1 ===================== 1 =====================
2 DRM Memory Management 2 DRM Memory Management
3 ===================== 3 =====================
4 4
5 Modern Linux systems require large amount of g 5 Modern Linux systems require large amount of graphics memory to store
6 frame buffers, textures, vertices and other gr 6 frame buffers, textures, vertices and other graphics-related data. Given
7 the very dynamic nature of many of that data, 7 the very dynamic nature of many of that data, managing graphics memory
8 efficiently is thus crucial for the graphics s 8 efficiently is thus crucial for the graphics stack and plays a central
9 role in the DRM infrastructure. 9 role in the DRM infrastructure.
10 10
11 The DRM core includes two memory managers, nam 11 The DRM core includes two memory managers, namely Translation Table Manager
12 (TTM) and Graphics Execution Manager (GEM). TT 12 (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory
13 manager to be developed and tried to be a one- 13 manager to be developed and tried to be a one-size-fits-them all
14 solution. It provides a single userspace API t 14 solution. It provides a single userspace API to accommodate the need of
15 all hardware, supporting both Unified Memory A 15 all hardware, supporting both Unified Memory Architecture (UMA) devices
16 and devices with dedicated video RAM (i.e. mos 16 and devices with dedicated video RAM (i.e. most discrete video cards).
17 This resulted in a large, complex piece of cod 17 This resulted in a large, complex piece of code that turned out to be
18 hard to use for driver development. 18 hard to use for driver development.
19 19
20 GEM started as an Intel-sponsored project in r 20 GEM started as an Intel-sponsored project in reaction to TTM's
21 complexity. Its design philosophy is completel 21 complexity. Its design philosophy is completely different: instead of
22 providing a solution to every graphics memory- 22 providing a solution to every graphics memory-related problems, GEM
23 identified common code between drivers and cre 23 identified common code between drivers and created a support library to
24 share it. GEM has simpler initialization and e 24 share it. GEM has simpler initialization and execution requirements than
25 TTM, but has no video RAM management capabilit 25 TTM, but has no video RAM management capabilities and is thus limited to
26 UMA devices. 26 UMA devices.
27 27
28 The Translation Table Manager (TTM) 28 The Translation Table Manager (TTM)
29 =================================== 29 ===================================
30 30
31 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_module 31 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_module.c
32 :doc: TTM 32 :doc: TTM
33 33
34 .. kernel-doc:: include/drm/ttm/ttm_caching.h 34 .. kernel-doc:: include/drm/ttm/ttm_caching.h
35 :internal: 35 :internal:
36 36
37 TTM device object reference 37 TTM device object reference
38 --------------------------- 38 ---------------------------
39 39
40 .. kernel-doc:: include/drm/ttm/ttm_device.h 40 .. kernel-doc:: include/drm/ttm/ttm_device.h
41 :internal: 41 :internal:
42 42
43 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_device 43 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_device.c
44 :export: 44 :export:
45 45
46 TTM resource placement reference 46 TTM resource placement reference
47 -------------------------------- 47 --------------------------------
48 48
49 .. kernel-doc:: include/drm/ttm/ttm_placement. 49 .. kernel-doc:: include/drm/ttm/ttm_placement.h
50 :internal: 50 :internal:
51 51
52 TTM resource object reference 52 TTM resource object reference
53 ----------------------------- 53 -----------------------------
54 54
55 .. kernel-doc:: include/drm/ttm/ttm_resource.h 55 .. kernel-doc:: include/drm/ttm/ttm_resource.h
56 :internal: 56 :internal:
57 57
58 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_resour 58 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_resource.c
59 :export: 59 :export:
60 60
61 TTM TT object reference 61 TTM TT object reference
62 ----------------------- 62 -----------------------
63 63
64 .. kernel-doc:: include/drm/ttm/ttm_tt.h 64 .. kernel-doc:: include/drm/ttm/ttm_tt.h
65 :internal: 65 :internal:
66 66
67 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_tt.c 67 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_tt.c
68 :export: 68 :export:
69 69
70 TTM page pool reference 70 TTM page pool reference
71 ----------------------- 71 -----------------------
72 72
73 .. kernel-doc:: include/drm/ttm/ttm_pool.h 73 .. kernel-doc:: include/drm/ttm/ttm_pool.h
74 :internal: 74 :internal:
75 75
76 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_pool.c 76 .. kernel-doc:: drivers/gpu/drm/ttm/ttm_pool.c
77 :export: 77 :export:
78 78
79 The Graphics Execution Manager (GEM) 79 The Graphics Execution Manager (GEM)
80 ==================================== 80 ====================================
81 81
82 The GEM design approach has resulted in a memo 82 The GEM design approach has resulted in a memory manager that doesn't
83 provide full coverage of all (or even all comm 83 provide full coverage of all (or even all common) use cases in its
84 userspace or kernel API. GEM exposes a set of 84 userspace or kernel API. GEM exposes a set of standard memory-related
85 operations to userspace and a set of helper fu 85 operations to userspace and a set of helper functions to drivers, and
86 let drivers implement hardware-specific operat 86 let drivers implement hardware-specific operations with their own
87 private API. 87 private API.
