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
  19 #include <asm/cpuidle.h>
  20 #include <asm/proc-fns.h>
  21
  22 static atomic_t master = ATOMIC_INIT(0);
  23 static DEFINE_SPINLOCK(master_lock);
  24
  25 static inline int ux500_enter_idle(struct cpuidle_device *dev,
  26                                    struct cpuidle_driver *drv, int index)
  27 {
  28         int this_cpu = smp_processor_id();
  29         bool recouple = false;
  30
  31         if (atomic_inc_return(&master) == num_online_cpus()) {
  32
  33                 /* With this lock, we prevent the other cpu to exit and enter
  34                  * this function again and become the master */
  35                 if (!spin_trylock(&master_lock))
  36                         goto wfi;
  37
  38                 /* decouple the gic from the A9 cores */
  39                 if (prcmu_gic_decouple()) {
  40                         spin_unlock(&master_lock);
  41                         goto out;
  42                 }
  43
  44                 /* If an error occur, we will have to recouple the gic
  45                  * manually */
  46                 recouple = true;
  47
  48                 /* At this state, as the gic is decoupled, if the other
  49                  * cpu is in WFI, we have the guarantee it won't be wake
  50                  * up, so we can safely go to retention */
  51                 if (!prcmu_is_cpu_in_wfi(this_cpu ? 0 : 1))
  52                         goto out;
  53
  54                 /* The prcmu will be in charge of watching the interrupts
  55                  * and wake up the cpus */
  56                 if (prcmu_copy_gic_settings())
  57                         goto out;
  58
  59                 /* Check in the meantime an interrupt did
  60                  * not occur on the gic ... */
  61                 if (prcmu_gic_pending_irq())
  62                         goto out;
  63
  64                 /* ... and the prcmu */
  65                 if (prcmu_pending_irq())
  66                         goto out;
  67
  68                 /* Go to the retention state, the prcmu will wait for the
  69                  * cpu to go WFI and this is what happens after exiting this
  70                  * 'master' critical section */
  71                 if (prcmu_set_power_state(PRCMU_AP_IDLE, true, true))
  72                         goto out;
  73
  74                 /* When we switch to retention, the prcmu is in charge
  75                  * of recoupling the gic automatically */
  76                 recouple = false;
  77
  78                 spin_unlock(&master_lock);
  79         }
  80 wfi:
  81         cpu_do_idle();
  82 out:
  83         atomic_dec(&master);
  84
  85         if (recouple) {
  86                 prcmu_gic_recouple();
  87                 spin_unlock(&master_lock);
  88         }
  89
  90         return index;
  91 }
  92
  93 static struct cpuidle_driver ux500_idle_driver = {
  94         .name = "ux500_idle",
  95         .owner = THIS_MODULE,
  96         .states = {
  97                 ARM_CPUIDLE_WFI_STATE,
  98                 {
  99                         .enter            = ux500_enter_idle,
 100                         .exit_latency     = 70,
 101                         .target_residency = 260,
 102                         .flags            = CPUIDLE_FLAG_TIME_VALID |
 103                                             CPUIDLE_FLAG_TIMER_STOP,
 104                         .name             = "ApIdle",
 105                         .desc             = "ARM Retention",
 106                 },
 107         },
 108         .safe_state_index = 0,
 109         .state_count = 2,
 110 };
 111
 112 int __init ux500_idle_init(void)
 113 {
 114         /* Configure wake up reasons */
 115         prcmu_enable_wakeups(PRCMU_WAKEUP(ARM) | PRCMU_WAKEUP(RTC) |
 116                              PRCMU_WAKEUP(ABB));
 117
 118         return cpuidle_register(&ux500_idle_driver, NULL);
 119 }
 120
 121 device_initcall(ux500_idle_init);