From: Fugang Duan <fugang.duan@nxp.com>
Date: Fri, 24 Jul 2020 15:08:15 +0800
Subject: tty: serial: imx: add imx earlycon driver
Git-commit: 699cc4dfd14071e4843e2fde8ce01f09871eb318
Patch-mainline: v5.9-rc1
References: jsc#SLE-16106

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>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
 drivers/tty/serial/Kconfig        |  8 +++++++
 drivers/tty/serial/imx_earlycon.c | 50 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 7fa2c78d1989..8a0352eb337c 100644
--- 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
index 000000000000..795606e1a22f
--- /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");