drm/i915: Fix glk watermark calculations

GLK wants the +1 adjustement for the "blocks per line" value
for x-tile/y-tile, just like cnl+.

Also the x-tile and linear cases are almost identical. The only
difference is this +1 which is always done for glk+, and only
done for linear on skl/bxt. Let's unify it to a single branch
with a special case for the +1, just like we do for y-tile.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200430125822.21985-1-ville.syrjala@linux.intel.comReviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -4868,7 +4868,7 @@ skl_wm_method1(const struct drm_i915_private *dev_priv, u32 pixel_rate,
 	wm_intermediate_val = latency * pixel_rate * cpp;
 	ret = div_fixed16(wm_intermediate_val, 1000 * dbuf_block_size);
 
-	if (INTEL_GEN(dev_priv) >= 10)
+	if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
 		ret = add_fixed16_u32(ret, 1);
 
 	return ret;
@@ -5003,18 +5003,19 @@ skl_compute_wm_params(const struct intel_crtc_state *crtc_state,
 					   wp->y_min_scanlines,
 					   wp->dbuf_block_size);
 
-		if (INTEL_GEN(dev_priv) >= 10)
+		if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
 			interm_pbpl++;
 
 		wp->plane_blocks_per_line = div_fixed16(interm_pbpl,
 							wp->y_min_scanlines);
-	} else if (wp->x_tiled && IS_GEN(dev_priv, 9)) {
-		interm_pbpl = DIV_ROUND_UP(wp->plane_bytes_per_line,
-					   wp->dbuf_block_size);
-		wp->plane_blocks_per_line = u32_to_fixed16(interm_pbpl);
 	} else {
 		interm_pbpl = DIV_ROUND_UP(wp->plane_bytes_per_line,
-					   wp->dbuf_block_size) + 1;
+					   wp->dbuf_block_size);
+
+		if (!wp->x_tiled ||
+		    INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
+			interm_pbpl++;
+
 		wp->plane_blocks_per_line = u32_to_fixed16(interm_pbpl);
 	}