drm/i915: Initial introduction of vma resources

Introduce vma resources, sort of similar to TTM resources,  needed for
asynchronous bind management. Initially we will use them to hold
completion of unbinding when we capture data from a vma, but they will
be used extensively in upcoming patches for asynchronous vma unbinding.

v6:
- Some documentation updates

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220110172219.107131-2-thomas.hellstrom@linux.intel.com

1 files changed, 69 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_vma_resource.h b/drivers/gpu/drm/i915/i915_vma_resource.h
new file mode 100644
index 000000000000..3353d32ceda8
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_vma_resource.h
@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2021 Intel Corporation
+ */
+
+#ifndef __I915_VMA_RESOURCE_H__
+#define __I915_VMA_RESOURCE_H__
+
+#include <linux/dma-fence.h>
+#include <linux/refcount.h>
+
+/**
+ * struct i915_vma_resource - Snapshotted unbind information.
+ * @unbind_fence: Fence to mark unbinding complete. Note that this fence
+ * is not considered published until unbind is scheduled, and as such it
+ * is illegal to access this fence before scheduled unbind other than
+ * for refcounting.
+ * @lock: The @unbind_fence lock.
+ * @hold_count: Number of holders blocking the fence from finishing.
+ * The vma itself is keeping a hold, which is released when unbind
+ * is scheduled.
+ *
+ * The lifetime of a struct i915_vma_resource is from a binding request to
+ * the actual possible asynchronous unbind has completed.
+ */
+struct i915_vma_resource {
+	struct dma_fence unbind_fence;
+	/* See above for description of the lock. */
+	spinlock_t lock;
+	refcount_t hold_count;
+};
+
+bool i915_vma_resource_hold(struct i915_vma_resource *vma_res,
+			    bool *lockdep_cookie);
+
+void i915_vma_resource_unhold(struct i915_vma_resource *vma_res,
+			      bool lockdep_cookie);
+
+struct i915_vma_resource *i915_vma_resource_alloc(void);
+
+struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res);
+
+/**
+ * i915_vma_resource_get - Take a reference on a vma resource
+ * @vma_res: The vma resource on which to take a reference.
+ *
+ * Return: The @vma_res pointer
+ */
+static inline struct i915_vma_resource
+*i915_vma_resource_get(struct i915_vma_resource *vma_res)
+{
+	dma_fence_get(&vma_res->unbind_fence);
+	return vma_res;
+}
+
+/**
+ * i915_vma_resource_put - Release a reference to a struct i915_vma_resource
+ * @vma_res: The resource
+ */
+static inline void i915_vma_resource_put(struct i915_vma_resource *vma_res)
+{
+	dma_fence_put(&vma_res->unbind_fence);
+}
+
+#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
+void i915_vma_resource_init(struct i915_vma_resource *vma_res);
+#endif
+
+#endif