drm/i915/display/tgl: Disable FBC with PSR2

There are some corner cases wrt underrun when we enable
FBC with PSR2 on TGL. Recommendation from hardware is to
keep this combination disabled.

Bspec: 50422 HSD: 14010260002

v2: Added psr2 enabled check from crtc_state (Anshuman)
Added Bspec link and HSD referneces (Jose)

v3: Moved the logic to disable fbc to intel_fbc_update_state_cache
and removed the crtc->config usages, as per Ville's recommendation.

v4: Introduced a variable in fbc state_cache instead of the earlier
plane.visible WA, as suggested by Jose.

v5: Dropped an extra check for fbc in intel_fbc_enable and addressed
review comments by Jose.

v6: Move WA to end of function and added Jose's RB.
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201201190406.1752-2-uma.shankar@intel.com

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

@@ -742,6 +742,8 @@ static void intel_fbc_update_state_cache(struct intel_crtc *crtc,
 		cache->fence_id = plane_state->vma->fence->id;
 	else
 		cache->fence_id = -1;
+
+	cache->psr2_active = crtc_state->has_psr2;
 }
 
 static bool intel_fbc_cfb_size_changed(struct drm_i915_private *dev_priv)
@@ -914,6 +916,16 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
 		return false;
 	}
 
+	/*
+	 * Tigerlake is not supporting FBC with PSR2.
+	 * Recommendation is to keep this combination disabled
+	 * Bspec: 50422 HSD: 14010260002
+	 */
+	if (fbc->state_cache.psr2_active && IS_TIGERLAKE(dev_priv)) {
+		fbc->no_fbc_reason = "not supported with PSR2";
+		return false;
+	}
+
 	return true;
 }
 

drivers/gpu/drm/i915/i915_drv.h

@@ -416,6 +416,7 @@ struct intel_fbc {
 		u16 gen9_wa_cfb_stride;
 		u16 interval;
 		s8 fence_id;
+		bool psr2_active;
 	} state_cache;
 
 	/*