Re: [Intel-gfx] [PATCH v2 4/5] drm/i915/display/dg2: Read CD clock from squasher table

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Fri, Nov 19, 2021 at 03:13:47PM +0200, Mika Kahola wrote:
> To calculate CD clock with squasher unit, we set CD clock ratio to fixed value of 34.
> The CD clock value is read from CD clock squasher table.
> 
> BSpec: 54034
> 
> v2: Read ratio from register (Ville)
>     Drop unnecessary local variable (Ville)
>     Get CD clock from the given table
> v3: Calculate CD clock frequency based on waveform bit pattern (Ville)
> [v4: vsyrjala: Actually do a proper blind readout from the hardware]
> [v5: vsyrjala: Use has_cdclk_squasher()]
>

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
 
> 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 | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> index 560383e8c5b6..5fcb393079f7 100644
> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> @@ -1466,6 +1466,7 @@ static void bxt_de_pll_readout(struct drm_i915_private *dev_priv,
>  static void bxt_get_cdclk(struct drm_i915_private *dev_priv,
>  			  struct intel_cdclk_config *cdclk_config)
>  {
> +	u32 squash_ctl = 0;
>  	u32 divider;
>  	int div;
>  
> @@ -1503,7 +1504,21 @@ static void bxt_get_cdclk(struct drm_i915_private *dev_priv,
>  		return;
>  	}
>  
> -	cdclk_config->cdclk = DIV_ROUND_CLOSEST(cdclk_config->vco, div);
> +	if (has_cdclk_squasher(dev_priv))
> +		squash_ctl = intel_de_read(dev_priv, CDCLK_SQUASH_CTL);
> +
> +	if (squash_ctl & CDCLK_SQUASH_ENABLE) {
> +		u16 waveform;
> +		int size;
> +
> +		size = REG_FIELD_GET(CDCLK_SQUASH_WINDOW_SIZE_MASK, squash_ctl) + 1;
> +		waveform = REG_FIELD_GET(CDCLK_SQUASH_WAVEFORM_MASK, squash_ctl) >> (16 - size);
> +
> +		cdclk_config->cdclk = DIV_ROUND_CLOSEST(hweight16(waveform) *
> +							cdclk_config->vco, size * div);
> +	} else {
> +		cdclk_config->cdclk = DIV_ROUND_CLOSEST(cdclk_config->vco, div);
> +	}
>  
>   out:
>  	/*
> -- 
> 2.27.0
>