Nouveau - Sep 2013 - [Bug 69083] New: using DVI to VGA adapter for CRT and specifying supported "PreferredMode" >EDID preferred mode, screen output is compressed into small fraction of top scan lines

https://bugs.freedesktop.org/show_bug.cgi?id=69083

          Priority: medium
            Bug ID: 69083
          Assignee: nouveau at lists.freedesktop.org
           Summary: using DVI to VGA adapter for CRT and specifying
                    supported "PreferredMode" >EDID preferred mode,
screen
                    output is compressed into small fraction of top scan
                    lines
        QA Contact: xorg-team at lists.x.org
          Severity: normal
    Classification: Unclassified
                OS: All
          Reporter: mrmazda at earthlink.net
          Hardware: All
            Status: NEW
           Version: unspecified
         Component: Driver/nouveau
           Product: xorg

Created attachment 85416
  --> https://bugs.freedesktop.org/attachment.cgi?id=85416&action=edit
Xorg.0.log from openSUSE 13.1 milestone 4

Initial summary:
using DVI to VGA adapter for CRT and specifying supported
"PreferredMode" >EDID
preferred mode, screen output is compressed into small fraction of top scan
lines

To reproduce:
1-connect DVI-I out from NVidia PCI express card (G84 here with only dual DVI
out; DVI-I-1 connected) to CRT supporting up to 2048x1536 but with 1600x1200
preferred (NEC FE2111SB here) via PCI to VGA adapter
2-set 'Option "PreferredMode" "1920x1440"' in
'Section "Monitor"' in
/etc/X11/xorg.conf*
3-start X server

Actual results:
1-entirety of video output displays into top scan lines, approximately 4mm or
less in height
2-usable desktop only for those who can use it without seeing video output

Expected results:
1-normal display output
2-normally usable desktop
3-"normal" even if fallback to EDID preferred 1600x1200 is necessary
to do so
due to gfx hardware device limitation

Notes:
1-Does not happen with pure VGA connection with any gfxchip or driver.
2-Does not happen with same 3 DVI-to-VGA adapters connected to Radeon (rv380;
S-video, VGA-0 & DVI-0 available; DVI-0 connected) DVI output.
3-Problem dates back at least to openSUSE 11.4 with
xorg-x11-driver-video-nouveau-0.0.16_20110115_b795ca6-3.1.i586 installed and
server 1.9.3.
4-Problem remains at least through server 1.14.2 and
xorg-x11-driver-video-nouveau-1.0.9-1.3 on openSUSE 13.1M4, and server 1.14.1
on Fedora 19 with xorg-x11-drv-nouveau-1.0.7-1.fc19.
5-Happens with or without specific port specified via Option in 'Section
"Device"'.
6-Happens on both 32 and 64 bit x86 installations.

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https://bugs.freedesktop.org/show_bug.cgi?id=69083

Ilia Mirkin <imirkin at alum.mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|using DVI to VGA adapter    |[NV84] using DVI to VGA
                   |for CRT and specifying      |adapter for CRT and
                   |supported "PreferredMode"   |specifying supported
                   |>EDID preferred mode,       |"PreferredMode"
>EDID
                   |screen output is compressed |preferred mode, screen
                   |into small fraction of top  |output is compressed into
                   |scan lines                  |small fraction of top scan
                   |                            |lines

--- Comment #1 from Ilia Mirkin <imirkin at alum.mit.edu> ---
Are you sure that the display is actually compressed into the top few
scanlines? e.g. do you see the mouse cursor in there when you move it around?
Does it show your normal background? Or is it just garbage that happens to not
have 0's for the top few scanlines' worth of data?

I've never used PreferredMode before. If you remove it, I assume everything
works fine? What happens if you run something like

xrandr --output DVI-I-1 --mode 1920x1440

does that fix things for you? Can you supply the output of

xrandr --verbose

after X has started? (You can e.g. ssh in and run DISPLAY=:0 xrandr --verbose)

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--- Comment #2 from Felix Miata <mrmazda at earthlink.net> ---
Created attachment 85420
  --> https://bugs.freedesktop.org/attachment.cgi?id=85420&action=edit
verbose xrandr output per comment infra

(In reply to comment #1)
> Are you sure that the display is actually compressed into the top few
> scanlines? e.g. do you see the mouse cursor in there when you move it
> around?
I started working out this problem 3 months ago. I spent mucho hours trying to
separate it from other bugs at the time. It took me more than two days. A small
sample of the 93 saved logs from that time:
http://fm.no-ip.com/Tmp/Linux/Xorg/PrefMode/

As the session begins to open I see the wallpaper colors, which later change as
Konsole and the panel should be painted. But, I can see the tip of the mouse
pointer in it at times.
> Does it show your normal background?
Can't really tell. My *normal* background is usually hidden under a pile of
windows.
> Or is it just garbage that
> happens to not have 0's for the top few scanlines' worth of data?
It's clearly a color pattern based upon the wallpaper and the panel and
Konsole.
> I've never used PreferredMode before. If you remove it, I assume
everything
> works fine?
Yup. Without it happily uses the EDID preference instead of mine.
> What happens if you run something like
> xrandr --output DVI-I-1 --mode 1920x1440
> does that fix things for you? Can you supply the output of
> xrandr --verbose
> after X has started? (You can e.g. ssh in and run DISPLAY=:0 xrandr
> --verbose)
Instead of trying to figure out ssh, I made this script:

xrandr --verbose  > xrandrout.txt
echo mark >> xrandrout.txt
xrandr --output DVI-I-1 --mode 1920x1440
echo mark >> xrandrout.txt
xrandr --verbose  >> xrandrout.txt

I closed a working prior session with Konsole open, added back to configfile
the non-working PreferredMode, started new session, and after a short wait for
Konsole to get open I ran the script.

