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>

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 7fa2c78d19896f8561ea590e43ec41e382ba0580..8a0352eb337c84ea5c9dd318edd7726b3946f583 100644 (file)
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -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

diff --git a/drivers/tty/serial/imx_earlycon.c b/drivers/tty/serial/imx_earlycon.c
new file mode 100644 (file)
index 0000000..795606e
--- /dev/null
+++ b/drivers/tty/serial/imx_earlycon.c
@@ -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");