drm/ttm: new TT backend allocation pool v3

This replaces the spaghetti code in the two existing page pools.

First of all depending on the allocation size it is between 3 (1GiB) and
5 (1MiB) times faster than the old implementation.

It makes better use of buddy pages to allow for larger physical contiguous
allocations which should result in better TLB utilization at least for
amdgpu.

Instead of a completely braindead approach of filling the pool with one
CPU while another one is trying to shrink it we only give back freed
pages.

This also results in much less locking contention and a trylock free MM
shrinker callback, so we can guarantee that pages are given back to the
system when needed.

Downside of this is that it takes longer for many small allocations until
the pool is filled up. We could address this, but I couldn't find an use
case where this actually matters. We also don't bother freeing large
chunks of pages any more since the CPU overhead in that path isn't really
that important.

The sysfs files are replaced with a single module parameter, allowing
users to override how many pages should be globally pooled in TTM. This
unfortunately breaks the UAPI slightly, but as far as we know nobody ever
depended on this.

Zeroing memory coming from the pool was handled inconsistently. The
alloc_pages() based pool was zeroing it, the dma_alloc_attr() based one
wasn't. For now the new implementation isn't zeroing pages from the pool
either and only sets the __GFP_ZERO flag when necessary.

The implementation has only 768 lines of code compared to the over 2600
of the old one, and also allows for saving quite a bunch of code in the
drivers since we don't need specialized handling there any more based on
kernel config.

Additional to all of that there was a neat bug with IOMMU, coherent DMA
mappings and huge pages which is now fixed in the new code as well.

v2: make ttm_pool_apply_caching static as reported by the kernel bot, add
    some more checks
v3: fix some more checkpatch.pl warnings

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Madhav Chauhan <madhav.chauhan@amd.com>
Tested-by: Huang Rui <ray.huang@amd.com>
Link: https://patchwork.freedesktop.org/patch/397080/?series=83051&rev=1

5 files changed, 764 insertions, 1 deletions

diff --git a/drivers/gpu/drm/ttm/Makefile b/drivers/gpu/drm/ttm/Makefile
index 90c0da88cc98..0096bacbcf32 100644
--- a/drivers/gpu/drm/ttm/Makefile
+++ b/drivers/gpu/drm/ttm/Makefile
@@ -5,7 +5,7 @@
 ttm-y := ttm_memory.o ttm_tt.o ttm_bo.o \
 	ttm_bo_util.o ttm_bo_vm.o ttm_module.o \
 	ttm_execbuf_util.o ttm_page_alloc.o ttm_range_manager.o \
-	ttm_resource.o
+	ttm_resource.o ttm_pool.o
 ttm-$(CONFIG_AGP) += ttm_agp_backend.o
 ttm-$(CONFIG_DRM_TTM_DMA_PAGE_POOL) += ttm_page_alloc_dma.o
 
diff --git a/drivers/gpu/drm/ttm/ttm_memory.c b/drivers/gpu/drm/ttm/ttm_memory.c
index 69cf622e79e5..3012d0388c51 100644
--- a/drivers/gpu/drm/ttm/ttm_memory.c
+++ b/drivers/gpu/drm/ttm/ttm_memory.c
@@ -38,6 +38,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
+#include <drm/ttm/ttm_pool.h>
 
 #define TTM_MEMORY_ALLOC_RETRIES 4
 
@@ -453,6 +454,7 @@ int ttm_mem_global_init(struct ttm_mem_global *glob)
 	}
 	ttm_page_alloc_init(glob, glob->zone_kernel->max_mem/(2*PAGE_SIZE));
 	ttm_dma_page_alloc_init(glob, glob->zone_kernel->max_mem/(2*PAGE_SIZE));
+	ttm_pool_mgr_init(glob->zone_kernel->max_mem/(2*PAGE_SIZE));
 	return 0;
 out_no_zone:
 	ttm_mem_global_release(glob);
@@ -467,6 +469,7 @@ void ttm_mem_global_release(struct ttm_mem_global *glob)
 	/* let the page allocator first stop the shrink work. */
 	ttm_page_alloc_fini();
 	ttm_dma_page_alloc_fini();
+	ttm_pool_mgr_fini();
 
