linux-kernel - [RFT PATCH v2 12/12] drm/renesas/shmobile: Call drm_helper_force_disable

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Date:   Thu, 21 Sep 2023 12:26:55 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     dri-devel@...ts.freedesktop.org, Maxime Ripard <mripard@...nel.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        airlied@...il.com, biju.das.jz@...renesas.com, daniel@...ll.ch,
        kieran.bingham+renesas@...asonboard.com,
        laurent.pinchart@...asonboard.com, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, paul@...pouillou.net,
        sam@...nborg.org, tzimmermann@...e.de
Subject: [RFT PATCH v2 12/12] drm/renesas/shmobile: Call drm_helper_force_disable_all() at shutdown/remove time

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@...nel.org>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
This commit is only compile-time tested.

As Geert pointed out in response to v1 [1], this patch conflicts with
the patches doing atomic conversion [2]. Since those patches don't
appear to be landed yet, I'm simply reposting v1. If those patches
land, I'm more than happy to re-post this one. I'm also more than
happy if someone wants to incorporate these changes into a different
patch.

[1] https://lore.kernel.org/r/CAMuHMdWOB7d-KE3F7aeZvVimNuy_U30uk=PND7=tWmPzCd7_eg@mail.gmail.com
[2] https://lore.kernel.org/dri-devel/fd7a6702490bd431f314d6591551bb39e77e3304.1692178020.git.geert+renesas@glider.be/

Changes in v2:
- Rebased and resolved conflicts.

 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 e5db4e0095ba..8c4c9d17a79e 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>
@@ -179,10 +180,18 @@ static void 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);
 }
 
+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;
@@ -287,6 +296,7 @@ static int shmob_drm_probe(struct platform_device *pdev)
 static struct platform_driver shmob_drm_platform_driver = {
 	.probe		= shmob_drm_probe,
 	.remove_new	= shmob_drm_remove,
+	.shutdown	= shmob_drm_shutdown,
 	.driver		= {
 		.name	= "shmob-drm",
 		.pm	= pm_sleep_ptr(&shmob_drm_pm_ops),
-- 
2.42.0.515.g380fc7ccd1-goog