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 <linux/io.h>
  21 #include <linux/export.h>
  22 #include <asm/proc-fns.h>
  23 #include <asm/cpuidle.h>
  24
  25 #include "pm.h"
  26
  27 #define AT91_MAX_STATES 2
  28
  29 static DEFINE_PER_CPU(struct cpuidle_device, at91_cpuidle_device);
  30
  31 /* Actual code that puts the SoC in different idle states */
  32 static int at91_enter_idle(struct cpuidle_device *dev,
  33                         struct cpuidle_driver *drv,
  34                                int index)
  35 {
  36         u32 saved_lpr;
  37
  38         __asm__("b 1f; .align 5; 1:\n"
  39         "       mcr p15, 0, r0, c7, c10, 4");   /* drain write buffer */
  40
  41         saved_lpr = sdram_selfrefresh_enable();
  42         cpu_do_idle();
  43         sdram_selfrefresh_disable(saved_lpr);
  44
  45         return index;
  46 }
  47
  48 static struct cpuidle_driver at91_idle_driver = {
  49         .name                   = "at91_idle",
  50         .owner                  = THIS_MODULE,
  51         .en_core_tk_irqen       = 1,
  52         .states[0]              = ARM_CPUIDLE_WFI_STATE,
  53         .states[1]              = {
  54                 .enter                  = at91_enter_idle,
  55                 .exit_latency           = 10,
  56                 .target_residency       = 100000,
  57                 .flags                  = CPUIDLE_FLAG_TIME_VALID,
  58                 .name                   = "RAM_SR",
  59                 .desc                   = "WFI and DDR Self Refresh",
  60         },
  61         .state_count = AT91_MAX_STATES,
  62 };
  63
  64 /* Initialize CPU idle by registering the idle states */
  65 static int at91_init_cpuidle(void)
  66 {
  67         struct cpuidle_device *device;
  68
  69         device = &per_cpu(at91_cpuidle_device, smp_processor_id());
  70         device->state_count = AT91_MAX_STATES;
  71
  72         cpuidle_register_driver(&at91_idle_driver);
  73
  74         if (cpuidle_register_device(device)) {
  75                 printk(KERN_ERR "at91_init_cpuidle: Failed registering\n");
  76                 return -EIO;
  77         }
  78         return 0;
  79 }
  80
  81 device_initcall(at91_init_cpuidle);