Re: [PATCH] drm/i915: configure the transcoder clocks before touching pipeconf on HSW+

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em Seg, 2018-04-30 às 21:12 +0300, Ville Syrjälä escreveu:
> On Fri, Apr 27, 2018 at 04:12:08PM -0700, Paulo Zanoni wrote:
> > For all platforms that run haswell_crtc_enable, our spec tells us
> > to
> > configure the transcoder clocks before it tells us to set pipeconf
> > and
> > the other pipe/transcoder/plane registers.
> > 
> > For some reason we've been able to get away with doing what we were
> > doing until now, but starting from Icelake, we get machine hangs if
> > we
> > try to touch the pipe/transcoder registers without having the
> > clocks
> > configured.
> > 
> > So this patch changes all the relevant platforms to call
> > intel_ddi_enable_pipe_clock at the point we're supposed to,
> > according
> > to the spec.
> 
> I don't think this really matches the spec. You're now enabling the
> clock before configuring the port stuff and link training. So AFAICS
> intel_ddi_enable_pipe_clock() seems to be in the correct place, but
> we're just configuring all the pipe/transcoder/etc. stuff way too
> early.

You're right, I missed the link training part, it needs to come before.

But anyway, moving enable_pipe_clock() + link_training ()up is the same
as moving all the pipe/transcoder/etc stuff down, the only difference
being when we set intel_crtc->active. I'll write a second version.

> 
> > 
> > It seems there is a way to work around this problem on ICL with
> > some
> > chicken bit, but I still couldn't find which one it is, and it's
> > better if we just do the right thing here.

We got the info we wanted and now know how to work around the problem,
but I still think we should go for the solution where we program the
hardware in the order it expects to be programmed.

Or we could do both: program correctly *and* enable the chicken bits.

Thanks,
Paulo

> > 
> > Cc: Arthur J Runyan <arthur.j.runyan@intel.com>
> > Cc: James Ausmus <james.ausmus@intel.com>
> > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > Luckily our CI system should be in a spot where it is able to tell
> > us
> > whether this patch is good with high confidence. I haven't tested
> > it
> > on every affected platform.
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > b/drivers/gpu/drm/i915/intel_display.c
> > index 48576ea2d36c..c93aed2ec16d 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -5578,8 +5578,11 @@ static void haswell_crtc_enable(struct
> > intel_crtc_state *pipe_config,
> >  				     &intel_crtc->config->fdi_m_n, 
> > NULL);
> >  	}
> >  
> > -	if (!transcoder_is_dsi(cpu_transcoder))
> > +	if (!transcoder_is_dsi(cpu_transcoder)) {
> > +		intel_ddi_enable_pipe_clock(pipe_config);
> > +
> >  		haswell_set_pipeconf(crtc);
> > +	}
> >  
> >  	haswell_set_pipemisc(crtc);
> >  
> > @@ -5589,9 +5592,6 @@ static void haswell_crtc_enable(struct
> > intel_crtc_state *pipe_config,
> >  
> >  	intel_encoders_pre_enable(crtc, pipe_config, old_state);
> >  
> > -	if (!transcoder_is_dsi(cpu_transcoder))
> > -		intel_ddi_enable_pipe_clock(pipe_config);
> > -
> >  	/* Display WA #1180: WaDisableScalarClockGating: glk, cnl
> > */
> >  	psl_clkgate_wa = (IS_GEMINILAKE(dev_priv) ||
> > IS_CANNONLAKE(dev_priv)) &&
> >  			 intel_crtc->config->pch_pfit.enabled;
> > -- 
> > 2.14.3
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> 
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