Re: Problem with first use of DRM using planes. Sama5d3

[Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>]

On Wed, 6 Jul 2016 12:17:23 +0200
Alex Vazquez <avazquez.dev@xxxxxxxxx> wrote:

> Hi All!
> I have a sama5d3 Explained with 4.3" LCD (TM4301).
> My problem is the next:
> 
> After booting the system and try to draw first using DRM using planes don't
> paint anything on the LCD displays, but from the second time is painted
> correctly on the LCD.
> 
> I have seen a couple of things:
> 
> - After starting / sys/class/drm/card0/card0-LVDS-1/enabled is disabled
> After running the program for the first time or paint something using the
> framebuffer, the state becomes enabled and can be drawn correctly using
> planes.
> 
> - If I don't use planes and use CRTC  it works correctly.
> - If I open the device with drmOpen() it works correctly. (works because
> this function calls drmAvailable(). I tried to modify the code libdrm and
> if we comment drmAvailable() does not work modetest using planes.)
> 
> Attached two codes: In the first I do not use drmAvailable() and the second
> use drmAvailable().
> I don't want to use drmOpen() because you have to indicate the driver and
> want to do it generically using the function open().
> 
> I tried to enable drm from kernel_mode_setting (video=LVDS-1:480x272-16:e)
> but don't work.
> 
> I am almost certain that the first time does not paint because DRM is
> disabled and using planes seems not enabled properly until the sample
> application is closed. Viewing code of drmAvailable() I can see that opens
> and closes the device with what happens to an enabled state.
> 
> I'm not sure if it's a bug in the driver or libdrm or is my mistake...

AFAIU, enabling/configuring a plane and a display pipeline is not the
same thing, so it's pretty much expected to get a black screen until
someone (etheir the fdev emulation or another userspace program through
the DRM APIs) has properly setup the display pipeline...

Regards,

Boris

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