+ *
+ * 2) We unnecessarily install the fence callbacks too early, forcing
+ * enable_signaling() too early causing extra driver effort. This is
likely
+ * not an issue if used with the drm_scheduler since it calls
+ * enable_signaling() early anyway.
+ *
+ * 3) Long processing in irq (disabled) context. We've mostly worked
around
+ * that already by using the idle_list. If that workaround is deemed to
+ * complex for little gain, we can remove it and use spin_lock_irq()
+ * throughout the manager. If we want to shorten processing in irq
context
+ * even further, we can skip the spin_trylock in
__drm_suballoc_free() and
+ * avoid freeing allocations from irq context altogeher. However drm_mm
+ * should be quite fast at freeing ranges.
+ *
+ * 4) Shrinker that starts processing the list items in 2) and 3) to
play
+ * better with the system.
+ */
+
+static void drm_suballoc_process_idle(struct drm_suballoc_manager
*sa_manager);
+
+/**
+ * drm_suballoc_manager_init() - Initialise the drm_suballoc_manager
+ * @sa_manager: pointer to the sa_manager
+ * @size: number of bytes we want to suballocate
+ * @align: alignment for each suballocated chunk
+ *
+ * Prepares the suballocation manager for suballocations.
+ */
+void drm_suballoc_manager_init(struct drm_suballoc_manager *sa_manager,
+ u64 size, u64 align)
+{
+ spin_lock_init(&sa_manager->lock);
+ spin_lock_init(&sa_manager->idle_list_lock);
+ mutex_init(&sa_manager->alloc_mutex);
+ drm_mm_init(&sa_manager->mm, 0, size);
+ init_waitqueue_head(&sa_manager->wq);
+ sa_manager->range_size = size;
+ sa_manager->alignment = align;
+ INIT_LIST_HEAD(&sa_manager->idle_list);
+}
+EXPORT_SYMBOL(drm_suballoc_manager_init);
+
+/**
+ * drm_suballoc_manager_fini() - Destroy the drm_suballoc_manager
+ * @sa_manager: pointer to the sa_manager
+ *
+ * Cleans up the suballocation manager after use. All fences added
+ * with drm_suballoc_free() must be signaled, or we cannot clean up
+ * the entire manager.
+ */
+void drm_suballoc_manager_fini(struct drm_suballoc_manager *sa_manager)
+{
+ drm_suballoc_process_idle(sa_manager);
+ drm_mm_takedown(&sa_manager->mm);
+ mutex_destroy(&sa_manager->alloc_mutex);
+}
+EXPORT_SYMBOL(drm_suballoc_manager_fini);
+
+static void __drm_suballoc_free(struct drm_suballoc *sa)
+{
+ struct drm_suballoc_manager *sa_manager = sa->manager;
+ struct dma_fence *fence;
+
+ /*
+ * In order to avoid protecting the potentially lengthy drm_mm
manager
+ * *allocation* processing with an irq-disabling lock,
+ * defer touching the drm_mm for freeing until we're in task
context,
+ * with no irqs disabled, or happen to succeed in taking the
manager
+ * lock.
+ */
+ if (!in_task() || irqs_disabled()) {
+ unsigned long irqflags;
+
+ if (spin_trylock(&sa_manager->lock))
+ goto locked;
+
+ spin_lock_irqsave(&sa_manager->idle_list_lock, irqflags);
+ list_add_tail(&sa->idle_link, &sa_manager->idle_list);
+ spin_unlock_irqrestore(&sa_manager->idle_list_lock, irqflags);
+ wake_up(&sa_manager->wq);
+ return;
+ }
+
+ spin_lock(&sa_manager->lock);
+locked:
+ drm_mm_remove_node(&sa->node);
+
+ fence = sa->fence;
+ sa->fence = NULL;
+ spin_unlock(&sa_manager->lock);
+ /* Maybe only wake if first mm hole is sufficiently large? */
+ wake_up(&sa_manager->wq);
+ dma_fence_put(fence);
+ kfree(sa);
+}
+
+/* Free all deferred idle allocations */
+static void drm_suballoc_process_idle(struct drm_suballoc_manager
*sa_manager)
+{
+ /*
+ * prepare_to_wait() / wake_up() semantics ensure that any list
+ * addition that was done before wake_up() is visible when
+ * this code is called from the wait loop.
