arch/mips/kernel/smp-cps.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2013 Imagination Technologies
   4  * Author: Paul Burton <[email protected]>
   5  */
   6
   7 #include <linux/cpu.h>
   8 #include <linux/delay.h>
   9 #include <linux/io.h>
  10 #include <linux/sched/task_stack.h>
  11 #include <linux/sched/hotplug.h>
  12 #include <linux/slab.h>
  13 #include <linux/smp.h>
  14 #include <linux/types.h>
  15
  16 #include <asm/bcache.h>
  17 #include <asm/mips-cps.h>
  18 #include <asm/mips_mt.h>
  19 #include <asm/mipsregs.h>
  20 #include <asm/pm-cps.h>
  21 #include <asm/r4kcache.h>
  22 #include <asm/smp-cps.h>
  23 #include <asm/time.h>
  24 #include <asm/uasm.h>
  25
  26 static bool threads_disabled;
  27 static DECLARE_BITMAP(core_power, NR_CPUS);
  28
  29 struct core_boot_config *mips_cps_core_bootcfg;
  30
  31 static int __init setup_nothreads(char *s)
  32 {
  33         threads_disabled = true;
  34         return 0;
  35 }
  36 early_param("nothreads", setup_nothreads);
  37
  38 static unsigned core_vpe_count(unsigned int cluster, unsigned core)
  39 {
  40         if (threads_disabled)
  41                 return 1;
  42
  43         return mips_cps_numvps(cluster, core);
  44 }
  45
  46 static void __init cps_smp_setup(void)
  47 {
  48         unsigned int nclusters, ncores, nvpes, core_vpes;
  49         unsigned long core_entry;
  50         int cl, c, v;
  51
  52         /* Detect & record VPE topology */
  53         nvpes = 0;
  54         nclusters = mips_cps_numclusters();
  55         pr_info("%s topology ", cpu_has_mips_r6 ? "VP" : "VPE");
  56         for (cl = 0; cl < nclusters; cl++) {
  57                 if (cl > 0)
  58                         pr_cont(",");
  59                 pr_cont("{");
  60
  61                 ncores = mips_cps_numcores(cl);
  62                 for (c = 0; c < ncores; c++) {
  63                         core_vpes = core_vpe_count(cl, c);
  64
  65                         if (c > 0)
  66                                 pr_cont(",");
  67                         pr_cont("%u", core_vpes);
  68
  69                         /* Use the number of VPEs in cluster 0 core 0 for smp_num_siblings */
  70                         if (!cl && !c)
  71                                 smp_num_siblings = core_vpes;
  72
  73                         for (v = 0; v < min_t(int, core_vpes, NR_CPUS - nvpes); v++) {
  74                                 cpu_set_cluster(&cpu_data[nvpes + v], cl);
  75                                 cpu_set_core(&cpu_data[nvpes + v], c);
  76                                 cpu_set_vpe_id(&cpu_data[nvpes + v], v);
  77                         }
  78
  79                         nvpes += core_vpes;
  80                 }
  81
  82                 pr_cont("}");
  83         }
  84         pr_cont(" total %u\n", nvpes);
  85
  86         /* Indicate present CPUs (CPU being synonymous with VPE) */
  87         for (v = 0; v < min_t(unsigned, nvpes, NR_CPUS); v++) {
  88                 set_cpu_possible(v, cpu_cluster(&cpu_data[v]) == 0);
  89                 set_cpu_present(v, cpu_cluster(&cpu_data[v]) == 0);
  90                 __cpu_number_map[v] = v;
  91                 __cpu_logical_map[v] = v;
  92         }
  93
  94         /* Set a coherent default CCA (CWB) */
  95         change_c0_config(CONF_CM_CMASK, 0x5);
  96
  97         /* Core 0 is powered up (we're running on it) */
  98         bitmap_set(core_power, 0, 1);
  99
 100         /* Initialise core 0 */
 101         mips_cps_core_init();
 102
 103         /* Make core 0 coherent with everything */
 104         write_gcr_cl_coherence(0xff);
 105
 106         if (mips_cm_revision() >= CM_REV_CM3) {
 107                 core_entry = CKSEG1ADDR((unsigned long)mips_cps_core_entry);
 108                 write_gcr_bev_base(core_entry);
 109         }
 110
 111 #ifdef CONFIG_MIPS_MT_FPAFF
 112         /* If we have an FPU, enroll ourselves in the FPU-full mask */
 113         if (cpu_has_fpu)
 114                 cpumask_set_cpu(0, &mt_fpu_cpumask);
