Re: [PATCH] drm/i915: Fix ICL HDMI clock readout

Rodrigo Vivi
2018-08-30T19:09:09Z

On Thu, Aug 30, 2018 at 06:48:45PM +0300, Ville Syrjälä wrote:
> On Tue, Aug 28, 2018 at 01:36:22PM -0700, Rodrigo Vivi wrote:
> > On Tue, Aug 28, 2018 at 06:32:01PM +0300, Ville Syrjala wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > >
> > > Copy the 38.4 vs. 19.2 MHz ref clock exception from the dpll
> > > mgr into the clock readout function as well.
> > >
> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107722
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > > drivers/gpu/drm/i915/intel_ddi.c | 7 +++++++
> > > 1 file changed, 7 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > > index f3b115ce4029..68b301e6f41d 100644
> > > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > > @@ -1416,6 +1416,13 @@ static int cnl_calc_wrpll_link(struct drm_i915_private *dev_priv,
> > >
> > > ref_clock = dev_priv->cdclk.hw.ref;
> >
> > could we move this up to the beginning of the function and
> > then reuse that if (INTEL_GEN(dev_priv) >= 11) { block?
>
> Possible? Sure. Clearer? Not so sure.

yeap... I'm not confident this would be clearer...

>
> Probably the correct answer would be to add some kind of
> cnl_pll_ref_clock() helper that encapsulats the magic exception,
> and then use that from all the places that need it.

hmm... probably

>
> >
> > Anyway, this change is needed and right so however you decide
> > to proceed:
> >
> > Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> >
> > >
> > > + /*
> > > + * For ICL, the spec states: if reference frequency is 38.4, use 19.2
> > > + * because the DPLL automatically divides that by 2.
> > > + */
> > > + if (IS_ICELAKE(dev_priv) && ref_clock == 38400)

what about to at least make it (INTEL_GEN(dev_priv) >= 11)
to be compatible with above's statement?

> > > + ref_clock = 19200;
> > > +
> > > dco_freq = (cfgcr0 & DPLL_CFGCR0_DCO_INTEGER_MASK) * ref_clock;
> > >
> > > dco_freq += (((cfgcr0 & DPLL_CFGCR0_DCO_FRACTION_MASK) >>
> > > --
> > > 2.16.4
> > >
> > > _______________________________________________
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> > > Intel-gfx@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Ville Syrjälä
> Intel