[Intel-gfx] [PATCH] drm/i915/gen9: fix the WM memory bandwidth WA for Y tiling cases

[Matt Roper]

On Tue, Nov 08, 2016 at 06:22:11PM -0200, Paulo Zanoni wrote:
> The previous spec version said "double Ytile planes minimum lines",
> and I interpreted this as referring to what the spec calls "Y tile
> minimum", but in fact it was referring to what the spec calls "Minimum
> Scanlines for Y tile". I noticed that Mahesh Kumar had a different
> interpretation, so I sent and email to the spec authors and got
> clarification on the correct meaning. Also, BSpec was updated and
> should be clear now.
> 
> Fixes: ee3d532fcb64 ("drm/i915/gen9: unconditionally apply the memory bandwidth WA")
> Cc: stable at vger.kernel.org
> Cc: Mahesh Kumar <mahesh1.kumar at intel.com>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

This seems to match my reading of the spec update from Nov 4th, so:

Reviewed-by: Matt Roper <matthew.d.roper at intel.com>


> ---
>  drivers/gpu/drm/i915/intel_pm.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index cc9e0c0..653525f 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3624,6 +3624,9 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
>  		y_min_scanlines = 4;
>  	}
>  
> +	if (apply_memory_bw_wa)
> +		y_min_scanlines *= 2;
> +
>  	plane_bytes_per_line = width * cpp;
>  	if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
>  	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
> @@ -3644,8 +3647,6 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
>  				 plane_blocks_per_line);
>  
>  	y_tile_minimum = plane_blocks_per_line * y_min_scanlines;
> -	if (apply_memory_bw_wa)
> -		y_tile_minimum *= 2;
>  
>  	if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
>  	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
> -- 
> 2.7.4
> 
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-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795