 	flush_workqueue(glob->swap_queue);
 	destroy_workqueue(glob->swap_queue);
diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
new file mode 100644
index 000000000000..1e50deefb5d5
--- /dev/null
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -0,0 +1,667 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright 2020 Advanced Micro Devices, Inc.
+ *
+ * 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, sublicense,
+ * 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 above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * 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 NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
+ *
+ * Authors: Christian König
+ */
+
+/* Pooling of allocated pages is necessary because changing the caching
+ * attributes on x86 of the linear mapping requires a costly cross CPU TLB
+ * invalidate for those addresses.
+ *
+ * Additional to that allocations from the DMA coherent API are pooled as well
+ * cause they are rather slow compared to alloc_pages+map.
+ */
+
+#include <linux/module.h>
+#include <linux/dma-mapping.h>
+
+#ifdef CONFIG_X86
+#include <asm/set_memory.h>
+#endif
+
+#include <drm/ttm/ttm_pool.h>
+#include <drm/ttm/ttm_bo_driver.h>
+#include <drm/ttm/ttm_tt.h>
+
+/**
+ * struct ttm_pool_dma - Helper object for coherent DMA mappings
+ *
+ * @addr: original DMA address returned for the mapping
+ * @vaddr: original vaddr return for the mapping and order in the lower bits
+ */
+struct ttm_pool_dma {
+	dma_addr_t addr;
+	unsigned long vaddr;
+};
+
+static unsigned long page_pool_size;
+
+MODULE_PARM_DESC(page_pool_size, "Number of pages in the WC/UC/DMA pool");
+module_param(page_pool_size, ulong, 0644);
+
+static atomic_long_t allocated_pages;
+
+static struct ttm_pool_type global_write_combined[MAX_ORDER];
+static struct ttm_pool_type global_uncached[MAX_ORDER];
+
+static spinlock_t shrinker_lock;
+static struct list_head shrinker_list;
+static struct shrinker mm_shrinker;
+
+/* Allocate pages of size 1 << order with the given gfp_flags */
+static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags,
+					unsigned int order)
+{
+	unsigned long attr = DMA_ATTR_FORCE_CONTIGUOUS;
+	struct ttm_pool_dma *dma;
+	struct page *p;
+	void *vaddr;
+
+	if (order) {
+		gfp_flags |= GFP_TRANSHUGE_LIGHT | __GFP_NORETRY |
+			__GFP_KSWAPD_RECLAIM;
+		gfp_flags &= ~__GFP_MOVABLE;
+		gfp_flags &= ~__GFP_COMP;
+	}
+
+	if (!pool->use_dma_alloc) {
+		p = alloc_pages(gfp_flags, order);
+		if (p)
+			p->private = order;
+		return p;
+	}
+
+	dma = kmalloc(sizeof(*dma), GFP_KERNEL);
+	if (!dma)
+		return NULL;
+
+	if (order)
+		attr |= DMA_ATTR_NO_WARN;
+
+	vaddr = dma_alloc_attrs(pool->dev, (1ULL << order) * PAGE_SIZE,
+				&dma->addr, gfp_flags, attr);
+	if (!vaddr)
+		goto error_free;
+
+	/* TODO: This is an illegal abuse of the DMA API, but we need to rework
+	 * TTM page fault handling and extend the DMA API to clean this up.
+	 */
+	if (is_vmalloc_addr(vaddr))
+		p = vmalloc_to_page(vaddr);
+	else
+		p = virt_to_page(vaddr);
+
+	dma->vaddr = (unsigned long)vaddr | order;
+	p->private = (unsigned long)dma;
+	return p;
+
+error_free:
+	kfree(dma);
+	return NULL;
+}
+
+/* Reset the caching and pages of size 1 << order */
+static void ttm_pool_free_page(struct ttm_pool *pool, enum ttm_caching caching,
+			       unsigned int order, struct page *p)
+{
