linux-kernel - [PATCH 5.18 122/141] drm/amd/display: Cap OLED brightness per max frame-average luminance

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Date:   Mon, 20 Jun 2022 14:51:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Hamza Mahfooz <hamza.mahfooz@....com>,
        Roman Li <roman.li@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>
Subject: [PATCH 5.18 122/141] drm/amd/display: Cap OLED brightness per max frame-average luminance

From: Roman Li <roman.li@....com>

commit 4fd17f2ac0aa4e48823ac2ede5b050fb70300bf4 upstream.

[Why]
For OLED eDP the Display Manager uses max_cll value as a limit
for brightness control.
max_cll defines the content light luminance for individual pixel.
Whereas max_fall defines frame-average level luminance.
The user may not observe the difference in brightness in between
max_fall and max_cll.
That negatively impacts the user experience.

[How]
Use max_fall value instead of max_cll as a limit for brightness control.

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@....com>
Signed-off-by: Roman Li <roman.li@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2835,7 +2835,7 @@ static struct drm_mode_config_helper_fun
 
 static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
 {
-	u32 max_cll, min_cll, max, min, q, r;
+	u32 max_avg, min_cll, max, min, q, r;
 	struct amdgpu_dm_backlight_caps *caps;
 	struct amdgpu_display_manager *dm;
 	struct drm_connector *conn_base;
@@ -2865,7 +2865,7 @@ static void update_connector_ext_caps(st
 	caps = &dm->backlight_caps[i];
 	caps->ext_caps = &aconnector->dc_link->dpcd_sink_ext_caps;
 	caps->aux_support = false;
-	max_cll = conn_base->hdr_sink_metadata.hdmi_type1.max_cll;
+	max_avg = conn_base->hdr_sink_metadata.hdmi_type1.max_fall;
 	min_cll = conn_base->hdr_sink_metadata.hdmi_type1.min_cll;
 
 	if (caps->ext_caps->bits.oled == 1 /*||
@@ -2893,8 +2893,8 @@ static void update_connector_ext_caps(st
 	 * The results of the above expressions can be verified at
 	 * pre_computed_values.
 	 */
-	q = max_cll >> 5;
-	r = max_cll % 32;
+	q = max_avg >> 5;
+	r = max_avg % 32;
 	max = (1 << q) * pre_computed_values[r];
 
 	// min luminance: maxLum * (CV/255)^2 / 100