[PATCH 3/3] serial: mps2-uart: add support for early console

Vladimir Murzin
2016-04-25T08:48:54Z

This adds support early console for MPS2 UART which can be enabled via
earlycon=mps2,0x40004000

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/mps2-uart.c | 28 ++++++++++++++++++++++++++++
2 files changed, 29 insertions(+)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 3673ef0..4e6d2d1 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1450,6 +1450,7 @@ config SERIAL_MPS2_UART_CONSOLE
bool "MPS2 UART console support"
depends on SERIAL_MPS2_UART
select SERIAL_CORE_CONSOLE
+ select SERIAL_EARLYCON

config SERIAL_MPS2_UART
bool "MPS2 UART port"
diff --git a/drivers/tty/serial/mps2-uart.c b/drivers/tty/serial/mps2-uart.c
index e571e4c..da9e27d 100644
--- a/drivers/tty/serial/mps2-uart.c
+++ b/drivers/tty/serial/mps2-uart.c
@@ -450,6 +450,34 @@ static struct console mps2_uart_console = {

#define MPS2_SERIAL_CONSOLE (&mps2_uart_console)

+static void mps2_early_putchar(struct uart_port *port, int ch)
+{
+ while (readb(port->membase + UARTn_STATE) & UARTn_STATE_TX_FULL)
+ cpu_relax();
+
+ writeb((unsigned char)ch, port->membase + UARTn_DATA);
+}
+
+static void mps2_early_write(struct console *con, const char *s, unsigned int n)
+{
+ struct earlycon_device *dev = con->data;
+
+ uart_console_write(&dev->port, s, n, mps2_early_putchar);
+}
+
+static int __init mps2_early_console_setup(struct earlycon_device *device,
+ const char *opt)
+{
+ if (!device->port.membase)
+ return -ENODEV;
+
+ device->con->write = mps2_early_write;
+
+ return 0;
+}
+
+OF_EARLYCON_DECLARE(mps2, "arm,mps2-uart", mps2_early_console_setup);
+
#else
#define MPS2_SERIAL_CONSOLE NULL
#endif
--
1.7.9.5