ARM64: TTY: hvc_dcc: Add support for ARM64 dcc

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>
This commit is contained in:
Abhimanyu Kapur 2015-09-12 12:44:39 -05:00 committed by Greg Kroah-Hartman
parent 3d27070108
commit 4cad4c57e0
2 changed files with 56 additions and 1 deletions

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@ -0,0 +1,55 @@
/* 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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@ -81,7 +81,7 @@ config HVC_UDBG
config HVC_DCC
bool "ARM JTAG DCC console"
depends on ARM
depends on ARM || ARM64
select HVC_DRIVER
help
This console uses the JTAG DCC on ARM to create a console under the HVC