LXR linux/arch/arm/kernel/thumbee.c

   1/*
   2 * arch/arm/kernel/thumbee.c
   3 *
   4 * Copyright (C) 2008 ARM Limited
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * This program is distributed in the hope that it will be useful,
  11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 * GNU General Public License for more details.
  14 *
  15 * You should have received a copy of the GNU General Public License
  16 * along with this program; if not, write to the Free Software
  17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  18 */
  19
  20#include <linux/kernel.h>
  21#include <linux/init.h>
  22
  23#include <asm/thread_notify.h>
  24
  25/*
  26 * Access to the ThumbEE Handler Base register
  27 */
  28static inline unsigned long teehbr_read(void)
  29{
  30        unsigned long v;
  31        asm("mrc        p14, 6, %0, c1, c0, 0\n" : "=r" (v));
  32        return v;
  33}
  34
  35static inline void teehbr_write(unsigned long v)
  36{
  37        asm("mcr        p14, 6, %0, c1, c0, 0\n" : : "r" (v));
  38}
  39
  40static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void *t)
  41{
  42        struct thread_info *thread = t;
  43
  44        switch (cmd) {
  45        case THREAD_NOTIFY_FLUSH:
  46                thread->thumbee_state = 0;
  47                break;
  48        case THREAD_NOTIFY_SWITCH:
  49                current_thread_info()->thumbee_state = teehbr_read();
  50                teehbr_write(thread->thumbee_state);
  51                break;
  52        }
  53
  54        return NOTIFY_DONE;
  55}
  56
  57static struct notifier_block thumbee_notifier_block = {
  58        .notifier_call  = thumbee_notifier,
  59};
  60
  61static int __init thumbee_init(void)
  62{
  63        unsigned long pfr0;
  64        unsigned int cpu_arch = cpu_architecture();
  65
  66        if (cpu_arch < CPU_ARCH_ARMv7)
  67                return 0;
  68
  69        /* processor feature register 0 */
  70        asm("mrc        p15, 0, %0, c0, c1, 0\n" : "=r" (pfr0));
  71        if ((pfr0 & 0x0000f000) != 0x00001000)
  72                return 0;
  73
  74        printk(KERN_INFO "ThumbEE CPU extension supported.\n");
  75        elf_hwcap |= HWCAP_THUMBEE;
  76        thread_register_notifier(&thumbee_notifier_block);
  77
  78        return 0;
  79}
  80
  81late_initcall(thumbee_init);
  82