Flicker with fb on Jetson TK1

[Thierry Reding]

On Sun, Jul 24, 2016 at 07:02:34PM -0700, Martin Michlmayr wrote:
> Running X with fb on the Jetson TK1, I get a flicker on the monitor
> from time to time.  I don't think I need to do anything to trigger it
> (such as moving the mouse).  It just happens from time to time.
> 
> I don't have the right X patches for nouveau, so X is using fbdev
> which I guess means the tegra-drm driver.
> 
> This is with mainline u-boot (2016.07-rc1) and mainline kernel (4.6).
> 
> I uploaded a video in which you can see the flicker several times
> (e.g. at 0:03, 0:16 and 0:28):
> http://www.cyrius.com/tmp/tk1/

What version of X do you use? Recent versions, I think starting with
1.18, the modesetting driver is built-in and is what you should use with
Tegra (and on top of an DRM/KMS driver, really).

The problem with fbdev is that it doesn't do double-buffering and hence
you can often see the kind of tearing as in the video. The modesetting
driver (which is also available as xf86-video-modesetting pre-1.18) can
do double-buffering (and I think will do by default), hence removing
the cause of such tearing.

Can you try running the test with the modesetting driver and report if
you're still experiencing the issue?

Thanks,
Thierry
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