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

Rodrigo Vivi
2018-08-28T20:36:23Z

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?

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)
> + 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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