88 88
89 The GEM userspace API is described in the `GEM 89 The GEM userspace API is described in the `GEM - the Graphics Execution
90 Manager <http://lwn.net/Articles/283798/>`__ a 90 Manager <http://lwn.net/Articles/283798/>`__ article on LWN. While
91 slightly outdated, the document provides a goo 91 slightly outdated, the document provides a good overview of the GEM API
92 principles. Buffer allocation and read and wri 92 principles. Buffer allocation and read and write operations, described
93 as part of the common GEM API, are currently i 93 as part of the common GEM API, are currently implemented using
94 driver-specific ioctls. 94 driver-specific ioctls.
95 95
96 GEM is data-agnostic. It manages abstract buff 96 GEM is data-agnostic. It manages abstract buffer objects without knowing
97 what individual buffers contain. APIs that req 97 what individual buffers contain. APIs that require knowledge of buffer
98 contents or purpose, such as buffer allocation 98 contents or purpose, such as buffer allocation or synchronization
99 primitives, are thus outside of the scope of G 99 primitives, are thus outside of the scope of GEM and must be implemented
100 using driver-specific ioctls. 100 using driver-specific ioctls.
101 101
102 On a fundamental level, GEM involves several o 102 On a fundamental level, GEM involves several operations:
103 103
104 - Memory allocation and freeing 104 - Memory allocation and freeing
105 - Command execution 105 - Command execution
106 - Aperture management at command execution ti 106 - Aperture management at command execution time
107 107
108 Buffer object allocation is relatively straigh 108 Buffer object allocation is relatively straightforward and largely
109 provided by Linux's shmem layer, which provide 109 provided by Linux's shmem layer, which provides memory to back each
110 object. 110 object.
111 111
112 Device-specific operations, such as command ex 112 Device-specific operations, such as command execution, pinning, buffer
113 read & write, mapping, and domain ownership tr 113 read & write, mapping, and domain ownership transfers are left to
114 driver-specific ioctls. 114 driver-specific ioctls.
115 115
116 GEM Initialization 116 GEM Initialization
117 ------------------ 117 ------------------
118 118
119 Drivers that use GEM must set the DRIVER_GEM b 119 Drivers that use GEM must set the DRIVER_GEM bit in the struct
120 :c:type:`struct drm_driver <drm_driver>` drive 120 :c:type:`struct drm_driver <drm_driver>` driver_features
121 field. The DRM core will then automatically in 121 field. The DRM core will then automatically initialize the GEM core
122 before calling the load operation. Behind the 122 before calling the load operation. Behind the scene, this will create a
123 DRM Memory Manager object which provides an ad 123 DRM Memory Manager object which provides an address space pool for
124 object allocation. 124 object allocation.
125 125
126 In a KMS configuration, drivers need to alloca 126 In a KMS configuration, drivers need to allocate and initialize a
127 command ring buffer following core GEM initial 127 command ring buffer following core GEM initialization if required by the
128 hardware. UMA devices usually have what is cal 128 hardware. UMA devices usually have what is called a "stolen" memory
129 region, which provides space for the initial f 129 region, which provides space for the initial framebuffer and large,
130 contiguous memory regions required by the devi 130 contiguous memory regions required by the device. This space is
131 typically not managed by GEM, and must be init 131 typically not managed by GEM, and must be initialized separately into
132 its own DRM MM object. 132 its own DRM MM object.
133 133
134 GEM Objects Creation 134 GEM Objects Creation
135 -------------------- 135 --------------------
136 136
137 GEM splits creation of GEM objects and allocat 137 GEM splits creation of GEM objects and allocation of the memory that
138 backs them in two distinct operations. 138 backs them in two distinct operations.
139 139
140 GEM objects are represented by an instance of 140 GEM objects are represented by an instance of struct :c:type:`struct
141 drm_gem_object <drm_gem_object>`. Drivers usua 141 drm_gem_object <drm_gem_object>`. Drivers usually need to
142 extend GEM objects with private information an 142 extend GEM objects with private information and thus create a
143 driver-specific GEM object structure type that 143 driver-specific GEM object structure type that embeds an instance of
144 struct :c:type:`struct drm_gem_object <drm_gem 144 struct :c:type:`struct drm_gem_object <drm_gem_object>`.
