linux-kernel - [RFT PATCH 3/6] drm/vc4: Call drm_atomic_helper

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Message-ID: <20230901163944.RFT.3.I10dbe099fb1059d304ba847d19fc45054f7ffe9f@changeid>
Date:   Fri,  1 Sep 2023 16:39:54 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     dri-devel@...ts.freedesktop.org, Maxime Ripard <mripard@...nel.org>
Cc:     Douglas Anderson <dianders@...omium.org>, airlied@...il.com,
        daniel@...ll.ch, emma@...olt.net, linux-kernel@...r.kernel.org
Subject: [RFT PATCH 3/6] drm/vc4: Call drm_atomic_helper_shutdown() at shutdown time

Based on grepping through the source code these drivers appear 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.

Suggested-by: Maxime Ripard <mripard@...nel.org>
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
This commit is only compile-time tested.

Though this patch could be squashed into the patch ("drm: Call
drm_atomic_helper_shutdown() at shutdown time for misc drivers"), I
kept it separate to call attention to this driver. While writing this
patch, I noticed that the bind() function is using "devm" and thus
assumes it doesn't need to do much explicit error handling. That's
actually a bug. As per kernel docs [1] "the lifetime of the aggregate
driver does not align with any of the underlying struct device
instances. Therefore devm cannot be used and all resources acquired or
allocated in this callback must be explicitly released in the unbind
callback". Fixing that is outside the scope of this commit.

[1] https://docs.kernel.org/driver-api/component.html

 drivers/gpu/drm/vc4/vc4_drv.c | 36 ++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_drv.c b/drivers/gpu/drm/vc4/vc4_drv.c
index 1b3531374967..c133e96b8aca 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.c
+++ b/drivers/gpu/drm/vc4/vc4_drv.c
@@ -324,21 +324,21 @@ static int vc4_drm_bind(struct device *dev)
 	if (!is_vc5) {
 		ret = drmm_mutex_init(drm, &vc4->bin_bo_lock);
 		if (ret)
-			return ret;
+			goto err;
 
 		ret = vc4_bo_cache_init(drm);
 		if (ret)
-			return ret;
+			goto err;
 	}
 
 	ret = drmm_mode_config_init(drm);
 	if (ret)
-		return ret;
+		goto err;
 
 	if (!is_vc5) {
 		ret = vc4_gem_init(drm);
 		if (ret)
-			return ret;
+			goto err;
 	}
 
 	node = of_find_compatible_node(NULL, NULL, "raspberrypi,bcm2835-firmware");
@@ -346,13 +346,15 @@ static int vc4_drm_bind(struct device *dev)
 		firmware = rpi_firmware_get(node);
 		of_node_put(node);
 
-		if (!firmware)
-			return -EPROBE_DEFER;
+		if (!firmware) {
+			ret = -EPROBE_DEFER;
+			goto err;
+		}
 	}
 
 	ret = drm_aperture_remove_framebuffers(driver);
 	if (ret)
-		return ret;
+		goto err;
 
 	if (firmware) {
 		ret = rpi_firmware_property(firmware,
@@ -366,32 +368,33 @@ static int vc4_drm_bind(struct device *dev)
 
 	ret = component_bind_all(dev, drm);
 	if (ret)
-		return ret;
+		goto err;
 
 	ret = devm_add_action_or_reset(dev, vc4_component_unbind_all, vc4);
 	if (ret)
-		return ret;
+		goto err;
 
 	ret = vc4_plane_create_additional_planes(drm);
 	if (ret)
-		goto unbind_all;
+		goto err;
 
 	ret = vc4_kms_load(drm);
 	if (ret < 0)
-		goto unbind_all;
+		goto err;
 
 	drm_for_each_crtc(crtc, drm)
 		vc4_crtc_disable_at_boot(crtc);
 
 	ret = drm_dev_register(drm, 0);
 	if (ret < 0)
-		goto unbind_all;
+		goto err;
 
 	drm_fbdev_dma_setup(drm, 16);
 
 	return 0;
 
-unbind_all:
+err:
+	platform_set_drvdata(pdev, NULL);
 	return ret;
 }
 
@@ -401,6 +404,7 @@ static void vc4_drm_unbind(struct device *dev)
 
 	drm_dev_unplug(drm);
 	drm_atomic_helper_shutdown(drm);
+	dev_set_drvdata(dev, NULL);
 }
 
 static const struct component_master_ops vc4_drm_ops = {
@@ -444,6 +448,11 @@ static void vc4_platform_drm_remove(struct platform_device *pdev)
 	component_master_del(&pdev->dev, &vc4_drm_ops);
 }
 
+static void vc4_platform_drm_shutdown(struct platform_device *pdev)
+{
+	drm_atomic_helper_shutdown(platform_get_drvdata(pdev));
+}
+
 static const struct of_device_id vc4_of_match[] = {
 	{ .compatible = "brcm,bcm2711-vc5", },
 	{ .compatible = "brcm,bcm2835-vc4", },
@@ -455,6 +464,7 @@ MODULE_DEVICE_TABLE(of, vc4_of_match);
 static struct platform_driver vc4_platform_driver = {
 	.probe		= vc4_platform_drm_probe,
 	.remove_new	= vc4_platform_drm_remove,
+	.shutdown	= vc4_platform_drm_shutdown,
 	.driver		= {
 		.name	= "vc4-drm",
 		.of_match_table = vc4_of_match,
-- 
2.42.0.283.g2d96d420d3-goog