>From: Ezequiel Garcia >>On 24 Jun 05:54 PM, Pekon Gupta wrote: >> This patch adds support for LCD4 cape as advertised on >> http://elinux.org/CircuitCo:BeagleBone_LCD4 >> >> This cape has: >> * 480x272 TFT-LCD panel >> - LCD panel datasheet and timing information are sourced from [1] >> - LCD backlight is connected to 'EHRPWM1A' on cape board, but its used for >> enabling backlight power-supply. So 'gpio-backlight' driver is used instead >> of 'pwm-backlight' driver (Kconfig: BACKLIGHT_GPIO=y). >> > >I'm confused about this, can you clarify why you are not using pwm-backlight? > As per the schematics of this LCD4 cape board, "EHRPWM1A" pin controls enabling/disabling of the power to backlight LED. It does not control the voltage levels (brightness levels) of the LED. Thus it wasn't making sense to use pwm-backlight driver which more suitable in cases where you have multiple levels of brightness. Here, you have only 2 levels "backlight=off | on", so I used gpio-backlight driver. Though you can use pwm-backlight driver also, but the backlight turns ON only when you set the /sys/class/backlight/<backlight_device>/brighteness to maximum level (as set in DT). with regards, pekon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
