drm/i915/gen9: minimum scanlines for Y tile is not always 4

During watermarks calculations, this value is used in 3 different
places. Only one of them was not using a hardcoded 4. Move the code up
so everybody can benefit from the actual value.

This should only help on situations with Y tiling + 90/270 rotation +
1 or 2 bpp or NV12.

Cc: stable@vger.kernel.org
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-6-git-send-email-paulo.r.zanoni@intel.com
(cherry picked from commit 1186fa85)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -3495,7 +3495,8 @@ static uint32_t skl_wm_method1(uint32_t pixel_rate, uint8_t cpp, uint32_t latenc
 
 static uint32_t skl_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal,
 			       uint32_t horiz_pixels, uint8_t cpp,
-			       uint64_t tiling, uint32_t latency)
+			       uint64_t tiling, uint32_t latency,
+			       uint32_t y_min_scanlines)
 {
 	uint32_t ret;
 	uint32_t plane_bytes_per_line, plane_blocks_per_line;
@@ -3508,9 +3509,9 @@ static uint32_t skl_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal,
 
 	if (tiling == I915_FORMAT_MOD_Y_TILED ||
 	    tiling == I915_FORMAT_MOD_Yf_TILED) {
-		plane_bytes_per_line *= 4;
+		plane_bytes_per_line *= y_min_scanlines;
 		plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
-		plane_blocks_per_line /= 4;
+		plane_blocks_per_line /= y_min_scanlines;
 	} else if (tiling == DRM_FORMAT_MOD_NONE) {
 		plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512) + 1;
 	} else {
@@ -3567,6 +3568,7 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 	uint8_t cpp;
 	uint32_t width = 0, height = 0;
 	uint32_t plane_pixel_rate;
+	uint32_t y_min_scanlines;
 
 	if (latency == 0 || !cstate->base.active || !intel_pstate->base.visible) {
 		*enabled = false;
@@ -3582,21 +3584,6 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 	cpp = drm_format_plane_cpp(fb->pixel_format, 0);
 	plane_pixel_rate = skl_adjusted_plane_pixel_rate(cstate, intel_pstate);
 
-	method1 = skl_wm_method1(plane_pixel_rate, cpp, latency);
-	method2 = skl_wm_method2(plane_pixel_rate,
-				 cstate->base.adjusted_mode.crtc_htotal,
-				 width,
-				 cpp,
-				 fb->modifier[0],
-				 latency);
-
-	plane_bytes_per_line = width * cpp;
-	plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
-
-	if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
-	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
-		uint32_t min_scanlines = 4;
-		uint32_t y_tile_minimum;
 	if (intel_rotation_90_or_270(pstate->rotation)) {
 		int cpp = (fb->pixel_format == DRM_FORMAT_NV12) ?
 			drm_format_plane_cpp(fb->pixel_format, 1) :
@@ -3604,16 +3591,37 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 
 		switch (cpp) {
 		case 1:
-				min_scanlines = 16;
+			y_min_scanlines = 16;
 			break;
 		case 2:
-				min_scanlines = 8;
+			y_min_scanlines = 8;
 			break;
-			case 8:
+		default:
 			WARN(1, "Unsupported pixel depth for rotation");
+		case 4:
+			y_min_scanlines = 4;
+			break;
 		}
+	} else {
+		y_min_scanlines = 4;
 	}
-		y_tile_minimum = plane_blocks_per_line * min_scanlines;
+
+	method1 = skl_wm_method1(plane_pixel_rate, cpp, latency);
+	method2 = skl_wm_method2(plane_pixel_rate,
+				 cstate->base.adjusted_mode.crtc_htotal,
+				 width,
+				 cpp,
+				 fb->modifier[0],
+				 latency,
+				 y_min_scanlines);
+
+	plane_bytes_per_line = width * cpp;
+	plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
+
+	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)
@@ -3628,7 +3636,7 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 	if (level >= 1 && level <= 7) {
 		if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
 		    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED)
-			res_lines += 4;
+			res_lines += y_min_scanlines;
 		else
 			res_blocks++;
 	}