Linux Kernel  3.7.1
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thumbee.c
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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  thread->thumbee_state = 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 
72  if ((pfr0 & 0x0000f000) != 0x00001000)
73  return 0;
74 
75  printk(KERN_INFO "ThumbEE CPU extension supported.\n");
77  thread_register_notifier(&thumbee_notifier_block);
78 
79  return 0;
80 }
81 
82 late_initcall(thumbee_init);