 115 #endif /* CONFIG_MIPS_MT_FPAFF */
 116 }
 117
 118 static void __init cps_prepare_cpus(unsigned int max_cpus)
 119 {
 120         unsigned ncores, core_vpes, c, cca;
 121         bool cca_unsuitable, cores_limited;
 122         u32 *entry_code;
 123
 124         mips_mt_set_cpuoptions();
 125
 126         /* Detect whether the CCA is unsuited to multi-core SMP */
 127         cca = read_c0_config() & CONF_CM_CMASK;
 128         switch (cca) {
 129         case 0x4: /* CWBE */
 130         case 0x5: /* CWB */
 131                 /* The CCA is coherent, multi-core is fine */
 132                 cca_unsuitable = false;
 133                 break;
 134
 135         default:
 136                 /* CCA is not coherent, multi-core is not usable */
 137                 cca_unsuitable = true;
 138         }
 139
 140         /* Warn the user if the CCA prevents multi-core */
 141         cores_limited = false;
 142         if (cca_unsuitable || cpu_has_dc_aliases) {
 143                 for_each_present_cpu(c) {
 144                         if (cpus_are_siblings(smp_processor_id(), c))
 145                                 continue;
 146
 147                         set_cpu_present(c, false);
 148                         cores_limited = true;
 149                 }
 150         }
 151         if (cores_limited)
 152                 pr_warn("Using only one core due to %s%s%s\n",
 153                         cca_unsuitable ? "unsuitable CCA" : "",
 154                         (cca_unsuitable && cpu_has_dc_aliases) ? " & " : "",
 155                         cpu_has_dc_aliases ? "dcache aliasing" : "");
 156
 157         /*
 158          * Patch the start of mips_cps_core_entry to provide:
 159          *
 160          * s0 = kseg0 CCA
 161          */
 162         entry_code = (u32 *)&mips_cps_core_entry;
 163         uasm_i_addiu(&entry_code, 16, 0, cca);
 164         blast_dcache_range((unsigned long)&mips_cps_core_entry,
 165                            (unsigned long)entry_code);
 166         bc_wback_inv((unsigned long)&mips_cps_core_entry,
 167                      (void *)entry_code - (void *)&mips_cps_core_entry);
 168         __sync();
 169
 170         /* Allocate core boot configuration structs */
 171         ncores = mips_cps_numcores(0);
 172         mips_cps_core_bootcfg = kcalloc(ncores, sizeof(*mips_cps_core_bootcfg),
 173                                         GFP_KERNEL);
 174         if (!mips_cps_core_bootcfg) {
 175                 pr_err("Failed to allocate boot config for %u cores\n", ncores);
 176                 goto err_out;
 177         }
 178
 179         /* Allocate VPE boot configuration structs */
 180         for (c = 0; c < ncores; c++) {
 181                 core_vpes = core_vpe_count(0, c);
 182                 mips_cps_core_bootcfg[c].vpe_config = kcalloc(core_vpes,
 183                                 sizeof(*mips_cps_core_bootcfg[c].vpe_config),
 184                                 GFP_KERNEL);
 185                 if (!mips_cps_core_bootcfg[c].vpe_config) {
 186                         pr_err("Failed to allocate %u VPE boot configs\n",
 187                                core_vpes);
 188                         goto err_out;
 189                 }
 190         }
 191
 192         /* Mark this CPU as booted */
 193         atomic_set(&mips_cps_core_bootcfg[cpu_core(&current_cpu_data)].vpe_mask,
 194                    1 << cpu_vpe_id(&current_cpu_data));
 195
 196         return;
 197 err_out:
 198         /* Clean up allocations */
 199         if (mips_cps_core_bootcfg) {
 200                 for (c = 0; c < ncores; c++)
 201                         kfree(mips_cps_core_bootcfg[c].vpe_config);
 202                 kfree(mips_cps_core_bootcfg);
 203                 mips_cps_core_bootcfg = NULL;
 204         }
 205
 206         /* Effectively disable SMP by declaring CPUs not present */
 207         for_each_possible_cpu(c) {
 208                 if (c == 0)
 209                         continue;
 210                 set_cpu_present(c, false);
 211         }
 212 }
 213
