arch/arm/kernel/crunch.c

   1 /*
   2  * arch/arm/kernel/crunch.c
   3  * Cirrus MaverickCrunch context switching and handling
   4  *
   5  * Copyright (C) 2006 Lennert Buytenhek <buytenh@wantstofly.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/config.h>
  14 #include <linux/types.h>
  15 #include <linux/kernel.h>
  16 #include <linux/signal.h>
  17 #include <linux/sched.h>
  18 #include <linux/init.h>
  19 #include <asm/arch/ep93xx-regs.h>
  20 #include <asm/thread_notify.h>
  21 #include <asm/io.h>
  22
  23 struct crunch_state *crunch_owner;
  24
  25 void crunch_task_release(struct thread_info *thread)
  26 {
  27         local_irq_disable();
  28         if (crunch_owner == &thread->crunchstate)
  29                 crunch_owner = NULL;
  30         local_irq_enable();
  31 }
  32
  33 static int crunch_enabled(u32 devcfg)
  34 {
  35         return !!(devcfg & EP93XX_SYSCON_DEVICE_CONFIG_CRUNCH_ENABLE);
  36 }
  37
  38 static int crunch_do(struct notifier_block *self, unsigned long cmd, void *t)
  39 {
  40         struct thread_info *thread = (struct thread_info *)t;
  41         struct crunch_state *crunch_state;
  42         u32 devcfg;
  43
  44         crunch_state = &thread->crunchstate;
  45
  46         switch (cmd) {
  47         case THREAD_NOTIFY_FLUSH:
  48                 memset(crunch_state, 0, sizeof(*crunch_state));
  49
  50                 /*
  51                  * FALLTHROUGH: Ensure we don't try to overwrite our newly
  52                  * initialised state information on the first fault.
  53                  */
  54
  55         case THREAD_NOTIFY_RELEASE:
  56                 crunch_task_release(thread);
  57                 break;
  58
  59         case THREAD_NOTIFY_SWITCH:
  60                 devcfg = __raw_readl(EP93XX_SYSCON_DEVICE_CONFIG);
  61                 if (crunch_enabled(devcfg) || crunch_owner == crunch_state) {
  62                         devcfg ^= EP93XX_SYSCON_DEVICE_CONFIG_CRUNCH_ENABLE;
  63                         __raw_writel(0xaa, EP93XX_SYSCON_SWLOCK);
  64                         __raw_writel(devcfg, EP93XX_SYSCON_DEVICE_CONFIG);
  65                 }
  66                 break;
  67         }
  68
  69         return NOTIFY_DONE;
  70 }
  71
  72 static struct notifier_block crunch_notifier_block = {
  73         .notifier_call  = crunch_do,
  74 };
  75
  76 static int __init crunch_init(void)
  77 {
  78         thread_register_notifier(&crunch_notifier_block);
  79
  80         return 0;
  81 }
  82
  83 late_initcall(crunch_init);