linux-kernel - [PATCH] tty: serial: atmel: add earlycon support

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Date:   Wed, 16 Feb 2022 17:18:22 +0100
From:   Michael Walle <michael@...le.cc>
To:     Richard Genoud <richard.genoud@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc:     linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Michael Walle <michael@...le.cc>
Subject: [PATCH] tty: serial: atmel: add earlycon support

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@...le.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