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 */ 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 */ 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 */ 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 */ 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 } 167 168 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 } 186 187 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 } 204 205 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 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 } 223 224 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 * 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 } 279 280 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 */ 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