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); 83