[Intel-gfx] [PATCH 05/11] drm/i915: Use 200MHz cdclk on vlv when all pipes are off

[Jesse Barnes]

On Fri, 13 Jun 2014 13:37:51 +0300
ville.syrjala at linux.intel.com wrote:

> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Drop the cdclk frequency to 200MHz on vlv when all pipes are off. In
> theory we should be able to use 200MHz also when the pixel clock is at
> most 90% of 200MHz. However in practice all we seem to get is a solid
> color picture or an otherwise corrupted display.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 1f3985f..3a9b017 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -4520,14 +4520,19 @@ static int valleyview_calc_cdclk(struct drm_i915_private *dev_priv,
>  	 *   400MHz
>  	 * So we check to see whether we're above 90% of the lower bin and
>  	 * adjust if needed.
> +	 *
> +	 * We seem to get an unstable or solid color picture at 200MHz.
> +	 * Not sure what's wrong. For now use 200MHz only when all pipes
> +	 * are off.
>  	 */
>  	if (max_pixclk > freq_320*9/10)
>  		return 400000;
>  	else if (max_pixclk > 266667*9/10)
>  		return freq_320;
> -	else
> +	else if (max_pixclk > 0)
>  		return 266667;
> -	/* Looks like the 200MHz CDclk freq doesn't work on some configs */
> +	else
> +		return 200000;
>  }
>  
>  /* compute the max pixel clock for new configuration */

I guess this is safe, but optional (won't we be shutting off the clocks
anyway?).

Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center