Most litex boards using RISC-V soft cores us the sbi earlycon, however
this is not available for non RISC-V litex SoC. 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@xxxxxxxxx>
Cc: Florent Kermarrec <florent@xxxxxxxxxxxxxxxx>
Cc: Mateusz Holenko <mholenko@xxxxxxxxxxxx>
Cc: Joel Stanley <joel@xxxxxxxxx>
Cc: Gabriel L. Somlo <gsomlo@xxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 5 +++
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/liteuart.c | 31 +++++++++++++++++++
3 files changed, 37 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..9ceffe6ab6fd 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1531,6 +1531,7 @@ config SERIAL_LITEUART
depends on OF || COMPILE_TEST
depends on LITEX
select SERIAL_CORE
+ select SERIAL_EARLYCON
help
This driver is for the FPGA-based LiteUART serial controller from LiteX
SoC builder.
diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index 64842f3539e1..38c472487e68 100644
--- a/drivers/tty/serial/liteuart.c
+++ b/drivers/tty/serial/liteuart.c
@@ -372,6 +372,37 @@ static int __init liteuart_console_init(void)
console_initcall(liteuart_console_init);
#endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
+#ifdef CONFIG_SERIAL_EARLYCON
+static void early_liteuart_putc(struct uart_port *port, int c)
+{
+ while (litex_read8(port->membase + OFF_TXFULL))
+ cpu_relax();
+
+ litex_write8(port->membase + OFF_RXTX, c);
+}
+
+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, early_liteuart_putc);
+}
+
+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_EARLYCON */
+
static int __init liteuart_init(void)
{
int res;
--
2.31.1
