drivers/cpuidle/cpuidle-pseries.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  cpuidle-pseries - idle state cpuidle driver.
   4  *  Adapted from drivers/idle/intel_idle.c and
   5  *  drivers/acpi/processor_idle.c
   6  *
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/moduleparam.h>
  13 #include <linux/cpuidle.h>
  14 #include <linux/cpu.h>
  15 #include <linux/notifier.h>
  16
  17 #include <asm/paca.h>
  18 #include <asm/reg.h>
  19 #include <asm/machdep.h>
  20 #include <asm/firmware.h>
  21 #include <asm/runlatch.h>
  22 #include <asm/plpar_wrappers.h>
  23
  24 struct cpuidle_driver pseries_idle_driver = {
  25         .name             = "pseries_idle",
  26         .owner            = THIS_MODULE,
  27 };
  28
  29 static int max_idle_state __read_mostly;
  30 static struct cpuidle_state *cpuidle_state_table __read_mostly;
  31 static u64 snooze_timeout __read_mostly;
  32 static bool snooze_timeout_en __read_mostly;
  33
  34 static inline void idle_loop_prolog(unsigned long *in_purr)
  35 {
  36         ppc64_runlatch_off();
  37         *in_purr = mfspr(SPRN_PURR);
  38         /*
  39          * Indicate to the HV that we are idle. Now would be
  40          * a good time to find other work to dispatch.
  41          */
  42         get_lppaca()->idle = 1;
  43 }
  44
  45 static inline void idle_loop_epilog(unsigned long in_purr)
  46 {
  47         u64 wait_cycles;
  48
  49         wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
  50         wait_cycles += mfspr(SPRN_PURR) - in_purr;
  51         get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
  52         get_lppaca()->idle = 0;
  53
  54         if (irqs_disabled())
  55                 local_irq_enable();
  56         ppc64_runlatch_on();
  57 }
  58
  59 static int snooze_loop(struct cpuidle_device *dev,
  60                         struct cpuidle_driver *drv,
  61                         int index)
  62 {
  63         unsigned long in_purr;
  64         u64 snooze_exit_time;
  65
  66         set_thread_flag(TIF_POLLING_NRFLAG);
  67
  68         idle_loop_prolog(&in_purr);
  69         local_irq_enable();
  70         snooze_exit_time = get_tb() + snooze_timeout;
  71
  72         while (!need_resched()) {
  73                 HMT_low();
  74                 HMT_very_low();
  75                 if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) {
  76                         /*
  77                          * Task has not woken up but we are exiting the polling
  78                          * loop anyway. Require a barrier after polling is
  79                          * cleared to order subsequent test of need_resched().
  80                          */
  81                         clear_thread_flag(TIF_POLLING_NRFLAG);
  82                         smp_mb();
  83                         break;
  84                 }
  85         }
  86
  87         HMT_medium();
  88         clear_thread_flag(TIF_POLLING_NRFLAG);
  89
  90         idle_loop_epilog(in_purr);
  91
  92         return index;
  93 }
  94
  95 static void check_and_cede_processor(void)
  96 {
  97         /*
  98          * Ensure our interrupt state is properly tracked,
  99          * also checks if no interrupt has occurred while we
 100          * were soft-disabled
 101          */
 102         if (prep_irq_for_idle()) {
 103                 cede_processor();
 104 #ifdef CONFIG_TRACE_IRQFLAGS
 105                 /* Ensure that H_CEDE returns with IRQs on */
 106                 if (WARN_ON(!(mfmsr() & MSR_EE)))
 107                         __hard_irq_enable();
 108 #endif
 109         }
 110 }
 111
 112 static int dedicated_cede_loop(struct cpuidle_device *dev,
 113                                 struct cpuidle_driver *drv,
 114                                 int index)
 115 {
 116         unsigned long in_purr;
 117
 118         idle_loop_prolog(&in_purr);
 119         get_lppaca()->donate_dedicated_cpu = 1;
 120
 121         HMT_medium();
 122         check_and_cede_processor();
 123
 124         get_lppaca()->donate_dedicated_cpu = 0;
 125
 126         idle_loop_epilog(in_purr);
 127
 128         return index;
 129 }
 130
 131 static int shared_cede_loop(struct cpuidle_device *dev,
 132                         struct cpuidle_driver *drv,
 133                         int index)
 134 {
 135         unsigned long in_purr;
 136
 137         idle_loop_prolog(&in_purr);
 138
 139         /*
 140          * Yield the processor to the hypervisor.  We return if
 141          * an external interrupt occurs (which are driven prior
 142          * to returning here) or if a prod occurs from another
 143          * processor. When returning here, external interrupts
 144          * are enabled.