+ */
+ if (!list_empty_careful(&sa_manager->idle_list)) {
+ struct drm_suballoc *sa, *next;
+ unsigned long irqflags;
+ LIST_HEAD(list);
+
+ spin_lock_irqsave(&sa_manager->idle_list_lock, irqflags);
+ list_splice_init(&sa_manager->idle_list, &list);
+ spin_unlock_irqrestore(&sa_manager->idle_list_lock, irqflags);
+
+ list_for_each_entry_safe(sa, next, &list, idle_link)
+ __drm_suballoc_free(sa);
+ }
+}
+
+static void
+drm_suballoc_fence_signaled(struct dma_fence *fence, struct
dma_fence_cb *cb)
+{
+ struct drm_suballoc *sa = container_of(cb, typeof(*sa), cb);
+
+ __drm_suballoc_free(sa);
+}
+
+static int drm_suballoc_tryalloc(struct drm_suballoc *sa, u64 size)
+{
+ struct drm_suballoc_manager *sa_manager = sa->manager;
+ int err;
+
+ drm_suballoc_process_idle(sa_manager);
+ spin_lock(&sa_manager->lock);
+ err = drm_mm_insert_node_generic(&sa_manager->mm, &sa->node, size,
+ sa_manager->alignment, 0,
+ DRM_MM_INSERT_EVICT);
+ spin_unlock(&sa_manager->lock);
+ return err;
+}
+
+/**
+ * drm_suballoc_new() - Make a suballocation.
+ * @sa_manager: pointer to the sa_manager
+ * @size: number of bytes we want to suballocate.
+ * @gfp: Allocation context.
+ * @intr: Whether to sleep interruptibly if sleeping.
+ *
+ * Try to make a suballocation of size @size, which will be rounded
+ * up to the alignment specified in specified in
drm_suballoc_manager_init().
+ *
+ * Returns a new suballocated bo, or an ERR_PTR.
+ */
+struct drm_suballoc*
+drm_suballoc_new(struct drm_suballoc_manager *sa_manager, u64 size,
+ gfp_t gfp, bool intr)
+{
+ struct drm_suballoc *sa;
+ DEFINE_WAIT(wait);
+ int err = 0;
+
+ if (size > sa_manager->range_size)
+ return ERR_PTR(-ENOSPC);
+
+ sa = kzalloc(sizeof(*sa), gfp);
+ if (!sa)
+ return ERR_PTR(-ENOMEM);
+
+ /* Avoid starvation using the alloc_mutex */
+ if (intr)
+ err = mutex_lock_interruptible(&sa_manager->alloc_mutex);
+ else
+ mutex_lock(&sa_manager->alloc_mutex);
+ if (err) {
+ kfree(sa);
+ return ERR_PTR(err);
+ }
+
+ sa->manager = sa_manager;
+ err = drm_suballoc_tryalloc(sa, size);
+ if (err != -ENOSPC)
+ goto out;
+
+ for (;;) {
+ prepare_to_wait(&sa_manager->wq, &wait,
+ intr ? TASK_INTERRUPTIBLE :
+ TASK_UNINTERRUPTIBLE);
+
+ err = drm_suballoc_tryalloc(sa, size);
+ if (err != -ENOSPC)
+ break;
+
+ if (intr && signal_pending(current)) {
+ err = -ERESTARTSYS;
+ break;
+ }
+
+ io_schedule();
+ }
+ finish_wait(&sa_manager->wq, &wait);
+
+out:
+ mutex_unlock(&sa_manager->alloc_mutex);
+ if (!sa->node.size) {
+ kfree(sa);
+ WARN_ON(!err);
+ sa = ERR_PTR(err);
+ }
+
+ return sa;
+}
+EXPORT_SYMBOL(drm_suballoc_new);
+
+/**
+ * drm_suballoc_free() - Free a suballocation
+ * @suballoc: pointer to the suballocation
+ * @fence: fence that signals when suballocation is idle
+ * @queue: the index to which queue the suballocation will be placed
on the free list.
+ *
+ * Free the suballocation. The suballocation can be re-used after
@fence
+ * signals.
+ */
+void
+drm_suballoc_free(struct drm_suballoc *sa, struct dma_fence *fence)
+{
+ if (!sa)
+ return;
+
+ if (!fence || dma_fence_is_signaled(fence)) {
+ __drm_suballoc_free(sa);
+ return;
+ }
+
+ sa->fence = dma_fence_get(fence);
+ if (dma_fence_add_callback(fence, &sa->cb,
drm_suballoc_fence_signaled))
+ __drm_suballoc_free(sa);
+}
+EXPORT_SYMBOL(drm_suballoc_free);
+
+#ifdef CONFIG_DEBUG_FS
+
+/**
+ * drm_suballoc_dump_debug_info() - Dump the suballocator state
+ * @sa_manager: The suballoc manager.
+ * @p: Pointer to a drm printer for output.
+ * @suballoc_base: Constant to add to the suballocated offsets on
printout.
+ *
+ * This function dumps the suballocator state. Note that the caller has
+ * to explicitly order frees and calls to this function in order for
the
+ * freed node to show up as protected by a fence.
