[PATCH 4/5] sun7i: add support for Micronova srl s027_3 board

[Andre Przywara <andre.przywara@arm.com>]

On Fri, 19 Feb 2021 11:12:08 +0100
Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:

Hi,

> On 2/19/21 2:44 AM, Andre Przywara wrote:
> > On Fri, 19 Feb 2021 00:26:19 +0100
> > Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:
> > 
> > Hi Giulio,
> >   
> >> From: Giulio Benetti <giulio.benetti@micronovasrl.com>
> >>
> >> Add support for Micronova srl s027_3 board by adding new vendor/board
> >> folders and using in local Makefile the already present
> >> board/sunxi/Makefile. The reason is that s027_3 needs a pin to be asserted
> >> to enable lcd before setting controller up and sunxi board doesn't provide
> >> a way to do this customization.  
> > 
> > Have you tried CONFIG_VIDEO_LCD_POWER?  
> 
> Yes, I already use that for DISPONOFF.

So what are these pins for, exactly? Backlight? A regulator to provide
power to the LCD?
If you grep for "gpio.CONFIG" in sunxi_display.c, there are more GPIOs
that we set, for various reasons. Can you pick some from there, and set
them in your defconfig?

> > I am strongly against introducing per-board code files, and we
> > definitely won't introduce them just for one GPIO.  
> 
> I knew it was a strange hack, but I have 2 different pins to be set high 
> before init video controller. Another idea that comes into my mind is to 
> handle CONFIG_VIDEO_LCD_POWER as a gpio list and iterate/enable, what 
> about that?

Do you really need *two* pins to switch the LCD power supply? If yes,
this might be an option. But I guess at this point we want to go more a
DT route.
Speaking of which, I don't see any video output device in the DT, I
guess you just rely on simplefb. But given that there is no bridge or
it seems to be transparent, at least, you might be able to describe
this in the DT as well, so Linux can use its own display driver?
Then we might be able to find a more sustainable solution, based on
pins in the DT.

Cheers,
Andre

P.S. Can you please try to apply
https://patchwork.ozlabs.org/project/uboot/patch/20210205010748.2646-1-andre.przywara at arm.com/
This would be merged around the same time, and I am curious if this
still works with an LCD.

> 
> >> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> >> Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>  
> > 
> > Please choose one email address, there is no point in having two
> > S-o-b's from the same person.  
> 
> I missed this as well as the repeated patch in patchset.
> 
> Thank you
> Best regards