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/system_info.h> 24 #include <asm/thread_notify.h> 25 26 /* 27 * Access to the ThumbEE Handler Base register 28 */ 29 static inline unsigned long teehbr_read(void) 30 { 31 unsigned long v; 32 asm("mrc p14, 6, %0, c1, c0, 0\n" : "=r" (v)); 33 return v; 34 } 35 36 static inline void teehbr_write(unsigned long v) 37 { 38 asm("mcr p14, 6, %0, c1, c0, 0\n" : : "r" (v)); 39 } 40 41 static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void *t) 42 { 43 struct thread_info *thread = t; 44 45 switch (cmd) { 46 case THREAD_NOTIFY_FLUSH: 47 thread->thumbee_state = 0; 48 break; 49 case THREAD_NOTIFY_SWITCH: 50 current_thread_info()->thumbee_state = teehbr_read(); 51 teehbr_write(thread->thumbee_state); 52 break; 53 } 54 55 return NOTIFY_DONE; 56 } 57 58 static struct notifier_block thumbee_notifier_block = { 59 .notifier_call = thumbee_notifier, 60 }; 61 62 static int __init thumbee_init(void) 63 { 64 unsigned long pfr0; 65 unsigned int cpu_arch = cpu_architecture(); 66 67 if (cpu_arch < CPU_ARCH_ARMv7) 68 return 0; 69 70 /* processor feature register 0 */ 71 asm("mrc p15, 0, %0, c0, c1, 0\n" : "=r" (pfr0)); 72 if ((pfr0 & 0x0000f000) != 0x00001000) 73 return 0; 74 75 printk(KERN_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); 83