Re: [PATCH 2/2] drm/i915: Round-up clock and limit drain latency

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Aug 05, 2014 at 11:15:54PM +0530, Gajanan Bhat wrote:
> Round up clock computation and limit drain latency to maximum of 0x7F.
> 
> Signed-off-by: Gajanan Bhat <gajanan.bhat@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index ea64675..5e81c49 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -1285,11 +1285,14 @@ static bool vlv_compute_drain_latency(struct drm_crtc *crtc,
>  	if (WARN(pixel_size == 0, "Pixel size is zero!\n"))
>  		return false;
>  
> -	entries = (clock / 1000) * pixel_size;
> +	entries = DIV_ROUND_UP(clock, 1000) * pixel_size;
>  	*prec_mult = (entries > 128) ? DRAIN_LATENCY_PRECISION_64 :
>  				       DRAIN_LATENCY_PRECISION_32;
>  	*drain_latency = (64 * (*prec_mult) * 4) / entries;
>  
> +	if (*drain_latency > DRAIN_LATENCY_MASK)
> +		*drain_latency = DRAIN_LATENCY_MASK;

I would have probably written this as:
*drain_latency = min(..., DRAIN_LATENCY_MASK);

But that's just a style I like. The patch looks fine to me so:
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +
>  	return true;
>  }
>  
> -- 
> 1.7.9.5
> 
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-- 
Ville Syrjälä
Intel OTC