Messages in this thread Patch in this message | | | From | Timur Tabi <> | Subject | [PATCH] ARM64: TTY: hvc_dcc: Add support for ARM64 dcc | Date | Fri, 19 Jun 2015 17:08:54 -0500 |
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From: Abhimanyu Kapur <abhimany@codeaurora.org>
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> --- arch/arm64/include/asm/dcc.h | 49 ++++++++++++++++++++++++++++++++++++++++++++ drivers/tty/hvc/Kconfig | 2 +- 2 files changed, 50 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/include/asm/dcc.h
diff --git a/arch/arm64/include/asm/dcc.h b/arch/arm64/include/asm/dcc.h new file mode 100644 index 0000000..f038d61 --- /dev/null +++ b/arch/arm64/include/asm/dcc.h @@ -0,0 +1,49 @@ +/* Copyright (c) 2014 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. + */ + +#include <asm/barrier.h> + +static inline u32 __dcc_getstatus(void) +{ + u32 __ret; + + asm volatile("mrs %0, mdccsr_el0" : "=r" (__ret) + : : "cc"); + + 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) +{ + asm volatile("msr dbgdtrtx_el0, %0" + : /* No output register */ + : "r" (c)); + isb(); +} diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig index 2c6883c..9a60d18 100644 --- a/drivers/tty/hvc/Kconfig +++ b/drivers/tty/hvc/Kconfig @@ -88,7 +88,7 @@ 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 -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/
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