[RFC PATCH 2/2] drm/xe/dma-buf: Add generic interconnect support framework

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

Negotiate to use an xe-specific interconnect.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/xe/tests/xe_dma_buf.c | 12 +++---
 drivers/gpu/drm/xe/xe_dma_buf.c       | 54 +++++++++++++++++++++++----
 drivers/gpu/drm/xe/xe_dma_buf.h       |  1 -
 drivers/gpu/drm/xe/xe_interconnect.h  | 22 +++++++++++
 4 files changed, 75 insertions(+), 14 deletions(-)
 create mode 100644 drivers/gpu/drm/xe/xe_interconnect.h

diff --git a/drivers/gpu/drm/xe/tests/xe_dma_buf.c b/drivers/gpu/drm/xe/tests/xe_dma_buf.c
index 5df98de5ba3c..8eaea6c2a3b7 100644
--- a/drivers/gpu/drm/xe/tests/xe_dma_buf.c
+++ b/drivers/gpu/drm/xe/tests/xe_dma_buf.c
@@ -210,9 +210,9 @@ static const struct dma_buf_attach_ops nop2p_attach_ops = {
  */
 static const struct dma_buf_test_params test_params[] = {
 	{.mem_mask = XE_BO_FLAG_VRAM0,
-	 .attach_ops = &xe_dma_buf_attach_ops},
+	 .attach_ops = &xe_dma_buf_attach_ops.dma_ops},
 	{.mem_mask = XE_BO_FLAG_VRAM0 | XE_BO_FLAG_NEEDS_CPU_ACCESS,
-	 .attach_ops = &xe_dma_buf_attach_ops,
+	 .attach_ops = &xe_dma_buf_attach_ops.dma_ops,
 	 .force_different_devices = true},
 
 	{.mem_mask = XE_BO_FLAG_VRAM0,
@@ -226,9 +226,9 @@ static const struct dma_buf_test_params test_params[] = {
 	 .force_different_devices = true},
 
 	{.mem_mask = XE_BO_FLAG_SYSTEM,
-	 .attach_ops = &xe_dma_buf_attach_ops},
+	 .attach_ops = &xe_dma_buf_attach_ops.dma_ops},
 	{.mem_mask = XE_BO_FLAG_SYSTEM,
-	 .attach_ops = &xe_dma_buf_attach_ops,
+	 .attach_ops = &xe_dma_buf_attach_ops.dma_ops,
 	 .force_different_devices = true},
 
 	{.mem_mask = XE_BO_FLAG_SYSTEM,
@@ -242,10 +242,10 @@ static const struct dma_buf_test_params test_params[] = {
 	 .force_different_devices = true},
 
 	{.mem_mask = XE_BO_FLAG_SYSTEM | XE_BO_FLAG_VRAM0,
-	 .attach_ops = &xe_dma_buf_attach_ops},
+	 .attach_ops = &xe_dma_buf_attach_ops.dma_ops},
 	{.mem_mask = XE_BO_FLAG_SYSTEM | XE_BO_FLAG_VRAM0 |
 		     XE_BO_FLAG_NEEDS_CPU_ACCESS,
-	 .attach_ops = &xe_dma_buf_attach_ops,
+	 .attach_ops = &xe_dma_buf_attach_ops.dma_ops,
 	 .force_different_devices = true},
 
 	{.mem_mask = XE_BO_FLAG_SYSTEM | XE_BO_FLAG_VRAM0,
diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c
index 54e42960daad..40e9a28eaf64 100644
--- a/drivers/gpu/drm/xe/xe_dma_buf.c
+++ b/drivers/gpu/drm/xe/xe_dma_buf.c
@@ -16,19 +16,40 @@
 #include "tests/xe_test.h"
 #include "xe_bo.h"
 #include "xe_device.h"
+#include "xe_interconnect.h"
 #include "xe_pm.h"
 #include "xe_ttm_vram_mgr.h"
 #include "xe_vm.h"
 
 MODULE_IMPORT_NS("DMA_BUF");
 
+struct xe_dma_buf_attach_ops {
+	struct dma_buf_attach_ops dma_ops;
+	struct xe_interconnect_attach_ops ic_ops;
+};
+
+static const struct xe_dma_buf_attach_ops *
+to_xe_dma_buf_attach_ops(struct dma_buf_attachment *attach)
+{
+	const struct dma_buf_attach_ops *aops = attach->importer_ops;
+
+	if (!aops || !aops->supports_interconnect)
+		return NULL;
+
+	return aops->supports_interconnect(attach, xe_interconnect);
+}
+
 static int xe_dma_buf_attach(struct dma_buf *dmabuf,
 			     struct dma_buf_attachment *attach)
 {
 	struct drm_gem_object *obj = attach->dmabuf->priv;
+	const struct xe_dma_buf_attach_ops *xe_attach_ops =
+		to_xe_dma_buf_attach_ops(attach);
 
