drm/i915: Introduce skl_watermark_max_latency()

The DSB code will want to know the maximum PkgC latency
it has to contend with. Add a helper to expose that
information.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230606191504.18099-16-ville.syrjala@linux.intel.comReviewed-by: Uma Shankar <uma.shankar@intel.com>

drivers/gpu/drm/i915/display/skl_watermark.c

@@ -3721,3 +3721,17 @@ void skl_watermark_debugfs_register(struct drm_i915_private *i915)
 		debugfs_create_file("i915_sagv_status", 0444, minor->debugfs_root, i915,
 				    &intel_sagv_status_fops);
 }
+
+unsigned int skl_watermark_max_latency(struct drm_i915_private *i915)
+{
+	int level;
+
+	for (level = i915->display.wm.num_levels - 1; level >= 0; level--) {
+		unsigned int latency = skl_wm_latency(i915, level, NULL);
+
+		if (latency)
+			return latency;
+	}
+
+	return 0;
+}

drivers/gpu/drm/i915/display/skl_watermark.h

@@ -46,6 +46,8 @@ void skl_watermark_ipc_update(struct drm_i915_private *i915);
 bool skl_watermark_ipc_enabled(struct drm_i915_private *i915);
 void skl_watermark_debugfs_register(struct drm_i915_private *i915);
 
+unsigned int skl_watermark_max_latency(struct drm_i915_private *i915);
+
 void skl_wm_init(struct drm_i915_private *i915);
 
 struct intel_dbuf_state {