145 145
146 To create a GEM object, a driver allocates mem 146 To create a GEM object, a driver allocates memory for an instance of its
147 specific GEM object type and initializes the e 147 specific GEM object type and initializes the embedded struct
148 :c:type:`struct drm_gem_object <drm_gem_object 148 :c:type:`struct drm_gem_object <drm_gem_object>` with a call
149 to drm_gem_object_init(). The function takes a 149 to drm_gem_object_init(). The function takes a pointer
150 to the DRM device, a pointer to the GEM object 150 to the DRM device, a pointer to the GEM object and the buffer object
151 size in bytes. 151 size in bytes.
152 152
153 GEM uses shmem to allocate anonymous pageable 153 GEM uses shmem to allocate anonymous pageable memory.
154 drm_gem_object_init() will create an shmfs fil 154 drm_gem_object_init() will create an shmfs file of the
155 requested size and store it into the struct :c 155 requested size and store it into the struct :c:type:`struct
156 drm_gem_object <drm_gem_object>` filp field. T 156 drm_gem_object <drm_gem_object>` filp field. The memory is
157 used as either main storage for the object whe 157 used as either main storage for the object when the graphics hardware
158 uses system memory directly or as a backing st 158 uses system memory directly or as a backing store otherwise.
159 159
160 Drivers are responsible for the actual physica 160 Drivers are responsible for the actual physical pages allocation by
161 calling shmem_read_mapping_page_gfp() for each 161 calling shmem_read_mapping_page_gfp() for each page.
162 Note that they can decide to allocate pages wh 162 Note that they can decide to allocate pages when initializing the GEM
163 object, or to delay allocation until the memor 163 object, or to delay allocation until the memory is needed (for instance
164 when a page fault occurs as a result of a user 164 when a page fault occurs as a result of a userspace memory access or
165 when the driver needs to start a DMA transfer 165 when the driver needs to start a DMA transfer involving the memory).
166 166
167 Anonymous pageable memory allocation is not al 167 Anonymous pageable memory allocation is not always desired, for instance
168 when the hardware requires physically contiguo 168 when the hardware requires physically contiguous system memory as is
169 often the case in embedded devices. Drivers ca 169 often the case in embedded devices. Drivers can create GEM objects with
170 no shmfs backing (called private GEM objects) 170 no shmfs backing (called private GEM objects) by initializing them with a call
171 to drm_gem_private_object_init() instead of dr 171 to drm_gem_private_object_init() instead of drm_gem_object_init(). Storage for
172 private GEM objects must be managed by drivers 172 private GEM objects must be managed by drivers.
173 173
174 GEM Objects Lifetime 174 GEM Objects Lifetime
175 -------------------- 175 --------------------
176 176
177 All GEM objects are reference-counted by the G 177 All GEM objects are reference-counted by the GEM core. References can be
178 acquired and release by calling drm_gem_object 178 acquired and release by calling drm_gem_object_get() and drm_gem_object_put()
179 respectively. 179 respectively.
180 180
181 When the last reference to a GEM object is rel 181 When the last reference to a GEM object is released the GEM core calls
182 the :c:type:`struct drm_gem_object_funcs <gem_ 182 the :c:type:`struct drm_gem_object_funcs <gem_object_funcs>` free
183 operation. That operation is mandatory for GEM 183 operation. That operation is mandatory for GEM-enabled drivers and must
184 free the GEM object and all associated resourc 184 free the GEM object and all associated resources.
185 185
186 void (\*free) (struct drm_gem_object \*obj); D 186 void (\*free) (struct drm_gem_object \*obj); Drivers are
187 responsible for freeing all GEM object resourc 187 responsible for freeing all GEM object resources. This includes the
188 resources created by the GEM core, which need 188 resources created by the GEM core, which need to be released with
189 drm_gem_object_release(). 189 drm_gem_object_release().
190 190
191 GEM Objects Naming 191 GEM Objects Naming
192 ------------------ 192 ------------------
193 193
194 Communication between userspace and the kernel 194 Communication between userspace and the kernel refers to GEM objects
195 using local handles, global names or, more rec 195 using local handles, global names or, more recently, file descriptors.
196 All of those are 32-bit integer values; the us 196 All of those are 32-bit integer values; the usual Linux kernel limits
197 apply to the file descriptors. 197 apply to the file descriptors.
198 198
199 GEM handles are local to a DRM file. Applicati 199 GEM handles are local to a DRM file. Applications get a handle to a GEM
200 object through a driver-specific ioctl, and ca 200 object through a driver-specific ioctl, and can use that handle to refer
201 to the GEM object in other standard or driver- 201 to the GEM object in other standard or driver-specific ioctls. Closing a
202 DRM file handle frees all its GEM handles and 202 DRM file handle frees all its GEM handles and dereferences the
203 associated GEM objects. 203 associated GEM objects.
