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