arch/arm/mach-at91/cpuidle.c

   1 /*
   2  * based on arch/arm/mach-kirkwood/cpuidle.c
   3  *
   4  * CPU idle support for AT91 SoC
   5  *
   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.
   9  *
  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
  14  */
  15
  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>
  21 #include <linux/io.h>
  22
  23 #include "pm.h"
  24
  25 #define AT91_MAX_STATES 2
  26
  27 static DEFINE_PER_CPU(struct cpuidle_device, at91_cpuidle_device);
  28
  29 static struct cpuidle_driver at91_idle_driver = {
  30         .name =         "at91_idle",
  31         .owner =        THIS_MODULE,
  32 };
  33
  34 /* Actual code that puts the SoC in different idle states */
  35 static int at91_enter_idle(struct cpuidle_device *dev,
  36                                int index)
  37 {
  38         struct timeval before, after;
  39         int idle_time;
  40         u32 saved_lpr;
  41
  42         local_irq_disable();
  43         do_gettimeofday(&before);
  44         if (index == 0)
  45                 /* Wait for interrupt state */
  46                 cpu_do_idle();
  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();
  51                 cpu_do_idle();
  52                 sdram_selfrefresh_disable(saved_lpr);
  53         }
  54         do_gettimeofday(&after);
  55         local_irq_enable();
  56         idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
  57                         (after.tv_usec - before.tv_usec);
  58
  59         dev->last_residency = idle_time;
  60         return index;
  61 }
  62
  63 /* Initialize CPU idle by registering the idle states */
  64 static int at91_init_cpuidle(void)
  65 {
  66         struct cpuidle_device *device;
  67
  68         cpuidle_register_driver(&at91_idle_driver);
  69
  70         device = &per_cpu(at91_cpuidle_device, smp_processor_id());
  71         device->state_count = AT91_MAX_STATES;
  72
  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");
  80
  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");
  88
  89         if (cpuidle_register_device(device)) {
  90                 printk(KERN_ERR "at91_init_cpuidle: Failed registering\n");
  91                 return -EIO;
  92         }
  93         return 0;
  94 }
  95
  96 device_initcall(at91_init_cpuidle);