[Intel-gfx] [PATCH v2] drm/i915: Fix MST disable sequence

[Ville Syrjälä]

On Wed, Jan 08, 2020 at 04:09:31PM +0000, Souza, Jose wrote:
> On Wed, 2020-01-08 at 16:45 +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > When moving the pipe disable & co. function calls from
> > haswell_crtc_disable() into the encoder .post_disable() hooks I
> > neglected to account for the MST vs. DDI interactions properly.
> > This now leads us to call these functions two times for the last
> > MST stream (once from the MST code and a second time from the DDI
> > code). The calls from the DDI code should only be done for SST
> > and not MST. Add the proper check for that.
> 
> Oohh I forgot that too.
> 
> > 
> > This results in an MCE on ICL. My vague theory is that we turn off
> > the transcoder clock from the MST code and then we proceed to touch
> > something in the DDI code which still depends on that clock causing
> > the hardware to become upset. Though I can't really explain why
> > Stan's hack of omitting the pipe disable in the MST code would avoid
> > the MCE since we should still be turning off the transcoder clock.
> > But maybe there's something magic in the hw that keeps the clock on
> > as long as the pipe is on. Or maybe the clock isn't the problem and
> > we now touch something in the DDI disable code that really does need
> > the pipe to be still enabled.
> > 
> > v2: Rebase to latest drm-tip
> > 
> > Cc: José Roberto de Souza <jose.souza at intel.com>
> > Cc: Manasi Navare <manasi.d.navare at intel.com>
> > Reported-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> > Closes: https://gitlab.freedesktop.org/drm/intel/issues/901
> > Fixes: 773b4b54351c ("drm/i915: Move stuff from
> > haswell_crtc_disable() into encoder .post_disable()")
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c | 22 ++++++++++++----------
> >  1 file changed, 12 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c
> > b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 07acd0daca25..6e0a75d1e6ca 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -3897,21 +3897,23 @@ static void intel_ddi_post_disable(struct
> > intel_encoder *encoder,
> >  	enum phy phy = intel_port_to_phy(dev_priv, encoder->port);
> >  	bool is_tc_port = intel_phy_is_tc(dev_priv, phy);
> >  
> > -	intel_crtc_vblank_off(old_crtc_state);
> > +	if (!intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DP_MST))
> > {
> > +		intel_crtc_vblank_off(old_crtc_state);
> >  
> > -	intel_disable_pipe(old_crtc_state);
> > +		intel_disable_pipe(old_crtc_state);
> >  
> > -	if (INTEL_GEN(dev_priv) >= 11)
> > -		icl_disable_transcoder_port_sync(old_crtc_state);
> > +		if (INTEL_GEN(dev_priv) >= 11)
> > +			icl_disable_transcoder_port_sync(old_crtc_state
> > );
> >  
> > -	intel_ddi_disable_transcoder_func(old_crtc_state);
> > +		intel_ddi_disable_transcoder_func(old_crtc_state);
> >  
> > -	intel_dsc_disable(old_crtc_state);
> > +		intel_dsc_disable(old_crtc_state);
> >  
> > -	if (INTEL_GEN(dev_priv) >= 9)
> > -		skl_scaler_disable(old_crtc_state);
> > -	else
> > -		ilk_pfit_disable(old_crtc_state);
> > +		if (INTEL_GEN(dev_priv) >= 9)
> > +			skl_scaler_disable(old_crtc_state);
> > +		else
> > +			ilk_pfit_disable(old_crtc_state);
> > +	}
> 
> 
> Other option would be replace
> intel_dig_port->base.post_disable(&intel_dig_port->base,
> old_crtc_state, NULL);
> in intel_mst_post_disable_dp() by:
> 
> 
> intel_ddi_post_disable_dp(encoder, old_crtc_state, old_conn_state);
> 
> if (INTEL_GEN(dev_priv) >= 11)
> 	icl_unmap_plls_to_ports(encoder);
> 
> if (intel_crtc_has_dp_encoder(old_crtc_state) || is_tc_port)
> 	intel_display_power_put_unchecked(dev_priv,
> intel_ddi_main_link_aux_domain(dig_port));
> 
> if (is_tc_port)
> 	intel_tc_port_put_link(dig_port);

Yeah, the current way is a bit of a mess. We probably want to think of
ways to make it less sucky.

> 
> I guess this goes more with changes that you did in the patch fixed.

Indeed, a more mechanichal change for now seems more in line with the
original patch.

> 
> 
> Anyway your changes looks good.
> 
> Reviewed-by: José Roberto de Souza <jose.souza at intel.com>

Ta.

-- 
Ville Syrjälä
Intel