diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 2 | ||||
| -rw-r--r-- | drivers/tty/serial/Kconfig | 10 | ||||
| -rw-r--r-- | drivers/tty/serial/Makefile | 1 | ||||
| -rw-r--r-- | drivers/tty/serial/earlycon-arm-semihost.c | 61 |
4 files changed, 74 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 2609ead7ff55..4946d8e58d53 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -899,6 +899,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. must already be setup and configured. Options are not yet supported. + smh Use ARM semihosting calls for early console. + earlyprintk= [X86,SH,BLACKFIN,ARM] earlyprintk=vga earlyprintk=efi diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig index 4290d05875b1..988fa2b6243b 100644 --- a/drivers/tty/serial/Kconfig +++ b/drivers/tty/serial/Kconfig @@ -73,6 +73,16 @@ config SERIAL_AMBA_PL011_CONSOLE your boot loader (lilo or loadlin) about how to pass options to the kernel at boot time.) +config SERIAL_EARLYCON_ARM_SEMIHOST + bool "Early console using ARM semihosting" + depends on ARM64 || ARM + select SERIAL_EARLYCON + help + Support for early debug console using ARM semihosting. This enables + the console before standard serial driver is probed. This is enabled + with "earlycon=smh" 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 diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile index 28048178f308..3a5be4633333 100644 --- a/drivers/tty/serial/Makefile +++ b/drivers/tty/serial/Makefile @@ -6,6 +6,7 @@ obj-$(CONFIG_SERIAL_CORE) += serial_core.o obj-$(CONFIG_SERIAL_21285) += 21285.o obj-$(CONFIG_SERIAL_EARLYCON) += earlycon.o +obj-$(CONFIG_SERIAL_EARLYCON_ARM_SEMIHOST) += earlycon-arm-semihost.o # These Sparc drivers have to appear before others such as 8250 # which share ttySx minor node space. Otherwise console device diff --git a/drivers/tty/serial/earlycon-arm-semihost.c b/drivers/tty/serial/earlycon-arm-semihost.c new file mode 100644 index 000000000000..383db10fbb49 --- /dev/null +++ b/drivers/tty/serial/earlycon-arm-semihost.c @@ -0,0 +1,61 @@ +/* + * Copyright (C) 2012 ARM Ltd. + * Author: Marc Zyngier <marc.zyngier@arm.com> + * + * Adapted for ARM and earlycon: + * Copyright (C) 2014 Linaro Ltd. + * Author: Rob Herring <robh@kernel.org> + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License 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. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ +#include <linux/kernel.h> +#include <linux/console.h> +#include <linux/init.h> +#include <linux/serial_core.h> + +#ifdef CONFIG_THUMB2_KERNEL +#define SEMIHOST_SWI "0xab" +#else +#define SEMIHOST_SWI "0x123456" +#endif + +/* + * Semihosting-based debug console + */ +static void smh_putc(struct uart_port *port, int c) +{ +#ifdef CONFIG_ARM64 + asm volatile("mov x1, %0\n" + "mov x0, #3\n" + "hlt 0xf000\n" + : : "r" (&c) : "x0", "x1", "memory"); +#else + asm volatile("mov r1, %0\n" + "mov r0, #3\n" + "svc " SEMIHOST_SWI "\n" + : : "r" (&c) : "r0", "r1", "memory"); +#endif +} + +static void smh_write(struct console *con, const char *s, unsigned n) +{ + struct earlycon_device *dev = con->data; + uart_console_write(&dev->port, s, n, smh_putc); +} + +int __init early_smh_setup(struct earlycon_device *device, const char *opt) +{ + device->con->write = smh_write; + return 0; +} +EARLYCON_DECLARE(smh, early_smh_setup); |