From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: [PATCH] serial: mps2-uart: Initialize early console Date: Mon, 18 Jun 2018 21:54:57 -0700 Message-ID: <1529384097-1631-1-git-send-email-linux@roeck-us.net> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: Greg Kroah-Hartman Cc: Jiri Slaby , Vladimir Murzin , linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Liviu Dudau , Sudeep Holla , Lorenzo Pieralisi , Guenter Roeck List-Id: linux-serial@vger.kernel.org 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 --- 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