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 | */ |
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 | |
25 | static inline void teehbr_write(unsigned long v) |
26 | { |
27 | asm("mcr p14, 6, %0, c1, c0, 0\n" : : "r" (v)); |
28 | } |
29 | |
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(v: 0); |
37 | break; |
38 | case THREAD_NOTIFY_SWITCH: |
39 | current_thread_info()->thumbee_state = teehbr_read(); |
40 | teehbr_write(v: 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 | |
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 | |