Hi,
We are using Debian kernel 4.14 and pwm_bl.c driver for controlling a MIPI backlight. We are facing issue in configuring the PM GPIO 5 pin as PWM pin for MIPI panel.
The driver is getting initiated successfully, but there is no effect/change in the brightness even after changing the brightness entries in driver and sysfs. Besides, there isn’t a PWM signal on the GPIO 5 (checked at the oscilloscope).
We tried to configure a PWM that outputs its signal on the MPP4 dtest-line 1 and have the GPIO 5 configured on this line. Configuring the GPIO on this line is what we’re struggling right now.
Here’s the actual device-tree configuration we tried:
//apq8096-db820c-pmic-pins.dtsi
&pm8994_gpios {
pinctrl-names = "default";
pinctrl-0 = <&ls_exp_gpio_f &bt_en_gpios>;
ls_exp_gpio_f: pm8994_gpio5 {
pinconf {
pins = "gpio5";
function = "dtest1";
output-low;
power-source = <PM8994_GPIO_S4>; // 1.8V
};
};
[...]
};
&pm8994_mpps {
pm8994_mpp2_wifi_led: mpp2-wifi-led-active {
pins = "mpp2";
function = "sink";
output-low;
qcom,dtest = <2>;
};
pm8994_mpp4_backlight: mpp4-backlight {
pins = "mpp4";
function = "digital";
output-low;
qcom,dtest = <1>;
};
[...]
};
//pm8994.dtsi
&spmi_bus {
[...]
pmic@1 {
compatible = "qcom,pm8994", "qcom,spmi-pmic";
reg = <0x1 SPMI_USID>;
#address-cells = <1>;
#size-cells = <0>;
pwm {
compatible = "qcom,pm8916-pwm";
#pwm-cells = <2>;
status = "disabled";
};
};
};
//apq8096-db820c.dtsi
backlight: backlight {
status = "okay";
compatible = "pwm-backlight";
pwms = <&pm8994_pwm 0 10000>;
brightness-levels = <0 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
power-supply = <&pm8994_l28>;
enable-gpios = <&msmgpio 135 0>;
};
[...]
&spmi_bus {
pmic@1 {
pm8994_pwm: pwm {
status = "okay";
qcom,power-source = <2>;
qcom,dtest = <1 1>;
pinctrl-names = "default";
pinctrl-0 = <&pm8994_mpp4_backlight>;
};
};
};
So, I would require some help on configuring the GPIO pin as PWM output.
Thanks.
