linux-kernel - [PATCH 2/2] drm/i915/backlight: Add get brightness support of DPCD via AUX

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Message-ID: <20250926085401.2808634-2-aaron.ma@canonical.com>
Date: Fri, 26 Sep 2025 16:54:01 +0800
From: Aaron Ma <aaron.ma@...onical.com>
To: dri-devel@...ts.freedesktop.org,
	intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Cc: maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch,
	jani.nikula@...ux.intel.com,
	rodrigo.vivi@...el.com,
	suraj.kandpal@...el.com,
	imre.deak@...el.com,
	joonas.lahtinen@...ux.intel.com,
	aaron.ma@...onical.com
Subject: [PATCH 2/2] drm/i915/backlight: Add get brightness support of DPCD via AUX

Use drm common helper to read brightness from
both luminance and AUX mode to support get_brightness from
DPCD via AUX.

Signed-off-by: Aaron Ma <aaron.ma@...onical.com>
---
 .../drm/i915/display/intel_dp_aux_backlight.c | 20 ++++++-------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
index 0a3a3f6a5f9d8..0ee6fd0f41ef0 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -454,24 +454,16 @@ static u32 intel_dp_aux_vesa_get_backlight(struct intel_connector *connector, en
 {
 	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
 	struct intel_panel *panel = &connector->panel;
-	u8 buf[3];
-	u32 val = 0;
-	int ret;
 
-	if (panel->backlight.edp.vesa.luminance_control_support) {
-		ret = drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_PANEL_TARGET_LUMINANCE_VALUE, buf,
-				       sizeof(buf));
-		if (ret < 0) {
-			drm_err(intel_dp->aux.drm_dev,
-				"[CONNECTOR:%d:%s] Failed to read Luminance from DPCD\n",
-				connector->base.base.id, connector->base.name);
-			return 0;
-		}
+	if (!panel->backlight.edp.vesa.info.aux_set) {
+		u32 pwm_level = panel->backlight.pwm_funcs->get(connector, unused);
 
-		val |= buf[0] | buf[1] << 8 | buf[2] << 16;
-		return val / 1000;
+		return intel_backlight_level_from_pwm(connector, pwm_level);
 	}
 
+	connector->panel.backlight.level =
+		drm_edp_backlight_get_level(&intel_dp->aux, &panel->backlight.edp.vesa.info);
+
 	return connector->panel.backlight.level;
 }
 
-- 
2.43.0