+	unsigned long attr = DMA_ATTR_FORCE_CONTIGUOUS;
+	struct ttm_pool_dma *dma;
+	void *vaddr;
+
+#ifdef CONFIG_X86
+	/* We don't care that set_pages_wb is inefficient here. This is only
+	 * used when we have to shrink and CPU overhead is irrelevant then.
+	 */
+	if (caching != ttm_cached && !PageHighMem(p))
+		set_pages_wb(p, 1 << order);
+#endif
+
+	if (!pool->use_dma_alloc) {
+		__free_pages(p, order);
+		return;
+	}
+
+	if (order)
+		attr |= DMA_ATTR_NO_WARN;
+
+	dma = (void *)p->private;
+	vaddr = (void *)(dma->vaddr & PAGE_MASK);
+	dma_free_attrs(pool->dev, (1UL << order) * PAGE_SIZE, vaddr, dma->addr,
+		       attr);
+	kfree(dma);
+}
+
+/* Apply a new caching to an array of pages */
+static int ttm_pool_apply_caching(struct page **first, struct page **last,
+				  enum ttm_caching caching)
+{
+#ifdef CONFIG_X86
+	unsigned int num_pages = last - first;
+
+	if (!num_pages)
+		return 0;
+
+	switch (caching) {
+	case ttm_cached:
+		break;
+	case ttm_write_combined:
+		return set_pages_array_wc(first, num_pages);
+	case ttm_uncached:
+		return set_pages_array_uc(first, num_pages);
+	}
+#endif
+	return 0;
+}
+
+/* Map pages of 1 << order size and fill the DMA address array  */
+static int ttm_pool_map(struct ttm_pool *pool, unsigned int order,
+			struct page *p, dma_addr_t **dma_addr)
+{
+	dma_addr_t addr;
+	unsigned int i;
+
+	if (pool->use_dma_alloc) {
+		struct ttm_pool_dma *dma = (void *)p->private;
+
+		addr = dma->addr;
+	} else {
+		size_t size = (1ULL << order) * PAGE_SIZE;
+
+		addr = dma_map_page(pool->dev, p, 0, size, DMA_BIDIRECTIONAL);
+		if (dma_mapping_error(pool->dev, **dma_addr))
+			return -EFAULT;
+	}
+
+	for (i = 1 << order; i ; --i) {
+		*(*dma_addr)++ = addr;
+		addr += PAGE_SIZE;
+	}
+
+	return 0;
+}
+
+/* Unmap pages of 1 << order size */
+static void ttm_pool_unmap(struct ttm_pool *pool, dma_addr_t dma_addr,
+			   unsigned int num_pages)
+{
+	/* Unmapped while freeing the page */
+	if (pool->use_dma_alloc)
+		return;
+
+	dma_unmap_page(pool->dev, dma_addr, (long)num_pages << PAGE_SHIFT,
+		       DMA_BIDIRECTIONAL);
+}
+
+/* Give pages into a specific pool_type */
+static void ttm_pool_type_give(struct ttm_pool_type *pt, struct page *p)
+{
+	spin_lock(&pt->lock);
+	list_add(&p->lru, &pt->pages);
+	spin_unlock(&pt->lock);
+	atomic_long_add(1 << pt->order, &allocated_pages);
+}
+
+/* Take pages from a specific pool_type, return NULL when nothing available */
+static struct page *ttm_pool_type_take(struct ttm_pool_type *pt)
+{
+	struct page *p;
+
+	spin_lock(&pt->lock);
+	p = list_first_entry_or_null(&pt->pages, typeof(*p), lru);
+	if (p) {
+		atomic_long_sub(1 << pt->order, &allocated_pages);
+		list_del(&p->lru);
+	}
+	spin_unlock(&pt->lock);
+
+	return p;
+}
+
+/* Count the number of pages available in a pool_type */
+static unsigned int ttm_pool_type_count(struct ttm_pool_type *pt)
+{
+	unsigned int count = 0;
+	struct page *p;
+
+	spin_lock(&pt->lock);
+	/* Only used for debugfs, the overhead doesn't matter */
+	list_for_each_entry(p, &pt->pages, lru)
+		++count;
+	spin_unlock(&pt->lock);
+
+	return count;
+}
+
+/* Initialize and add a pool type to the global shrinker list */
+static void ttm_pool_type_init(struct ttm_pool_type *pt, struct ttm_pool *pool,
+			       enum ttm_caching caching, unsigned int order)
+{
+	pt->pool = pool;
+	pt->caching = caching;
+	pt->order = order;
+	spin_lock_init(&pt->lock);
