linux-kernel - [PATCH 2/2] Revert "drm/amd/display: add panel_power

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Message-ID: <20240806184214.224672-2-sebastian.wick@redhat.com>
Date: Tue,  6 Aug 2024 20:42:10 +0200
From: Sebastian Wick <sebastian.wick@...hat.com>
To: dri-devel@...ts.freedesktop.org
Cc: Sebastian Wick <sebastian@...astianwick.net>,
	Xaver Hugl <xaver.hugl@...il.com>,
	Simon Ser <contact@...rsion.fr>,
	Pekka Paalanen <pekka.paalanen@...labora.com>,
	Harry Wentland <harry.wentland@....com>,
	Leo Li <sunpeng.li@....com>,
	Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	Xinhui Pan <Xinhui.Pan@....com>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Alex Hung <alex.hung@....com>,
	Hamza Mahfooz <hamza.mahfooz@....com>,
	Roman Li <roman.li@....com>,
	Mario Limonciello <mario.limonciello@....com>,
	Wayne Lin <Wayne.Lin@....com>,
	amd-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] Revert "drm/amd/display: add panel_power_savings sysfs entry to eDP connectors"

From: Sebastian Wick <sebastian@...astianwick.net>

This reverts commit 63d0b87213a0ba241b3fcfba3fe7b0aed0cd1cc5.

The panel_power_savings sysfs entry can be used to change the displayed
colorimetry which breaks color managed setups.

The "do not break userspace" rule which was violated here is enough
reason to revert this commit.

The bigger problem is that this feature is part of the display chain
which is supposed to be controlled by KMS. This sysfs entry bypasses the
DRM master process and splits control to two independent processes which
do not know about each other. This is what caused the broken user space.
It also causes modesets which can be extremely confusing for the DRM
master process, causing unexpected timings.

We should in general not allow anything other than KMS to control the
display path. If we make an exception to this rule, this must be first
discussed on dri-devel with all the stakeholders approving the
exception.

This has not happened which is the second reason to revert this commit.

Signed-off-by: Sebastian Wick <sebastian.wick@...hat.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 80 -------------------
 1 file changed, 80 deletions(-)

diff --git ./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c ../drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 4d4c75173fc3..16c9051d9ccf 100644
--- ./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ ../drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6772,82 +6772,10 @@ int amdgpu_dm_connector_atomic_get_property(struct drm_connector *connector,
 	return ret;
 }
 
-/**
- * DOC: panel power savings
- *
- * The display manager allows you to set your desired **panel power savings**
- * level (between 0-4, with 0 representing off), e.g. using the following::
- *
- *   # echo 3 > /sys/class/drm/card0-eDP-1/amdgpu/panel_power_savings
- *
- * Modifying this value can have implications on color accuracy, so tread
- * carefully.
- */
-
-static ssize_t panel_power_savings_show(struct device *device,
-					struct device_attribute *attr,
-					char *buf)
-{
-	struct drm_connector *connector = dev_get_drvdata(device);
-	struct drm_device *dev = connector->dev;
-	u8 val;
-
-	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
-	val = to_dm_connector_state(connector->state)->abm_level ==
-		ABM_LEVEL_IMMEDIATE_DISABLE ? 0 :
-		to_dm_connector_state(connector->state)->abm_level;
-	drm_modeset_unlock(&dev->mode_config.connection_mutex);
-
-	return sysfs_emit(buf, "%u\n", val);
-}
-
-static ssize_t panel_power_savings_store(struct device *device,
-					 struct device_attribute *attr,
-					 const char *buf, size_t count)
-{
-	struct drm_connector *connector = dev_get_drvdata(device);
-	struct drm_device *dev = connector->dev;
-	long val;
-	int ret;
-
-	ret = kstrtol(buf, 0, &val);
-
-	if (ret)
-		return ret;
-
-	if (val < 0 || val > 4)
-		return -EINVAL;
-
-	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
-	to_dm_connector_state(connector->state)->abm_level = val ?:
-		ABM_LEVEL_IMMEDIATE_DISABLE;
-	drm_modeset_unlock(&dev->mode_config.connection_mutex);
-
-	drm_kms_helper_hotplug_event(dev);
-
-	return count;
-}
-
-static DEVICE_ATTR_RW(panel_power_savings);
-
-static struct attribute *amdgpu_attrs[] = {
-	&dev_attr_panel_power_savings.attr,
-	NULL
-};
-
-static const struct attribute_group amdgpu_group = {
-	.name = "amdgpu",
-	.attrs = amdgpu_attrs
-};
-
 static void amdgpu_dm_connector_unregister(struct drm_connector *connector)
 {
 	struct amdgpu_dm_connector *amdgpu_dm_connector = to_amdgpu_dm_connector(connector);
 
-	if (connector->connector_type == DRM_MODE_CONNECTOR_eDP &&
-	    amdgpu_dm_abm_level < 0)
-		sysfs_remove_group(&connector->kdev->kobj, &amdgpu_group);
-
 	drm_dp_aux_unregister(&amdgpu_dm_connector->dm_dp_aux.aux);
 }
 
@@ -6952,14 +6880,6 @@ amdgpu_dm_connector_late_register(struct drm_connector *connector)
 		to_amdgpu_dm_connector(connector);
 	int r;
 
-	if (connector->connector_type == DRM_MODE_CONNECTOR_eDP &&
-	    amdgpu_dm_abm_level < 0) {
-		r = sysfs_create_group(&connector->kdev->kobj,
-				       &amdgpu_group);
-		if (r)
-			return r;
-	}
-
 	amdgpu_dm_register_backlight_device(amdgpu_dm_connector);
 
 	if ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) ||
-- 
2.45.2