From 4d6a580fdd76a6e6d63adb15ac025f69f5ab0e8a Mon Sep 17 00:00:00 2001
From: Dmitry Rokosov <ddrokosov@sberdevices.ru>
Date: Wed, 5 Jul 2023 21:18:29 +0300
Subject: [PATCH] tty: serial: meson: apply ttyS devname instead of ttyAML for
 new SoCs

References: bsc#1214683 (PREEMPT_RT prerequisite backports)
Patch-mainline: v6.6-rc1
Git-commit: e71aab9d613242bbb262f2344e377ecbc892df41

It is worth noting that the devname ttyS is a widely recognized tty name
and is commonly used by many uart device drivers. Given the established
usage and compatibility concerns, it may not be feasible to change the
devname for older SoCs. However, for new definitions, it is acceptable
and even recommended to use a new devname to help ensure clarity and
avoid any potential conflicts on lower or upper software levels.

For more information please refer to IRC discussion at [1].

Links:
    [1]: https://libera.irclog.whitequark.org/linux-amlogic/2023-07-03

Signed-off-by: Dmitry Rokosov <ddrokosov@sberdevices.ru>
Link: https://lore.kernel.org/r/20230705181833.16137-4-ddrokosov@sberdevices.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 drivers/tty/serial/meson_uart.c | 82 ++++++++++++++++++++++++++++-------------
 1 file changed, 56 insertions(+), 26 deletions(-)

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 523361569cb3..421706e10ebf 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -72,16 +72,22 @@
 
 #define AML_UART_PORT_NUM		12
 #define AML_UART_PORT_OFFSET		6
-#define AML_UART_DEV_NAME		"ttyAML"
 
 #define AML_UART_POLL_USEC		5
 #define AML_UART_TIMEOUT_USEC		10000
 
-static struct uart_driver meson_uart_driver;
+#define MESON_UART_DRIVER(_devname) meson_uart_driver_##_devname
+
+#define MESON_UART_DRIVER_DECLARE(_devname) \
+	static struct uart_driver MESON_UART_DRIVER(_devname)
+
+MESON_UART_DRIVER_DECLARE(ttyAML);
+MESON_UART_DRIVER_DECLARE(ttyS);
 
 static struct uart_port *meson_ports[AML_UART_PORT_NUM];
 
 struct meson_uart_data {
+	struct uart_driver *uart_driver;
 	bool has_xtal_div2;
 };
 
@@ -615,15 +621,21 @@ static int meson_serial_console_setup(struct console *co, char *options)
 	return uart_set_options(port, co, baud, parity, bits, flow);
 }
 
-static struct console meson_serial_console = {
-	.name		= AML_UART_DEV_NAME,
-	.write		= meson_serial_console_write,
-	.device		= uart_console_device,
-	.setup		= meson_serial_console_setup,
-	.flags		= CON_PRINTBUFFER,
-	.index		= -1,
-	.data		= &meson_uart_driver,
-};
+#define MESON_SERIAL_CONSOLE(_devname) meson_serial_console_##_devname
+
+#define MESON_SERIAL_CONSOLE_DEFINE(_devname)				\
+	static struct console MESON_SERIAL_CONSOLE(_devname) = {	\
+		.name		= __stringify(_devname),		\
+		.write		= meson_serial_console_write,		\
+		.device		= uart_console_device,			\
+		.setup		= meson_serial_console_setup,		\
+		.flags		= CON_PRINTBUFFER,			\
+		.index		= -1,					\
+		.data		= &MESON_UART_DRIVER(_devname),		\
+	}
+
+MESON_SERIAL_CONSOLE_DEFINE(ttyAML);
+MESON_SERIAL_CONSOLE_DEFINE(ttyS);
 
 static void meson_serial_early_console_write(struct console *co,
 					     const char *s,
@@ -648,18 +660,22 @@ meson_serial_early_console_setup(struct earlycon_device *device, const char *opt
 OF_EARLYCON_DECLARE(meson, "amlogic,meson-ao-uart",
 		    meson_serial_early_console_setup);
 
