1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * arch/arm/kernel/thumbee.c
4  *
5  * Copyright (C) 2008 ARM Limited
6  */
7 
8 #include <linux/kernel.h>
9 #include <linux/init.h>
10 
11 #include <asm/cputype.h>
12 #include <asm/system_info.h>
13 #include <asm/thread_notify.h>
14 
15 /*
16  * Access to the ThumbEE Handler Base register
17  */
teehbr_read(void)18 static inline unsigned long teehbr_read(void)
19 {
20 	unsigned long v;
21 	asm("mrc	p14, 6, %0, c1, c0, 0\n" : "=r" (v));
22 	return v;
23 }
24 
teehbr_write(unsigned long v)25 static inline void teehbr_write(unsigned long v)
26 {
27 	asm("mcr	p14, 6, %0, c1, c0, 0\n" : : "r" (v));
28 }
29 
thumbee_notifier(struct notifier_block * self,unsigned long cmd,void * t)30 static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void *t)
31 {
32 	struct thread_info *thread = t;
33 
34 	switch (cmd) {
35 	case THREAD_NOTIFY_FLUSH:
36 		teehbr_write(0);
37 		break;
38 	case THREAD_NOTIFY_SWITCH:
39 		current_thread_info()->thumbee_state = teehbr_read();
40 		teehbr_write(thread->thumbee_state);
41 		break;
42 	}
43 
44 	return NOTIFY_DONE;
45 }
46 
47 static struct notifier_block thumbee_notifier_block = {
48 	.notifier_call	= thumbee_notifier,
49 };
50 
thumbee_init(void)51 static int __init thumbee_init(void)
52 {
53 	unsigned long pfr0;
54 	unsigned int cpu_arch = cpu_architecture();
55 
56 	if (cpu_arch < CPU_ARCH_ARMv7)
57 		return 0;
58 
59 	pfr0 = read_cpuid_ext(CPUID_EXT_PFR0);
60 	if ((pfr0 & 0x0000f000) != 0x00001000)
61 		return 0;
62 
63 	pr_info("ThumbEE CPU extension supported.\n");
64 	elf_hwcap |= HWCAP_THUMBEE;
65 	thread_register_notifier(&thumbee_notifier_block);
66 
67 	return 0;
68 }
69 
70 late_initcall(thumbee_init);
71