drivers/firmware/psci.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License version 2 as
   4  * published by the Free Software Foundation.
   5  *
   6  * This program is distributed in the hope that it will be useful,
   7  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   8  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9  * GNU General Public License for more details.
  10  *
  11  * Copyright (C) 2015 ARM Limited
  12  */
  13
  14 #define pr_fmt(fmt) "psci: " fmt
  15
  16 #include <linux/acpi.h>
  17 #include <linux/arm-smccc.h>
  18 #include <linux/cpuidle.h>
  19 #include <linux/errno.h>
  20 #include <linux/linkage.h>
  21 #include <linux/of.h>
  22 #include <linux/pm.h>
  23 #include <linux/printk.h>
  24 #include <linux/psci.h>
  25 #include <linux/reboot.h>
  26 #include <linux/slab.h>
  27 #include <linux/suspend.h>
  28
  29 #include <uapi/linux/psci.h>
  30
  31 #include <asm/cpuidle.h>
  32 #include <asm/cputype.h>
  33 #include <asm/system_misc.h>
  34 #include <asm/smp_plat.h>
  35 #include <asm/suspend.h>
  36
  37 /*
  38  * While a 64-bit OS can make calls with SMC32 calling conventions, for some
  39  * calls it is necessary to use SMC64 to pass or return 64-bit values.
  40  * For such calls PSCI_FN_NATIVE(version, name) will choose the appropriate
  41  * (native-width) function ID.
  42  */
  43 #ifdef CONFIG_64BIT
  44 #define PSCI_FN_NATIVE(version, name)   PSCI_##version##_FN64_##name
  45 #else
  46 #define PSCI_FN_NATIVE(version, name)   PSCI_##version##_FN_##name
  47 #endif
  48
  49 /*
  50  * The CPU any Trusted OS is resident on. The trusted OS may reject CPU_OFF
  51  * calls to its resident CPU, so we must avoid issuing those. We never migrate
  52  * a Trusted OS even if it claims to be capable of migration -- doing so will
  53  * require cooperation with a Trusted OS driver.
  54  */
  55 static int resident_cpu = -1;
  56
  57 bool psci_tos_resident_on(int cpu)
  58 {
  59         return cpu == resident_cpu;
  60 }
  61
  62 struct psci_operations psci_ops = {
  63         .conduit = PSCI_CONDUIT_NONE,
  64         .smccc_version = SMCCC_VERSION_1_0,
  65 };
  66
  67 typedef unsigned long (psci_fn)(unsigned long, unsigned long,
  68                                 unsigned long, unsigned long);
  69 static psci_fn *invoke_psci_fn;
  70
  71 enum psci_function {
  72         PSCI_FN_CPU_SUSPEND,
  73         PSCI_FN_CPU_ON,
  74         PSCI_FN_CPU_OFF,
  75         PSCI_FN_MIGRATE,
  76         PSCI_FN_MAX,
  77 };
  78
  79 static u32 psci_function_id[PSCI_FN_MAX];
  80
  81 #define PSCI_0_2_POWER_STATE_MASK               \
  82                                 (PSCI_0_2_POWER_STATE_ID_MASK | \
  83                                 PSCI_0_2_POWER_STATE_TYPE_MASK | \
  84                                 PSCI_0_2_POWER_STATE_AFFL_MASK)
  85
  86 #define PSCI_1_0_EXT_POWER_STATE_MASK           \
  87                                 (PSCI_1_0_EXT_POWER_STATE_ID_MASK | \
  88                                 PSCI_1_0_EXT_POWER_STATE_TYPE_MASK)
  89
  90 static u32 psci_cpu_suspend_feature;
  91
  92 static inline bool psci_has_ext_power_state(void)
  93 {
  94         return psci_cpu_suspend_feature &
  95                                 PSCI_1_0_FEATURES_CPU_SUSPEND_PF_MASK;
  96 }
  97
  98 static inline bool psci_power_state_loses_context(u32 state)
  99 {
 100         const u32 mask = psci_has_ext_power_state() ?
 101                                         PSCI_1_0_EXT_POWER_STATE_TYPE_MASK :
 102                                         PSCI_0_2_POWER_STATE_TYPE_MASK;
 103
 104         return state & mask;
 105 }
 106
 107 static inline bool psci_power_state_is_valid(u32 state)
 108 {
 109         const u32 valid_mask = psci_has_ext_power_state() ?
