Re: [Intel-gfx] [PATCH v3 2/2] drm/i915/dp: Helper to check for DDI BUF status to get active

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Jun 25, 2020 at 03:04:33PM -0700, Manasi Navare wrote:
> On Fri, Jun 26, 2020 at 12:28:53AM +0300, Ville Syrjälä wrote:
> > On Wed, Jun 24, 2020 at 03:11:08PM -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.
> > > 
> > > 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 7d5c8ab88fc4..ff6b1e9d1b4e 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) <= 9) {
> > 
> > Didn't we want the poll approach for glk+?
> 
> Actually in the bspec I only see Gen10+ has a 500usecs timeout

glk has (mostly) gen10 display.

Defacto standard form to write that test is
'GEN < 10 && !IS_GLK'.

> 
> Manasi
> > 
> > > +		usleep_range(600, 1000);
> > > +		return;
> > > +	}
> > > +
> > > +	if (wait_for_us(!(intel_de_read(dev_priv, DDI_BUF_CTL(port)) &
> > > +			  DDI_BUF_IS_IDLE), 600))
> > > +		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);
> > 
> > Missed the FDI case.
> > 
> > Also we're still missing this for HDMI, on icl+ I think? Can't quite
> > remember if that was where the spec started to demand it.
> > 
> > >  }
> > >  
> > >  static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
> > > -- 
> > > 2.19.1
> > 
> > -- 
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel
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