Linux kernel mirror (for testing)
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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