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Unverified Commit 27de1f54 authored by Anup Patel's avatar Anup Patel Committed by Palmer Dabbelt
Browse files

tty/serial: Add RISC-V SBI earlycon support 



In RISC-V, the M-mode runtime firmware provide SBI calls for
debug prints. This patch adds earlycon support using RISC-V
SBI console calls. To enable it, just pass "earlycon=sbi" in
kernel parameters.

Signed-off-by: default avatarAnup Patel <anup@brainfault.org>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarPalmer Dabbelt <palmer@sifive.com>
Signed-off-by: default avatarPalmer Dabbelt <palmer@sifive.com>
parent 80100942

drivers/tty/serial/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -85,6 +85,18 @@ config SERIAL_EARLYCON_ARM_SEMIHOST 
	  with "earlycon=smh" on the kernel command line. The console is

	  enabled when early_param is processed.



config SERIAL_EARLYCON_RISCV_SBI

	bool "Early console using RISC-V SBI"

	depends on RISCV

	select SERIAL_CORE

	select SERIAL_CORE_CONSOLE

	select SERIAL_EARLYCON

	help

	  Support for early debug console using RISC-V SBI. This enables

	  the console before standard serial driver is probed. This is enabled

	  with "earlycon=sbi" on the kernel command line. The console is

	  enabled when early_param is processed.



config SERIAL_SB1250_DUART

	tristate "BCM1xxx on-chip DUART serial support"

	depends on SIBYTE_SB1xxx_SOC=y

drivers/tty/serial/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ obj-$(CONFIG_SERIAL_CORE) += serial_core.o 


obj-$(CONFIG_SERIAL_EARLYCON) += earlycon.o

obj-$(CONFIG_SERIAL_EARLYCON_ARM_SEMIHOST) += earlycon-arm-semihost.o

obj-$(CONFIG_SERIAL_EARLYCON_RISCV_SBI) += earlycon-riscv-sbi.o



# These Sparc drivers have to appear before others such as 8250

# which share ttySx minor node space.  Otherwise console device

drivers/tty/serial/earlycon-riscv-sbi.c

0 → 100644
+28 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * RISC-V SBI based earlycon

 *

 * Copyright (C) 2018 Anup Patel <anup@brainfault.org>

 */

#include <linux/kernel.h>

#include <linux/console.h>

#include <linux/init.h>

#include <linux/serial_core.h>

#include <asm/sbi.h>



static void sbi_console_write(struct console *con,

			      const char *s, unsigned int n)

{

	int i;



	for (i = 0; i < n; ++i)

		sbi_console_putchar(s[i]);

}



static int __init early_sbi_setup(struct earlycon_device *device,

				  const char *opt)

{

	device->con->write = sbi_console_write;

	return 0;

}

EARLYCON_DECLARE(sbi, early_sbi_setup);