[PATCH] tty: serial: atmel: add earlycon support

[Michael Walle]

Add early console support which relies on the bootloader for the
initialization of the UART.
Please note, that the compatibles are taken from at91-usart MFD
driver.

Signed-off-by: Michael Walle <michael at walle.cc>
---
 drivers/tty/serial/atmel_serial.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 2d09a89974a2..50fc6d51ff0d 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2673,6 +2673,30 @@ static struct console atmel_console = {
 	.data		= &atmel_uart,
 };
 
+static void atmel_serial_early_write(struct console *con, const char *s,
+				     unsigned int n)
+{
+	struct earlycon_device *dev = con->data;
+
+	uart_console_write(&dev->port, s, n, atmel_console_putchar);
+}
+
+static int __init atmel_early_console_setup(struct earlycon_device *device,
+					    const char *options)
+{
+	if (!device->port.membase)
+		return -ENODEV;
+
+	device->con->write = atmel_serial_early_write;
+
+	return 0;
+}
+
+OF_EARLYCON_DECLARE(atmelserial, "atmel,at91rm9200-usart",
+		    atmel_early_console_setup);
+OF_EARLYCON_DECLARE(atmelserial, "atmel,at91sam9260-usart",
+		    atmel_early_console_setup);
+
 #define ATMEL_CONSOLE_DEVICE	(&atmel_console)
 
 #else
-- 
2.30.2