[Intel-gfx] [PATCH] honor VBIOS SSC & TV settings

[Jin, Gordon]

Jesse Barnes wrote on Friday, June 27, 2008 12:37 AM:
> I've been doing some work lately to use more of the VBIOS settings
> where possible.  This patch adds support for using the VBIOS for TV
> connector detection and SSC information.  On my T61 at least, using
> this patch keeps me from having to use the T61 TV ignore quirk.
> 
> SSC (spread spectrum clock) is a EMI reducing feature 855+ chips
> support.  It allows the OEM to provide an external reference clock
> and connect it to the GPU to modulate the display clock frequency. 
> Since it requires an external part, information about its presence
> and frequency is supposed to be in the VBIOS general info block.
> 
> I'm not sure how accurate the VBIOS info is for either TV or SSC
> info, so I'd like to get some feedback.  Can people give this a try? 
> It disables the TV quirk logic, so it'll rely on the VBIOS for
> getting TV output presence info. And it will unconditionally use SSC
> if it finds it, so you'll see a message like
> (II) intel(0): using SSC reference clock of 100 MHz
> in your log if it ends up getting used.
> 
> Please provide testing feedback on both features as a reply to this
> message. 

Jesse,

I tested your patch on my Thinkpad T61 (GM965) and R52 (915GM, with
SVideo TV-out). It works as before, i.e.
https://bugs.freedesktop.org/show_bug.cgi?id=11366 isn't happening on
T61.

There's no SSC info in Xorg log. Is this expected? How can I know if the
external reference clock is actually available?

Below is the xrandr output:

[root at x-gm965 ~]# xrandr -q
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 2000 x 2000
VGA disconnected (normal left inverted right x axis y axis)
LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis)
331mm x 207mm
   1280x800       60.3*+   50.0
   1024x768       60.0
   800x600        60.3     56.2
   640x480        59.9
TMDS-1 disconnected (normal left inverted right x axis y axis)

  [root at x-915gm ~]# xrandr -q
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 2048 x 2048
VGA disconnected (normal left inverted right x axis y axis)
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis)
0mm x 0mm
   1024x768       60.0*+   85.0     75.0     70.1     60.0
   832x624        74.6
   800x600        85.1     72.2     75.0     60.3     56.2
   640x480        85.0     72.8     75.0     59.9
   720x400        85.0
   640x400        85.1
   640x350        85.1
TV disconnected (normal left inverted right x axis y axis)

-Gordon