[v8,1/5] drm: Add a sharable drm page-pool implementation

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index e392a90ca687..7cbcecb8f7df 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -177,6 +177,10 @@  config DRM_DP_CEC
 	  Note: not all adapters support this feature, and even for those
 	  that do support this they often do not hook up the CEC pin.
 
+config DRM_PAGE_POOL
+	bool
+	depends on DRM
+
 config DRM_TTM
 	tristate
 	depends on DRM && MMU
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 926adef289db..2dc7b2fe3fe5 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -39,6 +39,8 @@  obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
 drm_ttm_helper-y := drm_gem_ttm_helper.o
 obj-$(CONFIG_DRM_TTM_HELPER) += drm_ttm_helper.o
 
+drm-$(CONFIG_DRM_PAGE_POOL) += page_pool.o
+
 drm_kms_helper-y := drm_bridge_connector.o drm_crtc_helper.o drm_dp_helper.o \
 		drm_dsc.o drm_probe_helper.o \
 		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
diff --git a/drivers/gpu/drm/page_pool.c b/drivers/gpu/drm/page_pool.c
new file mode 100644
index 000000000000..a60b954cfe0f
--- /dev/null
+++ b/drivers/gpu/drm/page_pool.c
@@ -0,0 +1,214 @@ 
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Sharable page pool implementation
+ *
+ * Extracted from drivers/gpu/drm/ttm/ttm_pool.c
+ * Copyright 2020 Advanced Micro Devices, Inc.
+ * Copyright 2021 Linaro Ltd.
+ *
+ * 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, John Stultz
+ */
+
+#include <linux/module.h>
+#include <linux/highmem.h>
+#include <linux/shrinker.h>
+#include <drm/page_pool.h>
+
+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 mutex shrinker_lock;
+static struct list_head shrinker_list;
+static struct shrinker mm_shrinker;
+
+void drm_page_pool_set_max(unsigned long max)
+{
+	if (!page_pool_size)
+		page_pool_size = max;
+}
+
+unsigned long drm_page_pool_get_max(void)
+{
+	return page_pool_size;
+}
+
+unsigned long drm_page_pool_get_total(void)
+{
+	return atomic_long_read(&allocated_pages);
+}
+
+unsigned long drm_page_pool_get_size(struct drm_page_pool *pool)
+{
+	unsigned long size;
+
+	spin_lock(&pool->lock);
+	size = pool->page_count;
+	spin_unlock(&pool->lock);
+	return size;
+}
+
+/* Give pages into a specific pool */
+void drm_page_pool_add(struct drm_page_pool *pool, struct page *p)
+{
+	unsigned int i, num_pages = 1 << pool->order;
+
+	for (i = 0; i < num_pages; ++i) {
+		if (PageHighMem(p))
+			clear_highpage(p + i);
+		else
+			clear_page(page_address(p + i));
+	}
+
+	spin_lock(&pool->lock);
+	list_add(&p->lru, &pool->pages);
+	pool->page_count += 1 << pool->order;
+	spin_unlock(&pool->lock);
+	atomic_long_add(1 << pool->order, &allocated_pages);
+}
+
+/* Take pages from a specific pool, return NULL when nothing available */
+struct page *drm_page_pool_remove(struct drm_page_pool *pool)
+{
+	struct page *p;
+
+	spin_lock(&pool->lock);
+	p = list_first_entry_or_null(&pool->pages, typeof(*p), lru);
+	if (p) {
+		atomic_long_sub(1 << pool->order, &allocated_pages);
+		pool->page_count -= 1 << pool->order;
+		list_del(&p->lru);
+	}
+	spin_unlock(&pool->lock);
+
+	return p;
+}
+
+/* Initialize and add a pool type to the global shrinker list */
+void drm_page_pool_init(struct drm_page_pool *pool, unsigned int order,
+			unsigned long (*free_page)(struct drm_page_pool *pool, struct page *p))
+{
+	pool->order = order;
+	spin_lock_init(&pool->lock);
+	INIT_LIST_HEAD(&pool->pages);
+	pool->free = free_page;
+	pool->page_count = 0;
+
+	mutex_lock(&shrinker_lock);
+	list_add_tail(&pool->shrinker_list, &shrinker_list);
+	mutex_unlock(&shrinker_lock);
+}
+
+/* Remove a pool_type from the global shrinker list and free all pages */
+void drm_page_pool_fini(struct drm_page_pool *pool)
+{
+	struct page *p, *tmp;
+
+	mutex_lock(&shrinker_lock);
+	list_del(&pool->shrinker_list);
+	mutex_unlock(&shrinker_lock);
+
+	list_for_each_entry_safe(p, tmp, &pool->pages, lru)
+		pool->free(pool, p);
+}
+
+/* Free pages using the global shrinker list */
+static unsigned int drm_page_pool_shrink(void)
+{
+	struct drm_page_pool *pool;
+	unsigned int num_freed;
+	struct page *p;
+
+	mutex_lock(&shrinker_lock);
+	pool = list_first_entry(&shrinker_list, typeof(*pool), shrinker_list);
+
+	p = drm_page_pool_remove(pool);
+
+	list_move_tail(&pool->shrinker_list, &shrinker_list);
+	mutex_unlock(&shrinker_lock);
+
+	if (p) {
+		pool->free(pool, p);
+		num_freed = 1 << pool->order;
+	} else {
+		num_freed = 0;
+	}
+
+	return num_freed;
+}
+
+/* As long as pages are available make sure to release at least one */
+static unsigned long drm_page_pool_shrinker_scan(struct shrinker *shrink,
+						 struct shrink_control *sc)
+{
+	unsigned long num_freed = 0;
+
+	do
+		num_freed += drm_page_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 drm_page_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;
+}
+
+/**
+ * drm_page_pool_shrinker_setup - Initialize globals
+ *
+ * @num_pages: default number of pages
+ *
+ * Initialize the global locks and lists for the shrinker.
+ */
+int drm_page_pool_shrinker_setup(void)
+{
+	mutex_init(&shrinker_lock);
+	INIT_LIST_HEAD(&shrinker_list);
+
+	mm_shrinker.count_objects = drm_page_pool_shrinker_count;
+	mm_shrinker.scan_objects = drm_page_pool_shrinker_scan;
+	mm_shrinker.seeks = 1;
+	return register_shrinker(&mm_shrinker);
+}
+
+/**
+ * drm_page_pool_shrinker_teardown - Finalize globals
+ *
+ * Unregister the shrinker.
+ */
+void drm_page_pool_shrinker_teardown(void)
+{
+	unregister_shrinker(&mm_shrinker);
+	WARN_ON(!list_empty(&shrinker_list));
+}
+
+module_init(drm_page_pool_shrinker_setup);
+module_exit(drm_page_pool_shrinker_teardown);
+MODULE_LICENSE("Dual MIT/GPL");
diff --git a/include/drm/page_pool.h b/include/drm/page_pool.h
new file mode 100644
index 000000000000..d8b8a8415629
--- /dev/null
+++ b/include/drm/page_pool.h
@@ -0,0 +1,65 @@ 
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Extracted from include/drm/ttm/ttm_pool.h
+ * Copyright 2020 Advanced Micro Devices, Inc.
+ * Copyright 2021 Linaro Ltd
+ *
+ * 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, John Stultz
+ */
+
+#ifndef _DRM_PAGE_POOL_H_
+#define _DRM_PAGE_POOL_H_
+
+#include <linux/mmzone.h>
+#include <linux/llist.h>
+#include <linux/spinlock.h>
+
+/**
+ * drm_page_pool - Page Pool for a certain memory type
+ *
+ * @order: the allocation order our pages have
+ * @pages: the list of pages in the pool
+ * @shrinker_list: our place on the global shrinker list
+ * @lock: protection of the page list
+ * @page_count: number of pages currently in the pool
+ * @free: Function pointer to free the page
+ */
+struct drm_page_pool {
+	unsigned int order;
+	struct list_head pages;
+	struct list_head shrinker_list;
+	spinlock_t lock;
+
+	unsigned long page_count;
+	unsigned long (*free)(struct drm_page_pool *pool, struct page *p);
+};
+
+void drm_page_pool_set_max(unsigned long max);
+unsigned long drm_page_pool_get_max(void);
+unsigned long drm_page_pool_get_total(void);
+unsigned long drm_page_pool_get_size(struct drm_page_pool *pool);
+void drm_page_pool_add(struct drm_page_pool *pool, struct page *p);
+struct page *drm_page_pool_remove(struct drm_page_pool *pool);
+void drm_page_pool_init(struct drm_page_pool *pool, unsigned int order,
+			unsigned long (*free_page)(struct drm_page_pool *pool, struct page *p));
+void drm_page_pool_fini(struct drm_page_pool *pool);
+
+#endif