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 #include "id.h"
  25
  26 static atomic_t master = ATOMIC_INIT(0);
  27 static DEFINE_SPINLOCK(master_lock);
  28
  29 static inline int ux500_enter_idle(struct cpuidle_device *dev,
  30                                    struct cpuidle_driver *drv, int index)
  31 {
  32         int this_cpu = smp_processor_id();
  33         bool recouple = false;
  34
  35         if (atomic_inc_return(&master) == num_online_cpus()) {
  36
  37                 /* With this lock, we prevent the other cpu to exit and enter
  38                  * this function again and become the master */
  39                 if (!spin_trylock(&master_lock))
  40                         goto wfi;
  41
  42                 /* decouple the gic from the A9 cores */
  43                 if (prcmu_gic_decouple()) {
  44                         spin_unlock(&master_lock);
  45                         goto out;
  46                 }
  47
  48                 /* If an error occur, we will have to recouple the gic
  49                  * manually */
  50                 recouple = true;
  51
  52                 /* At this state, as the gic is decoupled, if the other
  53                  * cpu is in WFI, we have the guarantee it won't be wake
  54                  * up, so we can safely go to retention */
  55                 if (!prcmu_is_cpu_in_wfi(this_cpu ? 0 : 1))
  56                         goto out;
  57
  58                 /* The prcmu will be in charge of watching the interrupts
  59                  * and wake up the cpus */
  60                 if (prcmu_copy_gic_settings())
  61                         goto out;
  62
  63                 /* Check in the meantime an interrupt did
  64                  * not occur on the gic ... */
  65                 if (prcmu_gic_pending_irq())
  66                         goto out;
  67
  68                 /* ... and the prcmu */
  69                 if (prcmu_pending_irq())
  70                         goto out;
  71
  72                 /* Go to the retention state, the prcmu will wait for the
  73                  * cpu to go WFI and this is what happens after exiting this
  74                  * 'master' critical section */
  75                 if (prcmu_set_power_state(PRCMU_AP_IDLE, true, true))
  76                         goto out;
  77
  78                 /* When we switch to retention, the prcmu is in charge
  79                  * of recoupling the gic automatically */
  80                 recouple = false;
  81
  82                 spin_unlock(&master_lock);
  83         }
  84 wfi:
  85         cpu_do_idle();
  86 out:
  87         atomic_dec(&master);
  88
  89         if (recouple) {
  90                 prcmu_gic_recouple();
  91                 spin_unlock(&master_lock);
  92         }
  93
  94         return index;
  95 }
  96
  97 static struct cpuidle_driver ux500_idle_driver = {
  98         .name = "ux500_idle",
  99         .owner = THIS_MODULE,
 100         .states = {
 101                 ARM_CPUIDLE_WFI_STATE,
 102                 {
 103                         .enter            = ux500_enter_idle,
 104                         .exit_latency     = 70,
 105                         .target_residency = 260,
 106                         .flags            = CPUIDLE_FLAG_TIME_VALID |
 107                                             CPUIDLE_FLAG_TIMER_STOP,
 108                         .name             = "ApIdle",
 109                         .desc             = "ARM Retention",
 110                 },
 111         },
 112         .safe_state_index = 0,
 113         .state_count = 2,
 114 };
 115
 116 int __init ux500_idle_init(void)
 117 {
 118         if (!(cpu_is_u8500_family() || cpu_is_ux540_family()))
 119                 return -ENODEV;
 120
 121         /* Configure wake up reasons */
 122         prcmu_enable_wakeups(PRCMU_WAKEUP(ARM) | PRCMU_WAKEUP(RTC) |
 123                              PRCMU_WAKEUP(ABB));
 124
 125         return cpuidle_register(&ux500_idle_driver, NULL);
 126 }
 127
 128 device_initcall(ux500_idle_init);