Re: [PATCH 05/11] drm/i915: Round the AUX clock divider to closest on all platforms

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 30 Nov 2015, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Currently we round the AUX clock divider down on g4x, to closest
> on HSW/BDW port A, and up everywhere else. We are supposed to get
> as close to 2MHz as we can, so round to closest seems like the
> best option.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Makes sense.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


> ---
>  drivers/gpu/drm/i915/intel_dp.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 77ae5821e9c0..f335c92b4fa7 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -681,7 +681,7 @@ static uint32_t i9xx_get_aux_clock_divider(struct intel_dp *intel_dp, int index)
>  	 * The clock divider is based off the hrawclk, and would like to run at
>  	 * 2MHz.  So, take the hrawclk value and divide by 2 and use that
>  	 */
> -	return index ? 0 : intel_hrawclk(dev) / 2;
> +	return index ? 0 : DIV_ROUND_CLOSEST(intel_hrawclk(dev), 2);
>  }
>  
>  static uint32_t ilk_get_aux_clock_divider(struct intel_dp *intel_dp, int index)
> @@ -694,10 +694,10 @@ static uint32_t ilk_get_aux_clock_divider(struct intel_dp *intel_dp, int index)
>  		return 0;
>  
>  	if (intel_dig_port->port == PORT_A) {
> -		return DIV_ROUND_UP(dev_priv->cdclk_freq, 2000);
> +		return DIV_ROUND_CLOSEST(dev_priv->cdclk_freq, 2000);
>  
>  	} else {
> -		return DIV_ROUND_UP(intel_pch_rawclk(dev), 2);
> +		return DIV_ROUND_CLOSEST(intel_pch_rawclk(dev), 2);
>  	}
>  }
>  
> @@ -719,7 +719,7 @@ static uint32_t hsw_get_aux_clock_divider(struct intel_dp *intel_dp, int index)
>  		default: return 0;
>  		}
>  	} else  {
> -		return index ? 0 : DIV_ROUND_UP(intel_pch_rawclk(dev), 2);
> +		return index ? 0 : DIV_ROUND_CLOSEST(intel_pch_rawclk(dev), 2);
>  	}
>  }

-- 
Jani Nikula, Intel Open Source Technology Center
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