1 /* $NetBSD: intel_frontbuffer.c,v 1.3 2021/12/19 12:09:43 riastradh Exp $ */
2
3 /*
4 * Copyright © 2014 Intel Corporation
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice (including the next
14 * paragraph) shall be included in all copies or substantial portions of the
15 * Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
22 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
23 * DEALINGS IN THE SOFTWARE.
24 *
25 * Authors:
26 * Daniel Vetter <daniel.vetter@ffwll.ch>
27 */
28
29 /**
30 * DOC: frontbuffer tracking
31 *
32 * Many features require us to track changes to the currently active
33 * frontbuffer, especially rendering targeted at the frontbuffer.
34 *
35 * To be able to do so we track frontbuffers using a bitmask for all possible
36 * frontbuffer slots through intel_frontbuffer_track(). The functions in this
37 * file are then called when the contents of the frontbuffer are invalidated,
38 * when frontbuffer rendering has stopped again to flush out all the changes
39 * and when the frontbuffer is exchanged with a flip. Subsystems interested in
40 * frontbuffer changes (e.g. PSR, FBC, DRRS) should directly put their callbacks
41 * into the relevant places and filter for the frontbuffer slots that they are
42 * interested int.
43 *
44 * On a high level there are two types of powersaving features. The first one
45 * work like a special cache (FBC and PSR) and are interested when they should
46 * stop caching and when to restart caching. This is done by placing callbacks
47 * into the invalidate and the flush functions: At invalidate the caching must
48 * be stopped and at flush time it can be restarted. And maybe they need to know
49 * when the frontbuffer changes (e.g. when the hw doesn't initiate an invalidate
50 * and flush on its own) which can be achieved with placing callbacks into the
51 * flip functions.
52 *
53 * The other type of display power saving feature only cares about busyness
54 * (e.g. DRRS). In that case all three (invalidate, flush and flip) indicate
55 * busyness. There is no direct way to detect idleness. Instead an idle timer
56 * work delayed work should be started from the flush and flip functions and
57 * cancelled as soon as busyness is detected.
58 */
59
60 #include <sys/cdefs.h>
61 __KERNEL_RCSID(0, "$NetBSD: intel_frontbuffer.c,v 1.3 2021/12/19 12:09:43 riastradh Exp $");
62
63 #include "display/intel_dp.h"
64
65 #include "i915_drv.h"
66 #include "intel_display_types.h"
67 #include "intel_fbc.h"
68 #include "intel_frontbuffer.h"
69 #include "intel_psr.h"
70
71 /**
72 * frontbuffer_flush - flush frontbuffer
73 * @i915: i915 device
74 * @frontbuffer_bits: frontbuffer plane tracking bits
75 * @origin: which operation caused the flush
76 *
77 * This function gets called every time rendering on the given planes has
78 * completed and frontbuffer caching can be started again. Flushes will get
79 * delayed if they're blocked by some outstanding asynchronous rendering.
80 *
81 * Can be called without any locks held.
82 */
frontbuffer_flush(struct drm_i915_private * i915,unsigned int frontbuffer_bits,enum fb_op_origin origin)83 static void frontbuffer_flush(struct drm_i915_private *i915,
84 unsigned int frontbuffer_bits,
85 enum fb_op_origin origin)
86 {
87 /* Delay flushing when rings are still busy.*/
88 spin_lock(&i915->fb_tracking.lock);
89 frontbuffer_bits &= ~i915->fb_tracking.busy_bits;
90 spin_unlock(&i915->fb_tracking.lock);
91
92 if (!frontbuffer_bits)
93 return;
94
95 might_sleep();
96 intel_edp_drrs_flush(i915, frontbuffer_bits);
97 intel_psr_flush(i915, frontbuffer_bits, origin);
98 intel_fbc_flush(i915, frontbuffer_bits, origin);
99 }
100
101 /**
102 * intel_frontbuffer_flip_prepare - prepare asynchronous frontbuffer flip
103 * @i915: i915 device
104 * @frontbuffer_bits: frontbuffer plane tracking bits
105 *
106 * This function gets called after scheduling a flip on @obj. The actual
107 * frontbuffer flushing will be delayed until completion is signalled with
108 * intel_frontbuffer_flip_complete. If an invalidate happens in between this
109 * flush will be cancelled.
110 *
111 * Can be called without any locks held.