-#define MESON_SERIAL_CONSOLE	(&meson_serial_console)
+#define MESON_SERIAL_CONSOLE_PTR(_devname) (&MESON_SERIAL_CONSOLE(_devname))
 #else
-#define MESON_SERIAL_CONSOLE	NULL
+#define MESON_SERIAL_CONSOLE_PTR(_devname)	(NULL)
 #endif
 
-static struct uart_driver meson_uart_driver = {
-	.owner		= THIS_MODULE,
-	.driver_name	= "meson_uart",
-	.dev_name	= AML_UART_DEV_NAME,
-	.nr		= AML_UART_PORT_NUM,
-	.cons		= MESON_SERIAL_CONSOLE,
-};
+#define MESON_UART_DRIVER_DEFINE(_devname)  \
+	static struct uart_driver MESON_UART_DRIVER(_devname) = {	\
+		.owner		= THIS_MODULE,				\
+		.driver_name	= "meson_uart",				\
+		.dev_name	= __stringify(_devname),		\
+		.nr		= AML_UART_PORT_NUM,			\
+		.cons		= MESON_SERIAL_CONSOLE_PTR(_devname),	\
+	}
+
+MESON_UART_DRIVER_DEFINE(ttyAML);
+MESON_UART_DRIVER_DEFINE(ttyS);
 
 static int meson_uart_probe_clocks(struct platform_device *pdev,
 				   struct uart_port *port)
@@ -685,8 +701,16 @@ static int meson_uart_probe_clocks(struct platform_device *pdev,
 	return 0;
 }
 
+static struct uart_driver *meson_uart_current(const struct meson_uart_data *pd)
+{
+	return (pd && pd->uart_driver) ?
+		pd->uart_driver : &MESON_UART_DRIVER(ttyAML);
+}
+
 static int meson_uart_probe(struct platform_device *pdev)
 {
+	const struct meson_uart_data *priv_data;
+	struct uart_driver *uart_driver;
 	struct resource *res_mem;
 	struct uart_port *port;
 	u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
@@ -735,8 +759,12 @@ static int meson_uart_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	if (!meson_uart_driver.state) {
-		ret = uart_register_driver(&meson_uart_driver);
+	priv_data = device_get_match_data(&pdev->dev);
+
+	uart_driver = meson_uart_current(priv_data);
+
+	if (!uart_driver->state) {
+		ret = uart_register_driver(uart_driver);
 		if (ret)
 			return dev_err_probe(&pdev->dev, ret,
 					     "can't register uart driver\n");
@@ -756,7 +784,7 @@ static int meson_uart_probe(struct platform_device *pdev)
 	port->x_char = 0;
 	port->ops = &meson_uart_ops;
 	port->fifosize = fifosize;
-	port->private_data = (void *)device_get_match_data(&pdev->dev);
+	port->private_data = (void *)priv_data;
 
 	meson_ports[pdev->id] = port;
 	platform_set_drvdata(pdev, port);
@@ -767,7 +795,7 @@ static int meson_uart_probe(struct platform_device *pdev)
 		meson_uart_release_port(port);
 	}
 
-	ret = uart_add_one_port(&meson_uart_driver, port);
+	ret = uart_add_one_port(uart_driver, port);
 	if (ret)
 		meson_ports[pdev->id] = NULL;
 
@@ -776,10 +804,12 @@ static int meson_uart_probe(struct platform_device *pdev)
 
 static int meson_uart_remove(struct platform_device *pdev)
 {
+	struct uart_driver *uart_driver;
 	struct uart_port *port;
 
 	port = platform_get_drvdata(pdev);
-	uart_remove_one_port(&meson_uart_driver, port);
+	uart_driver = meson_uart_current(port->private_data);
+	uart_remove_one_port(uart_driver, port);
 	meson_ports[pdev->id] = NULL;
 
 	for (int id = 0; id < AML_UART_PORT_NUM; id++)
@@ -787,7 +817,7 @@ static int meson_uart_remove(struct platform_device *pdev)
 			return 0;
 
 	/* No more available uart ports, unregister uart driver */
-	uart_unregister_driver(&meson_uart_driver);
+	uart_unregister_driver(uart_driver);
 
 	return 0;
 }