On Thu, 26 Apr 2012 15:21:13 -0300 Eugeni Dodonov <eugeni.dodonov at intel.com> wrote: > The iCLKIP clock is used to drive the VGA pixel clock on the PCH. In order > to do so, it must be programmed to properly do the clock ticks according > to the divisor, phase direction, phase increments and a special auxiliary > divisor for 20MHz clock. > > Those values can be programmed individually, by doing some math; or we > could use a pre-defined table of values for each modeset. For speed and > simplification, the idea was to just adopt the table of valid pixel clocks > and select the matching iCLKIP values from there. > > As a possible idea for the future, it would be possible to add a fallback > and calculate those values manually in case no match is found. But I don't > think we'll encounter a mode not covered by those table, and VGA is pretty > much going away in the future anyway. > > Signed-off-by: Eugeni Dodonov <eugeni.dodonov at intel.com> > --- I don't mind the table and like the fact that it documents the PPM. But I think we should fuzzy match the clocks, since e.g. 1920x1080 at 60Hz with reduced blanking is a 138.5MHz clock, and we don't have a match for that it appears? Or do we already fuzzy match elsewhere? -- Jesse Barnes, Intel Open Source Technology Center
