arch/arm/mach-ux500/cpuidle.c

   1 /*
   2  * Copyright (c) 2012 Linaro : Daniel Lezcano <daniel.lezcano@linaro.org> (IBM)
   3  *
   4  * Based on the work of Rickard Andersson <rickard.andersson@stericsson.com>
   5  * and Jonas Aaberg <jonas.aberg@stericsson.com>.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/cpuidle.h>
  14 #include <linux/spinlock.h>
  15 #include <linux/atomic.h>
  16 #include <linux/smp.h>
  17 #include <linux/mfd/dbx500-prcmu.h>
  18 #include <linux/platform_data/arm-ux500-pm.h>
  19
  20 #include <asm/cpuidle.h>
  21 #include <asm/proc-fns.h>
  22
  23 #include "db8500-regs.h"
  24
  25 static atomic_t master = ATOMIC_INIT(0);
  26 static DEFINE_SPINLOCK(master_lock);
  27
  28 static inline int ux500_enter_idle(struct cpuidle_device *dev,
  29                                    struct cpuidle_driver *drv, int index)
  30 {
  31         int this_cpu = smp_processor_id();
  32         bool recouple = false;
  33
  34         if (atomic_inc_return(&master) == num_online_cpus()) {
  35
  36                 /* With this lock, we prevent the other cpu to exit and enter
  37                  * this function again and become the master */
  38                 if (!spin_trylock(&master_lock))
  39                         goto wfi;
  40
  41                 /* decouple the gic from the A9 cores */
  42                 if (prcmu_gic_decouple()) {
  43                         spin_unlock(&master_lock);
  44                         goto out;
  45                 }
  46
  47                 /* If an error occur, we will have to recouple the gic
  48                  * manually */
  49                 recouple = true;
  50
  51                 /* At this state, as the gic is decoupled, if the other
  52                  * cpu is in WFI, we have the guarantee it won't be wake
  53                  * up, so we can safely go to retention */
  54                 if (!prcmu_is_cpu_in_wfi(this_cpu ? 0 : 1))
  55                         goto out;
  56
  57                 /* The prcmu will be in charge of watching the interrupts
  58                  * and wake up the cpus */
  59                 if (prcmu_copy_gic_settings())
  60                         goto out;
  61
  62                 /* Check in the meantime an interrupt did
  63                  * not occur on the gic ... */
  64                 if (prcmu_gic_pending_irq())
  65                         goto out;
  66
  67                 /* ... and the prcmu */
  68                 if (prcmu_pending_irq())
  69                         goto out;
  70
  71                 /* Go to the retention state, the prcmu will wait for the
  72                  * cpu to go WFI and this is what happens after exiting this
  73                  * 'master' critical section */
  74                 if (prcmu_set_power_state(PRCMU_AP_IDLE, true, true))
  75                         goto out;
  76
  77                 /* When we switch to retention, the prcmu is in charge
  78                  * of recoupling the gic automatically */
  79                 recouple = false;
  80
  81                 spin_unlock(&master_lock);
  82         }
  83 wfi:
  84         cpu_do_idle();
  85 out:
  86         atomic_dec(&master);
  87
  88         if (recouple) {
  89                 prcmu_gic_recouple();
  90                 spin_unlock(&master_lock);
  91         }
  92
  93         return index;
  94 }
  95
  96 static struct cpuidle_driver ux500_idle_driver = {
  97         .name = "ux500_idle",
  98         .owner = THIS_MODULE,
  99         .states = {
 100                 ARM_CPUIDLE_WFI_STATE,
 101                 {
 102                         .enter            = ux500_enter_idle,
 103                         .exit_latency     = 70,
 104                         .target_residency = 260,
 105                         .flags            = CPUIDLE_FLAG_TIME_VALID |
 106                                             CPUIDLE_FLAG_TIMER_STOP,
 107                         .name             = "ApIdle",
 108                         .desc             = "ARM Retention",
 109                 },
 110         },
 111         .safe_state_index = 0,
 112         .state_count = 2,
 113 };
 114
 115 int __init ux500_idle_init(void)
 116 {
 117         /* Configure wake up reasons */
 118         prcmu_enable_wakeups(PRCMU_WAKEUP(ARM) | PRCMU_WAKEUP(RTC) |
 119                              PRCMU_WAKEUP(ABB));
 120
 121         return cpuidle_register(&ux500_idle_driver, NULL);
 122 }
 123
 124 device_initcall(ux500_idle_init);