drm/i915/alpm: Allow LOBF only if window1 > alpm check_entry lines

LOBF must be disabled if the number of lines within Window 1 is not greater
than ALPM_CTL[ALPM Entry Check]

v2: Consider the case where SCL is in the active region. (Ville)

Bspec:71041
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Michał Grzelak <michal.grzelak@intel.com>
Link: https://patch.msgid.link/20260204050250.762718-3-ankit.k.nautiyal@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c b/drivers/gpu/drm/i915/display/intel_alpm.c
index 055184a3c7d51151791be4f6e58a369d676c01d0..27b26e5813dc05587cb8252269fd2ecfda05dc3e 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_alpm.c
+++ b/drivers/gpu/drm/i915/display/intel_alpm.c
@@ -270,6 +270,23 @@ int intel_alpm_lobf_min_guardband(struct intel_crtc_state *crtc_state)
        return first_sdp_position + waketime_in_lines + crtc_state->set_context_latency;
 }
 
+static bool intel_alpm_lobf_is_window1_sufficient(struct intel_crtc_state *crtc_state)
+{
+       struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+       int vblank = adjusted_mode->crtc_vtotal - adjusted_mode->crtc_vdisplay;
+       int window1;
+
+       /*
+        * LOBF must be disabled if the number of lines within Window 1 is not
+        * greater than ALPM_CTL[ALPM Entry Check]
+        */
+       window1 = vblank - min(vblank,
+                              crtc_state->vrr.guardband +
+                              crtc_state->set_context_latency);
+
+       return window1 > crtc_state->alpm_state.check_entry_lines;
+}
+
 void intel_alpm_lobf_compute_config_late(struct intel_dp *intel_dp,
                                         struct intel_crtc_state *crtc_state)
 {
@@ -279,6 +296,11 @@ void intel_alpm_lobf_compute_config_late(struct intel_dp *intel_dp,
        if (!crtc_state->has_lobf)
                return;
 
+       if (!intel_alpm_lobf_is_window1_sufficient(crtc_state)) {
+               crtc_state->has_lobf = false;
+               return;
+       }
+
        /*
         * LOBF can only be enabled if the time from the start of the SCL+Guardband
         * window to the position of the first SDP is greater than the time it takes