112 */
intel_frontbuffer_flip_prepare(struct drm_i915_private * i915,unsigned frontbuffer_bits)113 void intel_frontbuffer_flip_prepare(struct drm_i915_private *i915,
114 unsigned frontbuffer_bits)
115 {
116 spin_lock(&i915->fb_tracking.lock);
117 i915->fb_tracking.flip_bits |= frontbuffer_bits;
118 /* Remove stale busy bits due to the old buffer. */
119 i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
120 spin_unlock(&i915->fb_tracking.lock);
121 }
122
123 /**
124 * intel_frontbuffer_flip_complete - complete asynchronous frontbuffer flip
125 * @i915: i915 device
126 * @frontbuffer_bits: frontbuffer plane tracking bits
127 *
128 * This function gets called after the flip has been latched and will complete
129 * on the next vblank. It will execute the flush if it hasn't been cancelled yet.
130 *
131 * Can be called without any locks held.
132 */
intel_frontbuffer_flip_complete(struct drm_i915_private * i915,unsigned frontbuffer_bits)133 void intel_frontbuffer_flip_complete(struct drm_i915_private *i915,
134 unsigned frontbuffer_bits)
135 {
136 spin_lock(&i915->fb_tracking.lock);
137 /* Mask any cancelled flips. */
138 frontbuffer_bits &= i915->fb_tracking.flip_bits;
139 i915->fb_tracking.flip_bits &= ~frontbuffer_bits;
140 spin_unlock(&i915->fb_tracking.lock);
141
142 if (frontbuffer_bits)
143 frontbuffer_flush(i915, frontbuffer_bits, ORIGIN_FLIP);
144 }
145
146 /**
147 * intel_frontbuffer_flip - synchronous frontbuffer flip
148 * @i915: i915 device
149 * @frontbuffer_bits: frontbuffer plane tracking bits
150 *
151 * This function gets called after scheduling a flip on @obj. This is for
152 * synchronous plane updates which will happen on the next vblank and which will
153 * not get delayed by pending gpu rendering.
154 *
155 * Can be called without any locks held.
156 */
intel_frontbuffer_flip(struct drm_i915_private * i915,unsigned frontbuffer_bits)157 void intel_frontbuffer_flip(struct drm_i915_private *i915,
158 unsigned frontbuffer_bits)
159 {
160 spin_lock(&i915->fb_tracking.lock);
161 /* Remove stale busy bits due to the old buffer. */
162 i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
163 spin_unlock(&i915->fb_tracking.lock);
164
165 frontbuffer_flush(i915, frontbuffer_bits, ORIGIN_FLIP);
166 }
167
__intel_fb_invalidate(struct intel_frontbuffer * front,enum fb_op_origin origin,unsigned int frontbuffer_bits)168 void __intel_fb_invalidate(struct intel_frontbuffer *front,
169 enum fb_op_origin origin,
170 unsigned int frontbuffer_bits)
171 {
172 struct drm_i915_private *i915 = to_i915(front->obj->base.dev);
173
174 if (origin == ORIGIN_CS) {
175 spin_lock(&i915->fb_tracking.lock);
176 i915->fb_tracking.busy_bits |= frontbuffer_bits;
177 i915->fb_tracking.flip_bits &= ~frontbuffer_bits;
178 spin_unlock(&i915->fb_tracking.lock);
179 }
180
181 might_sleep();
182 intel_psr_invalidate(i915, frontbuffer_bits, origin);
183 intel_edp_drrs_invalidate(i915, frontbuffer_bits);
184 intel_fbc_invalidate(i915, frontbuffer_bits, origin);
185 }
186
__intel_fb_flush(struct intel_frontbuffer * front,enum fb_op_origin origin,unsigned int frontbuffer_bits)187 void __intel_fb_flush(struct intel_frontbuffer *front,
188 enum fb_op_origin origin,
189 unsigned int frontbuffer_bits)
190 {
191 struct drm_i915_private *i915 = to_i915(front->obj->base.dev);
192
193 if (origin == ORIGIN_CS) {
194 spin_lock(&i915->fb_tracking.lock);
195 /* Filter out new bits since rendering started. */
196 frontbuffer_bits &= i915->fb_tracking.busy_bits;
197 i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
198 spin_unlock(&i915->fb_tracking.lock);
199 }
200
201 if (frontbuffer_bits)
202 frontbuffer_flush(i915, frontbuffer_bits, origin);
203 }
204
frontbuffer_active(struct i915_active * ref)205 static int frontbuffer_active(struct i915_active *ref)