 214 static void boot_core(unsigned int core, unsigned int vpe_id)
 215 {
 216         u32 stat, seq_state;
 217         unsigned timeout;
 218
 219         /* Select the appropriate core */
 220         mips_cm_lock_other(0, core, 0, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
 221
 222         /* Set its reset vector */
 223         write_gcr_co_reset_base(CKSEG1ADDR((unsigned long)mips_cps_core_entry));
 224
 225         /* Ensure its coherency is disabled */
 226         write_gcr_co_coherence(0);
 227
 228         /* Start it with the legacy memory map and exception base */
 229         write_gcr_co_reset_ext_base(CM_GCR_Cx_RESET_EXT_BASE_UEB);
 230
 231         /* Ensure the core can access the GCRs */
 232         set_gcr_access(1 << core);
 233
 234         if (mips_cpc_present()) {
 235                 /* Reset the core */
 236                 mips_cpc_lock_other(core);
 237
 238                 if (mips_cm_revision() >= CM_REV_CM3) {
 239                         /* Run only the requested VP following the reset */
 240                         write_cpc_co_vp_stop(0xf);
 241                         write_cpc_co_vp_run(1 << vpe_id);
 242
 243                         /*
 244                          * Ensure that the VP_RUN register is written before the
 245                          * core leaves reset.
 246                          */
 247                         wmb();
 248                 }
 249
 250                 write_cpc_co_cmd(CPC_Cx_CMD_RESET);
 251
 252                 timeout = 100;
 253                 while (true) {
 254                         stat = read_cpc_co_stat_conf();
 255                         seq_state = stat & CPC_Cx_STAT_CONF_SEQSTATE;
 256                         seq_state >>= __ffs(CPC_Cx_STAT_CONF_SEQSTATE);
 257
 258                         /* U6 == coherent execution, ie. the core is up */
 259                         if (seq_state == CPC_Cx_STAT_CONF_SEQSTATE_U6)
 260                                 break;
 261
 262                         /* Delay a little while before we start warning */
 263                         if (timeout) {
 264                                 timeout--;
 265                                 mdelay(10);
 266                                 continue;
 267                         }
 268
 269                         pr_warn("Waiting for core %u to start... STAT_CONF=0x%x\n",
 270                                 core, stat);
 271                         mdelay(1000);
 272                 }
 273
 274                 mips_cpc_unlock_other();
 275         } else {
 276                 /* Take the core out of reset */
 277                 write_gcr_co_reset_release(0);
 278         }
 279
 280         mips_cm_unlock_other();
 281
 282         /* The core is now powered up */
 283         bitmap_set(core_power, core, 1);
 284 }
 285
 286 static void remote_vpe_boot(void *dummy)
 287 {
 288         unsigned core = cpu_core(&current_cpu_data);
 289         struct core_boot_config *core_cfg = &mips_cps_core_bootcfg[core];
 290
 291         mips_cps_boot_vpes(core_cfg, cpu_vpe_id(&current_cpu_data));
 292 }
 293
 294 static int cps_boot_secondary(int cpu, struct task_struct *idle)
 295 {
 296         unsigned core = cpu_core(&cpu_data[cpu]);
 297         unsigned vpe_id = cpu_vpe_id(&cpu_data[cpu]);
 298         struct core_boot_config *core_cfg = &mips_cps_core_bootcfg[core];
 299         struct vpe_boot_config *vpe_cfg = &core_cfg->vpe_config[vpe_id];
 300         unsigned long core_entry;
 301         unsigned int remote;
 302         int err;
 303
 304         /* We don't yet support booting CPUs in other clusters */
 305         if (cpu_cluster(&cpu_data[cpu]) != cpu_cluster(&raw_current_cpu_data))
 306                 return -ENOSYS;
 307
 308         vpe_cfg->pc = (unsigned long)&smp_bootstrap;
 309         vpe_cfg->sp = __KSTK_TOS(idle);
 310         vpe_cfg->gp = (unsigned long)task_thread_info(idle);
 311
 312         atomic_or(1 << cpu_vpe_id(&cpu_data[cpu]), &core_cfg->vpe_mask);
 313
 314         preempt_disable();
 315
 316         if (!test_bit(core, core_power)) {
