Bug 87061 - 1600x1200 resolution breaks at startup, but works later with xrandr
Summary: 1600x1200 resolution breaks at startup, but works later with xrandr
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/openchrome (show other bugs)
Version: unspecified
Hardware: Other All
: medium normal
Assignee: Openchrome development list
QA Contact:
Depends on:
Reported: 2014-12-07 01:47 UTC by Daniel Gnoutcheff
Modified: 2019-09-18 20:48 UTC (History)
1 user (show)

See Also:
i915 platform:
i915 features:

maxres.Xorg.log (22.74 KB, text/plain)
2014-12-07 01:49 UTC, Daniel Gnoutcheff
no flags Details
maxres.xorg.conf (22.74 KB, text/plain)
2014-12-07 01:50 UTC, Daniel Gnoutcheff
no flags Details
workaround.Xorg.log (43.11 KB, text/plain)
2014-12-07 01:52 UTC, Daniel Gnoutcheff
no flags Details
workaround.xorg.conf (108 bytes, text/plain)
2014-12-07 01:53 UTC, Daniel Gnoutcheff
no flags Details

Description Daniel Gnoutcheff 2014-12-07 01:47:04 UTC
I have a large CRT monitor with a maximum resolution (as claimed by EDID) of 1600x1200.  If I try to start X with an xorg.conf that requests 1600x1200 as the initial resolution (or if I start it without an xorg.conf), then the server crashes with

> (II) CHROME(0): Required bandwidth is not available. (576000000 > 553000000)
> (II) CHROME(0): ViaDisplayDisableCRT
> (EE) 
> Fatal server error:
> (EE) AddScreen/ScreenInit failed for driver 0

However, if I start X with an xorg.conf that requests a lower resolution (e.g. 1280x1024), and if I later request 1600x1200 with

> $ xrandr --output VGA-1 --mode "1600x1200"

then the server accepts and switches to the higher resolution without complaint.

Openchrome 0.3.3 (as packaged in Debian testing)
Xorg server 1.16.2 RC 1 (also from Debian)

Logs and example attachments comming.
Comment 1 Daniel Gnoutcheff 2014-12-07 01:49:41 UTC
Created attachment 110522 [details]

Attaching Xorg.log from the X server's failed attempt to startup with a xorg.conf that requests 1600x1200 as the inital resolution.  I also get the same result (and almost exactly the same log) when starting X with no xorg.conf.
Comment 2 Daniel Gnoutcheff 2014-12-07 01:50:39 UTC
Created attachment 110523 [details]

The xorg.conf used to generate maxres.Xorg.log.
Comment 3 Daniel Gnoutcheff 2014-12-07 01:52:30 UTC
Created attachment 110524 [details]

The Xorg.log from a successful X server start with an xorg.conf requesting 1280x1024 as the inital resolution, followed by a successful switch to 1600x1200 via xrandr.
Comment 4 Daniel Gnoutcheff 2014-12-07 01:53:11 UTC
Created attachment 110525 [details]

The xorg.conf used to generate workaround.Xorg.log
Comment 5 Xavier Bachelot 2015-01-18 12:41:19 UTC
I think what happens is the following : the initial resolution is set to 1600x1200@75Hz, which exceed the memory bandwidth limit. When xrandr set the resolution, it set the mode to 1600x1200 @60Hz, which does not exceed the bandwidth.

The 1600x1200@75 mode is validated in iga1_crtc_mode_fixup by ViaFirstCRTCModeValid, but then rejected by the later bandwidth check. One would expect it then fallback to the next available mode in the EDID, that is 1600x1200@60, but it seems that doesn't happen. I'll try to dig more to understand what happens, but I'm stuck for now.
Comment 6 GitLab Migration User 2019-09-18 20:48:45 UTC
-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

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