drm/suballoc: Extract amdgpu_sa.c as generic suballocation helper

Suballocating a buffer object is something that is not driver-specific
and useful for many drivers.

Use a slightly modified version of amdgpu_sa.c

v2:
- Style cleanups.
- Added / Modified documentation.
- Use u64 for the sizes and offset. The code dates back to 2012 and
using unsigned int will probably soon come back to bite us.
We can consider size_t as well for better 32-bit efficiency.
- Add and document gfp, intr and align arguments to drm_suballoc_new().
- Use drm_printer for debug output.

v3:
- Remove stale author info (Christian König)

v4:
- Avoid 64-bit integer divisions (kernel test robot <[e-mail]>)
- Use size_t rather than u64 for the managed range. (Thomas)

Signed-off-by: Maarten Lankhorst <[e-mail]>
Co-developed-by: Thomas Hellström <[e-mail]>
Signed-off-by: Thomas Hellström <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Acked-by: Maarten Lankhorst <[e-mail]>
Acked-by: Alex Deucher <[e-mail]>
Acked-by: Christian König <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/Kconfig

···
 	help
 	  Choose this if you need the GEM shmem helper functions
 
+config DRM_SUBALLOC_HELPER
+	tristate
+	depends on DRM
+
 config DRM_SCHED
 	tristate
 	depends on DRM

drivers/gpu/drm/Makefile

···
 drm_shmem_helper-y := drm_gem_shmem_helper.o
 obj-$(CONFIG_DRM_GEM_SHMEM_HELPER) += drm_shmem_helper.o
 
+drm_suballoc_helper-y := drm_suballoc.o
+obj-$(CONFIG_DRM_SUBALLOC_HELPER) += drm_suballoc_helper.o
+
 drm_vram_helper-y := drm_gem_vram_helper.o
 obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
 

