AM5708: Linux pwm-backlight with ecap2

Scott Lin2

Part Number: AM5708

We have custom board with am5708 / SDK-05.03.00.07

The DTS file linux-4.14.79\arch\arm\boot\dts\am571x-idk.dts is modified to have

	lcd_bl: backlight {
		compatible = "pwm-backlight";
		pwms = <&ecap2 0 50000 0>;
		brightness-levels = <0 51 53 56 62 75 101 152 255>;
		default-brightness-level = <8>;
		power-supply = <&vsys_3v3>;
	};

&epwmss2 {
	status = "okay";

	ecap2: ecap@48442100 {
		status = "okay";
	};
};

\u-boot-2018.01\board\ti\am57xx\mux_data.h is modified to have

{MMC3_CMD, (M10 | PIN_OUTPUT_PULLUP)},

after issue the command below nothing change

# cat /sys/kernel/debug/pwm
platform/48442100.ecap, 1 PWM device
pwm-0 (backlight ): requested enabled period: 50000 ns duty: 50000 ns polarity: normal
#
# cat /sys/class/backlight/backlight/brightness
8
# echo 1 > /sys/class/backlight/backlight/brightness
# cat /sys/class/backlight/backlight/brightness
1
#

Can you help to let me know what is missing?

Regards,

Scott

over 6 years ago

0 Karthik Ramanan over 6 years ago

TI__Guru** 113810 points

Hi Scott,

Either me or my colleague will provide you a feedback on Monday/Tuesday next week. I do not have access to the board now to try some experiments to answer your question.

Regards

Karthik

0 Scott Lin2 over 6 years ago in reply to Karthik Ramanan

Expert 1400 points

the issue is resolved

{MMC3_CMD, (M10 | PIN_OUTPUT_PULLUP)}, which is eCAP2_in_PWM2_out

should change to ecap1 in DTS

    lcd_bl: backlight {
        compatible = "pwm-backlight";
        pwms = <&ecap1 0 50000 0>;
        brightness-levels = <0 51 53 56 62 75 101 152 255>;
        default-brightness-level = <8>;
        power-supply = <&vsys_3v3>;
    };

&epwmss1 {
    status = "okay";

    ecap1: ecap@48440100 {
        status = "okay";
    };
};

{MMC3_CMD, (M10 | PIN_OUTPUT_PULLUP)},

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AM5708: Linux pwm-backlight with ecap2