[PATCH v1 3/3] ARM: dts: am335x-bone: add support for beaglebone LCD4 cape

[Gupta, Pekon]

>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