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 #include <linux/export.h>
  23
  24 #include "pm.h"
  25
  26 #define AT91_MAX_STATES 2
  27
  28 static DEFINE_PER_CPU(struct cpuidle_device, at91_cpuidle_device);
  29
  30 static struct cpuidle_driver at91_idle_driver = {
  31         .name =         "at91_idle",
  32         .owner =        THIS_MODULE,
  33 };
  34
  35 /* Actual code that puts the SoC in different idle states */
  36 static int at91_enter_idle(struct cpuidle_device *dev,
  37                                struct cpuidle_state *state)
  38 {
  39         struct timeval before, after;
  40         int idle_time;
  41         u32 saved_lpr;
  42
  43         local_irq_disable();
  44         do_gettimeofday(&before);
  45         if (state == &dev->states[0])
  46                 /* Wait for interrupt state */
  47                 cpu_do_idle();
  48         else if (state == &dev->states[1]) {
  49                 asm("b 1f; .align 5; 1:");
  50                 asm("mcr p15, 0, r0, c7, c10, 4");      /* drain write buffer */
  51                 saved_lpr = sdram_selfrefresh_enable();
  52                 cpu_do_idle();
  53                 sdram_selfrefresh_disable(saved_lpr);
  54         }
  55         do_gettimeofday(&after);
  56         local_irq_enable();
  57         idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
  58                         (after.tv_usec - before.tv_usec);
  59         return idle_time;
  60 }
  61
  62 /* Initialize CPU idle by registering the idle states */
  63 static int at91_init_cpuidle(void)
  64 {
  65         struct cpuidle_device *device;
  66
  67         cpuidle_register_driver(&at91_idle_driver);
  68
  69         device = &per_cpu(at91_cpuidle_device, smp_processor_id());
  70         device->state_count = AT91_MAX_STATES;
  71
  72         /* Wait for interrupt state */
  73         device->states[0].enter = at91_enter_idle;
  74         device->states[0].exit_latency = 1;
  75         device->states[0].target_residency = 10000;
  76         device->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
  77         strcpy(device->states[0].name, "WFI");
  78         strcpy(device->states[0].desc, "Wait for interrupt");
  79
  80         /* Wait for interrupt and RAM self refresh state */
  81         device->states[1].enter = at91_enter_idle;
  82         device->states[1].exit_latency = 10;
  83         device->states[1].target_residency = 10000;
  84         device->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
  85         strcpy(device->states[1].name, "RAM_SR");
  86         strcpy(device->states[1].desc, "WFI and RAM Self Refresh");
  87
  88         if (cpuidle_register_device(device)) {
  89                 printk(KERN_ERR "at91_init_cpuidle: Failed registering\n");
  90                 return -EIO;
  91         }
  92         return 0;
  93 }
  94
  95 device_initcall(at91_init_cpuidle);