[PATCH 4.8 027/125] drm/i915/gen9: fix the watermark res_blocks value

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>

commit 73fed0ef8567f1e1cba079994353e60208ded964 upstream.

We forgot the "res_blocks += y_tile_minimum" that's described on step
V of our documentation.

Again, this should only affect the Y tiling cases.

It looks like the relevant code was introduced in 0fda65680e92, but
there's always the possibility that it matched our specification when
it was introduced, and then the specification changed while the code
stayed the same. So we can't really say this was a regression, but
let's try to add a "Fixes" tag anyway to help backporting.

v2: Try to add a "Fixes" tag (Maarten).

Fixes: 0fda65680e92 ("drm/i915/skl: Update watermarks for Y tiling")
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Reviewed-by: Lyude <cpaul@xxxxxxxxxx>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-8-git-send-email-paulo.r.zanoni@xxxxxxxxx
(cherry picked from commit 75676ed423a6acf9e2b1df52fbc036a51e11fb7a)
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/intel_pm.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3533,7 +3533,7 @@ static int skl_compute_plane_wm(const st
 	uint8_t cpp;
 	uint32_t width = 0, height = 0;
 	uint32_t plane_pixel_rate;
-	uint32_t y_min_scanlines;
+	uint32_t y_tile_minimum, y_min_scanlines;
 
 	if (latency == 0 || !cstate->base.active || !intel_pstate->visible) {
 		*enabled = false;
@@ -3590,10 +3590,10 @@ static int skl_compute_plane_wm(const st
 				 latency,
 				 plane_blocks_per_line);
 
+	y_tile_minimum = plane_blocks_per_line * y_min_scanlines;
+
 	if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
 	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
-		uint32_t y_tile_minimum = plane_blocks_per_line *
-					  y_min_scanlines;
 		selected_result = max(method2, y_tile_minimum);
 	} else {
 		if ((ddb_allocation / plane_blocks_per_line) >= 1)
@@ -3607,10 +3607,12 @@ static int skl_compute_plane_wm(const st
 
 	if (level >= 1 && level <= 7) {
 		if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
-		    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED)
+		    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
+			res_blocks += y_tile_minimum;
 			res_lines += y_min_scanlines;
-		else
+		} else {
 			res_blocks++;
+		}
 	}
 
 	if (res_blocks >= ddb_allocation || res_lines > 31) {