drm/i915: Extract intel_mode_vblank_end()

Extract intel_mode_vblank_end() in the same vein as
intel_mode_vblank_start(). While we have only one use
of this it seems nicer to unify the approach.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240528185647.7765-3-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -312,12 +312,10 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc,
 	hsync_start = mode->crtc_hsync_start;
 	vtotal = mode->crtc_vtotal;
 	vbl_start = intel_mode_vblank_start(mode);
-	vbl_end = mode->crtc_vblank_end;
+	vbl_end = intel_mode_vblank_end(mode);
 
-	if (mode->flags & DRM_MODE_FLAG_INTERLACE) {
-		vbl_end /= 2;
+	if (mode->flags & DRM_MODE_FLAG_INTERLACE)
 		vtotal /= 2;
-	}
 
 	/*
 	 * Enter vblank critical section, as we will do multiple
@@ -584,6 +582,16 @@ int intel_mode_vblank_start(const struct drm_display_mode *mode)
 	return vblank_start;
 }
 
+int intel_mode_vblank_end(const struct drm_display_mode *mode)
+{
+	int vblank_end = mode->crtc_vblank_end;
+
+	if (mode->flags & DRM_MODE_FLAG_INTERLACE)
+		vblank_end /= 2;
+
+	return vblank_end;
+}
+
 void intel_vblank_evade_init(const struct intel_crtc_state *old_crtc_state,
 			     const struct intel_crtc_state *new_crtc_state,
 			     struct intel_vblank_evade_ctx *evade)

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

@@ -21,6 +21,7 @@ struct intel_vblank_evade_ctx {
 };
 
 int intel_mode_vblank_start(const struct drm_display_mode *mode);
+int intel_mode_vblank_end(const struct drm_display_mode *mode);
 
 void intel_vblank_evade_init(const struct intel_crtc_state *old_crtc_state,
 			     const struct intel_crtc_state *new_crtc_state,