 145          */
 146         check_and_cede_processor();
 147
 148         idle_loop_epilog(in_purr);
 149
 150         return index;
 151 }
 152
 153 /*
 154  * States for dedicated partition case.
 155  */
 156 static struct cpuidle_state dedicated_states[] = {
 157         { /* Snooze */
 158                 .name = "snooze",
 159                 .desc = "snooze",
 160                 .exit_latency = 0,
 161                 .target_residency = 0,
 162                 .enter = &snooze_loop },
 163         { /* CEDE */
 164                 .name = "CEDE",
 165                 .desc = "CEDE",
 166                 .exit_latency = 10,
 167                 .target_residency = 100,
 168                 .enter = &dedicated_cede_loop },
 169 };
 170
 171 /*
 172  * States for shared partition case.
 173  */
 174 static struct cpuidle_state shared_states[] = {
 175         { /* Shared Cede */
 176                 .name = "Shared Cede",
 177                 .desc = "Shared Cede",
 178                 .exit_latency = 0,
 179                 .target_residency = 0,
 180                 .enter = &shared_cede_loop },
 181 };
 182
 183 static int pseries_cpuidle_cpu_online(unsigned int cpu)
 184 {
 185         struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
 186
 187         if (dev && cpuidle_get_driver()) {
 188                 cpuidle_pause_and_lock();
 189                 cpuidle_enable_device(dev);
 190                 cpuidle_resume_and_unlock();
 191         }
 192         return 0;
 193 }
 194
 195 static int pseries_cpuidle_cpu_dead(unsigned int cpu)
 196 {
 197         struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
 198
 199         if (dev && cpuidle_get_driver()) {
 200                 cpuidle_pause_and_lock();
 201                 cpuidle_disable_device(dev);
 202                 cpuidle_resume_and_unlock();
 203         }
 204         return 0;
 205 }
 206
 207 /*
 208  * pseries_cpuidle_driver_init()
 209  */
 210 static int pseries_cpuidle_driver_init(void)
 211 {
 212         int idle_state;
 213         struct cpuidle_driver *drv = &pseries_idle_driver;
 214
 215         drv->state_count = 0;
 216
 217         for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
 218                 /* Is the state not enabled? */
 219                 if (cpuidle_state_table[idle_state].enter == NULL)
 220                         continue;
 221
 222                 drv->states[drv->state_count] = /* structure copy */
 223                         cpuidle_state_table[idle_state];
 224
 225                 drv->state_count += 1;
 226         }
 227
 228         return 0;
 229 }
 230
 231 /*
 232  * pseries_idle_probe()
 233  * Choose state table for shared versus dedicated partition
 234  */
 235 static int pseries_idle_probe(void)
 236 {
 237
 238         if (cpuidle_disable != IDLE_NO_OVERRIDE)
 239                 return -ENODEV;
 240
 241         if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
 242                 /*
 243                  * Use local_paca instead of get_lppaca() since
 244                  * preemption is not disabled, and it is not required in
 245                  * fact, since lppaca_ptr does not need to be the value
 246                  * associated to the current CPU, it can be from any CPU.
 247                  */
 248                 if (lppaca_shared_proc(local_paca->lppaca_ptr)) {
 249                         cpuidle_state_table = shared_states;
 250                         max_idle_state = ARRAY_SIZE(shared_states);
 251                 } else {
 252                         cpuidle_state_table = dedicated_states;
 253                         max_idle_state = ARRAY_SIZE(dedicated_states);
 254                 }
 255         } else
 256                 return -ENODEV;
 257
 258         if (max_idle_state > 1) {
 259                 snooze_timeout_en = true;
 260                 snooze_timeout = cpuidle_state_table[1].target_residency *
 261                                  tb_ticks_per_usec;
 262         }
 263         return 0;
 264 }
 265
 266 static int __init pseries_processor_idle_init(void)
 267 {
 268         int retval;
 269
 270         retval = pseries_idle_probe();
 271         if (retval)
 272                 return retval;
 273
 274         pseries_cpuidle_driver_init();
 275         retval = cpuidle_register(&pseries_idle_driver, NULL);
 276         if (retval) {
 277                 printk(KERN_DEBUG "Registration of pseries driver failed.\n");
 278                 return retval;
 279         }
 280
 281         retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
 282                                            "cpuidle/pseries:online",
 283                                            pseries_cpuidle_cpu_online, NULL);
 284         WARN_ON(retval < 0);
 285         retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
 286                                            "cpuidle/pseries:DEAD", NULL,
 287                                            pseries_cpuidle_cpu_dead);
 288         WARN_ON(retval < 0);
 289         printk(KERN_DEBUG "pseries_idle_driver registered\n");
 290         return 0;
 291 }
 292
 293 device_initcall(pseries_processor_idle_init);