Dear NXP ,
SW version :
repo init -u https://github.com/nxp-imx/imx-manifest -b imx-linux-langdale -m imx-6.1.1-1.0.1.xml
HW : imx8mplus
The LVDS panel can display normally. I want to control pwm backlight .
GPIO1_IO11 : pwm backlight
Please refer to my imx8mp-evk.dts :
compatible = "panel-lvds";
backlight = <&lvds_backlight>;
power-supply = <®_lvds_pwr>;
data-mapping = "jeida-18";
data-width = <18>;
height-mm = <135>; /* 135.6 */
width-mm = <216>; /* 216.96 */
panel-timing {
clock-frequency = <74250000>;
hactive = <1280>;
vactive = <800>;
hback-porch = <64>;
hfront-porch = <42>;
vback-porch = <49>;
vfront-porch = <20>;
hsync-len = <22>;
vsync-len = <20>;
};
port {
panel_lvds_in: endpoint {
remote-endpoint = <&lvds_out>;
};
};
};
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_pwm2>;
status = "okay";
};
cat max_brightness : This value is 100
cat brightness : This value is 80
echo 0 > brightness
cat brightness : This value is 0 but the LVDS panel can still display normally.
I use an oscilloscope to measure the PWM voltage . It always keep 3.3 V .
I add some log in pwm_bl.c .Please refer the pwm_backlight.log and pwm_bl.c .
Please help to solve this problem .
From the hardware desgin you attached, the PWM will be pull up with the VDDEXT_3V3, so this is normal. You can remove R2389 to get low value when brightness =0.
Here is my test with same pwm node on EVK board.
Brightness=10
Brightness=1
Brightness =0
You can see that the PWM voltage is zero when brightness=0.
