[Intel-gfx] [PATCH 4/9] drm/i915: fix haswell linetime watermarks calculation

[Ville Syrjälä]

On Fri, May 03, 2013 at 05:23:40PM -0300, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> 
> Move the "*8"  calculation to the left side so we don't propagate
> rounding errors. Also use DIV_ROUND_CLOSEST because that's what the
> spec says we need to do.
> 
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_pm.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 4cc5f99..8468b40 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2035,7 +2035,7 @@ haswell_update_linetime_wm(struct drm_device *dev, struct drm_crtc *crtc)
>  	 * row at the given clock rate, multiplied by 8.
>  	 * */
>  	temp |= PIPE_WM_LINETIME_TIME(
> -		((mode->htotal * 1000) / mode->clock) * 8);
> +		DIV_ROUND_CLOSEST(mode->htotal * 1000 * 8, mode->clock));
>  
>  	/* IPS watermarks are only used by pipe A, and are ignored by
>  	 * pipes B and C.  They are calculated similarly to the common
> -- 
> 1.7.10.4
> 
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-- 
Ville Syrjälä
Intel OTC