[Nouveau] [Bug 40747] The new nouveau kernel module fails to use my monitor's native resolution

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=40747

--- Comment #10 from Francisco Jerez <currojerez at riseup.net> 2011-09-13 16:35:59 PDT ---
(In reply to comment #7)
> So, I tried to play with the video= parameter and I now have an acceptable
> workaround with "video=1600x1200 at 55" which gives me the right resolution
> without any complaint from my monitor.
> I tried to "M" and the "R" thingies as in "1600x1200MR" or "1600x1200R" but
> these seem to be ignored, or at least didn't make much difference (actually the
> "R" does the same as when nothing is specified and the "MR" gives a marginally
> higher pixel clock).  I expected the "R" to give a much more substantial
> reduction in dotclock, or maybe the R is somehow ignored in the "MR"
> combination ("cvt" gives me the same modeline as I got with 1600x1200MR, at
> 161MHz, whereas "cvs --reduced" drops the dotclock to 130MHz).
> 
That's a bug of the kernel command line parser... try "RM" instead of "MR".

> I haven't tried the Xorg nouveau driver on top to see whether it obeys my
> "video=" arg or whether I'm going to have to play the same dance in the
> xorg.conf file (because right now the Xorg driver gives me the familiar "error
> opening the drm").  But at least using the fbdev driver, this gives me a good
> workaround.
> 
It doesn't, right now you need to tell X to use a reduced blanking mode
separately.

> I see only two ways to improve the situation (modulo the handling of "R"
> mentioned above):
> - provide a way to override the 155MHz limit (apparently, the hardware does not
> prevent overclocking and at least in my case, it handles such overclocking
> without blinking).
> - when the monitor's preferred modeline can't be used because of dotclock
> limits, output a clear message in the dmesg about it, and cook up a different
> modeline that preserves the resolution (e.g. at the cost of lower refresh
> rate).  This is because on LCD displays, using the native resolution is a lot
> more important than using a high enough refresh rate.

The latter would be a better idea IMHO.

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