 110                                PSCI_1_0_EXT_POWER_STATE_MASK :
 111                                PSCI_0_2_POWER_STATE_MASK;
 112
 113         return !(state & ~valid_mask);
 114 }
 115
 116 static unsigned long __invoke_psci_fn_hvc(unsigned long function_id,
 117                         unsigned long arg0, unsigned long arg1,
 118                         unsigned long arg2)
 119 {
 120         struct arm_smccc_res res;
 121
 122         arm_smccc_hvc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
 123         return res.a0;
 124 }
 125
 126 static unsigned long __invoke_psci_fn_smc(unsigned long function_id,
 127                         unsigned long arg0, unsigned long arg1,
 128                         unsigned long arg2)
 129 {
 130         struct arm_smccc_res res;
 131
 132         arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
 133         return res.a0;
 134 }
 135
 136 static int psci_to_linux_errno(int errno)
 137 {
 138         switch (errno) {
 139         case PSCI_RET_SUCCESS:
 140                 return 0;
 141         case PSCI_RET_NOT_SUPPORTED:
 142                 return -EOPNOTSUPP;
 143         case PSCI_RET_INVALID_PARAMS:
 144         case PSCI_RET_INVALID_ADDRESS:
 145                 return -EINVAL;
 146         case PSCI_RET_DENIED:
 147                 return -EPERM;
 148         };
 149
 150         return -EINVAL;
 151 }
 152
 153 static u32 psci_get_version(void)
 154 {
 155         return invoke_psci_fn(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
 156 }
 157
 158 static int psci_cpu_suspend(u32 state, unsigned long entry_point)
 159 {
 160         int err;
 161         u32 fn;
 162
 163         fn = psci_function_id[PSCI_FN_CPU_SUSPEND];
 164         err = invoke_psci_fn(fn, state, entry_point, 0);
 165         return psci_to_linux_errno(err);
 166 }
 167
 168 static int psci_cpu_off(u32 state)
 169 {
 170         int err;
 171         u32 fn;
 172
 173         fn = psci_function_id[PSCI_FN_CPU_OFF];
 174         err = invoke_psci_fn(fn, state, 0, 0);
 175         return psci_to_linux_errno(err);
 176 }
 177
 178 static int psci_cpu_on(unsigned long cpuid, unsigned long entry_point)
 179 {
 180         int err;
 181         u32 fn;
 182
 183         fn = psci_function_id[PSCI_FN_CPU_ON];
 184         err = invoke_psci_fn(fn, cpuid, entry_point, 0);
 185         return psci_to_linux_errno(err);
 186 }
 187
 188 static int psci_migrate(unsigned long cpuid)
 189 {
 190         int err;
 191         u32 fn;
 192
 193         fn = psci_function_id[PSCI_FN_MIGRATE];
 194         err = invoke_psci_fn(fn, cpuid, 0, 0);
 195         return psci_to_linux_errno(err);
 196 }
 197
 198 static int psci_affinity_info(unsigned long target_affinity,
 199                 unsigned long lowest_affinity_level)
 200 {
 201         return invoke_psci_fn(PSCI_FN_NATIVE(0_2, AFFINITY_INFO),
 202                               target_affinity, lowest_affinity_level, 0);
 203 }
 204
 205 static int psci_migrate_info_type(void)
 206 {
 207         return invoke_psci_fn(PSCI_0_2_FN_MIGRATE_INFO_TYPE, 0, 0, 0);
 208 }
 209
 210 static unsigned long psci_migrate_info_up_cpu(void)
 211 {
 212         return invoke_psci_fn(PSCI_FN_NATIVE(0_2, MIGRATE_INFO_UP_CPU),
 213                               0, 0, 0);
 214 }
 215
 216 static void set_conduit(enum psci_conduit conduit)
 217 {
 218         switch (conduit) {
 219         case PSCI_CONDUIT_HVC:
 220                 invoke_psci_fn = __invoke_psci_fn_hvc;
 221                 break;
 222         case PSCI_CONDUIT_SMC:
 223                 invoke_psci_fn = __invoke_psci_fn_smc;
 224                 break;
 225         default:
 226                 WARN(1, "Unexpected PSCI conduit %d\n", conduit);
 227         }
 228
 229         psci_ops.conduit = conduit;
 230 }
 231
 232 static int get_set_conduit_method(struct device_node *np)
 233 {
 234         const char *method;
 235
 236         pr_info("probing for conduit method from DT.\n");
 237
 238         if (of_property_read_string(np, "method", &method)) {