 317                 /* Boot a VPE on a powered down core */
 318                 boot_core(core, vpe_id);
 319                 goto out;
 320         }
 321
 322         if (cpu_has_vp) {
 323                 mips_cm_lock_other(0, core, vpe_id, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
 324                 core_entry = CKSEG1ADDR((unsigned long)mips_cps_core_entry);
 325                 write_gcr_co_reset_base(core_entry);
 326                 mips_cm_unlock_other();
 327         }
 328
 329         if (!cpus_are_siblings(cpu, smp_processor_id())) {
 330                 /* Boot a VPE on another powered up core */
 331                 for (remote = 0; remote < NR_CPUS; remote++) {
 332                         if (!cpus_are_siblings(cpu, remote))
 333                                 continue;
 334                         if (cpu_online(remote))
 335                                 break;
 336                 }
 337                 if (remote >= NR_CPUS) {
 338                         pr_crit("No online CPU in core %u to start CPU%d\n",
 339                                 core, cpu);
 340                         goto out;
 341                 }
 342
 343                 err = smp_call_function_single(remote, remote_vpe_boot,
 344                                                NULL, 1);
 345                 if (err)
 346                         panic("Failed to call remote CPU\n");
 347                 goto out;
 348         }
 349
 350         BUG_ON(!cpu_has_mipsmt && !cpu_has_vp);
 351
 352         /* Boot a VPE on this core */
 353         mips_cps_boot_vpes(core_cfg, vpe_id);
 354 out:
 355         preempt_enable();
 356         return 0;
 357 }
 358
 359 static void cps_init_secondary(void)
 360 {
 361         /* Disable MT - we only want to run 1 TC per VPE */
 362         if (cpu_has_mipsmt)
 363                 dmt();
 364
 365         if (mips_cm_revision() >= CM_REV_CM3) {
 366                 unsigned int ident = read_gic_vl_ident();
 367
 368                 /*
 369                  * Ensure that our calculation of the VP ID matches up with
 370                  * what the GIC reports, otherwise we'll have configured
 371                  * interrupts incorrectly.
 372                  */
 373                 BUG_ON(ident != mips_cm_vp_id(smp_processor_id()));
 374         }
 375
 376         if (cpu_has_veic)
 377                 clear_c0_status(ST0_IM);
 378         else
 379                 change_c0_status(ST0_IM, STATUSF_IP2 | STATUSF_IP3 |
 380                                          STATUSF_IP4 | STATUSF_IP5 |
 381                                          STATUSF_IP6 | STATUSF_IP7);
 382 }
 383
 384 static void cps_smp_finish(void)
 385 {
 386         write_c0_compare(read_c0_count() + (8 * mips_hpt_frequency / HZ));
 387
 388 #ifdef CONFIG_MIPS_MT_FPAFF
 389         /* If we have an FPU, enroll ourselves in the FPU-full mask */
 390         if (cpu_has_fpu)
 391                 cpumask_set_cpu(smp_processor_id(), &mt_fpu_cpumask);
 392 #endif /* CONFIG_MIPS_MT_FPAFF */
 393
 394         local_irq_enable();
 395 }
 396
 397 #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_KEXEC)
 398
 399 enum cpu_death {
 400         CPU_DEATH_HALT,
 401         CPU_DEATH_POWER,
 402 };
 403
 404 static void cps_shutdown_this_cpu(enum cpu_death death)
 405 {
 406         unsigned int cpu, core, vpe_id;
 407
 408         cpu = smp_processor_id();
 409         core = cpu_core(&cpu_data[cpu]);
 410
 411         if (death == CPU_DEATH_HALT) {
 412                 vpe_id = cpu_vpe_id(&cpu_data[cpu]);
 413
 414                 pr_debug("Halting core %d VP%d\n", core, vpe_id);
 415                 if (cpu_has_mipsmt) {
 416                         /* Halt this TC */
 417                         write_c0_tchalt(TCHALT_H);
 418                         instruction_hazard();
 419                 } else if (cpu_has_vp) {
 420                         write_cpc_cl_vp_stop(1 << vpe_id);
 421
 422                         /* Ensure that the VP_STOP register is written */
