[Intel-gfx] [PATCH 4/7] drm/i915/dp: Power down sink before disable pipe/transcoder clock

[Souza, Jose]

On Wed, 2019-11-27 at 21:24 +0200, Ville Syrjälä wrote:
> On Tue, Nov 26, 2019 at 10:12:52PM +0000, Souza, Jose wrote:
> > On Tue, 2019-11-26 at 22:15 +0200, Ville Syrjälä wrote:
> > > On Fri, Nov 22, 2019 at 04:54:56PM -0800, José Roberto de Souza
> > > wrote:
> > > > Disabling pipe/transcoder clock before power down sink could
> > > > cause
> > > > sink lost signal, causing it to trigger a hotplug to notify
> > > > source
> > > > that link signal was lost.
> > > > 
> > > > Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> > > > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/display/intel_ddi.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c
> > > > b/drivers/gpu/drm/i915/display/intel_ddi.c
> > > > index d2f0d393d3ee..7d3a6e3c7f57 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > > > @@ -3808,12 +3808,12 @@ static void
> > > > intel_ddi_post_disable_dp(struct intel_encoder *encoder,
> > > >  	enum phy phy = intel_port_to_phy(dev_priv, encoder-
> > > > >port);
> > > >  
> > > >  	if (!is_mst) {
> > > > -		intel_ddi_disable_pipe_clock(old_crtc_state);
> > > >  		/*
> > > >  		 * Power down sink before disabling the port,
> > > > otherwise
> > > > we end
> > > >  		 * up getting interrupts from the sink on
> > > > detecting
> > > > link loss.
> > > >  		 */
> > > >  		intel_dp_sink_dpms(intel_dp,
> > > > DRM_MODE_DPMS_OFF);
> > > > +		intel_ddi_disable_pipe_clock(old_crtc_state);
> > > >  	}
> > > 
> > > The spec seems to say that we should do this after turning off
> > > DDI_BUF_CTL on tgl+.
> > 
> > What step? I can't find any step talking about AUX DP_SET_POWER.
> 
> I was talking about DDI_BUF disable vs. transcoder clock disable.
> 
> > My understating is that we should power off sink before interfering
> > in
> > the mainlink signal otherwise sink could trigger hotplugs to notify
> > source about link loss.
> 
> Pretty much. Nothing wrong with your patch for pre-tgl I think, but
> for
> tgl+ you didn't move the clock disable quite far enough to match the
> bspec sequence.

Aaahh
That is fixed patch 6 "drm/i915/display/tgl: Fix the order of the step
to turn transcoder clock off" :D

> 
> > > >  
> > > >  	intel_disable_ddi_buf(encoder, old_crtc_state);
> > > > -- 
> > > > 2.24.0
> > > > 
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