[PATCH 4/4] arm64: dts: qcom: mahua-t14s: wire backlight through pmk8850 pwm

[Srinivas Kandagatla]

Move TLMM 18 (EDP_BL_EN) out of the panel node into a pwm-backlight
node and wire real brightness control through the pmk8850 PWMR output
(EDP_BL/PWMR_BV_PS on the schematic).

panel-edp was asserting EDP_BL_EN before eDP link training, turning the
backlight on ahead of video. With a dedicated backlight node the
framework toggles EDP_BL_EN after the link is up; TLMM 18 remains the
LED-driver enable, now gated correctly.

The panel takes only its 3.3 V logic supply and references the
backlight via a phandle. Brightness drives the LPG/PWM channel on
pmk8850 routed out via pmk8850_gpios gpio5 (func3).

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxxxxxxxx>
---
 .../mahua-lenovo-thinkpad-t14s-gen7-lcd.dts   | 26 ++++++++++++++++---
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/mahua-lenovo-thinkpad-t14s-gen7-lcd.dts b/arch/arm64/boot/dts/qcom/mahua-lenovo-thinkpad-t14s-gen7-lcd.dts
index 26d6d8285e04..be094f9a6ef2 100644
--- a/arch/arm64/boot/dts/qcom/mahua-lenovo-thinkpad-t14s-gen7-lcd.dts
+++ b/arch/arm64/boot/dts/qcom/mahua-lenovo-thinkpad-t14s-gen7-lcd.dts
@@ -39,6 +39,16 @@ aliases {
 		serial1 = &uart14;
 	};
 
+	backlight: backlight {
+		compatible = "pwm-backlight";
+		pwms = <&pmk8850_pwm 0 4266537>;
+		enable-gpios = <&tlmm 18 GPIO_ACTIVE_HIGH>;
+		power-supply = <&vreg_edp_bl>;
+
+		pinctrl-0 = <&edp_bl_en>, <&edp_bl_pwm>;
+		pinctrl-names = "default";
+	};
+
 	chosen {
 		stdout-path = "serial0:115200n8";
 	};
@@ -773,11 +783,8 @@ &mdss_dp3 {
 	aux-bus {
 		panel {
 			compatible = "edp-panel";
-			enable-gpios = <&tlmm 18 GPIO_ACTIVE_HIGH>;
 			power-supply = <&vreg_edp_3p3>;
-
-			pinctrl-0 = <&edp_bl_en>;
-			pinctrl-names = "default";
+			backlight = <&backlight>;
 
 			port {
 				edp_panel_in: endpoint {
@@ -902,6 +909,17 @@ misc_3p3_reg_en: misc-3p3-reg-en-state {
 	};
 };
 
+&pmk8850_gpios {
+	edp_bl_pwm: edp-bl-pwm-state {
+		pins = "gpio5";
+		function = "func3";
+	};
+};
+
+&pmk8850_pwm {
+	status = "okay";
+};
+
 &pmk8850_rtc {
 	qcom,no-alarm;
 };
-- 
2.53.0