arch/arm/mach-shmobile/hotplug.c

   1 /*
   2  * SMP support for R-Mobile / SH-Mobile
   3  *
   4  * Copyright (C) 2010  Magnus Damm
   5  *
   6  * Based on realview, Copyright (C) 2002 ARM Ltd, All Rights Reserved
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12 #include <linux/kernel.h>
  13 #include <linux/errno.h>
  14 #include <linux/smp.h>
  15 #include <linux/cpumask.h>
  16 #include <linux/delay.h>
  17 #include <mach/common.h>
  18 #include <asm/cacheflush.h>
  19
  20 static cpumask_t dead_cpus;
  21
  22 int platform_cpu_kill(unsigned int cpu)
  23 {
  24         int k;
  25
  26         /* this function is running on another CPU than the offline target,
  27          * here we need wait for shutdown code in platform_cpu_die() to
  28          * finish before asking SoC-specific code to power off the CPU core.
  29          */
  30         for (k = 0; k < 1000; k++) {
  31                 if (cpumask_test_cpu(cpu, &dead_cpus))
  32                         return shmobile_platform_cpu_kill(cpu);
  33
  34                 mdelay(1);
  35         }
  36
  37         return 0;
  38 }
  39
  40 void platform_cpu_die(unsigned int cpu)
  41 {
  42         /* hardware shutdown code running on the CPU that is being offlined */
  43         flush_cache_all();
  44         dsb();
  45
  46         /* notify platform_cpu_kill() that hardware shutdown is finished */
  47         cpumask_set_cpu(cpu, &dead_cpus);
  48
  49         /* wait for SoC code in platform_cpu_kill() to shut off CPU core
  50          * power. CPU bring up starts from the reset vector.
  51          */
  52         while (1) {
  53                 /*
  54                  * here's the WFI
  55                  */
  56                 asm(".word      0xe320f003\n"
  57                     :
  58                     :
  59                     : "memory", "cc");
  60         }
  61 }
  62
  63 int platform_cpu_disable(unsigned int cpu)
  64 {
  65         cpumask_clear_cpu(cpu, &dead_cpus);
  66         /*
  67          * we don't allow CPU 0 to be shutdown (it is still too special
  68          * e.g. clock tick interrupts)
  69          */
  70         return cpu == 0 ? -EPERM : 0;
  71 }