drivers/gpu/drm/drm_suballoc.c

···
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright 2011 Red Hat Inc.
+ * Copyright 2023 Intel Corporation.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ */
+/* Algorithm:
+ *
+ * We store the last allocated bo in "hole", we always try to allocate
+ * after the last allocated bo. Principle is that in a linear GPU ring
+ * progression was is after last is the oldest bo we allocated and thus
+ * the first one that should no longer be in use by the GPU.
+ *
+ * If it's not the case we skip over the bo after last to the closest
+ * done bo if such one exist. If none exist and we are not asked to
+ * block we report failure to allocate.
+ *
+ * If we are asked to block we wait on all the oldest fence of all
+ * rings. We just wait for any of those fence to complete.
+ */
+
+#include <drm/drm_suballoc.h>
+#include <drm/drm_print.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/dma-fence.h>
+
+static void drm_suballoc_remove_locked(struct drm_suballoc *sa);
+static void drm_suballoc_try_free(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,
+			       size_t size, size_t align)
+{
+	unsigned int i;
+
+	BUILD_BUG_ON(!is_power_of_2(DRM_SUBALLOC_MAX_QUEUES));
+
+	if (!align)
+		align = 1;
+
+	/* alignment must be a power of 2 */
+	if (WARN_ON_ONCE(align & (align - 1)))
+		align = roundup_pow_of_two(align);
+
+	init_waitqueue_head(&sa_manager->wq);
+	sa_manager->size = size;
+	sa_manager->align = align;
+	sa_manager->hole = &sa_manager->olist;
+	INIT_LIST_HEAD(&sa_manager->olist);
+	for (i = 0; i < DRM_SUBALLOC_MAX_QUEUES; ++i)
+		INIT_LIST_HEAD(&sa_manager->flist[i]);
+}
+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)
+{
+	struct drm_suballoc *sa, *tmp;
+
+	if (!sa_manager->size)
+		return;
+
+	if (!list_empty(&sa_manager->olist)) {
+		sa_manager->hole = &sa_manager->olist;
+		drm_suballoc_try_free(sa_manager);
+		if (!list_empty(&sa_manager->olist))
+			DRM_ERROR("sa_manager is not empty, clearing anyway\n");
+	}
+	list_for_each_entry_safe(sa, tmp, &sa_manager->olist, olist) {
+		drm_suballoc_remove_locked(sa);
+	}
+
+	sa_manager->size = 0;
+}
+EXPORT_SYMBOL(drm_suballoc_manager_fini);
+
+static void drm_suballoc_remove_locked(struct drm_suballoc *sa)
+{
+	struct drm_suballoc_manager *sa_manager = sa->manager;
+
+	if (sa_manager->hole == &sa->olist)
+		sa_manager->hole = sa->olist.prev;
+
+	list_del_init(&sa->olist);
+	list_del_init(&sa->flist);
+	dma_fence_put(sa->fence);
+	kfree(sa);
+}
+
+static void drm_suballoc_try_free(struct drm_suballoc_manager *sa_manager)
+{
+	struct drm_suballoc *sa, *tmp;
+
+	if (sa_manager->hole->next == &sa_manager->olist)
+		return;
+
+	sa = list_entry(sa_manager->hole->next, struct drm_suballoc, olist);
+	list_for_each_entry_safe_from(sa, tmp, &sa_manager->olist, olist) {
+		if (!sa->fence || !dma_fence_is_signaled(sa->fence))
+			return;
+
+		drm_suballoc_remove_locked(sa);
+	}
+}
+
+static size_t drm_suballoc_hole_soffset(struct drm_suballoc_manager *sa_manager)
+{
+	struct list_head *hole = sa_manager->hole;
+
+	if (hole != &sa_manager->olist)
+		return list_entry(hole, struct drm_suballoc, olist)->eoffset;
+
+	return 0;
+}
+
+static size_t drm_suballoc_hole_eoffset(struct drm_suballoc_manager *sa_manager)
+{
+	struct list_head *hole = sa_manager->hole;
+
+	if (hole->next != &sa_manager->olist)
+		return list_entry(hole->next, struct drm_suballoc, olist)->soffset;
+	return sa_manager->size;
+}
+
+static bool drm_suballoc_try_alloc(struct drm_suballoc_manager *sa_manager,
+				   struct drm_suballoc *sa,
+				   size_t size, size_t align)
+{
+	size_t soffset, eoffset, wasted;
+
+	soffset = drm_suballoc_hole_soffset(sa_manager);
+	eoffset = drm_suballoc_hole_eoffset(sa_manager);
+	wasted = round_up(soffset, align) - soffset;
+
+	if ((eoffset - soffset) >= (size + wasted)) {
+		soffset += wasted;
+
+		sa->manager = sa_manager;