 423                         wmb();
 424                 }
 425         } else {
 426                 pr_debug("Gating power to core %d\n", core);
 427                 /* Power down the core */
 428                 cps_pm_enter_state(CPS_PM_POWER_GATED);
 429         }
 430 }
 431
 432 #ifdef CONFIG_KEXEC
 433
 434 static void cps_kexec_nonboot_cpu(void)
 435 {
 436         if (cpu_has_mipsmt || cpu_has_vp)
 437                 cps_shutdown_this_cpu(CPU_DEATH_HALT);
 438         else
 439                 cps_shutdown_this_cpu(CPU_DEATH_POWER);
 440 }
 441
 442 #endif /* CONFIG_KEXEC */
 443
 444 #endif /* CONFIG_HOTPLUG_CPU || CONFIG_KEXEC */
 445
 446 #ifdef CONFIG_HOTPLUG_CPU
 447
 448 static int cps_cpu_disable(void)
 449 {
 450         unsigned cpu = smp_processor_id();
 451         struct core_boot_config *core_cfg;
 452
 453         if (!cpu)
 454                 return -EBUSY;
 455
 456         if (!cps_pm_support_state(CPS_PM_POWER_GATED))
 457                 return -EINVAL;
 458
 459         core_cfg = &mips_cps_core_bootcfg[cpu_core(&current_cpu_data)];
 460         atomic_sub(1 << cpu_vpe_id(&current_cpu_data), &core_cfg->vpe_mask);
 461         smp_mb__after_atomic();
 462         set_cpu_online(cpu, false);
 463         calculate_cpu_foreign_map();
 464
 465         return 0;
 466 }
 467
 468 static unsigned cpu_death_sibling;
 469 static enum cpu_death cpu_death;
 470
 471 void play_dead(void)
 472 {
 473         unsigned int cpu;
 474
 475         local_irq_disable();
 476         idle_task_exit();
 477         cpu = smp_processor_id();
 478         cpu_death = CPU_DEATH_POWER;
 479
 480         pr_debug("CPU%d going offline\n", cpu);
 481
 482         if (cpu_has_mipsmt || cpu_has_vp) {
 483                 /* Look for another online VPE within the core */
 484                 for_each_online_cpu(cpu_death_sibling) {
 485                         if (!cpus_are_siblings(cpu, cpu_death_sibling))
 486                                 continue;
 487
 488                         /*
 489                          * There is an online VPE within the core. Just halt
 490                          * this TC and leave the core alone.
 491                          */
 492                         cpu_death = CPU_DEATH_HALT;
 493                         break;
 494                 }
 495         }
 496
 497         /* This CPU has chosen its way out */
 498         (void)cpu_report_death();
 499
 500         cps_shutdown_this_cpu(cpu_death);
 501
 502         /* This should never be reached */
 503         panic("Failed to offline CPU %u", cpu);
 504 }
 505
 506 static void wait_for_sibling_halt(void *ptr_cpu)
 507 {
 508         unsigned cpu = (unsigned long)ptr_cpu;
 509         unsigned vpe_id = cpu_vpe_id(&cpu_data[cpu]);
 510         unsigned halted;
 511         unsigned long flags;
 512
 513         do {
 514                 local_irq_save(flags);
 515                 settc(vpe_id);
 516                 halted = read_tc_c0_tchalt();
 517                 local_irq_restore(flags);
 518         } while (!(halted & TCHALT_H));
 519 }
 520
 521 static void cps_cpu_die(unsigned int cpu)
 522 {
 523         unsigned core = cpu_core(&cpu_data[cpu]);
 524         unsigned int vpe_id = cpu_vpe_id(&cpu_data[cpu]);
 525         ktime_t fail_time;
 526         unsigned stat;
 527         int err;
 528
 529         /* Wait for the cpu to choose its way out */
 530         if (!cpu_wait_death(cpu, 5)) {
 531                 pr_err("CPU%u: didn't offline\n", cpu);
 532                 return;
 533         }
 534
 535         /*
 536          * Now wait for the CPU to actually offline. Without doing this that
 537          * offlining may race with one or more of:
 538          *
 539          *   - Onlining the CPU again.
 540          *   - Powering down the core if another VPE within it is offlined.
 541          *   - A sibling VPE entering a non-coherent state.
 542          *
 543          * In the non-MT halt case (ie. infinite loop) the CPU is doing nothing
 544          * with which we could race, so do nothing.
