[PATCH v2] serial: liteuart: Add support for earlycon
From: Stafford Horne <shorne@gmail.com>
Date: 2021-05-17 11:55:21
Also in:
linux-serial, lkml
Subsystem:
documentation, litex platform, the rest, tty layer and serial drivers · Maintainers:
Jonathan Corbet, Karol Gugala, Mateusz Holenko, Gabriel Somlo, Joel Stanley, Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
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. Signed-off-by: Stafford Horne <shorne@gmail.com> Cc: Florent Kermarrec <redacted> 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 [off-list ref] --- Changes since v1: - Fixed subject - Fixed ifdef and config issues pointed out by Jiri - Use liteuart_putchar instead of early_liteuart_putc .../admin-guide/kernel-parameters.txt | 5 +++++ drivers/tty/serial/Kconfig | 1 + drivers/tty/serial/liteuart.c | 21 +++++++++++++++++++ 3 files changed, 27 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 04545725f187..2d4a43af8de2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt@@ -1084,6 +1084,11 @@ 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
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 0c4cd4a348f4..af41e534483c 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig@@ -1550,6 +1550,7 @@ 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
diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index 64842f3539e1..1b75a4bf7c56 100644
--- a/drivers/tty/serial/liteuart.c
+++ b/drivers/tty/serial/liteuart.c@@ -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)
--
2.31.1