+	INIT_LIST_HEAD(&pt->pages);
+
+	spin_lock(&shrinker_lock);
+	list_add_tail(&pt->shrinker_list, &shrinker_list);
+	spin_unlock(&shrinker_lock);
+}
+
+/* Remove a pool_type from the global shrinker list and free all pages */
+static void ttm_pool_type_fini(struct ttm_pool_type *pt)
+{
+	struct page *p, *tmp;
+
+	spin_lock(&shrinker_lock);
+	list_del(&pt->shrinker_list);
+	spin_unlock(&shrinker_lock);
+
+	list_for_each_entry_safe(p, tmp, &pt->pages, lru)
+		ttm_pool_free_page(pt->pool, pt->caching, pt->order, p);
+}
+
+/* Return the pool_type to use for the given caching and order */
+static struct ttm_pool_type *ttm_pool_select_type(struct ttm_pool *pool,
+						  enum ttm_caching caching,
+						  unsigned int order)
+{
+	if (pool->use_dma_alloc)
+		return &pool->caching[caching].orders[order];
+
+#ifdef CONFIG_X86
+	switch (caching) {
+	case ttm_write_combined:
+		return &global_write_combined[order];
+	case ttm_uncached:
+		return &global_uncached[order];
+	default:
+		break;
+	}
+#endif
+
+	return NULL;
+}
+
+/* Free pages using the global shrinker list */
+static unsigned int ttm_pool_shrink(void)
+{
+	struct ttm_pool_type *pt;
+	unsigned int num_freed;
+	struct page *p;
+
+	spin_lock(&shrinker_lock);
+	pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list);
+
+	p = ttm_pool_type_take(pt);
+	if (p) {
+		ttm_pool_free_page(pt->pool, pt->caching, pt->order, p);
+		num_freed = 1 << pt->order;
+	} else {
+		num_freed = 0;
+	}
+
+	list_move_tail(&pt->shrinker_list, &shrinker_list);
+	spin_unlock(&shrinker_lock);
+
+	return num_freed;
+}
+
+/* Return the allocation order based for a page */
+static unsigned int ttm_pool_page_order(struct ttm_pool *pool, struct page *p)
+{
+	if (pool->use_dma_alloc) {
+		struct ttm_pool_dma *dma = (void *)p->private;
+
+		return dma->vaddr & ~PAGE_MASK;
+	}
+
+	return p->private;
+}
+
+/**
+ * ttm_pool_alloc - Fill a ttm_tt object
+ *
+ * @pool: ttm_pool to use
+ * @tt: ttm_tt object to fill
+ * @ctx: operation context
+ *
+ * Fill the ttm_tt object with pages and also make sure to DMA map them when
+ * necessary.
+ *
+ * Returns: 0 on successe, negative error code otherwise.
+ */
+int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
+		   struct ttm_operation_ctx *ctx)
+{
+	unsigned long num_pages = tt->num_pages;
+	dma_addr_t *dma_addr = tt->dma_address;
+	struct page **caching = tt->pages;
+	struct page **pages = tt->pages;
+	gfp_t gfp_flags = GFP_USER;
+	unsigned int i, order;
+	struct page *p;
+	int r;
+
+	WARN_ON(!num_pages || ttm_tt_is_populated(tt));
+	WARN_ON(dma_addr && !pool->dev);
+
+	if (tt->page_flags & TTM_PAGE_FLAG_ZERO_ALLOC)
+		gfp_flags |= __GFP_ZERO;
+
+	if (tt->page_flags & TTM_PAGE_FLAG_NO_RETRY)
+		gfp_flags |= __GFP_RETRY_MAYFAIL;
+
+	if (pool->use_dma32)
+		gfp_flags |= GFP_DMA32;
+	else
+		gfp_flags |= GFP_HIGHUSER;
+
+	for (order = min(MAX_ORDER - 1UL, __fls(num_pages)); num_pages;
+	     order = min_t(unsigned int, order, __fls(num_pages))) {
+		bool apply_caching = false;
+		struct ttm_pool_type *pt;
+
+		pt = ttm_pool_select_type(pool, tt->caching, order);
+		p = pt ? ttm_pool_type_take(pt) : NULL;
+		if (p) {
+			apply_caching = true;
+		} else {
+			p = ttm_pool_alloc_page(pool, gfp_flags, order);
+			if (p && PageHighMem(p))
+				apply_caching = true;
+		}
+
+		if (!p) {
+			if (order) {
+				--order;
+				continue;
+			}
+			r = -ENOMEM;
