[PATCH v3 19/26] drm/{i915/xe}/writeback: Add a writeback helper to get ggtt address

[Suraj Kandpal <suraj.kandpal@intel.com>]

We need the ggtt address offset to write in the WD_SURF register.
With i915_vma being defined in xe and i915 and both having different
ways to extract the address this poses an issue.
Add a helper so that correct function is called to extract address
depending on xe/i915 driver.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 drivers/gpu/drm/i915/Makefile                       |  1 +
 drivers/gpu/drm/i915/display/intel_writeback.c      |  3 ++-
 .../gpu/drm/i915/display/intel_writeback_helper.c   | 12 ++++++++++++
 .../gpu/drm/i915/display/intel_writeback_helper.h   |  8 ++++++++
 drivers/gpu/drm/xe/Makefile                         |  3 ++-
 drivers/gpu/drm/xe/display/xe_writeback_helper.c    | 13 +++++++++++++
 6 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/display/intel_writeback_helper.c
 create mode 100644 drivers/gpu/drm/i915/display/intel_writeback_helper.h
 create mode 100644 drivers/gpu/drm/xe/display/xe_writeback_helper.c

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 1e9140e7713c..a1023de728e5 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -316,6 +316,7 @@ i915-y += \
 	display/intel_vga.o \
 	display/intel_wm.o \
 	display/intel_writeback.o \
+	display/intel_writeback_helper.o \
 	display/skl_prefill.o \
 	display/skl_scaler.o \
 	display/skl_universal_plane.o \
diff --git a/drivers/gpu/drm/i915/display/intel_writeback.c b/drivers/gpu/drm/i915/display/intel_writeback.c
index c79e7330b81c..d3c3716a28a9 100644
--- a/drivers/gpu/drm/i915/display/intel_writeback.c
+++ b/drivers/gpu/drm/i915/display/intel_writeback.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 /*
- * Copyright © 2025 Intel Corporation
+ * Copyright © 2026 Intel Corporation
  */
 
 #include <linux/slab.h>
@@ -25,6 +25,7 @@
 #include "intel_display_utils.h"
 #include "intel_fb_pin.h"
 #include "intel_writeback.h"
+#include "intel_writeback_helper.h"
 #include "intel_writeback_reg.h"
 
 struct intel_writeback_connector {
diff --git a/drivers/gpu/drm/i915/display/intel_writeback_helper.c b/drivers/gpu/drm/i915/display/intel_writeback_helper.c
new file mode 100644
index 000000000000..f483ed6ffc6b
--- /dev/null
+++ b/drivers/gpu/drm/i915/display/intel_writeback_helper.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2026 Intel Corporation
+ */
+
+#include "i915_vma.h"
+#include "intel_writeback_helper.h"
+
+u32 intel_get_ggtt_addr(struct i915_vma *vma)
+{
+	return i915_ggtt_offset(vma);
+}
diff --git a/drivers/gpu/drm/i915/display/intel_writeback_helper.h b/drivers/gpu/drm/i915/display/intel_writeback_helper.h
new file mode 100644
index 000000000000..b46f437c3875
--- /dev/null
+++ b/drivers/gpu/drm/i915/display/intel_writeback_helper.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2026 Intel Corporation
+ */
+
+struct i915_vma;
+
+u32 intel_get_ggtt_addr(struct i915_vma *vma);
diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
index 2e456070895a..4483e97153ba 100644
--- a/drivers/gpu/drm/xe/Makefile
+++ b/drivers/gpu/drm/xe/Makefile
@@ -224,7 +224,8 @@ xe-$(CONFIG_DRM_XE_DISPLAY) += \
 	display/xe_initial_plane.o \
 	display/xe_panic.o \
 	display/xe_stolen.o \
-	display/xe_tdf.o
+	display/xe_tdf.o \
+	display/xe_writeback_helper.o
 
 # Display code shared with i915
 xe-$(CONFIG_DRM_XE_DISPLAY) += \
diff --git a/drivers/gpu/drm/xe/display/xe_writeback_helper.c b/drivers/gpu/drm/xe/display/xe_writeback_helper.c
new file mode 100644
index 000000000000..5898984b129c
--- /dev/null
+++ b/drivers/gpu/drm/xe/display/xe_writeback_helper.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2026 Intel Corporation
+ */
+
+#include "xe_ggtt.h"
+#include "xe_display_vma.h"
+#include "intel_writeback_helper.h"
+
+u32 intel_get_ggtt_addr(struct i915_vma *vma)
+{
+	return lower_32_bits(xe_ggtt_node_addr(vma->node));
+}
-- 
2.34.1