204 204
205 To create a handle for a GEM object drivers ca 205 To create a handle for a GEM object drivers call drm_gem_handle_create(). The
206 function takes a pointer to the DRM file and t 206 function takes a pointer to the DRM file and the GEM object and returns a
207 locally unique handle. When the handle is no 207 locally unique handle. When the handle is no longer needed drivers delete it
208 with a call to drm_gem_handle_delete(). Finall 208 with a call to drm_gem_handle_delete(). Finally the GEM object associated with a
209 handle can be retrieved by a call to drm_gem_o 209 handle can be retrieved by a call to drm_gem_object_lookup().
210 210
211 Handles don't take ownership of GEM objects, t 211 Handles don't take ownership of GEM objects, they only take a reference
212 to the object that will be dropped when the ha 212 to the object that will be dropped when the handle is destroyed. To
213 avoid leaking GEM objects, drivers must make s 213 avoid leaking GEM objects, drivers must make sure they drop the
214 reference(s) they own (such as the initial ref 214 reference(s) they own (such as the initial reference taken at object
215 creation time) as appropriate, without any spe 215 creation time) as appropriate, without any special consideration for the
216 handle. For example, in the particular case of 216 handle. For example, in the particular case of combined GEM object and
217 handle creation in the implementation of the d 217 handle creation in the implementation of the dumb_create operation,
218 drivers must drop the initial reference to the 218 drivers must drop the initial reference to the GEM object before
219 returning the handle. 219 returning the handle.
220 220
221 GEM names are similar in purpose to handles bu 221 GEM names are similar in purpose to handles but are not local to DRM
222 files. They can be passed between processes to 222 files. They can be passed between processes to reference a GEM object
223 globally. Names can't be used directly to refe 223 globally. Names can't be used directly to refer to objects in the DRM
224 API, applications must convert handles to name 224 API, applications must convert handles to names and names to handles
225 using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GE 225 using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls
226 respectively. The conversion is handled by the 226 respectively. The conversion is handled by the DRM core without any
227 driver-specific support. 227 driver-specific support.
228 228
229 GEM also supports buffer sharing with dma-buf 229 GEM also supports buffer sharing with dma-buf file descriptors through
230 PRIME. GEM-based drivers must use the provided 230 PRIME. GEM-based drivers must use the provided helpers functions to
231 implement the exporting and importing correctl 231 implement the exporting and importing correctly. See ?. Since sharing
232 file descriptors is inherently more secure tha 232 file descriptors is inherently more secure than the easily guessable and
233 global GEM names it is the preferred buffer sh 233 global GEM names it is the preferred buffer sharing mechanism. Sharing
234 buffers through GEM names is only supported fo 234 buffers through GEM names is only supported for legacy userspace.
235 Furthermore PRIME also allows cross-device buf 235 Furthermore PRIME also allows cross-device buffer sharing since it is
236 based on dma-bufs. 236 based on dma-bufs.
237 237
238 GEM Objects Mapping 238 GEM Objects Mapping
239 ------------------- 239 -------------------
240 240
241 Because mapping operations are fairly heavywei 241 Because mapping operations are fairly heavyweight GEM favours
242 read/write-like access to buffers, implemented 242 read/write-like access to buffers, implemented through driver-specific
243 ioctls, over mapping buffers to userspace. How 243 ioctls, over mapping buffers to userspace. However, when random access
244 to the buffer is needed (to perform software r 244 to the buffer is needed (to perform software rendering for instance),
245 direct access to the object can be more effici 245 direct access to the object can be more efficient.
246 246
247 The mmap system call can't be used directly to 247 The mmap system call can't be used directly to map GEM objects, as they
248 don't have their own file handle. Two alternat 248 don't have their own file handle. Two alternative methods currently
249 co-exist to map GEM objects to userspace. The 249 co-exist to map GEM objects to userspace. The first method uses a
250 driver-specific ioctl to perform the mapping o 250 driver-specific ioctl to perform the mapping operation, calling
251 do_mmap() under the hood. This is often consid 251 do_mmap() under the hood. This is often considered
252 dubious, seems to be discouraged for new GEM-e 252 dubious, seems to be discouraged for new GEM-enabled drivers, and will
253 thus not be described here. 253 thus not be described here.
254 254
255 The second method uses the mmap system call on 255 The second method uses the mmap system call on the DRM file handle. void
256 \*mmap(void \*addr, size_t length, int prot, i 256 \*mmap(void \*addr, size_t length, int prot, int flags, int fd, off_t
257 offset); DRM identifies the GEM object to be m 257 offset); DRM identifies the GEM object to be mapped by a fake offset
258 passed through the mmap offset argument. Prior 258 passed through the mmap offset argument. Prior to being mapped, a GEM
259 object must thus be associated with a fake off 259 object must thus be associated with a fake offset. To do so, drivers
260 must call drm_gem_create_mmap_offset() on the 260 must call drm_gem_create_mmap_offset() on the object.