+			goto error_free_all;
+		}
+
+		if (apply_caching) {
+			r = ttm_pool_apply_caching(caching, pages,
+						   tt->caching);
+			if (r)
+				goto error_free_page;
+			caching = pages + (1 << order);
+		}
+
+		r = ttm_mem_global_alloc_page(&ttm_mem_glob, p,
+					      (1 << order) * PAGE_SIZE,
+					      ctx);
+		if (r)
+			goto error_free_page;
+
+		if (dma_addr) {
+			r = ttm_pool_map(pool, order, p, &dma_addr);
+			if (r)
+				goto error_global_free;
+		}
+
+		num_pages -= 1 << order;
+		for (i = 1 << order; i; --i)
+			*(pages++) = p++;
+	}
+
+	r = ttm_pool_apply_caching(caching, pages, tt->caching);
+	if (r)
+		goto error_free_all;
+
+	return 0;
+
+error_global_free:
+	ttm_mem_global_free_page(&ttm_mem_glob, p, (1 << order) * PAGE_SIZE);
+
+error_free_page:
+	ttm_pool_free_page(pool, tt->caching, order, p);
+
+error_free_all:
+	num_pages = tt->num_pages - num_pages;
+	for (i = 0; i < num_pages; ) {
+		order = ttm_pool_page_order(pool, tt->pages[i]);
+		ttm_pool_free_page(pool, tt->caching, order, tt->pages[i]);
+		i += 1 << order;
+	}
+
+	return r;
+}
+EXPORT_SYMBOL(ttm_pool_alloc);
+
+/**
+ * ttm_pool_free - Free the backing pages from a ttm_tt object
+ *
+ * @pool: Pool to give pages back to.
+ * @tt: ttm_tt object to unpopulate
+ *
+ * Give the packing pages back to a pool or free them
+ */
+void ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt)
+{
+	unsigned int i;
+
+	for (i = 0; i < tt->num_pages; ) {
+		struct page *p = tt->pages[i];
+		unsigned int order, num_pages;
+		struct ttm_pool_type *pt;
+
+		order = ttm_pool_page_order(pool, p);
+		num_pages = 1ULL << order;
+		ttm_mem_global_free_page(&ttm_mem_glob, p,
+					 num_pages * PAGE_SIZE);
+		if (tt->dma_address)
+			ttm_pool_unmap(pool, tt->dma_address[i], num_pages);
+
+		pt = ttm_pool_select_type(pool, tt->caching, order);
+		if (pt)
+			ttm_pool_type_give(pt, tt->pages[i]);
+		else
+			ttm_pool_free_page(pool, tt->caching, order,
+					   tt->pages[i]);
+
+		i += num_pages;
+	}
+
+	while (atomic_long_read(&allocated_pages) > page_pool_size)
+		ttm_pool_shrink();
+}
+EXPORT_SYMBOL(ttm_pool_free);
+
+/**
+ * ttm_pool_init - Initialize a pool
+ *
+ * @pool: the pool to initialize
+ * @dev: device for DMA allocations and mappings
+ * @use_dma_alloc: true if coherent DMA alloc should be used
+ * @use_dma32: true if GFP_DMA32 should be used
+ *
+ * Initialize the pool and its pool types.
+ */
+void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
+		   bool use_dma_alloc, bool use_dma32)
+{
+	unsigned int i, j;
+
+	WARN_ON(!dev && use_dma_alloc);
+
+	pool->dev = dev;
+	pool->use_dma_alloc = use_dma_alloc;
+	pool->use_dma32 = use_dma32;
+
+	for (i = 0; i < TTM_NUM_CACHING_TYPES; ++i)
+		for (j = 0; j < MAX_ORDER; ++j)
+			ttm_pool_type_init(&pool->caching[i].orders[j],
+					   pool, i, j);
+}
+EXPORT_SYMBOL(ttm_pool_init);
+
+/**
+ * ttm_pool_fini - Cleanup a pool
+ *
+ * @pool: the pool to clean up
+ *
+ * Free all pages in the pool and unregister the types from the global
+ * shrinker.
+ */
+void ttm_pool_fini(struct ttm_pool *pool)
+{
+	unsigned int i, j;
+
+	for (i = 0; i < TTM_NUM_CACHING_TYPES; ++i)
+		for (j = 0; j < MAX_ORDER; ++j)
+			ttm_pool_type_fini(&pool->caching[i].orders[j]);
+}
+EXPORT_SYMBOL(ttm_pool_fini);
+
+#ifdef CONFIG_DEBUG_FS
+
+/* Dump information about the different pool types */
+static void ttm_pool_debugfs_orders(struct ttm_pool_type *pt,
