drm/i915: Extract intel_mode_vblank_delay()

Extract the code that computes the hardware centric view
of the vblank delay into a helper. We'll need a slightly
different variant for VRR soon.

Signed-off-by: Ville Syrjälä <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Reviewed-by: Ankit Nautiyal <[e-mail]>

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

···
 
 static int dsb_vblank_delay(const struct intel_crtc_state *crtc_state)
 {
-	return intel_mode_vblank_start(&crtc_state->hw.adjusted_mode) -
-		intel_mode_vdisplay(&crtc_state->hw.adjusted_mode);
+	return intel_mode_vblank_delay(&crtc_state->hw.adjusted_mode);
 }
 
 static int dsb_vtotal(struct intel_atomic_state *state,

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

···
 	return vtotal;
 }
 
+int intel_mode_vblank_delay(const struct drm_display_mode *mode)
+{
+	return intel_mode_vblank_start(mode) - intel_mode_vdisplay(mode);
+}
+
 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)
···
 	 */
 	if (intel_color_uses_dsb(new_crtc_state) ||
 	    new_crtc_state->update_m_n || new_crtc_state->update_lrr)
-		evade->min -= intel_mode_vblank_start(adjusted_mode) -
-			intel_mode_vdisplay(adjusted_mode);
+		evade->min -= intel_mode_vblank_delay(adjusted_mode);
 }
 
 /* must be called with vblank interrupt already enabled! */

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

···
 int intel_mode_vblank_start(const struct drm_display_mode *mode);
 int intel_mode_vblank_end(const struct drm_display_mode *mode);
 int intel_mode_vtotal(const struct drm_display_mode *mode);
+int intel_mode_vblank_delay(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,