261 261
262 Once allocated, the fake offset value must be 262 Once allocated, the fake offset value must be passed to the application
263 in a driver-specific way and can then be used 263 in a driver-specific way and can then be used as the mmap offset
264 argument. 264 argument.
265 265
266 The GEM core provides a helper method drm_gem_ 266 The GEM core provides a helper method drm_gem_mmap() to
267 handle object mapping. The method can be set d 267 handle object mapping. The method can be set directly as the mmap file
268 operation handler. It will look up the GEM obj 268 operation handler. It will look up the GEM object based on the offset
269 value and set the VMA operations to the :c:typ 269 value and set the VMA operations to the :c:type:`struct drm_driver
270 <drm_driver>` gem_vm_ops field. Note that drm_ 270 <drm_driver>` gem_vm_ops field. Note that drm_gem_mmap() doesn't map memory to
271 userspace, but relies on the driver-provided f 271 userspace, but relies on the driver-provided fault handler to map pages
272 individually. 272 individually.
273 273
274 To use drm_gem_mmap(), drivers must fill the s 274 To use drm_gem_mmap(), drivers must fill the struct :c:type:`struct drm_driver
275 <drm_driver>` gem_vm_ops field with a pointer 275 <drm_driver>` gem_vm_ops field with a pointer to VM operations.
276 276
277 The VM operations is a :c:type:`struct vm_oper 277 The VM operations is a :c:type:`struct vm_operations_struct <vm_operations_struct>`
278 made up of several fields, the more interestin 278 made up of several fields, the more interesting ones being:
279 279
280 .. code-block:: c 280 .. code-block:: c
281 281
282 struct vm_operations_struct { 282 struct vm_operations_struct {
283 void (*open)(struct vm_area_st 283 void (*open)(struct vm_area_struct * area);
284 void (*close)(struct vm_area_s 284 void (*close)(struct vm_area_struct * area);
285 vm_fault_t (*fault)(struct vm_ 285 vm_fault_t (*fault)(struct vm_fault *vmf);
286 }; 286 };
287 287
288 288
289 The open and close operations must update the 289 The open and close operations must update the GEM object reference
290 count. Drivers can use the drm_gem_vm_open() a 290 count. Drivers can use the drm_gem_vm_open() and drm_gem_vm_close() helper
291 functions directly as open and close handlers. 291 functions directly as open and close handlers.
292 292
293 The fault operation handler is responsible for 293 The fault operation handler is responsible for mapping individual pages
294 to userspace when a page fault occurs. Dependi 294 to userspace when a page fault occurs. Depending on the memory
295 allocation scheme, drivers can allocate pages 295 allocation scheme, drivers can allocate pages at fault time, or can
296 decide to allocate memory for the GEM object a 296 decide to allocate memory for the GEM object at the time the object is
297 created. 297 created.
298 298
299 Drivers that want to map the GEM object upfron 299 Drivers that want to map the GEM object upfront instead of handling page
300 faults can implement their own mmap file opera 300 faults can implement their own mmap file operation handler.
301 301
302 For platforms without MMU the GEM core provide 302 For platforms without MMU the GEM core provides a helper method
303 drm_gem_dma_get_unmapped_area(). The mmap() ro 303 drm_gem_dma_get_unmapped_area(). The mmap() routines will call this to get a
304 proposed address for the mapping. 304 proposed address for the mapping.
305 305
306 To use drm_gem_dma_get_unmapped_area(), driver 306 To use drm_gem_dma_get_unmapped_area(), drivers must fill the struct
307 :c:type:`struct file_operations <file_operatio 307 :c:type:`struct file_operations <file_operations>` get_unmapped_area field with
308 a pointer on drm_gem_dma_get_unmapped_area(). 308 a pointer on drm_gem_dma_get_unmapped_area().
309 309
310 More detailed information about get_unmapped_a 310 More detailed information about get_unmapped_area can be found in
311 Documentation/admin-guide/mm/nommu-mmap.rst 311 Documentation/admin-guide/mm/nommu-mmap.rst
312 312
313 Memory Coherency 313 Memory Coherency
314 ---------------- 314 ----------------
315 315
316 When mapped to the device or used in a command 316 When mapped to the device or used in a command buffer, backing pages for
317 an object are flushed to memory and marked wri 317 an object are flushed to memory and marked write combined so as to be
318 coherent with the GPU. Likewise, if the CPU ac 318 coherent with the GPU. Likewise, if the CPU accesses an object after the
319 GPU has finished rendering to the object, then 319 GPU has finished rendering to the object, then the object must be made
320 coherent with the CPU's view of memory, usuall 320 coherent with the CPU's view of memory, usually involving GPU cache
321 flushing of various kinds. This core CPU<->GPU 321 flushing of various kinds. This core CPU<->GPU coherency management is
322 provided by a device-specific ioctl, which eva 322 provided by a device-specific ioctl, which evaluates an object's current
323 domain and performs any necessary flushing or 323 domain and performs any necessary flushing or synchronization to put the
324 object into the desired coherency domain (note 324 object into the desired coherency domain (note that the object may be
325 busy, i.e. an active render target; in that ca 325 busy, i.e. an active render target; in that case, setting the domain
326 blocks the client and waits for rendering to c 326 blocks the client and waits for rendering to complete before performing
327 any necessary flushing operations). 327 any necessary flushing operations).
