[Bug 67276] kernel-3.11 [drm:r600_uvd_ring_test] *ERROR* radeon: ring 5 test failed (0xCAFEDEAD)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=67276

--- Comment #15 from Joshua Cov. <joshuacov at gmail.com> ---
(In reply to comment #14)
> (In reply to comment #13)
> > 
> > I cannot forcibly trigger the problem. That's why I'm hoping for more
> > detailed debug messages. Maybe something connected with ring-testing or
> > maybe data feeding for those rings or anything that hs to do with the ring.
> > 
> > I'm also wondering why the problem don't appear when I restart the pc? Is it
> > some kind of a racing condition? How can I get the info that's in the ring
> > at the time the error occurs? How is the ring testing done?
> 
> I'm not sure.  I've never seen the problem.  It could be a problem with
> another one of the patches.  I've never tested backporting the patches to
> 3.10.  If you don't have problems with 3.9 or 3.11, it's hard to say.
> 
> The ring testing happens when we initially set up the ring.  The basic idea
> is to clear a scratch register or memory buffer to a known value, then write
> a new value to that register or buffer using the ring.  When the ring is
> done if the new value isn't there, the ring isn't working properly.

Do you have any idea, why this happens randomly on cold boots but not when
restarting the pc? I think the whole initialization process should be the same
everytime the system is booted, so that the ring initialization should fail
every time.

On I side note: Earlier I had an interesting problem. When rebooting the pc
after a drm-lockup I could see the last screen before the restart. This means
that some memory buffers were not completely cleared during the reboots.

Maybe I have a similar problem here: The faulty register isn't rewritten on
every reboot???

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