AnsweredAssumed Answered

Switch PWM off between U-Boot and Linux

Question asked by Steffen Doster on Feb 24, 2016
Latest reply on Mar 17, 2016 by Steffen Doster

Hi,

I have a (serious) problem with my LVDS-Display on an i.MX6:

The Brightness of this display is controlled by PWM1. I already managed to set different brightnes in u-boot and linux.

The Problem is on startup, when u-boot finished its work and Linux is just loaded:
Between u-boot end and linux start, the pin (GPIO_9__PWM1_OUT) is set to 1 regardless of what is set by u-boot. The result is a Image on my LVDS-Display that slowly fades to white.

If I get u-boot to set this pin to 0 before it closes itself, the display would turn off the Backlight and everything would be fine. Linux then would turn the pwm on again if it's ready to display its logo.

 

But I simply have no clue how tu turn this pin off on u-boot exit. I already tried to set the pin as gpio and turn it off with <gpio clear 9> in bootcmd. (This works as long as u-boot is active)

But just after u-boot exits the pin is high again. And it's driving the pin high. A Pull-Down didn't work either.

 

Any suggestions?

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