Commit 4bc2bd5a authored by Stafford Horne's avatar Stafford Horne Committed by Greg Kroah-Hartman
Browse files

serial: liteuart: Add support for earlycon 



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: default avatarGabriel Somlo <gsomlo@gmail.com>
Reviewed-by: default avatarJiri Slaby <jirislaby@kernel.org>
Reviewed-by: default avatarJoel Stanley <joel@jms.id.au>
Signed-off-by: default avatarStafford Horne <shorne@gmail.com>
Link: https://lore.kernel.org/r/20210517115453.24365-1-shorne@gmail.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 758dfe3d

Documentation/admin-guide/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -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

drivers/tty/serial/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

drivers/tty/serial/liteuart.c

+21 −0
Original line number Diff line number Diff line
@@ -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)