+ */
+void drm_suballoc_dump_debug_info(struct drm_suballoc_manager
*sa_manager,
+ struct drm_printer *p, u64 suballoc_base)
+{
+ const struct drm_mm_node *entry;
+
+ spin_lock(&sa_manager->lock);
+ drm_mm_for_each_node(entry, &sa_manager->mm) {
+ struct drm_suballoc *sa =
+ container_of(entry, typeof(*sa), node);
+
+ drm_printf(p, " ");
+ drm_printf(p, "[0x%010llx 0x%010llx] size %8lld",
+ (unsigned long long)suballoc_base + entry->start,
+ (unsigned long long)suballoc_base + entry->start +
+ entry->size, (unsigned long long)entry->size);
+
+ if (sa->fence)
+ drm_printf(p, " protected by 0x%016llx on context %llu",
+ (unsigned long long)sa->fence->seqno,
+ (unsigned long long)sa->fence->context);
+
+ drm_printf(p, "\n");
+ }
+ spin_unlock(&sa_manager->lock);
+}
+EXPORT_SYMBOL(drm_suballoc_dump_debug_info);
+#endif
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_DESCRIPTION("Simple range suballocator helper");
+MODULE_LICENSE("GPL and additional rights");
diff --git a/include/drm/drm_suballoc.h b/include/drm/drm_suballoc.h
new file mode 100644
index 000000000000..910952b3383b
--- /dev/null
+++ b/include/drm/drm_suballoc.h
@@ -0,0 +1,112 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2022 Intel Corporation
+ */
+#ifndef _DRM_SUBALLOC_H_
+#define _DRM_SUBALLOC_H_
+
+#include <drm/drm_mm.h>
+
+#include <linux/dma-fence.h>
+#include <linux/types.h>
+
+/**
+ * struct drm_suballoc_manager - Wrapper for fenced range allocations
+ * @mm: The range manager. Protected by @lock.
+ * @range_size: The total size of the range.
+ * @alignment: Range alignment.
+ * @wq: Wait queue for sleeping allocations on contention.
+ * @idle_list: List of idle but not yet freed allocations. Protected by
+ * @idle_list_lock.
+ * @task: Task waiting for allocation. Protected by @lock.
+ */
+struct drm_suballoc_manager {
+ /** @lock: Manager lock. Protects @mm. */
+ spinlock_t lock;
+ /**
+ * @idle_list_lock: Lock to protect the idle_list.
+ * Disable irqs when locking.
+ */
+ spinlock_t idle_list_lock;
+ /** @alloc_mutex: Mutex to protect against stavation. */
+ struct mutex alloc_mutex;
+ struct drm_mm mm;
+ u64 range_size;
+ u64 alignment;
+ wait_queue_head_t wq;
+ struct list_head idle_list;
+};
+
+/**
+ * struct drm_suballoc: Suballocated range.
+ * @node: The drm_mm representation of the range.
+ * @fence: dma-fence indicating whether allocation is active or idle.
+ * Assigned on call to free the allocation so doesn't need protection.
+ * @cb: dma-fence callback structure. Used for callbacks when the
fence signals.
+ * @manager: The struct drm_suballoc_manager the range belongs to.
Immutable.
+ * @idle_link: Link for the manager idle_list. Progected by the
+ * drm_suballoc_manager::idle_lock.
+ */
+struct drm_suballoc {
+ struct drm_mm_node node;
+ struct dma_fence *fence;
+ struct dma_fence_cb cb;
+ struct drm_suballoc_manager *manager;
+ struct list_head idle_link;
+};
+
+void drm_suballoc_manager_init(struct drm_suballoc_manager *sa_manager,
+ u64 size, u64 align);
+
+void drm_suballoc_manager_fini(struct drm_suballoc_manager
*sa_manager);
+
+struct drm_suballoc *drm_suballoc_new(struct drm_suballoc_manager
*sa_manager,
+ u64 size, gfp_t gfp, bool intr);
+
+void drm_suballoc_free(struct drm_suballoc *sa, struct dma_fence
*fence);
+
+/**
+ * drm_suballoc_soffset - Range start.
+ * @sa: The struct drm_suballoc.
+ *
+ * Return: The start of the allocated range.
+ */
+static inline u64 drm_suballoc_soffset(struct drm_suballoc *sa)
+{
+ return sa->node.start;
+}
+
+/**
+ * drm_suballoc_eoffset - Range end.
+ * @sa: The struct drm_suballoc.
+ *
+ * Return: The end of the allocated range + 1.
+ */
+static inline u64 drm_suballoc_eoffset(struct drm_suballoc *sa)
+{
+ return sa->node.start + sa->node.size;
+}
+
+/**
+ * drm_suballoc_size - Range size.
+ * @sa: The struct drm_suballoc.
+ *
+ * Return: The size of the allocated range.
+ */
+static inline u64 drm_suballoc_size(struct drm_suballoc *sa)
+{
+ return sa->node.size;
+}
+
+#ifdef CONFIG_DEBUG_FS
+void drm_suballoc_dump_debug_info(struct drm_suballoc_manager
*sa_manager,
+ struct drm_printer *p, u64 suballoc_base);
+#else
+static inline void
+drm_suballoc_dump_debug_info(struct drm_suballoc_manager *sa_manager,
+ struct drm_printer *p, u64 suballoc_base)
+{ }
+
+#endif
+
+#endif /* _DRM_SUBALLOC_H_ */
