LXR linux/arch/arm/kernel/thumbee.c

   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 */
  18static 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
  25static inline void teehbr_write(unsigned long v)
  26{
  27        asm("mcr        p14, 6, %0, c1, c0, 0\n" : : "r" (v));
  28}
  29
  30static 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
  47static struct notifier_block thumbee_notifier_block = {
  48        .notifier_call  = thumbee_notifier,
  49};
  50
  51static 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
  70late_initcall(thumbee_init);
  71