328 328
329 Command Execution 329 Command Execution
330 ----------------- 330 -----------------
331 331
332 Perhaps the most important GEM function for GP 332 Perhaps the most important GEM function for GPU devices is providing a
333 command execution interface to clients. Client 333 command execution interface to clients. Client programs construct
334 command buffers containing references to previ 334 command buffers containing references to previously allocated memory
335 objects, and then submit them to GEM. At that 335 objects, and then submit them to GEM. At that point, GEM takes care to
336 bind all the objects into the GTT, execute the 336 bind all the objects into the GTT, execute the buffer, and provide
337 necessary synchronization between clients acce 337 necessary synchronization between clients accessing the same buffers.
338 This often involves evicting some objects from 338 This often involves evicting some objects from the GTT and re-binding
339 others (a fairly expensive operation), and pro 339 others (a fairly expensive operation), and providing relocation support
340 which hides fixed GTT offsets from clients. Cl 340 which hides fixed GTT offsets from clients. Clients must take care not
341 to submit command buffers that reference more 341 to submit command buffers that reference more objects than can fit in
342 the GTT; otherwise, GEM will reject them and n 342 the GTT; otherwise, GEM will reject them and no rendering will occur.
343 Similarly, if several objects in the buffer re 343 Similarly, if several objects in the buffer require fence registers to
344 be allocated for correct rendering (e.g. 2D bl 344 be allocated for correct rendering (e.g. 2D blits on pre-965 chips),
345 care must be taken not to require more fence r 345 care must be taken not to require more fence registers than are
346 available to the client. Such resource managem 346 available to the client. Such resource management should be abstracted
347 from the client in libdrm. 347 from the client in libdrm.
348 348
349 GEM Function Reference 349 GEM Function Reference
350 ---------------------- 350 ----------------------
351 351
352 .. kernel-doc:: include/drm/drm_gem.h 352 .. kernel-doc:: include/drm/drm_gem.h
353 :internal: 353 :internal:
354 354
355 .. kernel-doc:: drivers/gpu/drm/drm_gem.c 355 .. kernel-doc:: drivers/gpu/drm/drm_gem.c
356 :export: 356 :export:
357 357
358 GEM DMA Helper Functions Reference 358 GEM DMA Helper Functions Reference
359 ---------------------------------- 359 ----------------------------------
360 360
361 .. kernel-doc:: drivers/gpu/drm/drm_gem_dma_he 361 .. kernel-doc:: drivers/gpu/drm/drm_gem_dma_helper.c
362 :doc: dma helpers 362 :doc: dma helpers
363 363
364 .. kernel-doc:: include/drm/drm_gem_dma_helper 364 .. kernel-doc:: include/drm/drm_gem_dma_helper.h
365 :internal: 365 :internal:
366 366
367 .. kernel-doc:: drivers/gpu/drm/drm_gem_dma_he 367 .. kernel-doc:: drivers/gpu/drm/drm_gem_dma_helper.c
368 :export: 368 :export:
369 369
370 GEM SHMEM Helper Function Reference 370 GEM SHMEM Helper Function Reference
371 ----------------------------------- 371 -----------------------------------
372 372
373 .. kernel-doc:: drivers/gpu/drm/drm_gem_shmem_ 373 .. kernel-doc:: drivers/gpu/drm/drm_gem_shmem_helper.c
374 :doc: overview 374 :doc: overview
375 375
376 .. kernel-doc:: include/drm/drm_gem_shmem_help 376 .. kernel-doc:: include/drm/drm_gem_shmem_helper.h
377 :internal: 377 :internal:
378 378
379 .. kernel-doc:: drivers/gpu/drm/drm_gem_shmem_ 379 .. kernel-doc:: drivers/gpu/drm/drm_gem_shmem_helper.c
380 :export: 380 :export:
381 381
382 GEM VRAM Helper Functions Reference 382 GEM VRAM Helper Functions Reference
383 ----------------------------------- 383 -----------------------------------
384 384
385 .. kernel-doc:: drivers/gpu/drm/drm_gem_vram_h 385 .. kernel-doc:: drivers/gpu/drm/drm_gem_vram_helper.c
386 :doc: overview 386 :doc: overview
387 387
388 .. kernel-doc:: include/drm/drm_gem_vram_helpe 388 .. kernel-doc:: include/drm/drm_gem_vram_helper.h
389 :internal: 389 :internal:
