[Intel-gfx] [RFT] drm/i915: enable/disable LVDS port at DPMS time

Jesse Barnes jbarnes at virtuousgeek.org
Fri Feb 12 02:44:36 CET 2010

On Fri, 12 Feb 2010 09:26:28 +0800
ykzhao <yakui.zhao at intel.com> wrote:

> On Fri, 2010-02-12 at 04:41 +0800, Jesse Barnes wrote:
> > It would be good to disable the LVDS port when we shut down the
> > panel to save power.  We haven't done so until now because we had
> > trouble getting the right LVDS parameters from the BIOS.  I think
> > we're past that now, so enabling and disabling the port should be
> > safe, though it would probably be made cleaner with some additional
> > changes to the display code, where we also bang on the LVDS reg to
> > set the pairing correctly etc.
> > 
> > Seems to save a bit of power (up to 300mW in my basic wattsup
> > meter testing).
> Hi, Jesse
>     Do you test it on the laptop based on Ironlake or
> crestline/cantiga platform?
>     On the ironlake the LVDS_PORT_EN bit will be enabled/disabled in
> course of CRTC DPMS.
> >From the spec this bit must be set before the display PLL is
> >enabled. 

Ah right, looks like on Ironlake we disable it there too, so this patch
isn't needed on Ironlake and above.

Jesse Barnes, Intel Open Source Technology Center

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