 545          */
 546         if (cpu_death == CPU_DEATH_POWER) {
 547                 /*
 548                  * Wait for the core to enter a powered down or clock gated
 549                  * state, the latter happening when a JTAG probe is connected
 550                  * in which case the CPC will refuse to power down the core.
 551                  */
 552                 fail_time = ktime_add_ms(ktime_get(), 2000);
 553                 do {
 554                         mips_cm_lock_other(0, core, 0, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
 555                         mips_cpc_lock_other(core);
 556                         stat = read_cpc_co_stat_conf();
 557                         stat &= CPC_Cx_STAT_CONF_SEQSTATE;
 558                         stat >>= __ffs(CPC_Cx_STAT_CONF_SEQSTATE);
 559                         mips_cpc_unlock_other();
 560                         mips_cm_unlock_other();
 561
 562                         if (stat == CPC_Cx_STAT_CONF_SEQSTATE_D0 ||
 563                             stat == CPC_Cx_STAT_CONF_SEQSTATE_D2 ||
 564                             stat == CPC_Cx_STAT_CONF_SEQSTATE_U2)
 565                                 break;
 566
 567                         /*
 568                          * The core ought to have powered down, but didn't &
 569                          * now we don't really know what state it's in. It's
 570                          * likely that its _pwr_up pin has been wired to logic
 571                          * 1 & it powered back up as soon as we powered it
 572                          * down...
 573                          *
 574                          * The best we can do is warn the user & continue in
 575                          * the hope that the core is doing nothing harmful &
 576                          * might behave properly if we online it later.
 577                          */
 578                         if (WARN(ktime_after(ktime_get(), fail_time),
 579                                  "CPU%u hasn't powered down, seq. state %u\n",
 580                                  cpu, stat))
 581                                 break;
 582                 } while (1);
 583
 584                 /* Indicate the core is powered off */
 585                 bitmap_clear(core_power, core, 1);
 586         } else if (cpu_has_mipsmt) {
 587                 /*
 588                  * Have a CPU with access to the offlined CPUs registers wait
 589                  * for its TC to halt.
 590                  */
 591                 err = smp_call_function_single(cpu_death_sibling,
 592                                                wait_for_sibling_halt,
 593                                                (void *)(unsigned long)cpu, 1);
 594                 if (err)
 595                         panic("Failed to call remote sibling CPU\n");
 596         } else if (cpu_has_vp) {
 597                 do {
 598                         mips_cm_lock_other(0, core, vpe_id, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
 599                         stat = read_cpc_co_vp_running();
 600                         mips_cm_unlock_other();
 601                 } while (stat & (1 << vpe_id));
 602         }
 603 }
 604
 605 #endif /* CONFIG_HOTPLUG_CPU */
 606
 607 static const struct plat_smp_ops cps_smp_ops = {
 608         .smp_setup              = cps_smp_setup,
 609         .prepare_cpus           = cps_prepare_cpus,
 610         .boot_secondary         = cps_boot_secondary,
 611         .init_secondary         = cps_init_secondary,
 612         .smp_finish             = cps_smp_finish,
 613         .send_ipi_single        = mips_smp_send_ipi_single,
 614         .send_ipi_mask          = mips_smp_send_ipi_mask,
 615 #ifdef CONFIG_HOTPLUG_CPU
 616         .cpu_disable            = cps_cpu_disable,
 617         .cpu_die                = cps_cpu_die,
 618 #endif
 619 #ifdef CONFIG_KEXEC
 620         .kexec_nonboot_cpu      = cps_kexec_nonboot_cpu,
 621 #endif
 622 };
 623
 624 bool mips_cps_smp_in_use(void)
 625 {
 626         extern const struct plat_smp_ops *mp_ops;
 627         return mp_ops == &cps_smp_ops;
 628 }
 629
 630 int register_cps_smp_ops(void)
 631 {
 632         if (!mips_cm_present()) {
 633                 pr_warn("MIPS CPS SMP unable to proceed without a CM\n");
 634                 return -ENODEV;
 635         }
 636
 637         /* check we have a GIC - we need one for IPIs */
 638         if (!(read_gcr_gic_status() & CM_GCR_GIC_STATUS_EX)) {
 639                 pr_warn("MIPS CPS SMP unable to proceed without a GIC\n");
 640                 return -ENODEV;
 641         }
 642
 643         register_smp_ops(&cps_smp_ops);
 644         return 0;
 645 }