+		sa->soffset = soffset;
+		sa->eoffset = soffset + size;
+		list_add(&sa->olist, sa_manager->hole);
+		INIT_LIST_HEAD(&sa->flist);
+		sa_manager->hole = &sa->olist;
+		return true;
+	}
+	return false;
+}
+
+static bool __drm_suballoc_event(struct drm_suballoc_manager *sa_manager,
+				 size_t size, size_t align)
+{
+	size_t soffset, eoffset, wasted;
+	unsigned int i;
+
+	for (i = 0; i < DRM_SUBALLOC_MAX_QUEUES; ++i)
+		if (!list_empty(&sa_manager->flist[i]))
+			return true;
+
+	soffset = drm_suballoc_hole_soffset(sa_manager);
+	eoffset = drm_suballoc_hole_eoffset(sa_manager);
+	wasted = round_up(soffset, align) - soffset;
+
+	return ((eoffset - soffset) >= (size + wasted));
+}
+
+/**
+ * drm_suballoc_event() - Check if we can stop waiting
+ * @sa_manager: pointer to the sa_manager
+ * @size: number of bytes we want to allocate
+ * @align: alignment we need to match
+ *
+ * Return: true if either there is a fence we can wait for or
+ * enough free memory to satisfy the allocation directly.
+ * false otherwise.
+ */
+static bool drm_suballoc_event(struct drm_suballoc_manager *sa_manager,
+			       size_t size, size_t align)
+{
+	bool ret;
+
+	spin_lock(&sa_manager->wq.lock);
+	ret = __drm_suballoc_event(sa_manager, size, align);
+	spin_unlock(&sa_manager->wq.lock);
+	return ret;
+}
+
+static bool drm_suballoc_next_hole(struct drm_suballoc_manager *sa_manager,
+				   struct dma_fence **fences,
+				   unsigned int *tries)
+{
+	struct drm_suballoc *best_bo = NULL;
+	unsigned int i, best_idx;
+	size_t soffset, best, tmp;
+
+	/* if hole points to the end of the buffer */
+	if (sa_manager->hole->next == &sa_manager->olist) {
+		/* try again with its beginning */
+		sa_manager->hole = &sa_manager->olist;
+		return true;
+	}
+
+	soffset = drm_suballoc_hole_soffset(sa_manager);
+	/* to handle wrap around we add sa_manager->size */
+	best = sa_manager->size * 2;
+	/* go over all fence list and try to find the closest sa
+	 * of the current last
+	 */
+	for (i = 0; i < DRM_SUBALLOC_MAX_QUEUES; ++i) {
+		struct drm_suballoc *sa;
+
+		fences[i] = NULL;
+
+		if (list_empty(&sa_manager->flist[i]))
+			continue;
+
+		sa = list_first_entry(&sa_manager->flist[i],
+				      struct drm_suballoc, flist);
+
+		if (!dma_fence_is_signaled(sa->fence)) {
+			fences[i] = sa->fence;
+			continue;
+		}
+
+		/* limit the number of tries each freelist gets */
+		if (tries[i] > 2)
+			continue;
+
+		tmp = sa->soffset;
+		if (tmp < soffset) {
+			/* wrap around, pretend it's after */
+			tmp += sa_manager->size;
+		}
+		tmp -= soffset;
+		if (tmp < best) {
+			/* this sa bo is the closest one */
+			best = tmp;
+			best_idx = i;
+			best_bo = sa;
+		}
+	}
+
+	if (best_bo) {
+		++tries[best_idx];
+		sa_manager->hole = best_bo->olist.prev;
+
+		/*
+		 * We know that this one is signaled,
+		 * so it's safe to remove it.
+		 */
+		drm_suballoc_remove_locked(best_bo);
+		return true;
+	}
+	return false;
+}
+
+/**
+ * drm_suballoc_new() - Make a suballocation.
+ * @sa_manager: pointer to the sa_manager
+ * @size: number of bytes we want to suballocate.
+ * @gfp: gfp flags used for memory allocation. Typically GFP_KERNEL but
+ *       the argument is provided for suballocations from reclaim context or
+ *       where the caller wants to avoid pipelining rather than wait for
+ *       reclaim.
+ * @intr: Whether to perform waits interruptible. This should typically
+ *        always be true, unless the caller needs to propagate a
+ *        non-interruptible context from above layers.
+ * @align: Alignment. Must not exceed the default manager alignment.
+ *         If @align is zero, then the manager alignment is used.
+ *
+ * Try to make a suballocation of size @size, which will be rounded
+ * up to the alignment specified in specified in drm_suballoc_manager_init().
+ *
+ * Return: a new suballocated bo, or an ERR_PTR.
+ */
+struct drm_suballoc *
