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); 82