390 390
391 .. kernel-doc:: drivers/gpu/drm/drm_gem_vram_h 391 .. kernel-doc:: drivers/gpu/drm/drm_gem_vram_helper.c
392 :export: 392 :export:
393 393
394 GEM TTM Helper Functions Reference 394 GEM TTM Helper Functions Reference
395 ----------------------------------- 395 -----------------------------------
396 396
397 .. kernel-doc:: drivers/gpu/drm/drm_gem_ttm_he 397 .. kernel-doc:: drivers/gpu/drm/drm_gem_ttm_helper.c
398 :doc: overview 398 :doc: overview
399 399
400 .. kernel-doc:: drivers/gpu/drm/drm_gem_ttm_he 400 .. kernel-doc:: drivers/gpu/drm/drm_gem_ttm_helper.c
401 :export: 401 :export:
402 402
403 VMA Offset Manager 403 VMA Offset Manager
404 ================== 404 ==================
405 405
406 .. kernel-doc:: drivers/gpu/drm/drm_vma_manage 406 .. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c
407 :doc: vma offset manager 407 :doc: vma offset manager
408 408
409 .. kernel-doc:: include/drm/drm_vma_manager.h 409 .. kernel-doc:: include/drm/drm_vma_manager.h
410 :internal: 410 :internal:
411 411
412 .. kernel-doc:: drivers/gpu/drm/drm_vma_manage 412 .. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c
413 :export: 413 :export:
414 414
415 .. _prime_buffer_sharing: 415 .. _prime_buffer_sharing:
416 416
417 PRIME Buffer Sharing 417 PRIME Buffer Sharing
418 ==================== 418 ====================
419 419
420 PRIME is the cross device buffer sharing frame 420 PRIME is the cross device buffer sharing framework in drm, originally
421 created for the OPTIMUS range of multi-gpu pla 421 created for the OPTIMUS range of multi-gpu platforms. To userspace PRIME
422 buffers are dma-buf based file descriptors. 422 buffers are dma-buf based file descriptors.
423 423
424 Overview and Lifetime Rules 424 Overview and Lifetime Rules
425 --------------------------- 425 ---------------------------
426 426
427 .. kernel-doc:: drivers/gpu/drm/drm_prime.c 427 .. kernel-doc:: drivers/gpu/drm/drm_prime.c
428 :doc: overview and lifetime rules 428 :doc: overview and lifetime rules
429 429
430 PRIME Helper Functions 430 PRIME Helper Functions
431 ---------------------- 431 ----------------------
432 432
433 .. kernel-doc:: drivers/gpu/drm/drm_prime.c 433 .. kernel-doc:: drivers/gpu/drm/drm_prime.c
434 :doc: PRIME Helpers 434 :doc: PRIME Helpers
435 435
436 PRIME Function References 436 PRIME Function References
437 ------------------------- 437 -------------------------
438 438
439 .. kernel-doc:: include/drm/drm_prime.h 439 .. kernel-doc:: include/drm/drm_prime.h
440 :internal: 440 :internal:
441 441
442 .. kernel-doc:: drivers/gpu/drm/drm_prime.c 442 .. kernel-doc:: drivers/gpu/drm/drm_prime.c
443 :export: 443 :export:
444 444
445 DRM MM Range Allocator 445 DRM MM Range Allocator
446 ====================== 446 ======================
447 447
448 Overview 448 Overview
449 -------- 449 --------
450 450
451 .. kernel-doc:: drivers/gpu/drm/drm_mm.c 451 .. kernel-doc:: drivers/gpu/drm/drm_mm.c
452 :doc: Overview 452 :doc: Overview
453 453
454 LRU Scan/Eviction Support 454 LRU Scan/Eviction Support
455 ------------------------- 455 -------------------------
456 456
457 .. kernel-doc:: drivers/gpu/drm/drm_mm.c 457 .. kernel-doc:: drivers/gpu/drm/drm_mm.c
458 :doc: lru scan roster 458 :doc: lru scan roster
459 459
460 DRM MM Range Allocator Function References 460 DRM MM Range Allocator Function References
461 ------------------------------------------ 461 ------------------------------------------
462 462
463 .. kernel-doc:: include/drm/drm_mm.h 463 .. kernel-doc:: include/drm/drm_mm.h
464 :internal: 464 :internal:
465 465
466 .. kernel-doc:: drivers/gpu/drm/drm_mm.c 466 .. kernel-doc:: drivers/gpu/drm/drm_mm.c
467 :export: 467 :export:
468 468
469 .. _drm_gpuvm: 469 .. _drm_gpuvm:
470 470
471 DRM GPUVM 471 DRM GPUVM
472 ========= 472 =========
473 473
474 Overview 474 Overview
475 -------- 475 --------
476 476
477 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c 477 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c
478 :doc: Overview 478 :doc: Overview
479 479