+				    struct seq_file *m)
+{
+	unsigned int i;
+
+	for (i = 0; i < MAX_ORDER; ++i)
+		seq_printf(m, " %8u", ttm_pool_type_count(&pt[i]));
+	seq_puts(m, "\n");
+}
+
+/**
+ * ttm_pool_debugfs - Debugfs dump function for a pool
+ *
+ * @pool: the pool to dump the information for
+ * @m: seq_file to dump to
+ *
+ * Make a debugfs dump with the per pool and global information.
+ */
+int ttm_pool_debugfs(struct ttm_pool *pool, struct seq_file *m)
+{
+	unsigned int i;
+
+	spin_lock(&shrinker_lock);
+
+	seq_puts(m, "\t ");
+	for (i = 0; i < MAX_ORDER; ++i)
+		seq_printf(m, " ---%2u---", i);
+	seq_puts(m, "\n");
+
+	seq_puts(m, "wc\t:");
+	ttm_pool_debugfs_orders(global_write_combined, m);
+	seq_puts(m, "uc\t:");
+	ttm_pool_debugfs_orders(global_uncached, m);
+
+	for (i = 0; i < TTM_NUM_CACHING_TYPES; ++i) {
+		seq_puts(m, "DMA ");
+		switch (i) {
+		case ttm_cached:
+			seq_puts(m, "\t:");
+			break;
+		case ttm_write_combined:
+			seq_puts(m, "wc\t:");
+			break;
+		case ttm_uncached:
+			seq_puts(m, "uc\t:");
+			break;
+		}
+		ttm_pool_debugfs_orders(pool->caching[i].orders, m);
+	}
+
+	seq_printf(m, "\ntotal\t: %8lu of %8lu\n",
+		   atomic_long_read(&allocated_pages), page_pool_size);
+
+	spin_unlock(&shrinker_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL(ttm_pool_debugfs);
+
+#endif
+
+/* As long as pages are available make sure to release at least one */
+static unsigned long ttm_pool_shrinker_scan(struct shrinker *shrink,
+					    struct shrink_control *sc)
+{
+	unsigned long num_freed = 0;
+
+	do
+		num_freed += ttm_pool_shrink();
+	while (!num_freed && atomic_long_read(&allocated_pages));
+
+	return num_freed;
+}
+
+/* Return the number of pages available or SHRINK_EMPTY if we have none */
+static unsigned long ttm_pool_shrinker_count(struct shrinker *shrink,
+					     struct shrink_control *sc)
+{
+	unsigned long num_pages = atomic_long_read(&allocated_pages);
+
+	return num_pages ? num_pages : SHRINK_EMPTY;
+}
+
+/**
+ * ttm_pool_mgr_init - Initialize globals
+ *
+ * @num_pages: default number of pages
+ *
+ * Initialize the global locks and lists for the MM shrinker.
+ */
+int ttm_pool_mgr_init(unsigned long num_pages)
+{
+	unsigned int i;
+
+	if (!page_pool_size)
+		page_pool_size = num_pages;
+
+	spin_lock_init(&shrinker_lock);
+	INIT_LIST_HEAD(&shrinker_list);
+
+	for (i = 0; i < MAX_ORDER; ++i) {
+		ttm_pool_type_init(&global_write_combined[i], NULL,
+				   ttm_write_combined, i);
+		ttm_pool_type_init(&global_uncached[i], NULL, ttm_uncached, i);
+	}
+
+	mm_shrinker.count_objects = ttm_pool_shrinker_count;
+	mm_shrinker.scan_objects = ttm_pool_shrinker_scan;
+	mm_shrinker.seeks = 1;
+	return register_shrinker(&mm_shrinker);
+}
+
+/**
+ * ttm_pool_mgr_fini - Finalize globals
+ *
+ * Cleanup the global pools and unregister the MM shrinker.
+ */
+void ttm_pool_mgr_fini(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < MAX_ORDER; ++i) {
+		ttm_pool_type_fini(&global_write_combined[i]);
+		ttm_pool_type_fini(&global_uncached[i]);
+	}
+
+	unregister_shrinker(&mm_shrinker);
+	WARN_ON(!list_empty(&shrinker_list));
+}
diff --git a/include/drm/ttm/ttm_caching.h b/include/drm/ttm/ttm_caching.h
index 161624dcf6be..a0b4a49fa432 100644
--- a/include/drm/ttm/ttm_caching.h
+++ b/include/drm/ttm/ttm_caching.h
@@ -25,6 +25,8 @@
 #ifndef _TTM_CACHING_H_
 #define _TTM_CACHING_H_
 