206 {
207 struct intel_frontbuffer *front =
208 container_of(ref, typeof(*front), write);
209
210 kref_get(&front->ref);
211 return 0;
212 }
213
214 __i915_active_call
frontbuffer_retire(struct i915_active * ref)215 static void frontbuffer_retire(struct i915_active *ref)
216 {
217 struct intel_frontbuffer *front =
218 container_of(ref, typeof(*front), write);
219
220 intel_frontbuffer_flush(front, ORIGIN_CS);
221 intel_frontbuffer_put(front);
222 }
223
frontbuffer_release(struct kref * ref)224 static void frontbuffer_release(struct kref *ref)
225 __releases(&to_i915(front->obj->base.dev)->fb_tracking.lock)
226 {
227 struct intel_frontbuffer *front =
228 container_of(ref, typeof(*front), ref);
229 struct drm_i915_gem_object *obj = front->obj;
230 struct i915_vma *vma;
231
232 spin_lock(&obj->vma.lock);
233 for_each_ggtt_vma(vma, obj)
234 vma->display_alignment = I915_GTT_MIN_ALIGNMENT;
235 spin_unlock(&obj->vma.lock);
236
237 RCU_INIT_POINTER(obj->frontbuffer, NULL);
238 spin_unlock(&to_i915(obj->base.dev)->fb_tracking.lock);
239
240 i915_gem_object_put(obj);
241 i915_active_fini(&front->write);
242 kfree_rcu(front, rcu);
243 }
244
245 struct intel_frontbuffer *
intel_frontbuffer_get(struct drm_i915_gem_object * obj)246 intel_frontbuffer_get(struct drm_i915_gem_object *obj)
247 {
248 struct drm_i915_private *i915 = to_i915(obj->base.dev);
249 struct intel_frontbuffer *front;
250
251 front = __intel_frontbuffer_get(obj);
252 if (front)
253 return front;
254
255 front = kmalloc(sizeof(*front), GFP_KERNEL);
256 if (!front)
257 return NULL;
258
259 front->obj = obj;
260 kref_init(&front->ref);
261 atomic_set(&front->bits, 0);
262 i915_active_init(&front->write,
263 frontbuffer_active,
264 i915_active_may_sleep(frontbuffer_retire));
265
266 spin_lock(&i915->fb_tracking.lock);
267 if (rcu_access_pointer(obj->frontbuffer)) {
268 kfree(front);
269 front = rcu_dereference_protected(obj->frontbuffer, true);
270 kref_get(&front->ref);
271 } else {
272 i915_gem_object_get(obj);
273 rcu_assign_pointer(obj->frontbuffer, front);
274 }
275 spin_unlock(&i915->fb_tracking.lock);
276
277 return front;
278 }
279
intel_frontbuffer_put(struct intel_frontbuffer * front)280 void intel_frontbuffer_put(struct intel_frontbuffer *front)
281 {
282 kref_put_lock(&front->ref,
283 frontbuffer_release,
284 &to_i915(front->obj->base.dev)->fb_tracking.lock);
285 }
286
287 /**
288 * intel_frontbuffer_track - update frontbuffer tracking
289 * @old: current buffer for the frontbuffer slots
290 * @new: new buffer for the frontbuffer slots
291 * @frontbuffer_bits: bitmask of frontbuffer slots
292 *
293 * This updates the frontbuffer tracking bits @frontbuffer_bits by clearing them
294 * from @old and setting them in @new. Both @old and @new can be NULL.
295 */
intel_frontbuffer_track(struct intel_frontbuffer * old,struct intel_frontbuffer * new,unsigned int frontbuffer_bits)296 void intel_frontbuffer_track(struct intel_frontbuffer *old,
297 struct intel_frontbuffer *new,
298 unsigned int frontbuffer_bits)
299 {
300 /*
301 * Control of individual bits within the mask are guarded by
302 * the owning plane->mutex, i.e. we can never see concurrent
303 * manipulation of individual bits. But since the bitfield as a whole
304 * is updated using RMW, we need to use atomics in order to update
305 * the bits.
306 */
307 BUILD_BUG_ON(INTEL_FRONTBUFFER_BITS_PER_PIPE * I915_MAX_PIPES >
308 BITS_PER_TYPE(atomic_t));
309
310 if (old) {
311 WARN_ON(!(atomic_read(&old->bits) & frontbuffer_bits));
312 atomic_andnot(frontbuffer_bits, &old->bits);
313 }
314
315 if (new) {
316 WARN_ON(atomic_read(&new->bits) & frontbuffer_bits);
317 atomic_or(frontbuffer_bits, &new->bits);
318 }
319 }
320