 239                 pr_warn("missing \"method\" property\n");
 240                 return -ENXIO;
 241         }
 242
 243         if (!strcmp("hvc", method)) {
 244                 set_conduit(PSCI_CONDUIT_HVC);
 245         } else if (!strcmp("smc", method)) {
 246                 set_conduit(PSCI_CONDUIT_SMC);
 247         } else {
 248                 pr_warn("invalid \"method\" property: %s\n", method);
 249                 return -EINVAL;
 250         }
 251         return 0;
 252 }
 253
 254 static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
 255 {
 256         invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
 257 }
 258
 259 static void psci_sys_poweroff(void)
 260 {
 261         invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
 262 }
 263
 264 static int __init psci_features(u32 psci_func_id)
 265 {
 266         return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
 267                               psci_func_id, 0, 0);
 268 }
 269
 270 #ifdef CONFIG_CPU_IDLE
 271 static DEFINE_PER_CPU_READ_MOSTLY(u32 *, psci_power_state);
 272
 273 static int psci_dt_cpu_init_idle(struct device_node *cpu_node, int cpu)
 274 {
 275         int i, ret, count = 0;
 276         u32 *psci_states;
 277         struct device_node *state_node;
 278
 279         /* Count idle states */
 280         while ((state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
 281                                               count))) {
 282                 count++;
 283                 of_node_put(state_node);
 284         }
 285
 286         if (!count)
 287                 return -ENODEV;
 288
 289         psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
 290         if (!psci_states)
 291                 return -ENOMEM;
 292
 293         for (i = 0; i < count; i++) {
 294                 u32 state;
 295
 296                 state_node = of_parse_phandle(cpu_node, "cpu-idle-states", i);
 297
 298                 ret = of_property_read_u32(state_node,
 299                                            "arm,psci-suspend-param",
 300                                            &state);
 301                 if (ret) {
 302                         pr_warn(" * %pOF missing arm,psci-suspend-param property\n",
 303                                 state_node);
 304                         of_node_put(state_node);
 305                         goto free_mem;
 306                 }
 307
 308                 of_node_put(state_node);
 309                 pr_debug("psci-power-state %#x index %d\n", state, i);
 310                 if (!psci_power_state_is_valid(state)) {
 311                         pr_warn("Invalid PSCI power state %#x\n", state);
 312                         ret = -EINVAL;
 313                         goto free_mem;
 314                 }
 315                 psci_states[i] = state;
 316         }
 317         /* Idle states parsed correctly, initialize per-cpu pointer */
 318         per_cpu(psci_power_state, cpu) = psci_states;
 319         return 0;
 320
 321 free_mem:
 322         kfree(psci_states);
 323         return ret;
 324 }
 325
 326 #ifdef CONFIG_ACPI
 327 #include <acpi/processor.h>
 328
 329 static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
 330 {
 331         int i, count;
 332         u32 *psci_states;
 333         struct acpi_lpi_state *lpi;
 334         struct acpi_processor *pr = per_cpu(processors, cpu);
 335
 336         if (unlikely(!pr || !pr->flags.has_lpi))
 337                 return -EINVAL;
 338
 339         count = pr->power.count - 1;
 340         if (count <= 0)
 341                 return -ENODEV;
 342
 343         psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
 344         if (!psci_states)
 345                 return -ENOMEM;
 346
 347         for (i = 0; i < count; i++) {
 348                 u32 state;
 349
 350                 lpi = &pr->power.lpi_states[i + 1];
 351                 /*
 352                  * Only bits[31:0] represent a PSCI power_state while
