[Bug 22229] New: Incorrect PLL values selected for RS690

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Thu Jun 11 02:47:48 PDT 2009


           Summary: Incorrect PLL values selected for RS690
           Product: xorg
           Version: git
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/Radeon
        AssignedTo: xorg-driver-ati at lists.x.org
        ReportedBy: tom at ipe-systems.co.uk
         QAContact: xorg-team at lists.x.org

I have had some problems with flickering using this chip and high resolution
displays over DVI/HDMI. The problem seems dependent on the model of screen,
some seem more sensitive to variations in pixel clock than others. I have
managed to resolve the issue by making 2 changes to radeon_crtc.c, one to
enable the use of the fractional fb divider and secondly by changing the
selection criteria for PLL values to choose the closest frequency that is less
than the target frequency, rather than just the closest. I have added these
changes unconditionally to the driver (it's basically a quick hack to make it
work and certainly could be much tidier), but can post a patch if required.

I don't have access to any other radeon cards so I can't say if this problem or
the solution affects them - I suspect from the looking at the commit logs that
the fractional fb div doesn't work on some cards, but it seems to be required
for the RS690. 

Any advice on how/where to properly incorporate these changes into the driver
would be appreciated.

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