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/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/signal.h>
  16 #include <linux/sched.h>
  17 #include <linux/init.h>
  18 #include <linux/io.h>
  19 #include <mach/ep93xx-regs.h>
  20 #include <asm/thread_notify.h>
  21
  22 struct crunch_state *crunch_owner;
  23
  24 void crunch_task_release(struct thread_info *thread)
  25 {
  26         local_irq_disable();
  27         if (crunch_owner == &thread->crunchstate)
  28                 crunch_owner = NULL;
  29         local_irq_enable();
  30 }
  31
  32 static int crunch_enabled(u32 devcfg)
  33 {
  34         return !!(devcfg & EP93XX_SYSCON_DEVCFG_CPENA);
  35 }
  36
  37 static int crunch_do(struct notifier_block *self, unsigned long cmd, void *t)
  38 {
  39         struct thread_info *thread = (struct thread_info *)t;
  40         struct crunch_state *crunch_state;
  41         u32 devcfg;
  42
  43         crunch_state = &thread->crunchstate;
  44
  45         switch (cmd) {
  46         case THREAD_NOTIFY_FLUSH:
  47                 memset(crunch_state, 0, sizeof(*crunch_state));
  48
  49                 /*
  50                  * FALLTHROUGH: Ensure we don't try to overwrite our newly
  51                  * initialised state information on the first fault.
  52                  */
  53
  54         case THREAD_NOTIFY_EXIT:
  55                 crunch_task_release(thread);
  56                 break;
  57
  58         case THREAD_NOTIFY_SWITCH:
  59                 devcfg = __raw_readl(EP93XX_SYSCON_DEVCFG);
  60                 if (crunch_enabled(devcfg) || crunch_owner == crunch_state) {
  61                         /*
  62                          * We don't use ep93xx_syscon_swlocked_write() here
  63                          * because we are on the context switch path and
  64                          * preemption is already disabled.
  65                          */
  66                         devcfg ^= EP93XX_SYSCON_DEVCFG_CPENA;
  67                         __raw_writel(0xaa, EP93XX_SYSCON_SWLOCK);
  68                         __raw_writel(devcfg, EP93XX_SYSCON_DEVCFG);
  69                 }
  70                 break;
  71         }
  72
  73         return NOTIFY_DONE;
  74 }
  75
  76 static struct notifier_block crunch_notifier_block = {
  77         .notifier_call  = crunch_do,
  78 };
  79
  80 static int __init crunch_init(void)
  81 {
  82         thread_register_notifier(&crunch_notifier_block);
  83         elf_hwcap |= HWCAP_CRUNCH;
  84
  85         return 0;
  86 }
  87
  88 late_initcall(crunch_init);