[PATCH V3] ARM: dts: da850-evm: Enable LCD and Backlight

[Adam Ford]

On Mon, May 14, 2018 at 12:29 AM, Sekhar Nori <nsekhar at ti.com> wrote:
> Hi Adam,
>
> On Monday 14 May 2018 04:50 AM, Adam Ford wrote:
>> When using the board files the LCD works, but not with the DT.
>> This adds enables the original da850-evm to work with the same
>> LCD in device tree mode.
>>
>> The EVM has a gpio for the regulator and a gpio enable.  The LCD and
>> the vpif display pins are mutually exclusive, so if using the LCD,
>> do not load the vpif driver.
>
> Its not sufficient just note this in patch description.
>
> a) Disable (status = "disabled") the VPIF node which clashes for pins
> with LCD.
> b) Add a comment on top of the status = "disabled" giving information on
> how user can enable it (disable lcdc node and then change to status =
> "okay").
>
>>
>> Signed-off-by: Adam Ford <aford173 at gmail.com>
>> ---
>> V3:  Fix errant GPIO, label GPIO pins, and rename the regulator to be more explict to
>>      backlight which better matches the schematic.  Updated the description to explain
>>      that it cannot be used at the same time as the vpif driver.
>>
>> V2:  Add regulator and GPIO enable pins. Remove PWM backlight and replace with GPIO
>>
>> diff --git a/arch/arm/boot/dts/da850-evm.dts b/arch/arm/boot/dts/da850-evm.dts
>> index 2e817da37fdb..3f1c8be07efe 100644
>> --- a/arch/arm/boot/dts/da850-evm.dts
>> +++ b/arch/arm/boot/dts/da850-evm.dts
>> @@ -27,6 +27,50 @@
>>               spi0 = &spi1;
>>       };
>>
>> +     backlight {
>> +             compatible = "gpio-backlight";
>> +             enable-gpios = <&gpio 7 GPIO_ACTIVE_HIGH>; /* GP0[7] */
>
> The gpio-backlight binding does not describe a property called
> enable-gpios. It should just be gpios.

I will fix that.

>
> a) Are you using gpio-backlight because you are not able to get the PWM
> to work?
>
Yes,  You told me not to worry about doing a PWM backlight because the
legacy board does not PWM either.

> b) What is GP0[7] connected to in the schematic you have? In the
> schematic I have I see LCD_PWM0 is connected to
> SPI1_SCS[0]/EPWM1B/GP2[14]/TM64P3_IN12.

I have schematic 1016572 dated Wednesday, August 18, 2010.  According
to it, AXR15 / EPWMN0_TZ[0] / ECAP2_APWM2 / GPIO0[7] connects to U25,
Pin 46 to generate M_LCD_PWM0.  You might have one of the early,
pre-release versions.

>
> c) The /* GP0[7] */ comment is not really useful on its own as it can be
> computed. What I wanted to see is the schematic symbol like "LCD_PWM0".
> Same for other places like this below.

I can do that.
>
>> @@ -35,6 +79,16 @@
>>               regulator-boot-on;
>>       };
>>
>> +     backlight_reg: backlight-regulator {
>> +             compatible = "regulator-fixed";
>> +             regulator-name = "lcd_backlight_pwr";
>> +             regulator-min-microvolt = <3300000>;
>> +             regulator-max-microvolt = <3300000>;
>> +             gpio = <&gpio 47 GPIO_ACTIVE_HIGH>; /* GP2[15] */
>> +             regulator-always-on;
>
> Why should this regulator never be disabled?

The gpio-backlight does not have a way that I can see to associate the
regulator to it.  I read through the bindings, but I didn't see an
option to associate a regulator it.  I use this regulator to drive
lcd_backlight_pwr and the backlight driver to write lcd_pwm0.  Without
this option, the system disables lcd_backlight_pwr and the screen is
blank


adam
>
> Thanks,
> Sekhar