Patch "drm/i915/gen9: fix the WM memory bandwidth WA for Y tiling cases" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

drm/i915/gen9: fix the WM memory bandwidth WA for Y tiling cases

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-i915-gen9-fix-the-wm-memory-bandwidth-wa-for-y-tiling-cases.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Paulo Zanoni <[email protected]>
Date: Tue, 8 Nov 2016 18:22:11 -0200
Subject: drm/i915/gen9: fix the WM memory bandwidth WA for Y tiling cases

From: Paulo Zanoni <[email protected]>

commit 2ef32dee97fcf41987722a37eb6ff1a983915e99 upstream.

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.

---
 drivers/gpu/drm/i915/intel_pm.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

@@ -3617,6 +3617,9 @@ static int skl_compute_plane_wm(const st
 		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) {

@@ -3637,8 +3640,6 @@ static int skl_compute_plane_wm(const st
 				 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) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/drm-i915-gen9-fix-the-wm-memory-bandwidth-wa-for-y-tiling-cases.patch queue-4.9/drm-i915-gen9-unconditionally-apply-the-memory-bandwidth-wa.patch queue-4.9/drm-i915-disable-psr-by-default-on-hsw-bdw.patch