[Intel-gfx] Broken LVDS output at mode changes

Keith Packard keithp at keithp.com
Thu Mar 29 18:57:41 CEST 2012

<#part sign=pgpmime>
On Thu, 29 Mar 2012 18:12:56 +0200, Takashi Iwai <tiwai at suse.de> wrote:

> The strange thing is that, although you can recover the display by
> turning off LVDS and on again once when the problem happens, but then
> the display starts flickering.  And, the flickering continues even
> after reboot on BIOS boot screen.

Yeah, it's clearly the panel which is confused. It would be nice to know
what happened to the LVDS signal which caused this problem with the

> BTW, now I tested to disable LVDS unconditionally on different
> platforms as Daniel suggested.  All worked fine, and I saw no
> regressions.  Tested on IVY, SNB, ILK, GM45 and PineView.

That's not surprising -- pre-PCH platforms disabled the LVDS

I wonder if we could fix this by being more careful about the order of
register operations during LVDS mode setting...

keith.packard at intel.com

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