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tty: serial: imx: add imx earlycon driver 

Split imx earlycon driver from imx serial driver "imx.c" as
separated driver. imx serial driver can be built as module,
but earlycon driver only support build in.

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Link: https://lore.kernel.org/r/20200724070815.11445-3-fugang.duan@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Fugang Duan 2020-07-24 15:08:15 +08:00 committed by Greg Kroah-Hartman
parent 0db4f9b91c
commit 699cc4dfd1
2 changed files with 58 additions and 0 deletions
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8
drivers/tty/serial/Kconfig
View File

@ -515,6 +515,14 @@ config SERIAL_IMX_CONSOLE
"console=ttymxc0". (Try "man bootparam" or see the documentation of
your bootloader about how to pass options to the kernel at boot time.)
config SERIAL_IMX_EARLYCON
bool "Earlycon on IMX serial port"
depends on OF
select SERIAL_EARLYCON
help
If you have enabled the earlycon on the Freescale IMX
CPU you can make it the earlycon by answering Y to this option.
config SERIAL_UARTLITE
tristate "Xilinx uartlite serial port support"
depends on HAS_IOMEM

50
drivers/tty/serial/imx_earlycon.c Normal file
View File

@ -0,0 +1,50 @@
// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright 2020 NXP
*/
#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/delay.h>
#include <linux/of.h>
#include <linux/io.h>
#define URTX0 0x40 /* Transmitter Register */
#define UTS_TXFULL (1<<4) /* TxFIFO full */
#define IMX21_UTS 0xb4 /* UART Test Register on all other i.mx*/
static void imx_uart_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_uart_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_uart_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_uart_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);
MODULE_AUTHOR("NXP");
MODULE_DESCRIPTION("IMX earlycon driver");
MODULE_LICENSE("GPL");