1 /*
2  * Copyright (C) 2012 Freescale Semiconductor, Inc.
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8 
9 #include <linux/cpuidle.h>
10 #include <linux/module.h>
11 #include <asm/cpuidle.h>
12 #include <asm/proc-fns.h>
13 
14 #include "common.h"
15 #include "cpuidle.h"
16 
17 static atomic_t master = ATOMIC_INIT(0);
18 static DEFINE_SPINLOCK(master_lock);
19 
20 static int imx6q_enter_wait(struct cpuidle_device *dev,
21 			    struct cpuidle_driver *drv, int index)
22 {
23 	if (atomic_inc_return(&master) == num_online_cpus()) {
24 		/*
25 		 * With this lock, we prevent other cpu to exit and enter
26 		 * this function again and become the master.
27 		 */
28 		if (!spin_trylock(&master_lock))
29 			goto idle;
30 		imx6q_set_lpm(WAIT_UNCLOCKED);
31 		cpu_do_idle();
32 		imx6q_set_lpm(WAIT_CLOCKED);
33 		spin_unlock(&master_lock);
34 		goto done;
35 	}
36 
37 idle:
38 	cpu_do_idle();
39 done:
40 	atomic_dec(&master);
41 
42 	return index;
43 }
44 
45 static struct cpuidle_driver imx6q_cpuidle_driver = {
46 	.name = "imx6q_cpuidle",
47 	.owner = THIS_MODULE,
48 	.states = {
49 		/* WFI */
50 		ARM_CPUIDLE_WFI_STATE,
51 		/* WAIT */
52 		{
53 			.exit_latency = 50,
54 			.target_residency = 75,
55 			.flags = CPUIDLE_FLAG_TIME_VALID |
56 			         CPUIDLE_FLAG_TIMER_STOP,
57 			.enter = imx6q_enter_wait,
58 			.name = "WAIT",
59 			.desc = "Clock off",
60 		},
61 	},
62 	.state_count = 2,
63 	.safe_state_index = 0,
64 };
65 
66 int __init imx6q_cpuidle_init(void)
67 {
68 	/* Need to enable SCU standby for entering WAIT modes */
69 	imx_scu_standby_enable();
70 
71 	/* Set chicken bit to get a reliable WAIT mode support */
72 	imx6q_set_chicken_bit();
73 
74 	return cpuidle_register(&imx6q_cpuidle_driver, NULL);
75 }
76