2 * based on arch/arm/mach-kirkwood/cpuidle.c
4 * CPU idle support for AT91 SoC
6 * This file is licensed under the terms of the GNU General Public
7 * License version 2. This program is licensed "as is" without any
8 * warranty of any kind, whether express or implied.
10 * The cpu idle uses wait-for-interrupt and RAM self refresh in order
11 * to implement two idle states -
12 * #1 wait-for-interrupt
13 * #2 wait-for-interrupt and RAM self refresh
16 #include <linux/kernel.h>
17 #include <linux/init.h>
18 #include <linux/platform_device.h>
19 #include <linux/cpuidle.h>
20 #include <asm/proc-fns.h>
25 #define AT91_MAX_STATES 2
27 static DEFINE_PER_CPU(struct cpuidle_device, at91_cpuidle_device);
29 static struct cpuidle_driver at91_idle_driver = {
34 /* Actual code that puts the SoC in different idle states */
35 static int at91_enter_idle(struct cpuidle_device *dev,
38 struct timeval before, after;
43 do_gettimeofday(&before);
45 /* Wait for interrupt state */
47 else if (index == 1) {
48 asm("b 1f; .align 5; 1:");
49 asm("mcr p15, 0, r0, c7, c10, 4"); /* drain write buffer */
50 saved_lpr = sdram_selfrefresh_enable();
52 sdram_selfrefresh_disable(saved_lpr);
54 do_gettimeofday(&after);
56 idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
57 (after.tv_usec - before.tv_usec);
59 dev->last_residency = idle_time;
63 /* Initialize CPU idle by registering the idle states */
64 static int at91_init_cpuidle(void)
66 struct cpuidle_device *device;
68 cpuidle_register_driver(&at91_idle_driver);
70 device = &per_cpu(at91_cpuidle_device, smp_processor_id());
71 device->state_count = AT91_MAX_STATES;
73 /* Wait for interrupt state */
74 device->states[0].enter = at91_enter_idle;
75 device->states[0].exit_latency = 1;
76 device->states[0].target_residency = 10000;
77 device->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
78 strcpy(device->states[0].name, "WFI");
79 strcpy(device->states[0].desc, "Wait for interrupt");
81 /* Wait for interrupt and RAM self refresh state */
82 device->states[1].enter = at91_enter_idle;
83 device->states[1].exit_latency = 10;
84 device->states[1].target_residency = 10000;
85 device->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
86 strcpy(device->states[1].name, "RAM_SR");
87 strcpy(device->states[1].desc, "WFI and RAM Self Refresh");
89 if (cpuidle_register_device(device)) {
90 printk(KERN_ERR "at91_init_cpuidle: Failed registering\n");
96 device_initcall(at91_init_cpuidle);