[PATCH v4 18/19] drm/i915/display: perform transient flush

[Balasubramani Vivekanandan]

From: Matthew Auld <matthew.auld at intel.com>

Perform manual transient cache flush prior to flip and at the end of
frontbuffer_flush. This is needed to ensure display engine doesn't see
garbage if the surface is L3:XD dirty.

Testcase: igt at xe-pat@display-vs-wb-transient
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan at intel.com>
Acked-by: Nirmoy Das <nirmoy.das at intel.com>
Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c  |  3 +++
 .../gpu/drm/i915/display/intel_frontbuffer.c  |  2 ++
 drivers/gpu/drm/i915/display/intel_tdf.h      | 25 +++++++++++++++++++
 drivers/gpu/drm/xe/Makefile                   |  3 ++-
 drivers/gpu/drm/xe/display/xe_tdf.c           | 13 ++++++++++
 5 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/i915/display/intel_tdf.h
 create mode 100644 drivers/gpu/drm/xe/display/xe_tdf.c

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 67697d9a559c..4fc46edcb4ad 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -110,6 +110,7 @@
 #include "intel_sdvo.h"
 #include "intel_snps_phy.h"
 #include "intel_tc.h"
+#include "intel_tdf.h"
 #include "intel_tv.h"
 #include "intel_vblank.h"
 #include "intel_vdsc.h"
@@ -7242,6 +7243,8 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
 
 	intel_atomic_commit_fence_wait(state);
 
+	intel_td_flush(dev_priv);
+
 	drm_atomic_helper_wait_for_dependencies(&state->base);
 	drm_dp_mst_atomic_wait_for_dependencies(&state->base);
 	intel_atomic_global_state_wait_for_dependencies(state);
diff --git a/drivers/gpu/drm/i915/display/intel_frontbuffer.c b/drivers/gpu/drm/i915/display/intel_frontbuffer.c
index 2ea37c0414a9..4923c340a0b6 100644
--- a/drivers/gpu/drm/i915/display/intel_frontbuffer.c
+++ b/drivers/gpu/drm/i915/display/intel_frontbuffer.c
@@ -65,6 +65,7 @@
 #include "intel_fbc.h"
 #include "intel_frontbuffer.h"
 #include "intel_psr.h"
+#include "intel_tdf.h"
 
 /**
  * frontbuffer_flush - flush frontbuffer
@@ -93,6 +94,7 @@ static void frontbuffer_flush(struct drm_i915_private *i915,
 	trace_intel_frontbuffer_flush(i915, frontbuffer_bits, origin);
 
 	might_sleep();
+	intel_td_flush(i915);
 	intel_drrs_flush(i915, frontbuffer_bits);
 	intel_psr_flush(i915, frontbuffer_bits, origin);
 	intel_fbc_flush(i915, frontbuffer_bits, origin);
diff --git a/drivers/gpu/drm/i915/display/intel_tdf.h b/drivers/gpu/drm/i915/display/intel_tdf.h
new file mode 100644
index 000000000000..353cde21f6c2
--- /dev/null
+++ b/drivers/gpu/drm/i915/display/intel_tdf.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef __INTEL_TDF_H__
+#define __INTEL_TDF_H__
+
+/*
+ * TDF (Transient-Data-Flush) is needed for Xe2+ where special L3:XD caching can
+ * be enabled through various PAT index modes. Idea is to use this caching mode
+ * when for example rendering onto the display surface, with the promise that
+ * KMD will ensure transient cache entries are always flushed by the time we do
+ * the display flip, since display engine is never coherent with CPU/GPU caches.
+ */
+
+struct drm_i915_private;
+
+#ifdef I915
+static inline void intel_td_flush(struct drm_i915_private *i915) {}
+#else
+void intel_td_flush(struct drm_i915_private *i915);
+#endif
+
+#endif
diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
index 18c650439716..97dba95f676a 100644
--- a/drivers/gpu/drm/xe/Makefile
+++ b/drivers/gpu/drm/xe/Makefile
@@ -204,7 +204,8 @@ xe-$(CONFIG_DRM_XE_DISPLAY) += \
 	display/xe_dsb_buffer.o \
 	display/xe_fb_pin.o \
 	display/xe_hdcp_gsc.o \
-	display/xe_plane_initial.o
+	display/xe_plane_initial.o \
+	display/xe_tdf.o
 
 # SOC code shared with i915
 xe-$(CONFIG_DRM_XE_DISPLAY) += \
diff --git a/drivers/gpu/drm/xe/display/xe_tdf.c b/drivers/gpu/drm/xe/display/xe_tdf.c
new file mode 100644
index 000000000000..2c0d4e144e09
--- /dev/null
+++ b/drivers/gpu/drm/xe/display/xe_tdf.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include "xe_device.h"
+#include "intel_display_types.h"
+#include "intel_tdf.h"
+
+void intel_td_flush(struct drm_i915_private *i915)
+{
+	xe_device_td_flush(i915);
+}
-- 
2.25.1