[PATCH tty/serial v2 1/1] tty: serial: imx: enable imx serial console port as module

[Fugang Duan <fugang.duan@nxp.com>]

GKI kernel requires drivers built as modules including
console driver, so add the support that imx serial console
driver can be built as module.

The changes of the patch:
- imx console driver can be built as module.
- move out earlycon code to separated driver like imx_earlycon.c,
  and imx earlycon driver only support build-in.

v2:
 - fix kbuild error

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
---
 drivers/tty/serial/Kconfig        | 18 +++++++----
 drivers/tty/serial/Makefile       |  1 +
 drivers/tty/serial/imx.c          | 37 ++---------------------
 drivers/tty/serial/imx_earlycon.c | 50 +++++++++++++++++++++++++++++++
 4 files changed, 66 insertions(+), 40 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 780908d43557..dabd06ca9b66 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -502,20 +502,28 @@ config SERIAL_IMX
 	  can enable its onboard serial port by enabling this option.
 
 config SERIAL_IMX_CONSOLE
-	bool "Console on IMX serial port"
-	depends on SERIAL_IMX=y
+	tristate "Console on IMX serial port"
+	depends on SERIAL_IMX
 	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.
+	  CPU you can make it the console by answering Y/M to this option.
 
-	  Even if you say Y here, the currently visible virtual console
+	  Even if you say Y/M here, the currently visible virtual console
 	  (/dev/tty0) will still be used as the system console by default, but
 	  you can alter that using a kernel command line option such as
 	  "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
+	default y
+	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/Makefile b/drivers/tty/serial/Makefile
index d056ee6cca33..caf167f0c10a 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -43,6 +43,7 @@ obj-$(CONFIG_SERIAL_ZS) += zs.o
 obj-$(CONFIG_SERIAL_SH_SCI) += sh-sci.o
 obj-$(CONFIG_SERIAL_CPM) += cpm_uart/
 obj-$(CONFIG_SERIAL_IMX) += imx.o
+obj-$(CONFIG_SERIAL_IMX_EARLYCON) += imx_earlycon.o
 obj-$(CONFIG_SERIAL_MPC52xx) += mpc52xx_uart.o
 obj-$(CONFIG_SERIAL_ICOM) += icom.o
 obj-$(CONFIG_SERIAL_MESON) += meson_uart.o
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 1265e8d86d8a..6814485cf255 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -361,7 +361,7 @@ static inline int imx_uart_is_imx6q(struct imx_port *sport)
 /*
  * Save and restore functions for UCR1, UCR2 and UCR3 registers
  */
-#if defined(CONFIG_SERIAL_IMX_CONSOLE)
+#if IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE)
 static void imx_uart_ucrs_save(struct imx_port *sport,
 			       struct imx_port_ucrs *ucr)
 {
@@ -1915,7 +1915,7 @@ static const struct uart_ops imx_uart_pops = {
 
 static struct imx_port *imx_uart_ports[UART_NR];
 
-#ifdef CONFIG_SERIAL_IMX_CONSOLE
+#if IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE)
 static void imx_uart_console_putchar(struct uart_port *port, int ch)
 {
 	struct imx_port *sport = (struct imx_port *)port;
@@ -2112,39 +2112,6 @@ static struct console imx_uart_console = {
 
 #define IMX_CONSOLE	&imx_uart_console
 
-#ifdef CONFIG_OF
-static void imx_uart_console_early_putchar(struct uart_port *port, int ch)
-{
-	struct imx_port *sport = (struct imx_port *)port;
-
-	while (imx_uart_readl(sport, IMX21_UTS) & UTS_TXFULL)
-		cpu_relax();
-
-	imx_uart_writel(sport, ch, 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);
-#endif
-
 #else
 #define IMX_CONSOLE	NULL
 #endif
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");
-- 
2.17.1