm     = &mtk_drm_pm_ops,
-- 
2.42.0.283.g2d96d420d3-goog