1 /* 2 * linux/drivers/clocksource/dummy_timer.c 3 * 4 * Copyright (C) 2013 ARM Ltd. 5 * All Rights Reserved 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 #include <linux/clockchips.h> 12 #include <linux/cpu.h> 13 #include <linux/init.h> 14 #include <linux/percpu.h> 15 #include <linux/cpumask.h> 16 17 static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt); 18 19 static void dummy_timer_set_mode(enum clock_event_mode mode, 20 struct clock_event_device *evt) 21 { 22 /* 23 * Core clockevents code will call this when exchanging timer devices. 24 * We don't need to do anything here. 25 */ 26 } 27 28 static void dummy_timer_setup(void) 29 { 30 int cpu = smp_processor_id(); 31 struct clock_event_device *evt = __this_cpu_ptr(&dummy_timer_evt); 32 33 evt->name = "dummy_timer"; 34 evt->features = CLOCK_EVT_FEAT_PERIODIC | 35 CLOCK_EVT_FEAT_ONESHOT | 36 CLOCK_EVT_FEAT_DUMMY; 37 evt->rating = 100; 38 evt->set_mode = dummy_timer_set_mode; 39 evt->cpumask = cpumask_of(cpu); 40 41 clockevents_register_device(evt); 42 } 43 44 static int dummy_timer_cpu_notify(struct notifier_block *self, 45 unsigned long action, void *hcpu) 46 { 47 if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING) 48 dummy_timer_setup(); 49 50 return NOTIFY_OK; 51 } 52 53 static struct notifier_block dummy_timer_cpu_nb = { 54 .notifier_call = dummy_timer_cpu_notify, 55 }; 56 57 static int __init dummy_timer_register(void) 58 { 59 int err = 0; 60 61 cpu_notifier_register_begin(); 62 err = __register_cpu_notifier(&dummy_timer_cpu_nb); 63 if (err) 64 goto out; 65 66 /* We won't get a call on the boot CPU, so register immediately */ 67 if (num_possible_cpus() > 1) 68 dummy_timer_setup(); 69 70 out: 71 cpu_notifier_register_done(); 72 return err; 73 } 74 early_initcall(dummy_timer_register); 75