480 Split and Merge 480 Split and Merge
481 --------------- 481 ---------------
482 482
483 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c 483 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c
484 :doc: Split and Merge 484 :doc: Split and Merge
485 485
486 .. _drm_gpuvm_locking: 486 .. _drm_gpuvm_locking:
487 487
488 Locking 488 Locking
489 ------- 489 -------
490 490
491 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c 491 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c
492 :doc: Locking 492 :doc: Locking
493 493
494 Examples 494 Examples
495 -------- 495 --------
496 496
497 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c 497 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c
498 :doc: Examples 498 :doc: Examples
499 499
500 DRM GPUVM Function References 500 DRM GPUVM Function References
501 ----------------------------- 501 -----------------------------
502 502
503 .. kernel-doc:: include/drm/drm_gpuvm.h 503 .. kernel-doc:: include/drm/drm_gpuvm.h
504 :internal: 504 :internal:
505 505
506 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c 506 .. kernel-doc:: drivers/gpu/drm/drm_gpuvm.c
507 :export: 507 :export:
508 508
509 DRM Buddy Allocator 509 DRM Buddy Allocator
510 =================== 510 ===================
511 511
512 DRM Buddy Function References 512 DRM Buddy Function References
513 ----------------------------- 513 -----------------------------
514 514
515 .. kernel-doc:: drivers/gpu/drm/drm_buddy.c 515 .. kernel-doc:: drivers/gpu/drm/drm_buddy.c
516 :export: 516 :export:
517 517
518 DRM Cache Handling and Fast WC memcpy() 518 DRM Cache Handling and Fast WC memcpy()
519 ======================================= 519 =======================================
520 520
521 .. kernel-doc:: drivers/gpu/drm/drm_cache.c 521 .. kernel-doc:: drivers/gpu/drm/drm_cache.c
522 :export: 522 :export:
523 523
524 .. _drm_sync_objects: 524 .. _drm_sync_objects:
525 525
526 DRM Sync Objects 526 DRM Sync Objects
527 ================ 527 ================
528 528
529 .. kernel-doc:: drivers/gpu/drm/drm_syncobj.c 529 .. kernel-doc:: drivers/gpu/drm/drm_syncobj.c
530 :doc: Overview 530 :doc: Overview
531 531
532 .. kernel-doc:: include/drm/drm_syncobj.h 532 .. kernel-doc:: include/drm/drm_syncobj.h
533 :internal: 533 :internal:
534 534
535 .. kernel-doc:: drivers/gpu/drm/drm_syncobj.c 535 .. kernel-doc:: drivers/gpu/drm/drm_syncobj.c
536 :export: 536 :export:
537 537
538 DRM Execution context 538 DRM Execution context
539 ===================== 539 =====================
540 540
541 .. kernel-doc:: drivers/gpu/drm/drm_exec.c 541 .. kernel-doc:: drivers/gpu/drm/drm_exec.c
542 :doc: Overview 542 :doc: Overview
543 543
544 .. kernel-doc:: include/drm/drm_exec.h 544 .. kernel-doc:: include/drm/drm_exec.h
545 :internal: 545 :internal:
546 546
547 .. kernel-doc:: drivers/gpu/drm/drm_exec.c 547 .. kernel-doc:: drivers/gpu/drm/drm_exec.c
548 :export: 548 :export:
549 549
550 GPU Scheduler 550 GPU Scheduler
551 ============= 551 =============
552 552
553 Overview 553 Overview
554 -------- 554 --------
555 555
556 .. kernel-doc:: drivers/gpu/drm/scheduler/sche 556 .. kernel-doc:: drivers/gpu/drm/scheduler/sched_main.c
557 :doc: Overview 557 :doc: Overview
558 558
559 Flow Control 559 Flow Control
560 ------------ 560 ------------
561 561
562 .. kernel-doc:: drivers/gpu/drm/scheduler/sche 562 .. kernel-doc:: drivers/gpu/drm/scheduler/sched_main.c
563 :doc: Flow Control 563 :doc: Flow Control
564 564
565 Scheduler Function References 565 Scheduler Function References
566 ----------------------------- 566 -----------------------------
567 567
568 .. kernel-doc:: include/drm/gpu_scheduler.h 568 .. kernel-doc:: include/drm/gpu_scheduler.h
569 :internal: 569 :internal:
570 570
571 .. kernel-doc:: drivers/gpu/drm/scheduler/sche 571 .. kernel-doc:: drivers/gpu/drm/scheduler/sched_main.c
572 :export: 572 :export:
573 573
574 .. kernel-doc:: drivers/gpu/drm/scheduler/sche 574 .. kernel-doc:: drivers/gpu/drm/scheduler/sched_entity.c
575 :export: 575 :export:
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