Commit db5489f4 authored by Bin Meng's avatar Bin Meng Committed by Greg Kroah-Hartman
Browse files

riscv: Implement semihost.h for earlycon semihost driver 

Per RISC-V semihosting spec [1], implement semihost.h for the existing
Arm semihosting earlycon driver to work on RISC-V.

Link: https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc

 [1]

Signed-off-by: default avatarBin Meng <bmeng@tinylab.org>
Tested-by: default avatarSergey Matyukevich <sergey.matyukevich@syntacore.com>
Acked-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20221209150437.795918-3-bmeng@tinylab.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 88907175

arch/riscv/include/asm/semihost.h

0 → 100644
+26 −0
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/* SPDX-License-Identifier: GPL-2.0 */

/*

 * Copyright (C) 2022 tinylab.org

 * Author: Bin Meng <bmeng@tinylab.org>

 */



#ifndef _RISCV_SEMIHOST_H_

#define _RISCV_SEMIHOST_H_



struct uart_port;



static inline void smh_putc(struct uart_port *port, unsigned char c)

{

	asm volatile("addi    a1, %0, 0\n"

		     "addi    a0, zero, 3\n"

		     ".balign 16\n"

		     ".option push\n"

		     ".option norvc\n"

		     "slli    zero, zero, 0x1f\n"

		     "ebreak\n"

		     "srai    zero, zero, 0x7\n"

		     ".option pop\n"

		     : : "r" (&c) : "a0", "a1", "memory");

}



#endif /* _RISCV_SEMIHOST_H_ */

drivers/tty/serial/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -75,7 +75,7 @@ config SERIAL_AMBA_PL011_CONSOLE 


config SERIAL_EARLYCON_ARM_SEMIHOST

	bool "Early console using ARM semihosting"

	depends on ARM64 || ARM

	depends on ARM64 || ARM || RISCV

	select SERIAL_CORE

	select SERIAL_CORE_CONSOLE

	select SERIAL_EARLYCON