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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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4cad4c57e0
Add support for debug communications channel based hvc console for arm64 cpus. Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org> Signed-off-by: Timur Tabi <timur@codeaurora.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
56 lines
1.4 KiB
C
56 lines
1.4 KiB
C
/* Copyright (c) 2014-2015 The Linux Foundation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 and
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* only version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* A call to __dcc_getchar() or __dcc_putchar() is typically followed by
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* a call to __dcc_getstatus(). We want to make sure that the CPU does
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* not speculative read the DCC status before executing the read or write
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* instruction. That's what the ISBs are for.
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*
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* The 'volatile' ensures that the compiler does not cache the status bits,
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* and instead reads the DCC register every time.
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*/
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#ifndef __ASM_DCC_H
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#define __ASM_DCC_H
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#include <asm/barrier.h>
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static inline u32 __dcc_getstatus(void)
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{
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u32 ret;
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asm volatile("mrs %0, mdccsr_el0" : "=r" (ret));
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return ret;
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}
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static inline char __dcc_getchar(void)
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{
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char c;
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asm volatile("mrs %0, dbgdtrrx_el0" : "=r" (c));
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isb();
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return c;
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}
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static inline void __dcc_putchar(char c)
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{
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/*
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* The typecast is to make absolutely certain that 'c' is
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* zero-extended.
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*/
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asm volatile("msr dbgdtrtx_el0, %0"
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: : "r" ((unsigned long)(unsigned char)c));
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isb();
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}
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#endif
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