[Intel-gfx] [PATCH] drm/i915/skl: Correct other-pipe watermark update condition check

[Ville Syrjälä]

On Mon, Sep 21, 2015 at 11:32:44PM +0530, Kumar, Mahesh wrote:
> If ddb allocation for planes in current CRTC is changed, that doesn't
> lead to ddb allocation change for other CRTCs, because our DDB allocation
> is not dynamic according to plane parameters, ddb is allocated according
> to number of CRTC enabled, & divided equally among CTRC's.
> 
> In current condition check during Watermark calculation, if number of
> plane/ddb allocation changes for current CRTC, Watermark for other pipes
> are recalculated. But there is no change in DDB allocation of other pipe
> so watermark is also not changed, This leads to warning messages.
> WARN_ON(!wm_changed)
> 
> This patch corrects this and check if DDB allocation for pipes is changed,
> then only recalculate watermarks.
> 
> Signed-off-by: Kumar, Mahesh <mahesh1.kumar at intel.com>

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 62de97e..a1ed920 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3127,14 +3127,12 @@ static bool skl_ddb_allocation_changed(const struct skl_ddb_allocation *new_ddb,
>  	struct drm_device *dev = intel_crtc->base.dev;
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	const struct skl_ddb_allocation *cur_ddb = &dev_priv->wm.skl_hw.ddb;
> -	enum pipe pipe = intel_crtc->pipe;
> -
> -	if (memcmp(new_ddb->plane[pipe], cur_ddb->plane[pipe],
> -		   sizeof(new_ddb->plane[pipe])))
> -		return true;
>  
> -	if (memcmp(&new_ddb->cursor[pipe], &cur_ddb->cursor[pipe],
> -		    sizeof(new_ddb->cursor[pipe])))
> +	/*
> +	 * If ddb allocation of pipes chenged, it may require recalculation of
> +	 * watermarks
> +	 */
> +	if (memcmp(new_ddb->pipe, cur_ddb->pipe, sizeof(new_ddb->pipe)))
>  		return true;

Hmm. Yeah we start from the previously calculated values for all pioes,
and just rewrite the entry for the current pipe, so doing the memset()
over the whole array is fine.

This function looks to have been this way from the start, and supposedly
I even reviewed it. Oh well, can't catch everything I guess.

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

>  	return false;
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC