1 /*
2  * Copyright © 2014 Intel Corporation
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice (including the next
12  * paragraph) shall be included in all copies or substantial portions of the
13  * Software.
14  *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21  * IN THE SOFTWARE.
22  *
23  */
24 
25 #include "i915_drv.h"
26 
27 /**
28  * DOC: batch pool
29  *
30  * In order to submit batch buffers as 'secure', the software command parser
31  * must ensure that a batch buffer cannot be modified after parsing. It does
32  * this by copying the user provided batch buffer contents to a kernel owned
33  * buffer from which the hardware will actually execute, and by carefully
34  * managing the address space bindings for such buffers.
35  *
36  * The batch pool framework provides a mechanism for the driver to manage a
37  * set of scratch buffers to use for this purpose. The framework can be
38  * extended to support other uses cases should they arise.
39  */
40 
41 /**
42  * i915_gem_batch_pool_init() - initialize a batch buffer pool
43  * @dev: the drm device
44  * @pool: the batch buffer pool
45  */
46 void i915_gem_batch_pool_init(struct drm_device *dev,
47 			      struct i915_gem_batch_pool *pool)
48 {
49 	pool->dev = dev;
50 	INIT_LIST_HEAD(&pool->cache_list);
51 }
52 
53 /**
54  * i915_gem_batch_pool_fini() - clean up a batch buffer pool
55  * @pool: the pool to clean up
56  *
57  * Note: Callers must hold the struct_mutex.
58  */
59 void i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool)
60 {
61 	WARN_ON(!mutex_is_locked(&pool->dev->struct_mutex));
62 
63 	while (!list_empty(&pool->cache_list)) {
64 		struct drm_i915_gem_object *obj =
65 			list_first_entry(&pool->cache_list,
66 					 struct drm_i915_gem_object,
67 					 batch_pool_list);
68 
69 		WARN_ON(obj->active);
70 
71 		list_del_init(&obj->batch_pool_list);
72 		drm_gem_object_unreference(&obj->base);
73 	}
74 }
75 
76 /**
77  * i915_gem_batch_pool_get() - select a buffer from the pool
78  * @pool: the batch buffer pool
79  * @size: the minimum desired size of the returned buffer
80  *
81  * Finds or allocates a batch buffer in the pool with at least the requested
82  * size. The caller is responsible for any domain, active/inactive, or
83  * purgeability management for the returned buffer.
84  *
85  * Note: Callers must hold the struct_mutex
86  *
87  * Return: the selected batch buffer object
88  */
89 struct drm_i915_gem_object *
90 i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
91 			size_t size)
92 {
93 	struct drm_i915_gem_object *obj = NULL;
94 	struct drm_i915_gem_object *tmp, *next;
95 
96 	WARN_ON(!mutex_is_locked(&pool->dev->struct_mutex));
97 
98 	list_for_each_entry_safe(tmp, next,
99 			&pool->cache_list, batch_pool_list) {
100 
101 		if (tmp->active)
102 			continue;
103 
104 		/* While we're looping, do some clean up */
105 		if (tmp->madv == __I915_MADV_PURGED) {
106 			list_del(&tmp->batch_pool_list);
107 			drm_gem_object_unreference(&tmp->base);
108 			continue;
109 		}
110 
111 		/*
112 		 * Select a buffer that is at least as big as needed
113 		 * but not 'too much' bigger. A better way to do this
114 		 * might be to bucket the pool objects based on size.
115 		 */
116 		if (tmp->base.size >= size &&
117 		    tmp->base.size <= (2 * size)) {
118 			obj = tmp;
119 			break;
120 		}
121 	}
122 
123 	if (!obj) {
124 		obj = i915_gem_alloc_object(pool->dev, size);
125 		if (!obj)
126 			return ERR_PTR(-ENOMEM);
127 
128 		list_add_tail(&obj->batch_pool_list, &pool->cache_list);
129 	}
130 	else
131 		/* Keep list in LRU order */
132 		list_move_tail(&obj->batch_pool_list, &pool->cache_list);
133 
134 	obj->madv = I915_MADV_WILLNEED;
135 
136 	return obj;
137 }
138