+#define TTM_NUM_CACHING_TYPES	3
+
 enum ttm_caching {
 	ttm_uncached,
 	ttm_write_combined,
diff --git a/include/drm/ttm/ttm_pool.h b/include/drm/ttm/ttm_pool.h
new file mode 100644
index 000000000000..4321728bdd11
--- /dev/null
+++ b/include/drm/ttm/ttm_pool.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright 2020 Advanced Micro Devices, Inc.
+ *
+ * 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, sublicense,
+ * 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 above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * 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 NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
+ *
+ * Authors: Christian König
+ */
+
+#ifndef _TTM_PAGE_POOL_H_
+#define _TTM_PAGE_POOL_H_
+
+#include <linux/mmzone.h>
+#include <linux/llist.h>
+#include <linux/spinlock.h>
+#include <drm/ttm/ttm_caching.h>
+
+struct device;
+struct ttm_tt;
+struct ttm_pool;
+struct ttm_operation_ctx;
+
+/**
+ * ttm_pool_type - Pool for a certain memory type
+ *
+ * @pool: the pool we belong to, might be NULL for the global ones
+ * @order: the allocation order our pages have
+ * @caching: the caching type our pages have
+ * @shrinker_list: our place on the global shrinker list
+ * @lock: protection of the page list
+ * @pages: the list of pages in the pool
+ */
+struct ttm_pool_type {
+	struct ttm_pool *pool;
+	unsigned int order;
+	enum ttm_caching caching;
+
+	struct list_head shrinker_list;
+
+	spinlock_t lock;
+	struct list_head pages;
+};
+
+/**
+ * ttm_pool - Pool for all caching and orders
+ *
+ * @use_dma_alloc: if coherent DMA allocations should be used
+ * @use_dma32: if GFP_DMA32 should be used
+ * @caching: pools for each caching/order
+ */
+struct ttm_pool {
+	struct device *dev;
+
+	bool use_dma_alloc;
+	bool use_dma32;
+
+	struct {
+		struct ttm_pool_type orders[MAX_ORDER];
+	} caching[TTM_NUM_CACHING_TYPES];
+};
+
+int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
+		   struct ttm_operation_ctx *ctx);
+void ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt);
+
+void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
+		   bool use_dma_alloc, bool use_dma32);
+void ttm_pool_fini(struct ttm_pool *pool);
+
+int ttm_pool_debugfs(struct ttm_pool *pool, struct seq_file *m);
+
+int ttm_pool_mgr_init(unsigned long num_pages);
+void ttm_pool_mgr_fini(void);
+
+#endif