[Intel-gfx] [PATCH 1/2] drm/i915: remove unexplained vblank wait in the DP off code

[Daniel Vetter]

On Thu, Apr 17, 2014 at 03:21:27PM +0300, Ville Syrjälä wrote:
> On Fri, Apr 11, 2014 at 02:25:41PM -0700, Jesse Barnes wrote:
> > I don't think this is necessary; at least it doesn't appear to be on my
> > BYT.  Dropping it speeds up our shutdown code a little, in some cases
> > resulting in faster init times.
> > 
> > Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 3 ---
> >  1 file changed, 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index e48d47c..728a5db 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -2756,9 +2756,6 @@ intel_dp_link_down(struct intel_dp *intel_dp)
> >  	}
> >  	POSTING_READ(intel_dp->output_reg);
> >  
> > -	/* We don't really know why we're doing this */
> > -	intel_wait_for_vblank(dev, intel_crtc->pipe);
> > -
> 
> Maybe this was here to guarantee we send the magic five idle patterns
> specified in the DP spec. But since we're going to be turning off the
> port anyway I don't see why we switch to transmitting the idle pattern
> at all.
> 
> I guess switching to the idle pattern might make sense for the IBX
> transcoder select workaround to avoid sending some garbage on the main
> link. Although we don't seem to be doing that workaround quite according
> to spec. The spec says we should first disable the port, and then
> re-enable it temporarily w/ transcoder A. What we do is switch the port
> over to transcoder A while it's still enabled, and only then disable it.
> 
> So I guess killing the wait here is fine, but looks like the IBX
> workaround stuff needs a better look. I can try to clean it up a bit.
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Queued for -next, thanks for the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch