drivers/gpu/drm/panfrost/panfrost_gpu.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright 2018 Marty E. Plummer <hanetzer@startmail.com> */
   3 /* Copyright 2019 Linaro, Ltd., Rob Herring <robh@kernel.org> */
   4 /* Copyright 2019 Collabora ltd. */
   5 #include <linux/bitfield.h>
   6 #include <linux/bitmap.h>
   7 #include <linux/delay.h>
   8 #include <linux/dma-mapping.h>
   9 #include <linux/interrupt.h>
  10 #include <linux/io.h>
  11 #include <linux/iopoll.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/pm_runtime.h>
  14
  15 #include "panfrost_device.h"
  16 #include "panfrost_features.h"
  17 #include "panfrost_issues.h"
  18 #include "panfrost_gpu.h"
  19 #include "panfrost_perfcnt.h"
  20 #include "panfrost_regs.h"
  21
  22 static irqreturn_t panfrost_gpu_irq_handler(int irq, void *data)
  23 {
  24         struct panfrost_device *pfdev = data;
  25         u32 fault_status, state;
  26
  27         if (test_bit(PANFROST_COMP_BIT_GPU, pfdev->is_suspended))
  28                 return IRQ_NONE;
  29
  30         fault_status = gpu_read(pfdev, GPU_FAULT_STATUS);
  31         state = gpu_read(pfdev, GPU_INT_STAT);
  32         if (!state)
  33                 return IRQ_NONE;
  34
  35         if (state & GPU_IRQ_MASK_ERROR) {
  36                 u64 address = (u64) gpu_read(pfdev, GPU_FAULT_ADDRESS_HI) << 32;
  37                 address |= gpu_read(pfdev, GPU_FAULT_ADDRESS_LO);
  38
  39                 dev_warn(pfdev->dev, "GPU Fault 0x%08x (%s) at 0x%016llx\n",
  40                          fault_status, panfrost_exception_name(fault_status & 0xFF),
  41                          address);
  42
  43                 if (state & GPU_IRQ_MULTIPLE_FAULT)
  44                         dev_warn(pfdev->dev, "There were multiple GPU faults - some have not been reported\n");
  45
  46                 gpu_write(pfdev, GPU_INT_MASK, 0);
  47         }
  48
  49         if (state & GPU_IRQ_PERFCNT_SAMPLE_COMPLETED)
  50                 panfrost_perfcnt_sample_done(pfdev);
  51
  52         if (state & GPU_IRQ_CLEAN_CACHES_COMPLETED)
  53                 panfrost_perfcnt_clean_cache_done(pfdev);
  54
  55         gpu_write(pfdev, GPU_INT_CLEAR, state);
  56
  57         return IRQ_HANDLED;
  58 }
  59
  60 int panfrost_gpu_soft_reset(struct panfrost_device *pfdev)
  61 {
  62         int ret;
  63         u32 val;
  64
  65         gpu_write(pfdev, GPU_INT_MASK, 0);
  66         gpu_write(pfdev, GPU_INT_CLEAR, GPU_IRQ_RESET_COMPLETED);
  67
  68         clear_bit(PANFROST_COMP_BIT_GPU, pfdev->is_suspended);
  69
  70         gpu_write(pfdev, GPU_CMD, GPU_CMD_SOFT_RESET);
  71         ret = readl_relaxed_poll_timeout(pfdev->iomem + GPU_INT_RAWSTAT,
  72                 val, val & GPU_IRQ_RESET_COMPLETED, 10, 10000);
  73
  74         if (ret) {
  75                 dev_err(pfdev->dev, "gpu soft reset timed out, attempting hard reset\n");
  76
  77                 gpu_write(pfdev, GPU_CMD, GPU_CMD_HARD_RESET);
  78                 ret = readl_relaxed_poll_timeout(pfdev->iomem + GPU_INT_RAWSTAT, val,
  79                                                  val & GPU_IRQ_RESET_COMPLETED, 100, 10000);
  80                 if (ret) {
  81                         dev_err(pfdev->dev, "gpu hard reset timed out\n");
  82                         return ret;
  83                 }
  84         }
  85
  86         gpu_write(pfdev, GPU_INT_CLEAR, GPU_IRQ_MASK_ALL);
  87
  88         /* Only enable the interrupts we care about */
  89         gpu_write(pfdev, GPU_INT_MASK,
  90                   GPU_IRQ_MASK_ERROR |
  91                   GPU_IRQ_PERFCNT_SAMPLE_COMPLETED |
  92                   GPU_IRQ_CLEAN_CACHES_COMPLETED);
  93
  94         /*
  95          * All in-flight jobs should have released their cycle
  96          * counter references upon reset, but let us make sure
  97          */
  98         if (drm_WARN_ON(pfdev->ddev, atomic_read(&pfdev->cycle_counter.use_count) != 0))
  99                 atomic_set(&pfdev->cycle_counter.use_count, 0);
 100
 101         return 0;
 102 }
 103
 104 void panfrost_gpu_amlogic_quirk(struct panfrost_device *pfdev)
 105 {
 106         /*
 107          * The Amlogic integrated Mali-T820, Mali-G31 & Mali-G52 needs
 108          * these undocumented bits in GPU_PWR_OVERRIDE1 to be set in order
 109          * to operate correctly.
 110          */
 111         gpu_write(pfdev, GPU_PWR_KEY, GPU_PWR_KEY_UNLOCK);
 112         gpu_write(pfdev, GPU_PWR_OVERRIDE1, 0xfff | (0x20 << 16));
 113 }
 114
 115 static void panfrost_gpu_init_quirks(struct panfrost_device *pfdev)
 116 {
 117         u32 quirks = 0;
 118
 119         if (panfrost_has_hw_issue(pfdev, HW_ISSUE_8443) ||
 120             panfrost_has_hw_issue(pfdev, HW_ISSUE_11035))
 121                 quirks |= SC_LS_PAUSEBUFFER_DISABLE;
 122
 123         if (panfrost_has_hw_issue(pfdev, HW_ISSUE_10327))
 124                 quirks |= SC_SDC_DISABLE_OQ_DISCARD;
 125
 126         if (panfrost_has_hw_issue(pfdev, HW_ISSUE_10797))
 127                 quirks |= SC_ENABLE_TEXGRD_FLAGS;
 128
 129         if (!panfrost_has_hw_issue(pfdev, GPUCORE_1619)) {
 130                 if (panfrost_model_cmp(pfdev, 0x750) < 0) /* T60x, T62x, T72x */
 131                         quirks |= SC_LS_ATTR_CHECK_DISABLE;
 132                 else if (panfrost_model_cmp(pfdev, 0x880) <= 0) /* T76x, T8xx */
 133                         quirks |= SC_LS_ALLOW_ATTR_TYPES;
 134         }
 135
 136         if (panfrost_has_hw_issue(pfdev, HW_ISSUE_TTRX_2968_TTRX_3162))
 137                 quirks |= SC_VAR_ALGORITHM;
 138
 139         if (panfrost_has_hw_feature(pfdev, HW_FEATURE_TLS_HASHING))
 140                 quirks |= SC_TLS_HASH_ENABLE;
 141
 142         if (quirks)
 143                 gpu_write(pfdev, GPU_SHADER_CONFIG, quirks);
 144
 145
 146         quirks = gpu_read(pfdev, GPU_TILER_CONFIG);
 147
 148         /* Set tiler clock gate override if required */
 149         if (panfrost_has_hw_issue(pfdev, HW_ISSUE_T76X_3953))
 150                 quirks |= TC_CLOCK_GATE_OVERRIDE;
 151
 152         gpu_write(pfdev, GPU_TILER_CONFIG, quirks);
 153
 154
 155         quirks = 0;
 156         if ((panfrost_model_eq(pfdev, 0x860) || panfrost_model_eq(pfdev, 0x880)) &&
 157             pfdev->features.revision >= 0x2000)
 158                 quirks |= JM_MAX_JOB_THROTTLE_LIMIT << JM_JOB_THROTTLE_LIMIT_SHIFT;
 159         else if (panfrost_model_eq(pfdev, 0x6000) &&
 160                  pfdev->features.coherency_features == COHERENCY_ACE)
 161                 quirks |= (COHERENCY_ACE_LITE | COHERENCY_ACE) <<
 162                            JM_FORCE_COHERENCY_FEATURES_SHIFT;
 163
 164         if (panfrost_has_hw_feature(pfdev, HW_FEATURE_IDVS_GROUP_SIZE))
 165                 quirks |= JM_DEFAULT_IDVS_GROUP_SIZE << JM_IDVS_GROUP_SIZE_SHIFT;
 166
 167         if (quirks)
 168                 gpu_write(pfdev, GPU_JM_CONFIG, quirks);
 169
 170         /* Here goes platform specific quirks */
 171         if (pfdev->comp->vendor_quirk)
 172                 pfdev->comp->vendor_quirk(pfdev);
 173 }
 174
 175 #define MAX_HW_REVS 6
 176
 177 struct panfrost_model {
 178         const char *name;
 179         u32 id;
 180         u32 id_mask;
 181         u64 features;
 182         u64 issues;
 183         struct {
 184                 u32 revision;
 185                 u64 issues;
 186         } revs[MAX_HW_REVS];
 187 };
 188
 189 #define GPU_MODEL(_name, _id, ...) \
 190 {\
 191         .name = __stringify(_name),                             \
 192         .id = _id,                                              \
 193         .features = hw_features_##_name,                        \
 194         .issues = hw_issues_##_name,                            \
 195         .revs = { __VA_ARGS__ },                                \
 196 }
 197
 198 #define GPU_REV_EXT(name, _rev, _p, _s, stat) \
 199 {\
 200         .revision = (_rev) << 12 | (_p) << 4 | (_s),            \
 201         .issues = hw_issues_##name##_r##_rev##p##_p##stat,      \
 202 }
 203 #define GPU_REV(name, r, p) GPU_REV_EXT(name, r, p, 0, )
 204
 205 static const struct panfrost_model gpu_models[] = {
 206         /* T60x has an oddball version */
 207         GPU_MODEL(t600, 0x600,
 208                 GPU_REV_EXT(t600, 0, 0, 1, _15dev0)),
 209         GPU_MODEL(t620, 0x620,
 210                 GPU_REV(t620, 0, 1), GPU_REV(t620, 1, 0)),
 211         GPU_MODEL(t720, 0x720),
 212         GPU_MODEL(t760, 0x750,
 213                 GPU_REV(t760, 0, 0), GPU_REV(t760, 0, 1),
 214                 GPU_REV_EXT(t760, 0, 1, 0, _50rel0),
 215                 GPU_REV(t760, 0, 2), GPU_REV(t760, 0, 3)),
 216         GPU_MODEL(t820, 0x820),
 217         GPU_MODEL(t830, 0x830),
 218         GPU_MODEL(t860, 0x860),
 219         GPU_MODEL(t880, 0x880),
 220
 221         GPU_MODEL(g71, 0x6000,
 222                 GPU_REV_EXT(g71, 0, 0, 1, _05dev0)),
 223         GPU_MODEL(g72, 0x6001),
 224         GPU_MODEL(g51, 0x7000),
 225         GPU_MODEL(g76, 0x7001),
 226         GPU_MODEL(g52, 0x7002),
 227         GPU_MODEL(g31, 0x7003,
 228                 GPU_REV(g31, 1, 0)),
 229
 230         GPU_MODEL(g57, 0x9001,
 231                 GPU_REV(g57, 0, 0)),
 232
 233         /* MediaTek MT8192 has a Mali-G57 with a different GPU ID from the
 234          * standard. Arm's driver does not appear to handle this model.
 235          * ChromeOS has a hack downstream for it. Treat it as equivalent to
 236          * standard Mali-G57 for now.
 237          */
 238         GPU_MODEL(g57, 0x9003,
 239                 GPU_REV(g57, 0, 0)),
 240 };
 241
 242 static void panfrost_gpu_init_features(struct panfrost_device *pfdev)
 243 {
 244         u32 gpu_id, num_js, major, minor, status, rev;
 245         const char *name = "unknown";
 246         u64 hw_feat = 0;
 247         u64 hw_issues = hw_issues_all;
 248         const struct panfrost_model *model;
 249         int i;
 250
 251         pfdev->features.l2_features = gpu_read(pfdev, GPU_L2_FEATURES);
 252         pfdev->features.core_features = gpu_read(pfdev, GPU_CORE_FEATURES);
 253         pfdev->features.tiler_features = gpu_read(pfdev, GPU_TILER_FEATURES);
 254         pfdev->features.mem_features = gpu_read(pfdev, GPU_MEM_FEATURES);
 255         pfdev->features.mmu_features = gpu_read(pfdev, GPU_MMU_FEATURES);
 256         pfdev->features.thread_features = gpu_read(pfdev, GPU_THREAD_FEATURES);
 257         pfdev->features.max_threads = gpu_read(pfdev, GPU_THREAD_MAX_THREADS);
 258         pfdev->features.thread_max_workgroup_sz = gpu_read(pfdev, GPU_THREAD_MAX_WORKGROUP_SIZE);
 259         pfdev->features.thread_max_barrier_sz = gpu_read(pfdev, GPU_THREAD_MAX_BARRIER_SIZE);
 260         pfdev->features.coherency_features = gpu_read(pfdev, GPU_COHERENCY_FEATURES);
 261         pfdev->features.afbc_features = gpu_read(pfdev, GPU_AFBC_FEATURES);
 262         for (i = 0; i < 4; i++)
 263                 pfdev->features.texture_features[i] = gpu_read(pfdev, GPU_TEXTURE_FEATURES(i));
 264
 265         pfdev->features.as_present = gpu_read(pfdev, GPU_AS_PRESENT);
 266
 267         pfdev->features.js_present = gpu_read(pfdev, GPU_JS_PRESENT);
 268         num_js = hweight32(pfdev->features.js_present);
 269         for (i = 0; i < num_js; i++)
 270                 pfdev->features.js_features[i] = gpu_read(pfdev, GPU_JS_FEATURES(i));
 271
 272         pfdev->features.shader_present = gpu_read(pfdev, GPU_SHADER_PRESENT_LO);
 273         pfdev->features.shader_present |= (u64)gpu_read(pfdev, GPU_SHADER_PRESENT_HI) << 32;
 274
 275         pfdev->features.tiler_present = gpu_read(pfdev, GPU_TILER_PRESENT_LO);
 276         pfdev->features.tiler_present |= (u64)gpu_read(pfdev, GPU_TILER_PRESENT_HI) << 32;
 277
 278         pfdev->features.l2_present = gpu_read(pfdev, GPU_L2_PRESENT_LO);
 279         pfdev->features.l2_present |= (u64)gpu_read(pfdev, GPU_L2_PRESENT_HI) << 32;
 280         pfdev->features.nr_core_groups = hweight64(pfdev->features.l2_present);
 281
 282         pfdev->features.stack_present = gpu_read(pfdev, GPU_STACK_PRESENT_LO);
 283         pfdev->features.stack_present |= (u64)gpu_read(pfdev, GPU_STACK_PRESENT_HI) << 32;
 284
 285         pfdev->features.thread_tls_alloc = gpu_read(pfdev, GPU_THREAD_TLS_ALLOC);
 286
 287         gpu_id = gpu_read(pfdev, GPU_ID);
 288         pfdev->features.revision = gpu_id & 0xffff;
 289         pfdev->features.id = gpu_id >> 16;
 290
 291         /* The T60x has an oddball ID value. Fix it up to the standard Midgard
 292          * format so we (and userspace) don't have to special case it.
 293          */
 294         if (pfdev->features.id == 0x6956)
 295                 pfdev->features.id = 0x0600;
 296
 297         major = (pfdev->features.revision >> 12) & 0xf;
 298         minor = (pfdev->features.revision >> 4) & 0xff;
 299         status = pfdev->features.revision & 0xf;
 300         rev = pfdev->features.revision;
 301
 302         gpu_id = pfdev->features.id;
 303
 304         for (model = gpu_models; model->name; model++) {
 305                 int best = -1;
 306
 307                 if (!panfrost_model_eq(pfdev, model->id))
 308                         continue;
 309
 310                 name = model->name;
 311                 hw_feat = model->features;
 312                 hw_issues |= model->issues;
 313                 for (i = 0; i < MAX_HW_REVS; i++) {
 314                         if (model->revs[i].revision == rev) {
 315                                 best = i;
 316                                 break;
 317                         } else if (model->revs[i].revision == (rev & ~0xf))
 318                                 best = i;
 319                 }
 320
 321                 if (best >= 0)
 322                         hw_issues |= model->revs[best].issues;
 323
 324                 break;
 325         }
 326
 327         bitmap_from_u64(pfdev->features.hw_features, hw_feat);
 328         bitmap_from_u64(pfdev->features.hw_issues, hw_issues);
 329
 330         dev_info(pfdev->dev, "mali-%s id 0x%x major 0x%x minor 0x%x status 0x%x",
 331                  name, gpu_id, major, minor, status);
 332         dev_info(pfdev->dev, "features: %64pb, issues: %64pb",
 333                  pfdev->features.hw_features,
 334                  pfdev->features.hw_issues);
 335
 336         dev_info(pfdev->dev, "Features: L2:0x%08x Shader:0x%08x Tiler:0x%08x Mem:0x%0x MMU:0x%08x AS:0x%x JS:0x%x",
 337                  pfdev->features.l2_features,
 338                  pfdev->features.core_features,
 339                  pfdev->features.tiler_features,
 340                  pfdev->features.mem_features,
 341                  pfdev->features.mmu_features,
 342                  pfdev->features.as_present,
 343                  pfdev->features.js_present);
 344
 345         dev_info(pfdev->dev, "shader_present=0x%0llx l2_present=0x%0llx",
 346                  pfdev->features.shader_present, pfdev->features.l2_present);
 347 }
 348
 349 void panfrost_cycle_counter_get(struct panfrost_device *pfdev)
 350 {
 351         if (atomic_inc_not_zero(&pfdev->cycle_counter.use_count))
 352                 return;
 353
 354         spin_lock(&pfdev->cycle_counter.lock);
 355         if (atomic_inc_return(&pfdev->cycle_counter.use_count) == 1)
 356                 gpu_write(pfdev, GPU_CMD, GPU_CMD_CYCLE_COUNT_START);
 357         spin_unlock(&pfdev->cycle_counter.lock);
 358 }
 359
 360 void panfrost_cycle_counter_put(struct panfrost_device *pfdev)
 361 {
 362         if (atomic_add_unless(&pfdev->cycle_counter.use_count, -1, 1))
 363                 return;
 364
 365         spin_lock(&pfdev->cycle_counter.lock);
 366         if (atomic_dec_return(&pfdev->cycle_counter.use_count) == 0)
 367                 gpu_write(pfdev, GPU_CMD, GPU_CMD_CYCLE_COUNT_STOP);
 368         spin_unlock(&pfdev->cycle_counter.lock);
 369 }
 370
 371 unsigned long long panfrost_cycle_counter_read(struct panfrost_device *pfdev)
 372 {
 373         u32 hi, lo;
 374
 375         do {
 376                 hi = gpu_read(pfdev, GPU_CYCLE_COUNT_HI);
 377                 lo = gpu_read(pfdev, GPU_CYCLE_COUNT_LO);
 378         } while (hi != gpu_read(pfdev, GPU_CYCLE_COUNT_HI));
 379
 380         return ((u64)hi << 32) | lo;
 381 }
 382
 383 static u64 panfrost_get_core_mask(struct panfrost_device *pfdev)
 384 {
 385         u64 core_mask;
 386
 387         if (pfdev->features.l2_present == 1)
 388                 return U64_MAX;
 389
 390         /*
 391          * Only support one core group now.
 392          * ~(l2_present - 1) unsets all bits in l2_present except
 393          * the bottom bit. (l2_present - 2) has all the bits in
 394          * the first core group set. AND them together to generate
 395          * a mask of cores in the first core group.
 396          */
 397         core_mask = ~(pfdev->features.l2_present - 1) &
 398                      (pfdev->features.l2_present - 2);
 399         dev_info_once(pfdev->dev, "using only 1st core group (%lu cores from %lu)\n",
 400                       hweight64(core_mask),
 401                       hweight64(pfdev->features.shader_present));
 402
 403         return core_mask;
 404 }
 405
 406 void panfrost_gpu_power_on(struct panfrost_device *pfdev)
 407 {
 408         int ret;
 409         u32 val;
 410         u64 core_mask;
 411
 412         panfrost_gpu_init_quirks(pfdev);
 413         core_mask = panfrost_get_core_mask(pfdev);
 414
 415         gpu_write(pfdev, L2_PWRON_LO, pfdev->features.l2_present & core_mask);
 416         ret = readl_relaxed_poll_timeout(pfdev->iomem + L2_READY_LO,
 417                 val, val == (pfdev->features.l2_present & core_mask),
 418                 10, 20000);
 419         if (ret)
 420                 dev_err(pfdev->dev, "error powering up gpu L2");
 421
 422         gpu_write(pfdev, SHADER_PWRON_LO,
 423                   pfdev->features.shader_present & core_mask);
 424         ret = readl_relaxed_poll_timeout(pfdev->iomem + SHADER_READY_LO,
 425                 val, val == (pfdev->features.shader_present & core_mask),
 426                 10, 20000);
 427         if (ret)
 428                 dev_err(pfdev->dev, "error powering up gpu shader");
 429
 430         gpu_write(pfdev, TILER_PWRON_LO, pfdev->features.tiler_present);
 431         ret = readl_relaxed_poll_timeout(pfdev->iomem + TILER_READY_LO,
 432                 val, val == pfdev->features.tiler_present, 10, 1000);
 433         if (ret)
 434                 dev_err(pfdev->dev, "error powering up gpu tiler");
 435 }
 436
 437 void panfrost_gpu_power_off(struct panfrost_device *pfdev)
 438 {
 439         int ret;
 440         u32 val;
 441
 442         gpu_write(pfdev, SHADER_PWROFF_LO, pfdev->features.shader_present);
 443         ret = readl_relaxed_poll_timeout(pfdev->iomem + SHADER_PWRTRANS_LO,
 444                                          val, !val, 1, 2000);
 445         if (ret)
 446                 dev_err(pfdev->dev, "shader power transition timeout");
 447
 448         gpu_write(pfdev, TILER_PWROFF_LO, pfdev->features.tiler_present);
 449         ret = readl_relaxed_poll_timeout(pfdev->iomem + TILER_PWRTRANS_LO,
 450                                          val, !val, 1, 2000);
 451         if (ret)
 452                 dev_err(pfdev->dev, "tiler power transition timeout");
 453
 454         gpu_write(pfdev, L2_PWROFF_LO, pfdev->features.l2_present);
 455         ret = readl_poll_timeout(pfdev->iomem + L2_PWRTRANS_LO,
 456                                  val, !val, 0, 2000);
 457         if (ret)
 458                 dev_err(pfdev->dev, "l2 power transition timeout");
 459 }
 460
 461 void panfrost_gpu_suspend_irq(struct panfrost_device *pfdev)
 462 {
 463         set_bit(PANFROST_COMP_BIT_GPU, pfdev->is_suspended);
 464
 465         gpu_write(pfdev, GPU_INT_MASK, 0);
 466         synchronize_irq(pfdev->gpu_irq);
 467 }
 468
 469 int panfrost_gpu_init(struct panfrost_device *pfdev)
 470 {
 471         int err;
 472
 473         err = panfrost_gpu_soft_reset(pfdev);
 474         if (err)
 475                 return err;
 476
 477         panfrost_gpu_init_features(pfdev);
 478
 479         err = dma_set_mask_and_coherent(pfdev->dev,
 480                 DMA_BIT_MASK(FIELD_GET(0xff00, pfdev->features.mmu_features)));
 481         if (err)
 482                 return err;
 483
 484         dma_set_max_seg_size(pfdev->dev, UINT_MAX);
 485
 486         pfdev->gpu_irq = platform_get_irq_byname(to_platform_device(pfdev->dev), "gpu");
 487         if (pfdev->gpu_irq < 0)
 488                 return pfdev->gpu_irq;
 489
 490         err = devm_request_irq(pfdev->dev, pfdev->gpu_irq, panfrost_gpu_irq_handler,
 491                                IRQF_SHARED, KBUILD_MODNAME "-gpu", pfdev);
 492         if (err) {
 493                 dev_err(pfdev->dev, "failed to request gpu irq");
 494                 return err;
 495         }
 496
 497         panfrost_gpu_power_on(pfdev);
 498
 499         return 0;
 500 }
 501
 502 void panfrost_gpu_fini(struct panfrost_device *pfdev)
 503 {
 504         panfrost_gpu_power_off(pfdev);
 505 }
 506
 507 u32 panfrost_gpu_get_latest_flush_id(struct panfrost_device *pfdev)
 508 {
 509         u32 flush_id;
 510
 511         if (panfrost_has_hw_feature(pfdev, HW_FEATURE_FLUSH_REDUCTION)) {
 512                 /* Flush reduction only makes sense when the GPU is kept powered on between jobs */
 513                 if (pm_runtime_get_if_in_use(pfdev->dev)) {
 514                         flush_id = gpu_read(pfdev, GPU_LATEST_FLUSH_ID);
 515                         pm_runtime_put(pfdev->dev);
 516                         return flush_id;
 517                 }
 518         }
 519
 520         return 0;
 521 }