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AM335x: Location of LCD, GPIO Init files in Kernel.

hoyoun lyu
Intellectual 420 points
Other Parts Discussed in Thread: AM3358

Hi, all.

I use TISDK-01.00.00.03 in BBB.

I used LCD, GPIO, SPI in U-Boot and displayed image to LCD.

But, During Kernel init, Image disappear in display.

I want not disappear in display during Kernel init.

Please let me know, LCD and GPIO init location in Kernel.

Help ! 

  • 0
    TI__Guru**** 393215 points
    Hi,

    I will forward this to the software team.
  • 0
    TI__Guru**** 161600 points

    Hi,

    In kernel lcdc controller parameters are described in am335x-boneblack.dts and the actual lcdc init is done in the driver -> drivers/gpu/drm/tilcdc/tilcdc_drv.c

    However, you should have in mind that the tisdk kernel for BBB uses hdmi as a primary display, not the lcd.

    Best Regards,
    Yordan

  • 0 in reply to Yordan Kovachev
    Intellectual 420 points
    Hi, Yordan.

    Thank you for reply.

    I want to know AM3358 GPIO Init File in Kernel.
    LCD Backlight turn-on in u-boot.
    But Backlight turn-off in Kernel Init.
    So I want to prevent Backlight GPIO Init in Kernel Init.

    Help !
  • 0 in reply to hoyoun lyu
    TI__Guru**** 161600 points
    Hi,

    To prevent GPIO from initialization, you can just add status = "disabled"; in your &gpioX device tree node.

    However, if you haven't changed linux kernel source code, the backlight is controlled through the PWMSS ECAP in AM335x:
    backlight {
    compatible = "pwm-backlight";
    pwms = <&ecap2 0 50000 PWM_POLARITY_INVERTED>;
    brightness-levels = <0 58 61 66 75 90 125 170 255>;
    default-brightness-level = <8>;
    };

    You could prevent this from initialization, by commenting out the above backlight fragment.

    Hope this helps.

    Best Regards,
    Yordan