arch/arm/mach-kirkwood/cpuidle.c

   1 /*
   2  * arch/arm/mach-kirkwood/cpuidle.c
   3  *
   4  * CPU idle Marvell Kirkwood SoCs
   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 DDR self refresh in order
  11  * to implement two idle states -
  12  * #1 wait-for-interrupt
  13  * #2 wait-for-interrupt and DDR 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 <asm/proc-fns.h>
  22 #include <mach/kirkwood.h>
  23
  24 #define KIRKWOOD_MAX_STATES     2
  25
  26 static struct cpuidle_driver kirkwood_idle_driver = {
  27         .name =         "kirkwood_idle",
  28         .owner =        THIS_MODULE,
  29 };
  30
  31 static DEFINE_PER_CPU(struct cpuidle_device, kirkwood_cpuidle_device);
  32
  33 /* Actual code that puts the SoC in different idle states */
  34 static int kirkwood_enter_idle(struct cpuidle_device *dev,
  35                                int index)
  36 {
  37         struct timeval before, after;
  38         int idle_time;
  39
  40         local_irq_disable();
  41         do_gettimeofday(&before);
  42         if (index == 0)
  43                 /* Wait for interrupt state */
  44                 cpu_do_idle();
  45         else if (index == 1) {
  46                 /*
  47                  * Following write will put DDR in self refresh.
  48                  * Note that we have 256 cycles before DDR puts it
  49                  * self in self-refresh, so the wait-for-interrupt
  50                  * call afterwards won't get the DDR from self refresh
  51                  * mode.
  52                  */
  53                 writel(0x7, DDR_OPERATION_BASE);
  54                 cpu_do_idle();
  55         }
  56         do_gettimeofday(&after);
  57         local_irq_enable();
  58         idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
  59                         (after.tv_usec - before.tv_usec);
  60
  61         /* Update last residency */
  62         dev->last_residency = idle_time;
  63
  64         return index;
  65 }
  66
  67 /* Initialize CPU idle by registering the idle states */
  68 static int kirkwood_init_cpuidle(void)
  69 {
  70         struct cpuidle_device *device;
  71
  72         cpuidle_register_driver(&kirkwood_idle_driver);
  73
  74         device = &per_cpu(kirkwood_cpuidle_device, smp_processor_id());
  75         device->state_count = KIRKWOOD_MAX_STATES;
  76
  77         /* Wait for interrupt state */
  78         device->states[0].enter = kirkwood_enter_idle;
  79         device->states[0].exit_latency = 1;
  80         device->states[0].target_residency = 10000;
  81         device->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
  82         strcpy(device->states[0].name, "WFI");
  83         strcpy(device->states[0].desc, "Wait for interrupt");
  84
  85         /* Wait for interrupt and DDR self refresh state */
  86         device->states[1].enter = kirkwood_enter_idle;
  87         device->states[1].exit_latency = 10;
  88         device->states[1].target_residency = 10000;
  89         device->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
  90         strcpy(device->states[1].name, "DDR SR");
  91         strcpy(device->states[1].desc, "WFI and DDR Self Refresh");
  92
  93         if (cpuidle_register_device(device)) {
  94                 printk(KERN_ERR "kirkwood_init_cpuidle: Failed registering\n");
  95                 return -EIO;
  96         }
  97         return 0;
  98 }
  99
 100 device_initcall(kirkwood_init_cpuidle);