arch/arm/mach-ep93xx/crunch.c

   1 /*
   2  * arch/arm/kernel/crunch.c
   3  * Cirrus MaverickCrunch context switching and handling
   4  *
   5  * Copyright (C) 2006 Lennert Buytenhek <[email protected]>
   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
  20 #include <asm/thread_notify.h>
  21
  22 #include "soc.h"
  23
  24 struct crunch_state *crunch_owner;
  25
  26 void crunch_task_release(struct thread_info *thread)
  27 {
  28         local_irq_disable();
  29         if (crunch_owner == &thread->crunchstate)
  30                 crunch_owner = NULL;
  31         local_irq_enable();
  32 }
  33
  34 static int crunch_enabled(u32 devcfg)
  35 {
  36         return !!(devcfg & EP93XX_SYSCON_DEVCFG_CPENA);
  37 }
  38
  39 static int crunch_do(struct notifier_block *self, unsigned long cmd, void *t)
  40 {
  41         struct thread_info *thread = (struct thread_info *)t;
  42         struct crunch_state *crunch_state;
  43         u32 devcfg;
  44
  45         crunch_state = &thread->crunchstate;
  46
  47         switch (cmd) {
  48         case THREAD_NOTIFY_FLUSH:
  49                 memset(crunch_state, 0, sizeof(*crunch_state));
  50
  51                 /*
  52                  * FALLTHROUGH: Ensure we don't try to overwrite our newly
  53                  * initialised state information on the first fault.
  54                  */
  55
  56         case THREAD_NOTIFY_EXIT:
  57                 crunch_task_release(thread);
  58                 break;
  59
  60         case THREAD_NOTIFY_SWITCH:
  61                 devcfg = __raw_readl(EP93XX_SYSCON_DEVCFG);
  62                 if (crunch_enabled(devcfg) || crunch_owner == crunch_state) {
  63                         /*
  64                          * We don't use ep93xx_syscon_swlocked_write() here
  65                          * because we are on the context switch path and
  66                          * preemption is already disabled.
  67                          */
  68                         devcfg ^= EP93XX_SYSCON_DEVCFG_CPENA;
  69                         __raw_writel(0xaa, EP93XX_SYSCON_SWLOCK);
  70                         __raw_writel(devcfg, EP93XX_SYSCON_DEVCFG);
  71                 }
  72                 break;
  73         }
  74
  75         return NOTIFY_DONE;
  76 }
  77
  78 static struct notifier_block crunch_notifier_block = {
  79         .notifier_call  = crunch_do,
  80 };
  81
  82 int __init crunch_init(void)
  83 {
  84         thread_register_notifier(&crunch_notifier_block);
  85         elf_hwcap |= HWCAP_CRUNCH;
  86
  87         return 0;
  88 }