It changed nothing WRT to the bug, display still mostly just black. Good thing
Ctrl-Alt-BS works.

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--- Comment #3 from Ilia Mirkin <imirkin at alum.mit.edu> ---
What if you run

xrandr -s 1920x1440 -r 60

I wonder if something's breaking down at the 75Hz refresh rate it ends up
picking. (You can do this from a "working" session, it should just
switch
resolutions... you can also be careful about it and do like xrandr -s 1920x1440
-r 60 && sleep 10 && xrandr -s 1600x1200 to make sure that you
get back to a
working state.)

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--- Comment #4 from Felix Miata <mrmazda at earthlink.net> ---
'xrandr -s 1920x1440 -r 60 && sleep 10 && xrandr -s
1600x1200' scrunched
everything into the top 1/8" of the display and after a brief sleep
restored
the working EDID preferred 1600x1200 state.

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Ilia Mirkin <imirkin at alum.mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[NV84] using DVI to VGA     |[NV84] Using 1920x1440 mode
                   |adapter for CRT and         |on DVI-I -> VGA adapter
                   |specifying supported        |causes output to be
                   |"PreferredMode" >EDID       |compressed into
small
                   |preferred mode, screen      |fraction of top scan lines
                   |output is compressed into   |
                   |small fraction of top scan  |
                   |lines                       |

--- Comment #5 from Ilia Mirkin <imirkin at alum.mit.edu> ---
OK, so this has nothing to do with setting the PreferredMode. Good, that would
have been weird. Something's not being computed correctly. I wouldn't be
surprised if the mode data in the EDID were somehow wrong for those modes, and
other drivers are just better at dealing with the incorrectness. Or perhaps
we're setting some clock incorrectly.

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Felix Miata <mrmazda at earthlink.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[NV84] Using 1920x1440 mode |[NV84] specifying higher
                   |on DVI-I -> VGA adapter     |than EDID-preferred 4:3
                   |causes output to be         |mode on DVI-I -> VGA
                   |compressed into small       |adapter causes output to be
                   |fraction of top scan lines  |compressed into small
                   |                            |fraction of CRT's top scan
                   |                            |lines

--- Comment #6 from Felix Miata <mrmazda at earthlink.net> ---
1920x1440 was an example of a broken mode >EDID preferred. The broader
description is xorg.conf* PreferredMode is broken WRT all traditional 4:3 modes
higher than the EDID preferred mode, same as those modes set via xrandr -s.
Other broken modes on this FE2111SB/G84 combination include 1792x1344 and
1856x1392, proven using comment 4 method. Interestingly, this CRT has
previously proven to have no objection to non-4:3 modes, and 'xrandr -s
1920x1200 -r 60 && sleep 10 && xrandr -s 1600x1200' does not
produce this bug,
just a normal 1920x1200 squeezed into a 4:3 space for the sleep duration.
1920x1080, 1440x900 and 1680x1050 also work in same manner. Both 1920x1200 and
1920x1080 (and presumably 1440x900 and 1680x1050) work via PreferredMode as
well.

Considering the dozens of gfxchips using non-nouveau drivers I've connected
via
VGA outputs to this CRT exhibiting no such trouble, I doubt EDID is the root.
Using this very same G84 and DVI to VGA adapter with nv driver and disabled KMS
this CRT works as well as Intel and Radeon and even does 2048x1536 at 60.

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--- Comment #7 from Ilia Mirkin <imirkin at alum.mit.edu> ---
Up until recently, we defaulted to forcing panel scaling by default (except for
VGA). Perhaps we were misdetecting something wrt auto-enabling it (normally
disabled for VGA). Does this still happen with recent kernels? Or with the
randr property 'scaling mode' set to 'None'?

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Felix Miata <mrmazda at earthlink.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |WORKSFORME

--- Comment #8 from Felix Miata <mrmazda at earthlink.net> ---
The NEC FE2111SB of comment 0 is no longer available. With a Sony Trinitron
G520 this is not reproducible with any kernel/server/nouveau combination tried,
including k3.7.10/s1.13.2/n1.0.6, k3.11.10/s1.14.3/n1.0.9,
k3.16.7/s1.16.1/n1.0.11 and k4.2.3/s1.17.2/n1.0.11 among others, all using the
same G84 and 32 bit Prescott host. So I'm of the opinion this was more
likely a
CRT quirk than a nouveau bug.

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