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serial: liteuart: Add support for earlycon

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Most litex boards using RISC-V soft cores us the sbi earlycon, however
this is not available for non RISC-V litex SoC's.  This patch enables
earlycon for liteuart which is available on all Litex SoC's making
support for earycon debugging more widely available.

Cc: Florent Kermarrec <florent@enjoy-digital.fr>
Cc: Mateusz Holenko <mholenko@antmicro.com>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Gabriel L. Somlo <gsomlo@gmail.com>
Reviewed-and-tested-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stafford Horne <shorne@gmail.com>
Link: https://lore.kernel.org/r/20210517115453.24365-1-shorne@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Stafford Horne 2021-05-17 20:54:52 +09:00 committed by Greg Kroah-Hartman
parent 758dfe3ddc
commit 4bc2bd5aef
3 changed files with 27 additions and 0 deletions
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5
Documentation/admin-guide/kernel-parameters.txt
View File

@ -1092,6 +1092,11 @@
the driver will use only 32-bit accessors to read/write
the device registers.
liteuart,<addr>
Start an early console on a litex serial port at the
specified address. The serial port must already be
setup and configured. Options are not yet supported.
meson,<addr>
Start an early, polled-mode console on a meson serial
port at the specified address. The serial port must

1
drivers/tty/serial/Kconfig
View File

@ -1553,6 +1553,7 @@ config SERIAL_LITEUART_CONSOLE
bool "LiteUART serial port console support"
depends on SERIAL_LITEUART=y
select SERIAL_CORE_CONSOLE
select SERIAL_EARLYCON
help
Say 'Y' or 'M' here if you wish to use the FPGA-based LiteUART serial
controller from LiteX SoC builder as the system console

21
drivers/tty/serial/liteuart.c
View File

@ -370,6 +370,27 @@ static int __init liteuart_console_init(void)
return 0;
}
console_initcall(liteuart_console_init);
static void early_liteuart_write(struct console *console, const char *s,
unsigned int count)
{
struct earlycon_device *device = console->data;
struct uart_port *port = &device->port;
uart_console_write(port, s, count, liteuart_putchar);
}
static int __init early_liteuart_setup(struct earlycon_device *device,
const char *options)
{
if (!device->port.membase)
return -ENODEV;
device->con->write = early_liteuart_write;
return 0;
}
OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup);
#endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
static int __init liteuart_init(void)