LXR linux/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
  22struct crunch_state *crunch_owner;
  23
  24void 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
  32static int crunch_enabled(u32 devcfg)
  33{
  34        return !!(devcfg & EP93XX_SYSCON_DEVCFG_CPENA);
  35}
  36
  37static 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
  76static struct notifier_block crunch_notifier_block = {
  77        .notifier_call  = crunch_do,
  78};
  79
  80static int __init crunch_init(void)
  81{
  82        thread_register_notifier(&crunch_notifier_block);
  83        elf_hwcap |= HWCAP_CRUNCH;
  84
  85        return 0;
  86}
  87
  88late_initcall(crunch_init);
  89