[PATCH] tty: serial: lantiq: implement earlycon support

[Martin Blumenstingl]

This allows enabling earlycon for devices with a Lantiq serial console
by splitting lqasc_serial_port_write() from lqasc_console_write() and
re-using the new function for earlycon's write callback.

The kernel-parameter name matches the driver name ("lantiq"), similar
to how other drivers implement this.

Signed-off-by: Martin Blumenstingl <martin.blumensti...@googlemail.com>
---
 Documentation/kernel-parameters.txt |  6 ++++++
 drivers/tty/serial/Kconfig          |  1 +
 drivers/tty/serial/lantiq.c         | 38 ++++++++++++++++++++++++++++++-------
 3 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/Documentation/kernel-parameters.txt 
b/Documentation/kernel-parameters.txt
index 37babf9..72fd841 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1156,6 +1156,12 @@ bytes respectively. Such letter suffixes can also be 
entirely omitted.
                        serial port must already be setup and configured.
                        Options are not yet supported.
 
+               lantiq,<addr>
+                       Start an early, polled-mode console on a lantiq serial
+                       (lqasc) port at the specified address. The serial port
+                       must already be setup and configured. Options are not
+                       yet supported.
+
                lpuart,<addr>
                lpuart32,<addr>
                        Use early console provided by Freescale LP UART driver
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 25c1d7b..13e280d 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1148,6 +1148,7 @@ config SERIAL_LANTIQ
        depends on LANTIQ
        select SERIAL_CORE
        select SERIAL_CORE_CONSOLE
+       select SERIAL_EARLYCON
        help
          Support for console and UART on Lantiq SoCs.
 
diff --git a/drivers/tty/serial/lantiq.c b/drivers/tty/serial/lantiq.c
index b88832e..7c9a3f2 100644
--- a/drivers/tty/serial/lantiq.c
+++ b/drivers/tty/serial/lantiq.c
@@ -590,13 +590,20 @@ lqasc_console_putchar(struct uart_port *port, int ch)
        ltq_w8(ch, port->membase + LTQ_ASC_TBUF);
 }
 
+static void lqasc_serial_port_write(struct uart_port *port, const char *s,
+                                   u_int count)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&ltq_asc_lock, flags);
+       uart_console_write(port, s, count, lqasc_console_putchar);
+       spin_unlock_irqrestore(&ltq_asc_lock, flags);
+}
 
 static void
 lqasc_console_write(struct console *co, const char *s, u_int count)
 {
        struct ltq_uart_port *ltq_port;
-       struct uart_port *port;
-       unsigned long flags;
 
        if (co->index >= MAXPORTS)
                return;
@@ -605,11 +612,7 @@ lqasc_console_write(struct console *co, const char *s, 
u_int count)
        if (!ltq_port)
                return;
 
-       port = &ltq_port->port;
-
-       spin_lock_irqsave(&ltq_asc_lock, flags);
-       uart_console_write(port, s, count, lqasc_console_putchar);
-       spin_unlock_irqrestore(&ltq_asc_lock, flags);
+       lqasc_serial_port_write(&ltq_port->port, s, count);
 }
 
 static int __init
@@ -659,6 +662,27 @@ lqasc_console_init(void)
 }
 console_initcall(lqasc_console_init);
 
+static void lqasc_serial_early_console_write(struct console *co,
+                                            const char *s,
+                                            u_int count)
+{
+       struct earlycon_device *dev = co->data;
+
+       lqasc_serial_port_write(&dev->port, s, count);
+}
+
+static int __init
+lqasc_serial_early_console_setup(struct earlycon_device *device,
+                                const char *opt)
+{
+       if (!device->port.membase)
+               return -ENODEV;
+
+       device->con->write = lqasc_serial_early_console_write;
+       return 0;
+}
+OF_EARLYCON_DECLARE(lantiq, DRVNAME, lqasc_serial_early_console_setup);
+
 static struct uart_driver lqasc_reg = {
        .owner =        THIS_MODULE,
        .driver_name =  DRVNAME,
-- 
2.10.2

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