tty: serial: meson: Implement earlycon support

Split off the bulk of the existing meson_serial_console_write()
implementation into meson_serial_port_write() for implementing
meson_serial_early_console_write().

Use "meson" as the earlycon driver name, courtesy of Nicolas.

Signed-off-by: Nicolas Saenz Julienne <nicolassaenzj@gmail.com>
Acked-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 0b3de80..36e1c7b 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1039,6 +1039,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        the driver will use only 32-bit accessors to read/write
                        the device registers.
 
+               meson,<addr>
+                       Start an early, polled-mode console on a meson serial
+                       port at the specified address. The serial port must
+                       already be setup and configured. Options are not yet
+                       supported.
+
                msm_serial,<addr>
                        Start an early, polled-mode console on an msm serial
                        port at the specified address. The serial port

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 13d4ed6..aa86994 100644 (file)
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -213,6 +213,7 @@ config SERIAL_MESON_CONSOLE
        bool "Support for console on meson"
        depends on SERIAL_MESON=y
        select SERIAL_CORE_CONSOLE
+       select SERIAL_EARLYCON
        help
          Say Y here if you wish to use a Amlogic MesonX UART as the
          system console (the system console is the device which

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 024445a..6aea0f4 100644 (file)
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -481,18 +481,13 @@ static void meson_console_putchar(struct uart_port *port, int ch)
        writel(ch, port->membase + AML_UART_WFIFO);
 }
 
-static void meson_serial_console_write(struct console *co, const char *s,
-                                      u_int count)
+static void meson_serial_port_write(struct uart_port *port, const char *s,
+                                   u_int count)
 {
-       struct uart_port *port;
        unsigned long flags;
        int locked;
        u32 val, tmp;
 
-       port = meson_ports[co->index];
-       if (!port)
-               return;
-
        local_irq_save(flags);
        if (port->sysrq) {
                locked = 0;
@@ -516,6 +511,18 @@ static void meson_serial_console_write(struct console *co, const char *s,
        local_irq_restore(flags);
 }
 
+static void meson_serial_console_write(struct console *co, const char *s,
+                                      u_int count)
+{
+       struct uart_port *port;
+
+       port = meson_ports[co->index];
+       if (!port)
+               return;
+
+       meson_serial_port_write(port, s, count);
+}
+
 static int meson_serial_console_setup(struct console *co, char *options)
 {
        struct uart_port *port;
@@ -554,6 +561,27 @@ static int __init meson_serial_console_init(void)
 }
 console_initcall(meson_serial_console_init);
 
+static void meson_serial_early_console_write(struct console *co,
+                                            const char *s,
+                                            u_int count)
+{
+       struct earlycon_device *dev = co->data;
+
+       meson_serial_port_write(&dev->port, s, count);
+}
+
+static int __init
+meson_serial_early_console_setup(struct earlycon_device *device, const char *opt)
+{
+       if (!device->port.membase)
+               return -ENODEV;
+
+       device->con->write = meson_serial_early_console_write;
+       return 0;
+}
+OF_EARLYCON_DECLARE(meson, "amlogic,meson-uart",
+                   meson_serial_early_console_setup);
+
 #define MESON_SERIAL_CONSOLE   (&meson_serial_console)
 #else
 #define MESON_SERIAL_CONSOLE   NULL