 353                  * bits[63:32] must be 0x0 as per ARM ACPI FFH Specification
 354                  */
 355                 state = lpi->address;
 356                 if (!psci_power_state_is_valid(state)) {
 357                         pr_warn("Invalid PSCI power state %#x\n", state);
 358                         kfree(psci_states);
 359                         return -EINVAL;
 360                 }
 361                 psci_states[i] = state;
 362         }
 363         /* Idle states parsed correctly, initialize per-cpu pointer */
 364         per_cpu(psci_power_state, cpu) = psci_states;
 365         return 0;
 366 }
 367 #else
 368 static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
 369 {
 370         return -EINVAL;
 371 }
 372 #endif
 373
 374 int psci_cpu_init_idle(unsigned int cpu)
 375 {
 376         struct device_node *cpu_node;
 377         int ret;
 378
 379         /*
 380          * If the PSCI cpu_suspend function hook has not been initialized
 381          * idle states must not be enabled, so bail out
 382          */
 383         if (!psci_ops.cpu_suspend)
 384                 return -EOPNOTSUPP;
 385
 386         if (!acpi_disabled)
 387                 return psci_acpi_cpu_init_idle(cpu);
 388
 389         cpu_node = of_get_cpu_node(cpu, NULL);
 390         if (!cpu_node)
 391                 return -ENODEV;
 392
 393         ret = psci_dt_cpu_init_idle(cpu_node, cpu);
 394
 395         of_node_put(cpu_node);
 396
 397         return ret;
 398 }
 399
 400 static int psci_suspend_finisher(unsigned long index)
 401 {
 402         u32 *state = __this_cpu_read(psci_power_state);
 403
 404         return psci_ops.cpu_suspend(state[index - 1],
 405                                     __pa_symbol(cpu_resume));
 406 }
 407
 408 int psci_cpu_suspend_enter(unsigned long index)
 409 {
 410         int ret;
 411         u32 *state = __this_cpu_read(psci_power_state);
 412         /*
 413          * idle state index 0 corresponds to wfi, should never be called
 414          * from the cpu_suspend operations
 415          */
 416         if (WARN_ON_ONCE(!index))
 417                 return -EINVAL;
 418
 419         if (!psci_power_state_loses_context(state[index - 1]))
 420                 ret = psci_ops.cpu_suspend(state[index - 1], 0);
 421         else
 422                 ret = cpu_suspend(index, psci_suspend_finisher);
 423
 424         return ret;
 425 }
 426
 427 /* ARM specific CPU idle operations */
 428 #ifdef CONFIG_ARM
 429 static const struct cpuidle_ops psci_cpuidle_ops __initconst = {
 430         .suspend = psci_cpu_suspend_enter,
 431         .init = psci_dt_cpu_init_idle,
 432 };
 433
 434 CPUIDLE_METHOD_OF_DECLARE(psci, "psci", &psci_cpuidle_ops);
 435 #endif
 436 #endif
 437
 438 static int psci_system_suspend(unsigned long unused)
 439 {
 440         return invoke_psci_fn(PSCI_FN_NATIVE(1_0, SYSTEM_SUSPEND),
 441                               __pa_symbol(cpu_resume), 0, 0);
 442 }
 443
 444 static int psci_system_suspend_enter(suspend_state_t state)
 445 {
 446         return cpu_suspend(0, psci_system_suspend);
 447 }
 448
 449 static const struct platform_suspend_ops psci_suspend_ops = {
 450         .valid          = suspend_valid_only_mem,
 451         .enter          = psci_system_suspend_enter,
 452 };
 453
 454 static void __init psci_init_system_suspend(void)
 455 {
 456         int ret;
 457
 458         if (!IS_ENABLED(CONFIG_SUSPEND))
 459                 return;
 460
 461         ret = psci_features(PSCI_FN_NATIVE(1_0, SYSTEM_SUSPEND));
 462
 463         if (ret != PSCI_RET_NOT_SUPPORTED)
 464                 suspend_set_ops(&psci_suspend_ops);
 465 }
 466
 467 static void __init psci_init_cpu_suspend(void)
 468 {
 469         int feature = psci_features(psci_function_id[PSCI_FN_CPU_SUSPEND]);
 470
 471         if (feature != PSCI_RET_NOT_SUPPORTED)
 472                 psci_cpu_suspend_feature = feature;
 473 }
 474
 475 /*
 476  * Detect the presence of a resident Trusted OS which may cause CPU_OFF to
 477  * return DENIED (which would be fatal).
