On Fri, 23 Sep 2011 20:07:52 +0100, Chris Wilson <ch...@chris-wilson.co.uk> wrote: > On Fri, 23 Sep 2011 09:15:05 -0700, Keith Packard <kei...@keithp.com> wrote: > > What I didn't find there was any mention of the display_clock_mode > > field; perhaps jbarnes has newer VBIOS sources or actual BDB > > documentation. > > iirc display_clock_mode was found in the Capella VBIOS assembly, so > indeed comparatively ancient.
Ok, so it appears to have disappeared in more recent hardware. I'm betting that with PCH hardware, there is always a CK505 source to use, so the BIOS just uses it unconditionally and may not actually be configured in the VBT. > I do enjoy how our best guides for programming the hardware comes from > RE the bioses. :( It's not the best, it's just yet another source of information :-) So, what I think we should be doing is using display_clock_mode to select between ck505 and internal clock source on pre-PCH hardware. For PCH hardware, we unconditionally use the ck505 source for the non-SSC reference. When we need to drive two outputs and are *not* using ck505, then we disable SSC. Seem reasonable? -- keith.pack...@intel.com
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