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

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

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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