-	if (attach->peer2peer &&
-	    pci_p2pdma_distance(to_pci_dev(obj->dev->dev), attach->dev, false) < 0)
+	if (xe_attach_ops && xe_attach_ops->ic_ops.allow_ic)
+		attach->interconnect = xe_interconnect;
+	else if (attach->peer2peer &&
+		 pci_p2pdma_distance(to_pci_dev(obj->dev->dev), attach->dev, false) < 0)
 		attach->peer2peer = false;
 
 	if (!attach->peer2peer && !xe_bo_can_migrate(gem_to_xe_bo(obj), XE_PL_TT))
@@ -285,9 +306,27 @@ static void xe_dma_buf_move_notify(struct dma_buf_attachment *attach)
 	XE_WARN_ON(xe_bo_evict(bo, exec));
 }
 
-static const struct dma_buf_attach_ops xe_dma_buf_attach_ops = {
-	.allow_peer2peer = true,
-	.move_notify = xe_dma_buf_move_notify
+static const void *xe_dma_buf_supports_interconnect(struct dma_buf_attachment *attach,
+						    const void *interconnect)
+{
+	if (interconnect == xe_interconnect) {
+		return &container_of(attach->importer_ops,
+				     const struct xe_dma_buf_attach_ops,
+				     dma_ops)->ic_ops;
+	}
+
+	return NULL;
+}
+
+static const struct xe_dma_buf_attach_ops xe_dma_buf_attach_ops = {
+	.dma_ops = {
+		.allow_peer2peer = true,
+		.move_notify = xe_dma_buf_move_notify,
+		.supports_interconnect = xe_dma_buf_supports_interconnect,
+	},
+	.ic_ops = {
+		.allow_ic = true,
+	}
 };
 
 #if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
@@ -336,12 +375,11 @@ struct drm_gem_object *xe_gem_prime_import(struct drm_device *dev,
 	if (IS_ERR(bo))
 		return ERR_CAST(bo);
 
-	attach_ops = &xe_dma_buf_attach_ops;
+	attach_ops = &xe_dma_buf_attach_ops.dma_ops;
 #if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
 	if (test)
 		attach_ops = test->attach_ops;
 #endif
-
 	attach = dma_buf_dynamic_attach(dma_buf, dev->dev, attach_ops, &bo->ttm.base);
 	if (IS_ERR(attach)) {
 		obj = ERR_CAST(attach);
@@ -364,6 +402,8 @@ struct drm_gem_object *xe_gem_prime_import(struct drm_device *dev,
 	return obj;
 }
 
+void *xe_interconnect = "XE_INTERCONNECT";
+
 #if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
 #include "tests/xe_dma_buf.c"
 #endif
diff --git a/drivers/gpu/drm/xe/xe_dma_buf.h b/drivers/gpu/drm/xe/xe_dma_buf.h
index 861dd28a862c..6b381ce4b7c1 100644
--- a/drivers/gpu/drm/xe/xe_dma_buf.h
+++ b/drivers/gpu/drm/xe/xe_dma_buf.h
@@ -11,5 +11,4 @@
 struct dma_buf *xe_gem_prime_export(struct drm_gem_object *obj, int flags);
 struct drm_gem_object *xe_gem_prime_import(struct drm_device *dev,
 					   struct dma_buf *dma_buf);
-
 #endif
diff --git a/drivers/gpu/drm/xe/xe_interconnect.h b/drivers/gpu/drm/xe/xe_interconnect.h
new file mode 100644
index 000000000000..1fa052623d05
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_interconnect.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2025 Intel Corporation
+ */
+#ifndef _XE_INTERCONNECT_H_
+#define _XE_INTERCONNECT_H_
+
+#include <linux/types.h>
+
+/* This file needs to be shared between the importer and exporter of the interconnect */
+
+extern void *xe_interconnect;
+
+struct xe_interconnect_attach_ops {
+	/*
+	 * Here interconnect-private stuff can be added.
+	 * Like a function to check interconnect possibility.
+	 */
+	bool allow_ic;
+};
+
+#endif
-- 
2.51.0