How to change the backlight level ?

wangvictor — Thu, 21 Dec 2017 08:36:23 GMT

Hi All,

I'm using Linux 4.1.15 and i.MX6 sabreSD for my layer.

I'm trying to modify the backlight level like below.

pwm-backlight {
compatible = "pwm-backlight";
pwms = <&pwm1 0 PANEL_PWM_PERIOD>;

brightness-levels = <
5 5 5 5 5 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 50 50 50 50 50 50 50 50 50
50 50 50 50 50 50 50 50 50 50
50 50 50 50 50 50 50 50 50 50
50 50 50 50 50 50 50 50 50 50
50 50 50 50 50 50 50 50 50 50
50
>;
default-brightness-level = <100>;
status = "okay";
};

But the backlight nits is still up to 730.

The value 730 is when the balcklight settings still like below.

brightness-levels = <
/*0 1 2 3 4 5 6 7 8 9*/
5 5 5 5 5 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
>;

Why the backlight Maximum is not changing ?

Thanks in Advanced!

Re: How to change the backlight level ?

igorpadykov — Thu, 21 Dec 2017 10:41:01 GMT

Hi victor

please check linux/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt:
"default-brightness-level: the default brightness level (index into the array defined by the "brightness-levels" property)"

So <100> is index in array of brightness elements.
It may be more debugged in linux/drivers/pwm-imx.c and using oscilloscope.

Best regards
igor
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topic How to change the backlight level ? in i.MX Processors

How to change the backlight level ?

Re: How to change the backlight level ?