Re: [Intel-gfx] [PATCH 3/4] drm/i915/display/dg2: Sanitize CD clock

["Kahola, Mika" <mika.kahola@intel.com>]

> -----Original Message-----
> From: Jani Nikula <jani.nikula@linux.intel.com>
> Sent: Thursday, November 18, 2021 12:12 PM
> To: Kahola, Mika <mika.kahola@intel.com>; intel-gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH 3/4] drm/i915/display/dg2: Sanitize CD clock
> 
> On Thu, 18 Nov 2021, Mika Kahola <mika.kahola@intel.com> wrote:
> > In case of CD clock squashing the divider is always 1. We don't need
> > to calculate the divider in use so let's skip that for DG2.
> >
> > v2: Drop unnecessary local variable (Ville)
> > v3: Avoid if-else structure (Ville)
> > [v4: vsyrjala: Fix cd2x divider calculation (Uma),
> >                Introduce has_cdclk_squasher()]
> >
> > Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_cdclk.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c
> > b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > index 630a53d4f882..e8c58779c2a8 100644
> > --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> > +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > @@ -1212,6 +1212,11 @@ static void skl_cdclk_uninit_hw(struct
> drm_i915_private *dev_priv)
> >  	skl_set_cdclk(dev_priv, &cdclk_config, INVALID_PIPE);  }
> >
> > +static bool has_cdclk_squasher(struct drm_i915_private *i915) {
> > +	return IS_DG2(i915);
> > +}
> 
> The obvious problem is that you use this function already in patch 2.

I couldn't find the original cover-letter and hence the patches might have slipped in wrong order. Thanks for pointing that out!

> 
> I'm also not sure we want to start sprinkling the has_ or HAS_ query stuff all over
> the place in .c. files. Or if we do, we should do it in a more planned manner, not
> by starting to sneak these in.

Well, what would be the alternative? How we should handle the cases where a feature is supported by a platform and perhaps platforms in the future?

Cheers,
Mika 
> 
> BR,
> Jani.
> 
> > +
> >  static const struct intel_cdclk_vals bxt_cdclk_table[] = {
> >  	{ .refclk = 19200, .cdclk = 144000, .divider = 8, .ratio = 60 },
> >  	{ .refclk = 19200, .cdclk = 288000, .divider = 4, .ratio = 60 }, @@
> > -1750,7 +1755,7 @@ static void bxt_set_cdclk(struct drm_i915_private
> > *dev_priv,  static void bxt_sanitize_cdclk(struct drm_i915_private
> > *dev_priv)  {
> >  	u32 cdctl, expected;
> > -	int cdclk, vco;
> > +	int cdclk, clock, vco;
> >
> >  	intel_update_cdclk(dev_priv);
> >  	intel_dump_cdclk_config(&dev_priv->cdclk.hw, "Current CDCLK"); @@
> > -1786,8 +1791,12 @@ static void bxt_sanitize_cdclk(struct drm_i915_private
> *dev_priv)
> >  	expected = skl_cdclk_decimal(cdclk);
> >
> >  	/* Figure out what CD2X divider we should be using for this cdclk */
> > -	expected |= bxt_cdclk_cd2x_div_sel(dev_priv,
> > -					   dev_priv->cdclk.hw.cdclk,
> > +	if (has_cdclk_squasher(dev_priv))
> > +		clock = dev_priv->cdclk.hw.vco / 2;
> > +	else
> > +		clock = dev_priv->cdclk.hw.cdclk;
> > +
> > +	expected |= bxt_cdclk_cd2x_div_sel(dev_priv, clock,
> >  					   dev_priv->cdclk.hw.vco);
> >
> >  	/*
> 
> --
> Jani Nikula, Intel Open Source Graphics Center