[RFT PATCH 15/15] drm/renesas/shmobile: Call drm_helper_force_disable_all() at shutdown/remove time

[Douglas Anderson]

Based on grepping through the source code, this driver appears to be
missing a call to drm_atomic_helper_shutdown(), or in this case the
non-atomic equivalent drm_helper_force_disable_all(), at system
shutdown time and at driver remove time. This is important because
drm_helper_force_disable_all() will cause panels to get disabled
cleanly which may be important for their power sequencing. Future
changes will remove any custom powering off in individual panel
drivers so the DRM drivers need to start getting this right.

The fact that we should call drm_atomic_helper_shutdown(), or in this
case the non-atomic equivalent drm_helper_force_disable_all(), in the
case of OS shutdown/restart comes straight out of the kernel doc
"driver instance overview" in drm_drv.c.

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/renesas/shmobile/shmob_drm_drv.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c b/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
index 30493ce87419..d6dd46c925c5 100644
--- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
+++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
@@ -15,6 +15,7 @@
 #include <linux/pm.h>
 #include <linux/slab.h>
 
+#include <drm/drm_crtc_helper.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_fbdev_generic.h>
 #include <drm/drm_gem_dma_helper.h>
@@ -179,12 +180,20 @@ static int shmob_drm_remove(struct platform_device *pdev)
 
 	drm_dev_unregister(ddev);
 	drm_kms_helper_poll_fini(ddev);
+	drm_helper_force_disable_all(ddev);
 	free_irq(sdev->irq, ddev);
 	drm_dev_put(ddev);
 
 	return 0;
 }
 
+static void shmob_drm_shutdown(struct platform_device *pdev)
+{
+	struct shmob_drm_device *sdev = platform_get_drvdata(pdev);
+
+	drm_helper_force_disable_all(sdev->ddev);
+}
+
 static int shmob_drm_probe(struct platform_device *pdev)
 {
 	struct shmob_drm_platform_data *pdata = pdev->dev.platform_data;
@@ -289,6 +298,7 @@ static int shmob_drm_probe(struct platform_device *pdev)
 static struct platform_driver shmob_drm_platform_driver = {
 	.probe		= shmob_drm_probe,
 	.remove		= shmob_drm_remove,
+	.shutdown	= shmob_drm_shutdown,
 	.driver		= {
 		.name	= "shmob-drm",
 		.pm	= pm_sleep_ptr(&shmob_drm_pm_ops),
-- 
2.42.0.283.g2d96d420d3-goog