The early console code for mps2-uart assumes that the serial hardware is
enabled for transmit when the system boots. However, this is not the case
after reset. This results in a hang in mps2_early_putchar() if the serial
transmitter is not enabled by a boot loader or ROM monitor.
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
drivers/tty/serial/mps2-uart.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/tty/serial/mps2-uart.c b/drivers/tty/serial/mps2-uart.c
index 9f8f63719126..0743a0551ce1 100644
--- a/drivers/tty/serial/mps2-uart.c
+++ b/drivers/tty/serial/mps2-uart.c
@@ -448,6 +448,14 @@ static struct console mps2_uart_console = {
#define MPS2_SERIAL_CONSOLE (&mps2_uart_console)
+static void mps2_early_init(struct uart_port *port)
+{
+ u8 control = readb(port->membase + UARTn_CTRL);
+
+ control |= UARTn_CTRL_TX_ENABLE;
+ writeb(control, port->membase + UARTn_CTRL);
+}
+
static void mps2_early_putchar(struct uart_port *port, int ch)
{
while (readb(port->membase + UARTn_STATE) & UARTn_STATE_TX_FULL)
@@ -469,6 +477,7 @@ static int __init mps2_early_console_setup(struct earlycon_device *device,
if (!device->port.membase)
return -ENODEV;
+ mps2_early_init(&device->port);
device->con->write = mps2_early_write;
return 0;
--
2.7.4
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