Video tearing with modesetting driver and Intel Sandybridge graphics

[Tino Mettler]

Hi,

I get tearing video with the modesetting driver on a Debian Sid
installation.  It happens at least in VLC and Firefox in Gnome3 using
HDMI output of the Sandybridge graphics.

I does not happen when using the Intel DDX driver with the TearFree
option enabled.

According to several sources in the internet, modesetting together with
DRI3 should solve the tearing issue. However, this doesn't seem to be
the case for me.

Can you please give some hints and/or instructions how I can solve or
at least debug this issue, e.g. how to create useful diagnostic output
or test alternative software in case both Firefox and VLC do things
wrong.

I use a video projector connected to the HDMI output and video tearing
in this setup ist very disturbing.

Regards,
Tino