 478  */
 479 static void __init psci_init_migrate(void)
 480 {
 481         unsigned long cpuid;
 482         int type, cpu = -1;
 483
 484         type = psci_ops.migrate_info_type();
 485
 486         if (type == PSCI_0_2_TOS_MP) {
 487                 pr_info("Trusted OS migration not required\n");
 488                 return;
 489         }
 490
 491         if (type == PSCI_RET_NOT_SUPPORTED) {
 492                 pr_info("MIGRATE_INFO_TYPE not supported.\n");
 493                 return;
 494         }
 495
 496         if (type != PSCI_0_2_TOS_UP_MIGRATE &&
 497             type != PSCI_0_2_TOS_UP_NO_MIGRATE) {
 498                 pr_err("MIGRATE_INFO_TYPE returned unknown type (%d)\n", type);
 499                 return;
 500         }
 501
 502         cpuid = psci_migrate_info_up_cpu();
 503         if (cpuid & ~MPIDR_HWID_BITMASK) {
 504                 pr_warn("MIGRATE_INFO_UP_CPU reported invalid physical ID (0x%lx)\n",
 505                         cpuid);
 506                 return;
 507         }
 508
 509         cpu = get_logical_index(cpuid);
 510         resident_cpu = cpu >= 0 ? cpu : -1;
 511
 512         pr_info("Trusted OS resident on physical CPU 0x%lx\n", cpuid);
 513 }
 514
 515 static void __init psci_init_smccc(void)
 516 {
 517         u32 ver = ARM_SMCCC_VERSION_1_0;
 518         int feature;
 519
 520         feature = psci_features(ARM_SMCCC_VERSION_FUNC_ID);
 521
 522         if (feature != PSCI_RET_NOT_SUPPORTED) {
 523                 u32 ret;
 524                 ret = invoke_psci_fn(ARM_SMCCC_VERSION_FUNC_ID, 0, 0, 0);
 525                 if (ret == ARM_SMCCC_VERSION_1_1) {
 526                         psci_ops.smccc_version = SMCCC_VERSION_1_1;
 527                         ver = ret;
 528                 }
 529         }
 530
 531         /*
 532          * Conveniently, the SMCCC and PSCI versions are encoded the
 533          * same way. No, this isn't accidental.
 534          */
 535         pr_info("SMC Calling Convention v%d.%d\n",
 536                 PSCI_VERSION_MAJOR(ver), PSCI_VERSION_MINOR(ver));
 537
 538 }
 539
 540 static void __init psci_0_2_set_functions(void)
 541 {
 542         pr_info("Using standard PSCI v0.2 function IDs\n");
 543         psci_ops.get_version = psci_get_version;
 544
 545         psci_function_id[PSCI_FN_CPU_SUSPEND] =
 546                                         PSCI_FN_NATIVE(0_2, CPU_SUSPEND);
 547         psci_ops.cpu_suspend = psci_cpu_suspend;
 548
 549         psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
 550         psci_ops.cpu_off = psci_cpu_off;
 551
 552         psci_function_id[PSCI_FN_CPU_ON] = PSCI_FN_NATIVE(0_2, CPU_ON);
 553         psci_ops.cpu_on = psci_cpu_on;
 554
 555         psci_function_id[PSCI_FN_MIGRATE] = PSCI_FN_NATIVE(0_2, MIGRATE);
 556         psci_ops.migrate = psci_migrate;
 557
 558         psci_ops.affinity_info = psci_affinity_info;
 559
 560         psci_ops.migrate_info_type = psci_migrate_info_type;
 561
 562         arm_pm_restart = psci_sys_reset;
 563
 564         pm_power_off = psci_sys_poweroff;
 565 }
 566
 567 /*
 568  * Probe function for PSCI firmware versions >= 0.2
 569  */
 570 static int __init psci_probe(void)
 571 {
 572         u32 ver = psci_get_version();
 573
 574         pr_info("PSCIv%d.%d detected in firmware.\n",
 575                         PSCI_VERSION_MAJOR(ver),
 576                         PSCI_VERSION_MINOR(ver));
 577
 578         if (PSCI_VERSION_MAJOR(ver) == 0 && PSCI_VERSION_MINOR(ver) < 2) {
 579                 pr_err("Conflicting PSCI version detected.\n");
 580                 return -EINVAL;
 581         }
 582
 583         psci_0_2_set_functions();
 584
 585         psci_init_migrate();
 586
 587         if (PSCI_VERSION_MAJOR(ver) >= 1) {
