Re: [PATCH 1/2] drm/i915: Allow pixel clock up to 95% of cdclk on CHV

["Purushothaman, Vijay A" <vijay.a.purushothaman@linux.intel.com>]

On 3/2/2015 11:37 PM, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Supposedly CHV can sustain a pixel clock of up to 95% of
> cdclk, as opposed to the 90% limit that was used old older
> platforms. Update the cdclk selection code to allow for this.
>
> This will allow eg. HDMI 4k modes with their 297MHz pixel clock
> while still respecting the 320 MHz cdclk limit on CHV.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Thanks for forwarding the post si team confirmation. We were in the dark 
about this as usual.

Reviewed-by: Vijay Purushothaman <vijay.a.purushothaman@linux.intel.com>

Thanks,
Vijay
> ---
>   drivers/gpu/drm/i915/intel_display.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 3fe9598..94ff310 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -4926,6 +4926,7 @@ static int valleyview_calc_cdclk(struct drm_i915_private *dev_priv,
>   				 int max_pixclk)
>   {
>   	int freq_320 = (dev_priv->hpll_freq <<  1) % 320000 != 0 ? 333333 : 320000;
> +	int limit = IS_CHERRYVIEW(dev_priv) ? 95 : 90;
>   
>   	/* FIXME: Punit isn't quite ready yet */
>   	if (IS_CHERRYVIEW(dev_priv->dev))
> @@ -4936,17 +4937,18 @@ static int valleyview_calc_cdclk(struct drm_i915_private *dev_priv,
>   	 *   200MHz
>   	 *   267MHz
>   	 *   320/333MHz (depends on HPLL freq)
> -	 *   400MHz
> -	 * So we check to see whether we're above 90% of the lower bin and
> -	 * adjust if needed.
> +	 *   400MHz (VLV only)
> +	 * So we check to see whether we're above 90% (VLV) or 95% (CHV)
> +	 * 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)
> +	if (!IS_CHERRYVIEW(dev_priv) &&
> +	    max_pixclk > freq_320*limit/100)
>   		return 400000;
> -	else if (max_pixclk > 266667*9/10)
> +	else if (max_pixclk > 266667*limit/100)
>   		return freq_320;
>   	else if (max_pixclk > 0)
>   		return 266667;

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