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

[Souza, Jose]

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.

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.

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