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  */
  28 static 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
  35 static inline void teehbr_write(unsigned long v)
  36 {
  37         asm("mcr        p14, 6, %0, c1, c0, 0\n" : : "r" (v));
  38 }
  39
  40 static 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
  57 static struct notifier_block thumbee_notifier_block = {
  58         .notifier_call  = thumbee_notifier,
  59 };
  60
  61 static 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
  81 late_initcall(thumbee_init);