[Intel-gfx] [PATCH 1/2] drm/i915: Restore lost DPLL register write on gen2-4

[Daniel Vetter]

On Tue, Oct 13, 2015 at 04:10:19PM +0300, Jani Nikula wrote:
> On Thu, 08 Oct 2015, Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
> > On Thu, Oct 08, 2015 at 10:17:30AM +0200, Daniel Vetter wrote:
> >> On Wed, Oct 07, 2015 at 10:08:24PM +0300, ville.syrjala at linux.intel.com wrote:
> >> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >> > 
> >> > We accidentally lost the initial DPLL register write in
> >> > 1c4e02746147 drm/i915: Fix DVO 2x clock enable on 830M
> >> > 
> >> > The "three times for luck" hack probably saved us from a total
> >> > disaster. But anyway, bring the initial write back so that the
> >> > code actually makes some sense.
> >> > 
> >> > Cc: stable at vger.kernel.org
> >> > Cc: Nick Bowler <nbowler at draconx.ca>
> >> Reported-and-tested-by: Nick Bowler <nbowler at draconx.ca>
> >> References: http://lists.freedesktop.org/archives/intel-gfx/2015-October/077463.html
> >> 
> >> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >> > ---
> >> >  drivers/gpu/drm/i915/intel_display.c | 2 ++
> >> >  1 file changed, 2 insertions(+)
> >> > 
> >> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> >> > index 147e700..f4fdff9 100644
> >> > --- a/drivers/gpu/drm/i915/intel_display.c
> >> > +++ b/drivers/gpu/drm/i915/intel_display.c
> >> > @@ -1743,6 +1743,8 @@ static void i9xx_enable_pll(struct intel_crtc *crtc)
> >> >  			   I915_READ(DPLL(!crtc->pipe)) | DPLL_DVO_2X_MODE);
> >> 
> >> Don't we also need a POSTING_READ here to make sure the two-step 2x mode
> >> sequence is still followed?
> >
> > We don't do write combining on registers, and there are no shadow
> > register type of things to consider in this case either.
> >
> >> 
> >> With that addressed Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> 
> Daniel, are you happy with the responses about posting reads, for both
> patches?

Yeah, acked on irc but forgot to follow up.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch