LXR linux/arch/arm64/include/asm/dcc.h

   1/* Copyright (c) 2014-2015 The Linux Foundation. All rights reserved.
   2 *
   3 * This program is free software; you can redistribute it and/or modify
   4 * it under the terms of the GNU General Public License version 2 and
   5 * only version 2 as published by the Free Software Foundation.
   6 *
   7 * This program is distributed in the hope that it will be useful,
   8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10 * GNU General Public License for more details.
  11 *
  12 * A call to __dcc_getchar() or __dcc_putchar() is typically followed by
  13 * a call to __dcc_getstatus().  We want to make sure that the CPU does
  14 * not speculative read the DCC status before executing the read or write
  15 * instruction.  That's what the ISBs are for.
  16 *
  17 * The 'volatile' ensures that the compiler does not cache the status bits,
  18 * and instead reads the DCC register every time.
  19 */
  20#ifndef __ASM_DCC_H
  21#define __ASM_DCC_H
  22
  23#include <asm/barrier.h>
  24#include <asm/sysreg.h>
  25
  26static inline u32 __dcc_getstatus(void)
  27{
  28        return read_sysreg(mdccsr_el0);
  29}
  30
  31static inline char __dcc_getchar(void)
  32{
  33        char c = read_sysreg(dbgdtrrx_el0);
  34        isb();
  35
  36        return c;
  37}
  38
  39static inline void __dcc_putchar(char c)
  40{
  41        /*
  42         * The typecast is to make absolutely certain that 'c' is
  43         * zero-extended.
  44         */
  45        write_sysreg((unsigned char)c, dbgdtrtx_el0);
  46        isb();
  47}
  48
  49#endif
  50