[Bug 48880] Set mode has different timings than requested on VGA

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Thu Apr 19 00:51:25 PDT 2012


--- Comment #11 from Tvrtko Ursulin <tvrtko.ursulin at onelan.co.uk> 2012-04-19 00:51:25 PDT ---
(In reply to comment #10)
> Is it only problematic on VGA or TMDS?  I.e., does one only one or the other,
> but not both?

Just tried DVI and that works fine. Plus  monitor is displaying the expected
pixel clock, unlike over VGA.

Modeline is the same as fetched over VGA:
[61901.797355] [drm:drm_mode_debug_printmodeline], Modeline 18:"1920x1080" 60
148500 1920 2008 2052 2200 1080 1084 1089 1125 0x48 0x5

>  It seems to be something specific to your monitor.  I can't
> reproduce this on my ontario hardware or monitors.  I manually added the

Hm, we thought it may be the monitor, but, what is worrying is that monitor
thinks pixel clock is way different than what KMS is setting for 1920x1080,
while for other modes both KMS and monitor agree there.

> modeline you were using and it works fine here.  Can you try slightly different
> timing?  Some monitors are really picky about the clocks and sometimes they do
> not like certain pll divider combinations even though the result is the the
> same clock.  You might try setting the  RADEON_PLL_PREFER_MINM_OVER_MAXP or
> RADEON_PLL_USE_FRAC_FB_DIV pll flags in atombios_adjust_pll() and see if either
> of those helps.

I'll try this next.

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