+drm_suballoc_new(struct drm_suballoc_manager *sa_manager, size_t size,
+		 gfp_t gfp, bool intr, size_t align)
+{
+	struct dma_fence *fences[DRM_SUBALLOC_MAX_QUEUES];
+	unsigned int tries[DRM_SUBALLOC_MAX_QUEUES];
+	unsigned int count;
+	int i, r;
+	struct drm_suballoc *sa;
+
+	if (WARN_ON_ONCE(align > sa_manager->align))
+		return ERR_PTR(-EINVAL);
+	if (WARN_ON_ONCE(size > sa_manager->size || !size))
+		return ERR_PTR(-EINVAL);
+
+	if (!align)
+		align = sa_manager->align;
+
+	sa = kmalloc(sizeof(*sa), gfp);
+	if (!sa)
+		return ERR_PTR(-ENOMEM);
+	sa->manager = sa_manager;
+	sa->fence = NULL;
+	INIT_LIST_HEAD(&sa->olist);
+	INIT_LIST_HEAD(&sa->flist);
+
+	spin_lock(&sa_manager->wq.lock);
+	do {
+		for (i = 0; i < DRM_SUBALLOC_MAX_QUEUES; ++i)
+			tries[i] = 0;
+
+		do {
+			drm_suballoc_try_free(sa_manager);
+
+			if (drm_suballoc_try_alloc(sa_manager, sa,
+						   size, align)) {
+				spin_unlock(&sa_manager->wq.lock);
+				return sa;
+			}
+
+			/* see if we can skip over some allocations */
+		} while (drm_suballoc_next_hole(sa_manager, fences, tries));
+
+		for (i = 0, count = 0; i < DRM_SUBALLOC_MAX_QUEUES; ++i)
+			if (fences[i])
+				fences[count++] = dma_fence_get(fences[i]);
+
+		if (count) {
+			long t;
+
+			spin_unlock(&sa_manager->wq.lock);
+			t = dma_fence_wait_any_timeout(fences, count, intr,
+						       MAX_SCHEDULE_TIMEOUT,
+						       NULL);
+			for (i = 0; i < count; ++i)
+				dma_fence_put(fences[i]);
+
+			r = (t > 0) ? 0 : t;
+			spin_lock(&sa_manager->wq.lock);
+		} else if (intr) {
+			/* if we have nothing to wait for block */
+			r = wait_event_interruptible_locked
+				(sa_manager->wq,
+				 __drm_suballoc_event(sa_manager, size, align));
+		} else {
+			spin_unlock(&sa_manager->wq.lock);
+			wait_event(sa_manager->wq,
+				   drm_suballoc_event(sa_manager, size, align));
+			r = 0;
+			spin_lock(&sa_manager->wq.lock);
+		}
+	} while (!r);
+
+	spin_unlock(&sa_manager->wq.lock);
+	kfree(sa);
+	return ERR_PTR(r);
+}
+EXPORT_SYMBOL(drm_suballoc_new);
+
+/**
+ * drm_suballoc_free - Free a suballocation
+ * @suballoc: pointer to the suballocation
+ * @fence: fence that signals when suballocation is idle
+ *
+ * Free the suballocation. The suballocation can be re-used after @fence signals.
+ */
+void drm_suballoc_free(struct drm_suballoc *suballoc,
+		       struct dma_fence *fence)
+{
+	struct drm_suballoc_manager *sa_manager;
+
+	if (!suballoc)
+		return;
+
+	sa_manager = suballoc->manager;
+
+	spin_lock(&sa_manager->wq.lock);
+	if (fence && !dma_fence_is_signaled(fence)) {
+		u32 idx;
+
+		suballoc->fence = dma_fence_get(fence);
+		idx = fence->context & (DRM_SUBALLOC_MAX_QUEUES - 1);
+		list_add_tail(&suballoc->flist, &sa_manager->flist[idx]);
+	} else {
+		drm_suballoc_remove_locked(suballoc);
+	}
+	wake_up_all_locked(&sa_manager->wq);
+	spin_unlock(&sa_manager->wq.lock);
+}
+EXPORT_SYMBOL(drm_suballoc_free);
+
+#ifdef CONFIG_DEBUG_FS
+void drm_suballoc_dump_debug_info(struct drm_suballoc_manager *sa_manager,
+				  struct drm_printer *p,
+				  unsigned long long suballoc_base)
+{
+	struct drm_suballoc *i;
+
+	spin_lock(&sa_manager->wq.lock);
+	list_for_each_entry(i, &sa_manager->olist, olist) {
+		unsigned long long soffset = i->soffset;
+		unsigned long long eoffset = i->eoffset;
+
+		if (&i->olist == sa_manager->hole)
+			drm_puts(p, ">");
+		else
+			drm_puts(p, " ");
+
+		drm_printf(p, "[0x%010llx 0x%010llx] size %8lld",
+			   suballoc_base + soffset, suballoc_base + eoffset,
+			   eoffset - soffset);
+
+		if (i->fence)
+			drm_printf(p, " protected by 0x%016llx on context %llu",
+				   (unsigned long long)i->fence->seqno,
+				   (unsigned long long)i->fence->context);
+
+		drm_puts(p, "\n");
+	}
+	spin_unlock(&sa_manager->wq.lock);
+}
+EXPORT_SYMBOL(drm_suballoc_dump_debug_info);
+#endif
+MODULE_AUTHOR("Multiple");
+MODULE_DESCRIPTION("Range suballocator helper");
+MODULE_LICENSE("Dual MIT/GPL");

