drm/i915: Extract intel_crtc_scanline_offset()

Pull the scanline_offset calculation into its own function. Might
have further use for this later with DSB scanline waits.
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230310235828.17439-4-ville.syrjala@linux.intel.com

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

@@ -441,6 +441,53 @@ void intel_wait_for_pipe_scanline_moving(struct intel_crtc *crtc)
 	wait_for_pipe_scanline_moving(crtc, true);
 }
 
+static int intel_crtc_scanline_offset(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+
+	/*
+	 * The scanline counter increments at the leading edge of hsync.
+	 *
+	 * On most platforms it starts counting from vtotal-1 on the
+	 * first active line. That means the scanline counter value is
+	 * always one less than what we would expect. Ie. just after
+	 * start of vblank, which also occurs at start of hsync (on the
+	 * last active line), the scanline counter will read vblank_start-1.
+	 *
+	 * On gen2 the scanline counter starts counting from 1 instead
+	 * of vtotal-1, so we have to subtract one (or rather add vtotal-1
+	 * to keep the value positive), instead of adding one.
+	 *
+	 * On HSW+ the behaviour of the scanline counter depends on the output
+	 * type. For DP ports it behaves like most other platforms, but on HDMI
+	 * there's an extra 1 line difference. So we need to add two instead of
+	 * one to the value.
+	 *
+	 * On VLV/CHV DSI the scanline counter would appear to increment
+	 * approx. 1/3 of a scanline before start of vblank. Unfortunately
+	 * that means we can't tell whether we're in vblank or not while
+	 * we're on that particular line. We must still set scanline_offset
+	 * to 1 so that the vblank timestamps come out correct when we query
+	 * the scanline counter from within the vblank interrupt handler.
+	 * However if queried just before the start of vblank we'll get an
+	 * answer that's slightly in the future.
+	 */
+	if (DISPLAY_VER(i915) == 2) {
+		int vtotal;
+
+		vtotal = adjusted_mode->crtc_vtotal;
+		if (adjusted_mode->flags & DRM_MODE_FLAG_INTERLACE)
+			vtotal /= 2;
+
+		return vtotal - 1;
+	} else if (HAS_DDI(i915) && intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI)) {
+		return 2;
+	} else {
+		return 1;
+	}
+}
+
 void intel_crtc_update_active_timings(const struct intel_crtc_state *crtc_state)
 {
 	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
@@ -479,47 +526,7 @@ void intel_crtc_update_active_timings(const struct intel_crtc_state *crtc_state)
 
 	crtc->mode_flags = crtc_state->mode_flags;
 
-	/*
-	 * The scanline counter increments at the leading edge of hsync.
-	 *
-	 * On most platforms it starts counting from vtotal-1 on the
-	 * first active line. That means the scanline counter value is
-	 * always one less than what we would expect. Ie. just after
-	 * start of vblank, which also occurs at start of hsync (on the
-	 * last active line), the scanline counter will read vblank_start-1.
-	 *
-	 * On gen2 the scanline counter starts counting from 1 instead
-	 * of vtotal-1, so we have to subtract one (or rather add vtotal-1
-	 * to keep the value positive), instead of adding one.
-	 *
-	 * On HSW+ the behaviour of the scanline counter depends on the output
-	 * type. For DP ports it behaves like most other platforms, but on HDMI
-	 * there's an extra 1 line difference. So we need to add two instead of
-	 * one to the value.
-	 *
-	 * On VLV/CHV DSI the scanline counter would appear to increment
-	 * approx. 1/3 of a scanline before start of vblank. Unfortunately
-	 * that means we can't tell whether we're in vblank or not while
-	 * we're on that particular line. We must still set scanline_offset
-	 * to 1 so that the vblank timestamps come out correct when we query
-	 * the scanline counter from within the vblank interrupt handler.
-	 * However if queried just before the start of vblank we'll get an
-	 * answer that's slightly in the future.
-	 */
-	if (DISPLAY_VER(i915) == 2) {
-		int vtotal;
-
-		vtotal = adjusted_mode.crtc_vtotal;
-		if (adjusted_mode.flags & DRM_MODE_FLAG_INTERLACE)
-			vtotal /= 2;
-
-		crtc->scanline_offset = vtotal - 1;
-	} else if (HAS_DDI(i915) &&
-		   intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI)) {
-		crtc->scanline_offset = 2;
-	} else {
-		crtc->scanline_offset = 1;
-	}
+	crtc->scanline_offset = intel_crtc_scanline_offset(crtc_state);
 
 	spin_unlock(&i915->uncore.lock);
 	spin_unlock_irqrestore(&i915->drm.vblank_time_lock, irqflags);