AM5708: PWM ecap function for LCM brightness

Hi Daniel,

Apologies for the long silence on this. I will get back to you after checking with the expert in couple of days.

Best Regards,
Keerthy

Hi Daniel,

I am checking the 6.03 SDK. "arch/arm/boot/dts/am57xx-evm-common.dtsi"

lcd_bl: backlight {
compatible = "pwm-backlight";
pwms = <&ehrpwm1 0 50000 0>;

/* Anything lower than 241 is no longer visible */
brightness-levels = <0 243 245 247 249 251 252 253 255>;

default-brightness-level = <8>;
};

Have you tried with the default. Does it work for you?

Best Regards,
Keerthy

Hi

Change to 

lcd_bl: backlight {
compatible = "pwm-backlight";
pwms = <&ecap1 0 50000 0>;
#if 1
brightness-levels = <0 243 245 247 249 251 252 253 255>;
default-brightness-level = <8>;
#else
brightness-levels = <0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100>;
default-brightness-level = <100>;
#endif /* 1 */
};

But issue is still same

Regards,

Scott

Hi Scott,

What i meant is: pwms = <&ehrpwm1 0 50000 0>;

while you are trying: pwms = <&ecap1 0 50000 0>;

Best Regards,
Keerthy

Hi Keerthy

We can try, but why ecap could not be set to OFF status?

Regards,

Scott 

Hi Keerthy

For ehrpwm1 it could be turn off 

# echo 0 > /sys/devices/platform/backlight/backlight/backlight/brightness
# cat /sys/kernel/debug/pwm
platform/48440200.pwm, 2 PWM devices
pwm-0 (backlight ): requested period: 50000 ns duty: 0 ns polarity: normal
pwm-1 ((null) ): period: 0 ns duty: 0 ns polarity: normal

platform/4843e200.pwm, 2 PWM devices
pwm-0 ((null) ): period: 0 ns duty: 0 ns polarity: normal
pwm-1 ((null) ): period: 0 ns duty: 0 ns polarity: normal
# 
# echo 50 > /sys/devices/platform/backlight/backlight/backlight/brightness
# cat /sys/kernel/debug/pwm
platform/48440200.pwm, 2 PWM devices
pwm-0 (backlight ): requested enabled period: 50000 ns duty: 25000 ns polarity: normal
pwm-1 ((null) ): period: 0 ns duty: 0 ns polarity: normal

platform/4843e200.pwm, 2 PWM devices
pwm-0 ((null) ): period: 0 ns duty: 0 ns polarity: normal
pwm-1 ((null) ): period: 0 ns duty: 0 ns polarity: normal
# 

Regards,

Scott

Scott,

Cool. Do we have any other question on this?

Best Regards,
Keerthy

Hi Keerthy

For ecap1, is it HW issue which it can not be turn off ?

Regards,

Scott

Hi Scott,

I will check on this internally & get back to you. I hope you are unblocked with ehrpwm.

Regards,
Keerthy

Hi Keerthy

Please know that our design will use ecap, due to customer request.

Regards,

Scott

Hi Keerthy

We are using ecap, the ehrpwm we just measure the signal  for you, not directly connect to backlight.

Therefore, we would like to solve that how to turn off ecap signal.

Regards,

Scott

Hi Scott,

I currently do not have the hardware to verify this. I will get back in few days.

Best Regards,
Keerthy

Hi Scott,

Apologies. I still do not have the display to verify the ecap signal effect.

Best Regards,
Keerthy

Hi Scott,

Did you have a chance to look further with ecap? Apologies for the delay. Do you have an IDK
or a custom board?

- Keerthy

Hi Keerthy

We do have an IDK, please let us know what to do, thanks.

Regards,

Scott

Unlocking thread as we continue to explore options to enable this.