drm/i915/dsb: Use safe window path when VRR TG is used

When the VRR timing generator is always used, the hardware behaves
as VRR-active regardless of crtc_state->vrr.enable.

The DSB paths that depend on the VRR safe window therefore need to follow
the VRR code paths in that case too:
- dsb_chicken(): program the SAFE_WINDOW chicken bits,
- intel_dsb_vblank_evade(): use vmin/vmax vblank starts for the
  wait window,
- intel_dsb_wait_for_delayed_vblank(): wait inside the vmin safe window
  before the scanline-based delayed vblank wait.

Introduce helper pre_commit_use_safe_window() and use it in the three sites

v2: Instead of modifying pre_commit_is_vrr_active() use a new helper and
    use it only in the required places. (Ville).

v3: -Keep using pre_commit_is_vrr_active() for DCB path. (Ville)
    -Add a separate check for fixed RR with VRR TG and use
     fixed mode vblank start there. (Ville)

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260617051417.2223526-1-ankit.k.nautiyal@intel.com

1 files changed, 20 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
index 07dd6318d9cc..d9a270362a82 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.c
+++ b/drivers/gpu/drm/i915/display/intel_dsb.c
@@ -210,6 +210,18 @@ static int dsb_scanline_to_hw(struct intel_atomic_state *state,
 	return (scanline + vtotal - intel_crtc_scanline_offset(crtc_state)) % vtotal;
 }
 
+static
+bool pre_commit_use_safe_window(struct intel_atomic_state *state,
+				struct intel_crtc *crtc)
+{
+	struct intel_display *display = to_intel_display(crtc->base.dev);
+
+	if (intel_vrr_always_use_vrr_tg(display))
+		return true;
+
+	return pre_commit_is_vrr_active(state, crtc);
+}
+
 /*
  * Bspec suggests that we should always set DSB_SKIP_WAITS_EN. We have approach
  * different from what is explained in Bspec on how flip is considered being
@@ -229,7 +241,7 @@ static u32 dsb_chicken(struct intel_atomic_state *state,
 	u32 chicken = intel_psr_use_trans_push(new_crtc_state) ?
 		DSB_SKIP_WAITS_EN : 0;
 
-	if (pre_commit_is_vrr_active(state, crtc))
+	if (pre_commit_use_safe_window(state, crtc))
 		chicken |= DSB_CTRL_WAIT_SAFE_WINDOW |
 			DSB_CTRL_NO_WAIT_VBLANK |
 			DSB_INST_WAIT_SAFE_WINDOW |
@@ -798,6 +810,12 @@ void intel_dsb_vblank_evade(struct intel_atomic_state *state,
 		end = intel_vrr_vmax_vblank_start(crtc_state);
 		start = end - vblank_delay - latency;
 		intel_dsb_wait_scanline_out(state, dsb, start, end);
+	} else if (pre_commit_use_safe_window(state, crtc)) {
+		int vblank_delay = crtc_state->set_context_latency;
+
+		end = intel_mode_vblank_start(&crtc_state->hw.adjusted_mode);
+		start = end - vblank_delay - latency;
+		intel_dsb_wait_scanline_out(state, dsb, start, end);
 	} else {
 		int vblank_delay = intel_mode_vblank_delay(&crtc_state->hw.adjusted_mode);
 
@@ -891,7 +909,7 @@ void intel_dsb_wait_for_delayed_vblank(struct intel_atomic_state *state,
 		&crtc_state->hw.adjusted_mode;
 	int wait_scanlines;
 
-	if (pre_commit_is_vrr_active(state, crtc)) {
+	if (pre_commit_use_safe_window(state, crtc)) {
 		/*
 		 * If the push happened before the vmin decision boundary
 		 * we don't know how far we are from the undelayed vblank.