I have developed a custom device tree that has two LVDS outputs with independent backlights. Neither of the backlights get enabled or configured. Below is the device tree entries. Any idea what I am missing? Thanks in advance.
backlight { | |||
backlight-0 { | |||
compatible = "pwm-backlight"; | |||
pwms = <&pwm1 0 5000000>; | |||
brightness-levels = <0 4 8 16 32 64 128 255>; | |||
default-brightness-level = <7>; | |||
enable-gpios = <&gpio1 5 0>; | |||
}; |
backlight-1 { | |||
compatible = "pwm-backlight"; | |||
pwms = <&pwm2 0 5000000>; | |||
brightness-levels = <0 4 8 16 32 64 128 255>; | |||
default-brightness-level = <7>; | |||
enable-gpios = <&gpio7 13 0>; | |||
}; | |||
}; |
&pwm1 {
pinctrl-names = "default"; | |
pinctrl-0 = <&pinctrl_pwm1>; | |
status = "okay"; |
};
&pwm2 {
pinctrl-names = "default"; | |
pinctrl-0 = <&pinctrl_pwm2>; | |
status = "okay"; |
};
pinctrl_pwm1: pwm1grp { | ||||
fsl,pins = < | ||||
MX6QDL_PAD_GPIO_9__PWM1_OUT 0x1b0b1 // backlight lvds1 | ||||
>; | ||||
}; |
pinctrl_pwm2: pwm2grp { | ||||
fsl,pins = < | ||||
MX6QDL_PAD_DISP0_DAT9__PWM2_OUT 0x1b0b1 // backlight lvds2 | ||||
>; | ||||
}; |
I have almost solved this issue. I am new to the device tree world, but I thought that the device tree configurations would set up the device according to my custom settings. I had to add code to my custom u-boot file to actually configure the PWM registers. After doing this the LVDS backlight was functional.
This leads to a larger question: How is the device tree data used by the kernel to configure the specific functions in the device? Where in the kernel boot process is the DTB file used?
Hi Paul
for pwm dts configuration one can look at
linux-2.6-imx.git - Freescale i.MX Linux Tree
Best regards
igor
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