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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>
This commit is contained in:
Lucas Stach 2015-08-28 11:56:19 +02:00 committed by Greg Kroah-Hartman
parent 4cad4c57e0
commit 913c6c0e94
2 changed files with 33 additions and 0 deletions
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1
drivers/tty/serial/Kconfig
View File

@ -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.

32
drivers/tty/serial/imx.c
View File

@ -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