On Fri, 29 Jul 2011 18:01:39 -0400, Gene Heskett <gene.heskett@xxxxxxxxx> wrote: > On Friday, July 29, 2011, Keith Packard wrote: > >On Fri, 29 Jul 2011 13:55:35 +0100, Ben Brewer > <ben.brewer@xxxxxxxxxxxxxxx> wrote: > >> I've added a global SSC (Spread Spectrum Clock) parameter to the i915 > >> driver, since having SSC enabled breaks (distorts) VGA output on some > >> Core i5/i7 chips (see > >> https://bugs.freedesktop.org/show_bug.cgi?id=38750). SSC is still > >> enabled by default so the behaviour won't change but setting the > >> global_use_ssc parameter will turn this feature off and allow affected > >> devices to function correctly (notably the Dell Vostro 3300). > > > >The question I have is why is SSC enabled on the VGA output at all? I > >don't see any way VGA could ever tolerate it. > > Something does not make sense here Keith, so I'm with you, and my > background is from about 60 years in tv maintenance and 45 in > broadcasting. Right, I think the basic problem is that we aren't switching SSC on and off based on whether there's an output which can't tolerate it. Making this user-configurable doesn't make any sense, it clearly needs to be done in the driver automatically, based on whether there's an analog output running (VGA or TV). > Hardware design error in the Dell? Nope, just a driver bug :-) -- keith.packard@xxxxxxxxx
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