serial: imx: add earlycon support

Earlycon allows to have an early debugging console that doesn't need
to be statically configured in the kernel config, like earlyprintk,
but is set up through the stdout-path DT property.

This allows to have the early debugging always built into the
kernel and enabled on demand without clashing between different boards
or architectures.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index f57bb907dc541e57ab8606f40c9351c32d87d7f3..9e2cc51d205a75d8c27b5127187a4eb9a3bbbc0e 100644 (file)
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -582,6 +582,7 @@ config SERIAL_IMX_CONSOLE
        bool "Console on IMX serial port"
        depends on SERIAL_IMX=y
        select SERIAL_CORE_CONSOLE
+       select SERIAL_EARLYCON if OF
        help
          If you have enabled the serial port on the Freescale IMX
          CPU you can make it the console by answering Y to this option.

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index fe3d41cc841632134fd907b1fb7af08f0e9d6e81..52629ca80437ccb584574a7ad7b3f3d6f1219b3f 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1795,6 +1795,38 @@ static struct console imx_console = {
 };
 
 #define IMX_CONSOLE    &imx_console
+
+#ifdef CONFIG_OF
+static void imx_console_early_putchar(struct uart_port *port, int ch)
+{
+       while (readl_relaxed(port->membase + IMX21_UTS) & UTS_TXFULL)
+               cpu_relax();
+
+       writel_relaxed(ch, port->membase + URTX0);
+}
+
+static void imx_console_early_write(struct console *con, const char *s,
+                                   unsigned count)
+{
+       struct earlycon_device *dev = con->data;
+
+       uart_console_write(&dev->port, s, count, imx_console_early_putchar);
+}
+
+static int __init
+imx_console_early_setup(struct earlycon_device *dev, const char *opt)
+{
+       if (!dev->port.membase)
+               return -ENODEV;
+
+       dev->con->write = imx_console_early_write;
+
+       return 0;
+}
+OF_EARLYCON_DECLARE(ec_imx6q, "fsl,imx6q-uart", imx_console_early_setup);
+OF_EARLYCON_DECLARE(ec_imx21, "fsl,imx21-uart", imx_console_early_setup);
+#endif
+
 #else
 #define IMX_CONSOLE    NULL
 #endif