include/drm/drm_suballoc.h

···
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright 2011 Red Hat Inc.
+ * 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>
+
+#define DRM_SUBALLOC_MAX_QUEUES 32
+/**
+ * struct drm_suballoc_manager - fenced range allocations
+ * @wq: Wait queue for sleeping allocations on contention.
+ * @hole: Pointer to first hole node.
+ * @olist: List of allocated ranges.
+ * @flist: Array[fence context hash] of queues of fenced allocated ranges.
+ * @size: Size of the managed range.
+ * @align: Default alignment for the managed range.
+ */
+struct drm_suballoc_manager {
+	wait_queue_head_t wq;
+	struct list_head *hole;
+	struct list_head olist;
+	struct list_head flist[DRM_SUBALLOC_MAX_QUEUES];
+	size_t size;
+	size_t align;
+};
+
+/**
+ * struct drm_suballoc - Sub-allocated range
+ * @olist: List link for list of allocated ranges.
+ * @flist: List linkk for the manager fenced allocated ranges queues.
+ * @manager: The drm_suballoc_manager.
+ * @soffset: Start offset.
+ * @eoffset: End offset + 1 so that @eoffset - @soffset = size.
+ * @dma_fence: The fence protecting the allocation.
+ */
+struct drm_suballoc {
+	struct list_head olist;
+	struct list_head flist;
+	struct drm_suballoc_manager *manager;
+	size_t soffset;
+	size_t eoffset;
+	struct dma_fence *fence;
+};
+
+void drm_suballoc_manager_init(struct drm_suballoc_manager *sa_manager,
+			       size_t size, size_t align);
+
+void drm_suballoc_manager_fini(struct drm_suballoc_manager *sa_manager);
+
+struct drm_suballoc *
+drm_suballoc_new(struct drm_suballoc_manager *sa_manager, size_t size,
+		 gfp_t gfp, bool intr, size_t align);
+
+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 size_t drm_suballoc_soffset(struct drm_suballoc *sa)
+{
+	return sa->soffset;
+}
+
+/**
+ * drm_suballoc_eoffset - Range end.
+ * @sa: The struct drm_suballoc.
+ *
+ * Return: The end of the allocated range + 1.
+ */
+static inline size_t drm_suballoc_eoffset(struct drm_suballoc *sa)
+{
+	return sa->eoffset;
+}
+
+/**
+ * drm_suballoc_size - Range size.
+ * @sa: The struct drm_suballoc.
+ *
+ * Return: The size of the allocated range.
+ */
+static inline size_t drm_suballoc_size(struct drm_suballoc *sa)
+{
+	return sa->eoffset - sa->soffset;
+}
+
+#ifdef CONFIG_DEBUG_FS
+void drm_suballoc_dump_debug_info(struct drm_suballoc_manager *sa_manager,
+				  struct drm_printer *p,
+				  unsigned long long suballoc_base);
+#else
+static inline void
+drm_suballoc_dump_debug_info(struct drm_suballoc_manager *sa_manager,
+			     struct drm_printer *p,
+			     unsigned long long suballoc_base)
+{ }
+
+#endif
+
+#endif /* _DRM_SUBALLOC_H_ */