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/cputype.h>
  24 #include <asm/system_info.h>
  25 #include <asm/thread_notify.h>
  26
  27 /*
  28  * Access to the ThumbEE Handler Base register
  29  */
  30 static inline unsigned long teehbr_read(void)
  31 {
  32         unsigned long v;
  33         asm("mrc        p14, 6, %0, c1, c0, 0\n" : "=r" (v));
  34         return v;
  35 }
  36
  37 static inline void teehbr_write(unsigned long v)
  38 {
  39         asm("mcr        p14, 6, %0, c1, c0, 0\n" : : "r" (v));
  40 }
  41
  42 static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void *t)
  43 {
  44         struct thread_info *thread = t;
  45
  46         switch (cmd) {
  47         case THREAD_NOTIFY_FLUSH:
  48                 teehbr_write(0);
  49                 break;
  50         case THREAD_NOTIFY_SWITCH:
  51                 current_thread_info()->thumbee_state = teehbr_read();
  52                 teehbr_write(thread->thumbee_state);
  53                 break;
  54         }
  55
  56         return NOTIFY_DONE;
  57 }
  58
  59 static struct notifier_block thumbee_notifier_block = {
  60         .notifier_call  = thumbee_notifier,
  61 };
  62
  63 static int __init thumbee_init(void)
  64 {
  65         unsigned long pfr0;
  66         unsigned int cpu_arch = cpu_architecture();
  67
  68         if (cpu_arch < CPU_ARCH_ARMv7)
  69                 return 0;
  70
  71         pfr0 = read_cpuid_ext(CPUID_EXT_PFR0);
  72         if ((pfr0 & 0x0000f000) != 0x00001000)
  73                 return 0;
  74
  75         pr_info("ThumbEE CPU extension supported.\n");
  76         elf_hwcap |= HWCAP_THUMBEE;
  77         thread_register_notifier(&thumbee_notifier_block);
  78
  79         return 0;
  80 }
  81
  82 late_initcall(thumbee_init);