Re: [Intel-gfx] [PATCH 3/5] drm/i915/icl: Cross check the combo PLL WRPLL parameters wrt. hard-coded PLL freqs

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

On Thu, Oct 01, 2020 at 07:44:29PM +0300, Ville Syrjälä wrote:
> On Tue, Sep 29, 2020 at 03:29:27AM +0300, Imre Deak wrote:
> > When selecting the WRPLL dividers for a given port clock/PLL freq, the
> > hard-coded PLL freq in a table entry can be calculated using the rest of
> > parameters in the same entry. Cross-check if the hard coded values match
> > what we calculate with the formula.
> 
> We've never done this on any other plaform I think. Why is this special?

I think if we do this we should do at init time for all such tables.
Ideally we'd do it at compile time but no constexpr in C :(

> Also, shouldn't the state checker catch this anyway?
> 
> > 
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 26 ++++++++++++++++++-
> >  1 file changed, 25 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> > index e3370c8dccc8..ded2b2dfe319 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> > @@ -3002,6 +3002,30 @@ static const struct skl_wrpll_params tgl_tbt_pll_38_4MHz_values = {
> >  	.pdiv = 0, .kdiv = 0, .qdiv_mode = 0, .qdiv_ratio = 0,
> >  };
> >  
> > +static int icl_wrpll_ref_clock(struct drm_i915_private *i915);
> > +
> > +static bool icl_dp_combo_pll_clock_match(struct drm_i915_private *i915, int clock,
> > +					 const struct icl_combo_pll_params *p)
> > +{
> > +	int ref_clock = icl_wrpll_ref_clock(i915);
> > +	int pll_freq;
> > +	u32 pdiv;
> > +	u32 qdiv;
> > +	u32 kdiv;
> > +
> > +	cnl_wrpll_decode_divs(&p->wrpll, &pdiv, &qdiv, &kdiv);
> > +
> > +	pll_freq = skl_wrpll_calc_freq(ref_clock,
> > +				       p->wrpll.dco_integer, p->wrpll.dco_fraction,
> > +				       pdiv, qdiv, kdiv);
> > +	drm_WARN_ON(&i915->drm, pll_freq != p->clock);
> > +
> > +	if (clock == pll_freq)
> > +		return true;
> > +
> > +	return false;
> > +}
> > +
> >  static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
> >  				  struct skl_wrpll_params *pll_params)
> >  {
> > @@ -3014,7 +3038,7 @@ static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
> >  	int i;
> >  
> >  	for (i = 0; i < ARRAY_SIZE(icl_dp_combo_pll_24MHz_values); i++) {
> > -		if (clock == params[i].clock) {
> > +		if (icl_dp_combo_pll_clock_match(dev_priv, clock, &params[i])) {
> >  			*pll_params = params[i].wrpll;
> >  			return true;
> >  		}
> > -- 
> > 2.25.1
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ville Syrjälä
> Intel

-- 
Ville Syrjälä
Intel
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