On Fri, 29 Jul 2011 18:01:39 -0400, Gene Heskett gene.heskett@gmail.com wrote:
On Friday, July 29, 2011, Keith Packard wrote:
On Fri, 29 Jul 2011 13:55:35 +0100, Ben Brewer
ben.brewer@codethink.co.uk 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 :-)