[PATCH 1/4] drm/i915/vrr: Use vrr.sync_start for getting vtotal

[Ankit Nautiyal]

Currently, in intel_vrr_get_config() crtc_vtotal is computed from
vrr.vmin vtotal, since the VTOTAL.Vtotal bits are deprecated.
Since vmin is currently set to crtc_vtotal, this gives us the vtotal.
However, as we move to optimized guardband, vmin will be modified to set
to the minimum Vtotal for highest refresh rate supported.

Instead of depending on vmin, compute vtotal from crtc_vsync_start and
vrr.vsync_start. This works since vrr.vsync_start is measured from the
end of vblank, and crtc_vsync_start is measured from start of the
scanline. Together their sum is equal to the crtc_vtotal.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_vrr.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
index 3eed37f271b0..46a85720411f 100644
--- a/drivers/gpu/drm/i915/display/intel_vrr.c
+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
@@ -735,17 +735,6 @@ void intel_vrr_get_config(struct intel_crtc_state *crtc_state)
 						     TRANS_VRR_VMAX(display, cpu_transcoder)) + 1;
 		crtc_state->vrr.vmin = intel_de_read(display,
 						     TRANS_VRR_VMIN(display, cpu_transcoder)) + 1;
-
-		/*
-		 * For platforms that always use VRR Timing Generator, the VTOTAL.Vtotal
-		 * bits are not filled. Since for these platforms TRAN_VMIN is always
-		 * filled with crtc_vtotal, use TRAN_VRR_VMIN to get the vtotal for
-		 * adjusted_mode.
-		 */
-		if (intel_vrr_always_use_vrr_tg(display))
-			crtc_state->hw.adjusted_mode.crtc_vtotal =
-				intel_vrr_vmin_vtotal(crtc_state);
-
 		if (HAS_AS_SDP(display)) {
 			trans_vrr_vsync =
 				intel_de_read(display,
@@ -755,6 +744,16 @@ void intel_vrr_get_config(struct intel_crtc_state *crtc_state)
 			crtc_state->vrr.vsync_end =
 				REG_FIELD_GET(VRR_VSYNC_END_MASK, trans_vrr_vsync);
 		}
+		/*
+		 * For platforms that always use VRR Timing Generator, the VTOTAL.Vtotal
+		 * bits are not filled. Since vrr.vsync_start is computed as:
+		 * crtc_vtotal - crtc_vsync_start, we can derive vtotal from
+		 * vrr.vsync_start and crtc_vsync_start.
+		 */
+		if (intel_vrr_always_use_vrr_tg(display))
+			crtc_state->hw.adjusted_mode.crtc_vtotal =
+				crtc_state->hw.adjusted_mode.crtc_vsync_start +
+				crtc_state->vrr.vsync_start;
 	}
 
 	vrr_enable = trans_vrr_ctl & VRR_CTL_VRR_ENABLE;
-- 
2.45.2