tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
tty/serial: add arm/arm64 semihosting earlycon
Add earlycon support for the arm/arm64 semihosting debug serial
interface. This allows enabling a debug console when early_params are
processed. This is based on the arm64 earlyprintk smh support and is
intended to replace it.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
authored by
Rob Herring
and committed by
Greg Kroah-Hartman
d50d7269
0d3c673e
+74
+2
Documentation/kernel-parameters.txt
+2
Documentation/kernel-parameters.txt
+10
drivers/tty/serial/Kconfig
+10
drivers/tty/serial/Kconfig
···
73
73
your boot loader (lilo or loadlin) about how to pass options to the
74
74
kernel at boot time.)
75
75
76
+
config SERIAL_EARLYCON_ARM_SEMIHOST
77
+
bool "Early console using ARM semihosting"
78
+
depends on ARM64 || ARM
79
+
select SERIAL_EARLYCON
80
+
help
81
+
Support for early debug console using ARM semihosting. This enables
82
+
the console before standard serial driver is probed. This is enabled
83
+
with "earlycon=smh" on the kernel command line. The console is
84
+
enabled when early_param is processed.
85
+
76
86
config SERIAL_SB1250_DUART
77
87
tristate "BCM1xxx on-chip DUART serial support"
78
88
depends on SIBYTE_SB1xxx_SOC=y
+1
drivers/tty/serial/Makefile
+1
drivers/tty/serial/Makefile
···
6
6
obj-$(CONFIG_SERIAL_21285) += 21285.o
7
7
8
8
obj-$(CONFIG_SERIAL_EARLYCON) += earlycon.o
9
+
obj-$(CONFIG_SERIAL_EARLYCON_ARM_SEMIHOST) += earlycon-arm-semihost.o
9
10
10
11
# These Sparc drivers have to appear before others such as 8250
11
12
# which share ttySx minor node space. Otherwise console device
+61
drivers/tty/serial/earlycon-arm-semihost.c
+61
drivers/tty/serial/earlycon-arm-semihost.c
···
1
+
/*
2
+
* Copyright (C) 2012 ARM Ltd.
3
+
* Author: Marc Zyngier <marc.zyngier@arm.com>
4
+
*
5
+
* Adapted for ARM and earlycon:
6
+
* Copyright (C) 2014 Linaro Ltd.
7
+
* Author: Rob Herring <robh@kernel.org>
8
+
*
9
+
* This program is free software: you can redistribute it and/or modify
10
+
* it under the terms of the GNU General Public License version 2 as
11
+
* published by the Free Software Foundation.
12
+
*
13
+
* This program is distributed in the hope that it will be useful,
14
+
* but WITHOUT ANY WARRANTY; without even the implied warranty of
15
+
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16
+
* GNU General Public License for more details.
17
+
*
18
+
* You should have received a copy of the GNU General Public License
19
+
* along with this program. If not, see <http://www.gnu.org/licenses/>.
20
+
*/
21
+
#include <linux/kernel.h>
22
+
#include <linux/console.h>
23
+
#include <linux/init.h>
24
+
#include <linux/serial_core.h>
25
+
26
+
#ifdef CONFIG_THUMB2_KERNEL
27
+
#define SEMIHOST_SWI "0xab"
28
+
#else
29
+
#define SEMIHOST_SWI "0x123456"
30
+
#endif
31
+
32
+
/*
33
+
* Semihosting-based debug console
34
+
*/
35
+
static void smh_putc(struct uart_port *port, int c)
36
+
{
37
+
#ifdef CONFIG_ARM64
38
+
asm volatile("mov x1, %0\n"
39
+
"mov x0, #3\n"
40
+
"hlt 0xf000\n"
41
+
: : "r" (&c) : "x0", "x1", "memory");
42
+
#else
43
+
asm volatile("mov r1, %0\n"
44
+
"mov r0, #3\n"
45
+
"svc " SEMIHOST_SWI "\n"
46
+
: : "r" (&c) : "r0", "r1", "memory");
47
+
#endif
48
+
}
49
+
50
+
static void smh_write(struct console *con, const char *s, unsigned n)
51
+
{
52
+
struct earlycon_device *dev = con->data;
53
+
uart_console_write(&dev->port, s, n, smh_putc);
54
+
}
55
+
56
+
int __init early_smh_setup(struct earlycon_device *device, const char *opt)
57
+
{
58
+
device->con->write = smh_write;
59
+
return 0;
60
+
}
61
+
EARLYCON_DECLARE(smh, early_smh_setup);