drm timing problems in sama5d3 Xplained.

[Boris Brezillon]

Hi Alex,

On Mon, 5 Sep 2016 11:04:51 +0200
Alex Vazquez <avazquez.dev at gmail.com> wrote:

> Hi All.
> I am using DRM in a sama5d3 Xplained with display TM43 and I've found with
> the following problem:
> I deleted the network interfaces in the device tree for my system to boot
> faster. My problem is that now the startup script run before the driver has
> loaded correctly.
> I explain better:
> The startup script begin to appear before the creation of the framebuffer
> message appears. (See LogKernel.txt)
> 
> atmel-hlcdc-display-controller atmel-hlcdc-dc: fb0:  frame buffer device
> 
> 
> 1 - I can't use the framebuffer until the message is not displayed. (This
> did not matter. I want to use drm.)
> 2 - DRM don't work fine. If I try to paint on the screen (using planes)
> before the message it is created framebuffer appears, nothing appears on
> the display.
> 
> This problem I can replicate with the demo atmel if I remove network
> interfaces in the device tree and adding a startup script that uses drm.
> 
> I add the demo with the modified device tree so you can prove that occurs.
> 
> https://drive.google.com/file/d/0B3EMwEbIHhkAbDhGMU1BcEVoYkU/view?usp=sharing
> 
> You only need to add the startup script in /etc/rcS.d/
> 
> #!/bin/sh
> > modetest -M atmel-hlcdc -P 26:480x272+0+0 at AR15  
> 
> 
> I also tested with the latest version of kernel 4.8 RC3 and the problem is
> still happening.

It seems that the atmel-hlcdc DRM device probe is deferred because some
elements in the display pipeline are missing (the display itself, the
backlight attached to the display, or even the PWM attached to the
backlight).

Can you check if the /dev/dri/xxx files are present when you reach your
init script?

If that's not the case, can you make sure you compiled the different
drivers needed for the display pipeline to work correctly statically?

Thanks,

Boris