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

Zhenyu Wang zhenyuw at linux.intel.com
Fri Feb 12 04:14:50 CET 2010


On 2010.02.11 17:44:36 -0800, Jesse Barnes 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.
> 

yeah, some order is required told by the spec, maybe applied to older mobile
chips too? I haven't checked that out, but this is good thing to have for them,
hopefully we can do more testing.

-- 
Open Source Technology Center, Intel ltd.

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