[Bug 71035] New: EVO engine failure, probably (not?) related to EDID corruption

[bugzilla-daemon-CC+yJ3UmIYqDUpFQwHEjaQ@public.gmane.org]

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https://bugs.freedesktop.org/show_bug.cgi?id=71035

          Priority: medium
            Bug ID: 71035
          Assignee: nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org
           Summary: EVO engine failure, probably (not?) related to EDID
                    corruption
        QA Contact: xorg-team-go0+a7rfsptAfugRpC6u6w@public.gmane.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: nik-c8FWWMckPjiPRyzcNaLxHw@public.gmane.org
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: unspecified
         Component: Driver/nouveau
           Product: xorg

Created attachment 88342
  --> https://bugs.freedesktop.org/attachment.cgi?id=88342&action=edit
dmesg output

** Slightly modified version from Debian Bug #728278 **

The nouveau driver fails on this hardware. A talk in #nouveau on
Freenode turned up that the failure is related to the EVO engine
responsible for modesetting. Here are the relevant parts of that chat,
more explanations follow below:

08:02 < imirkin> nouveau E[   PDISP][0000:01:00.0] chid 0 mthd 0x0080 data
0x00000000 0x000d5080
08:02 < Natureshadow> that means?
08:02 < imirkin> that's a bit unfortunate
08:02 < imirkin> dunno, gimme a min
08:02 < Natureshadow> sorry, I am not a kernel hacker ;) ...
08:03 < imirkin> oh, that's the EVO flush
08:03 < imirkin> and the d5080 is probably the fifo position or something
08:03 < imirkin> uhm, silly question... do you have any indication that this
hardware actually works?
08:05 < imirkin> (e.g. on windows, or using the nvidia blob or using the nv
driver)
08:08 < Natureshadow> imirkin: it works with the nvidia driver
08:08 < imirkin> hm, ok
08:09 < Natureshadow> And GRUB can set the 1440x900 mode
08:09 < Natureshadow> So I assume VESA works as well
08:09 < imirkin> right, but that's a different mechanism
08:09 < Natureshadow> ok
08:09 < imirkin> what makes you say that edid is broken? is it broken with
nvidia driver as well?
08:09 < Natureshadow> In any case, installing the nvidia-glx driver and loading
the EDID file with X.org rather than at boot (nvidia does
                      not support modesetting) works
08:10 < Natureshadow> imirkin: Yes, it is.
08:10 < imirkin> k
08:10 < Natureshadow> The display EDID is corrupted, I have been loading that
EDID file forever with the nvidia driver
08:10 < Natureshadow> But as nouveau works great on all other hardware I have,
I wanted to get rid of that unnecessary binary blob ;)
08:11 < imirkin> yeah, for some reason the EVO commands just aren't working
08:11 < Natureshadow> Is that something I can fix ;)?
08:11 < imirkin> (these are commands used to control the display engine, which
controls the mode/etc)
08:11 < imirkin> well, if the nvidia driver works, it must be fixable
08:11 < Natureshadow> ok :D
08:11 < imirkin> the question is... how
08:12 < Natureshadow> I'm sure that question is a lot easier for you than for
me ;)
08:12 < Natureshadow> I'm ready for any debugging, may it be as crazy as you
like .)
08:14 < imirkin> well, the command likely comes from evo_sync() in
nv50_display.c
08:14 < imirkin> or perhaps nv50_display_flip_stop
08:15 < imirkin> but why does it error out? who knows. i don't know much about
the evo bits.
08:16 < Natureshadow> imirkin: hmm. so, seeing that the nvidia driver works, is
this a bug in nouveau I should report, or is it due to my
                      broken hardware?
08:16 < imirkin> given that the nvidia driver can work, it seems likely that
it's a bug in nouveau
[...]
08:33 < imirkin> it kinda feels like the evo engine isn't being turned on at
all
08:34 < imirkin> probably some missed register write somewhere
08:34 < imirkin> (whereby it normally starts out as 'on' for everone except
you)

I must add two things:

 1. The display EDID of this device is corrupted, but I have worked
    around that by ...
 2. ... loading a corrected version of the EDID binary from a file. That worked 
    (see dmesg), so I think it is irrelevant for the bug.

The effect of this issue is that when modesetting, some garbage is
written to the screen, the scrollback buffer is scrolled up a bit, but
modesetting never really happens.

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