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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 13 Oct 2015, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Tue, Oct 13, 2015 at 04:10:19PM +0300, Jani Nikula wrote:
>> On Thu, 08 Oct 2015, Ville Syrjälä <ville.syrjala@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@linux.intel.com wrote:
>> >> > From: Ville Syrjälä <ville.syrjala@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@vger.kernel.org
>> >> > Cc: Nick Bowler <nbowler@draconx.ca>
>> >> Reported-and-tested-by: Nick Bowler <nbowler@draconx.ca>
>> >> References: http://lists.freedesktop.org/archives/intel-gfx/2015-October/077463.html
>> >> 
>> >> > Signed-off-by: Ville Syrjälä <ville.syrjala@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@ffwll.ch>
>> 
>> 
>> Daniel, are you happy with the responses about posting reads, for both
>> patches?
>
> Yeah, acked on irc but forgot to follow up.

Both pushed to drm-intel-fixes, thanks for the patches and review.

BR,
Jani.


> -Daniel
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Jani Nikula, Intel Open Source Technology Center