Re: [Intel-gfx] [PATCH v4 2/2] drm/i915/dp: Helper to check for DDI BUF status to get active

[Manasi Navare <manasi.d.navare@intel.com>]

On Wed, Jul 01, 2020 at 12:20:26AM +0300, Ville Syrjälä wrote:
> On Fri, Jun 26, 2020 at 04:26:41PM -0700, Manasi Navare wrote:
> > Based on the platform, Bspec expects us to wait or poll with
> > timeout for DDI BUF IDLE bit to be set to 0 (non idle) or get active
> > after enabling DDI_BUF_CTL.
> > 
> > v4:
> > * Use the timeout for GLK (Ville)
> > v3:
> > * Add a new function _active for DDI BUF CTL to be non idle (Ville)
> > v2:
> > * Based on platform, fixed delay or poll (Ville)
> > * Use a helper to do this (Imre, Ville)
> > 
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Imre Deak <imre.deak@intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 052a74625a61..94d57b57139b 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -1195,6 +1195,20 @@ static void intel_wait_ddi_buf_idle(struct drm_i915_private *dev_priv,
> >  			port_name(port));
> >  }
> >  
> > +static void intel_wait_ddi_buf_active(struct drm_i915_private *dev_priv,
> > +				      enum port port)
> > +{
> > +	if (INTEL_GEN(dev_priv) < 10 && !IS_GEMINILAKE(dev_priv) ) {
> > +		usleep_range(600, 1000);
> 
> I would probably put a spec quote here to make it clear what this is:
> "Wait >518 us for buffers to enable..."
> 
> Or we could s/600/518/ to make it easier to figure out. But that could
> be a followup.

Yes I can change this to 518,1000 and add a comment in the next rev

> 
> > +		return;
> > +	}
> > +
> > +	if (wait_for_us(!(intel_de_read(dev_priv, DDI_BUF_CTL(port)) &
> > +			  DDI_BUF_IS_IDLE), 600))
> 
> Spec says 500 usec for this. Is there a reason to not go with the spec
> value? I guess one argument is that we didn't do it before. But I'd
> probably change it, if not in this patch then as a followup.

Hmm yes probably the HSDs said 600 but since spec says 500usecs, I will change
the timeout to 500

Manasi

> 
> > +		drm_err(&dev_priv->drm, "Timeout waiting for DDI BUF %c to get active\n",
> > +			port_name(port));
> > +}
> > +
> >  static u32 hsw_pll_to_ddi_pll_sel(const struct intel_shared_dpll *pll)
> >  {
> >  	switch (pll->info->id) {
> > @@ -4020,7 +4034,7 @@ static void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp)
> >  	intel_de_write(dev_priv, DDI_BUF_CTL(port), intel_dp->DP);
> >  	intel_de_posting_read(dev_priv, DDI_BUF_CTL(port));
> >  
> > -	udelay(600);
> > +	intel_wait_ddi_buf_active(dev_priv, port);
> 
> Still can't see fdi anywhere.
> 
> Whatever
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> >  }
> >  
> >  static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
> > -- 
> > 2.19.1
> 
> -- 
> Ville Syrjälä
> Intel
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