drm/i915/display: Ensure enough lines between delayed VBlank and VBlank

To deterministically capture the transition of the state machine going from
SRDOFFACK to IDLE, the delayed V. Blank should be at least one line after
the non-delayed V. Blank.

Ensure this by adding new interface into intel_psr to query number of lines
needed for vblank delay and call it from intel_crtc_vblank_delay.

v3: use existing intel_crtc_vblank_delay mechanism
v2: apply limits only when needed (VRR TG vs. Legacy TG)

Bspec: 69897
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Link: https://lore.kernel.org/r/20250423102704.1368310-1-jouni.hogander@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 58845b74f17d2f1a42642b523af3871c1fabf3e3..a4445a29927c68fdc3e7cdb76ee62e260a860b20 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -2426,6 +2426,8 @@ static int intel_crtc_vblank_delay(const struct intel_crtc_state *crtc_state)
        if (intel_crtc_needs_wa_14015401596(crtc_state))
                vblank_delay = max(vblank_delay, 1);
 
+       vblank_delay = max(vblank_delay, intel_psr_min_vblank_delay(crtc_state));
+
        return vblank_delay;
 }
 

diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
index cc0cec0e85e99fdc28c80d3ef5f135f7f9184138..af76c1db86cd44f2f2692abcd28c73372d3270e6 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_psr.c
+++ b/drivers/gpu/drm/i915/display/intel_psr.c
@@ -2348,6 +2348,45 @@ void intel_psr_trigger_frame_change_event(struct intel_dsb *dsb,
                                   CURSURFLIVE(display, crtc->pipe), 0);
 }
 
+/**
+ * intel_psr_min_vblank_delay - Minimum vblank delay needed by PSR
+ * @crtc_state: the crtc state
+ *
+ * Return minimum vblank delay needed by PSR.
+ */
+int intel_psr_min_vblank_delay(const struct intel_crtc_state *crtc_state)
+{
+       struct intel_display *display = to_intel_display(crtc_state);
+
+       if (!crtc_state->has_psr || DISPLAY_VER(display) < 20)
+               return 0;
+
+       /*
+        * Comment on SRD_STATUS register in Bspec for LunarLake and onwards:
+        *
+        * To deterministically capture the transition of the state machine
+        * going from SRDOFFACK to IDLE, the delayed V. Blank should be at least
+        * one line after the non-delayed V. Blank.
+        *
+        * Legacy TG: TRANS_SET_CONTEXT_LATENCY > 0
+        * VRR TG: TRANS_VRR_CTL[ VRR Guardband ] < (TRANS_VRR_VMAX[ VRR Vmax ]
+        * - TRANS_VTOTAL[ Vertical Active ])
+        *
+        * SRD_STATUS is used only by PSR1 on PantherLake.
+        * SRD_STATUS is used by PSR1 and Panel Replay DP on LunarLake.
+        */
+
+       if (DISPLAY_VER(display) >= 30 && (crtc_state->has_panel_replay ||
+                                          crtc_state->has_sel_update))
+               return 0;
+       else if (DISPLAY_VER(display) < 30 && (crtc_state->has_sel_update ||
+                                              intel_crtc_has_type(crtc_state,
+                                                                  INTEL_OUTPUT_EDP)))
+               return 0;
+       else
+               return 1;
+}
+
 static u32 man_trk_ctl_enable_bit_get(struct intel_display *display)
 {
        return display->platform.alderlake_p || DISPLAY_VER(display) >= 14 ? 0 :

diff --git a/drivers/gpu/drm/i915/display/intel_psr.h b/drivers/gpu/drm/i915/display/intel_psr.h
index 601e47ad3297342900d8f44a585e1ded29536c69..73c3fa40844bc6193b598968fde8af9a4f2b8fcd 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_psr.h
+++ b/drivers/gpu/drm/i915/display/intel_psr.h
@@ -73,6 +73,7 @@ void intel_psr_unlock(const struct intel_crtc_state *crtc_state);
 void intel_psr_trigger_frame_change_event(struct intel_dsb *dsb,
                                          struct intel_atomic_state *state,
                                          struct intel_crtc *crtc);
+int intel_psr_min_vblank_delay(const struct intel_crtc_state *crtc_state);
 void intel_psr_connector_debugfs_add(struct intel_connector *connector);
 void intel_psr_debugfs_register(struct intel_display *display);
 bool intel_psr_needs_alpm(struct intel_dp *intel_dp, const struct intel_crtc_state *crtc_state);