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kernel add
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/* Copyright (c) 2014-2015 The Linux Foundation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 and
* only version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* A call to __dcc_getchar() or __dcc_putchar() is typically followed by
* a call to __dcc_getstatus(). We want to make sure that the CPU does
* not speculative read the DCC status before executing the read or write
* instruction. That's what the ISBs are for.
*
* The 'volatile' ensures that the compiler does not cache the status bits,
* and instead reads the DCC register every time.
*/
#ifndef __ASM_DCC_H
#define __ASM_DCC_H
#include <asm/barrier.h>
static inline u32 __dcc_getstatus(void)
{
u32 ret;
asm volatile("mrs %0, mdccsr_el0" : "=r" (ret));
return ret;
}
static inline char __dcc_getchar(void)
{
char c;
asm volatile("mrs %0, dbgdtrrx_el0" : "=r" (c));
isb();
return c;
}
static inline void __dcc_putchar(char c)
{
/*
* The typecast is to make absolutely certain that 'c' is
* zero-extended.
*/
asm volatile("msr dbgdtrtx_el0, %0"
: : "r" ((unsigned long)(unsigned char)c));
isb();
}
#endif
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