 588                 psci_init_smccc();
 589                 psci_init_cpu_suspend();
 590                 psci_init_system_suspend();
 591         }
 592
 593         return 0;
 594 }
 595
 596 typedef int (*psci_initcall_t)(const struct device_node *);
 597
 598 /*
 599  * PSCI init function for PSCI versions >=0.2
 600  *
 601  * Probe based on PSCI PSCI_VERSION function
 602  */
 603 static int __init psci_0_2_init(struct device_node *np)
 604 {
 605         int err;
 606
 607         err = get_set_conduit_method(np);
 608
 609         if (err)
 610                 goto out_put_node;
 611         /*
 612          * Starting with v0.2, the PSCI specification introduced a call
 613          * (PSCI_VERSION) that allows probing the firmware version, so
 614          * that PSCI function IDs and version specific initialization
 615          * can be carried out according to the specific version reported
 616          * by firmware
 617          */
 618         err = psci_probe();
 619
 620 out_put_node:
 621         of_node_put(np);
 622         return err;
 623 }
 624
 625 /*
 626  * PSCI < v0.2 get PSCI Function IDs via DT.
 627  */
 628 static int __init psci_0_1_init(struct device_node *np)
 629 {
 630         u32 id;
 631         int err;
 632
 633         err = get_set_conduit_method(np);
 634
 635         if (err)
 636                 goto out_put_node;
 637
 638         pr_info("Using PSCI v0.1 Function IDs from DT\n");
 639
 640         if (!of_property_read_u32(np, "cpu_suspend", &id)) {
 641                 psci_function_id[PSCI_FN_CPU_SUSPEND] = id;
 642                 psci_ops.cpu_suspend = psci_cpu_suspend;
 643         }
 644
 645         if (!of_property_read_u32(np, "cpu_off", &id)) {
 646                 psci_function_id[PSCI_FN_CPU_OFF] = id;
 647                 psci_ops.cpu_off = psci_cpu_off;
 648         }
 649
 650         if (!of_property_read_u32(np, "cpu_on", &id)) {
 651                 psci_function_id[PSCI_FN_CPU_ON] = id;
 652                 psci_ops.cpu_on = psci_cpu_on;
 653         }
 654
 655         if (!of_property_read_u32(np, "migrate", &id)) {
 656                 psci_function_id[PSCI_FN_MIGRATE] = id;
 657                 psci_ops.migrate = psci_migrate;
 658         }
 659
 660 out_put_node:
 661         of_node_put(np);
 662         return err;
 663 }
 664
 665 static const struct of_device_id psci_of_match[] __initconst = {
 666         { .compatible = "arm,psci",     .data = psci_0_1_init},
 667         { .compatible = "arm,psci-0.2", .data = psci_0_2_init},
 668         { .compatible = "arm,psci-1.0", .data = psci_0_2_init},
 669         {},
 670 };
 671
 672 int __init psci_dt_init(void)
 673 {
 674         struct device_node *np;
 675         const struct of_device_id *matched_np;
 676         psci_initcall_t init_fn;
 677
 678         np = of_find_matching_node_and_match(NULL, psci_of_match, &matched_np);
 679
 680         if (!np || !of_device_is_available(np))
 681                 return -ENODEV;
 682
 683         init_fn = (psci_initcall_t)matched_np->data;
 684         return init_fn(np);
 685 }
 686
 687 #ifdef CONFIG_ACPI
 688 /*
 689  * We use PSCI 0.2+ when ACPI is deployed on ARM64 and it's
 690  * explicitly clarified in SBBR
 691  */
 692 int __init psci_acpi_init(void)
 693 {
 694         if (!acpi_psci_present()) {
 695                 pr_info("is not implemented in ACPI.\n");
 696                 return -EOPNOTSUPP;
 697         }
 698
 699         pr_info("probing for conduit method from ACPI.\n");
 700
 701         if (acpi_psci_use_hvc())
 702                 set_conduit(PSCI_CONDUIT_HVC);
 703         else
 704                 set_conduit(PSCI_CONDUIT_SMC);
 705
 706         return psci_probe();
 707 }
 708 #endif