From e8df9fc9b64087f1230ae8dbb97f52541a0c927d Mon Sep 17 00:00:00 2001
From: Dmitry Rokosov <ddrokosov@sberdevices.ru>
Date: Wed, 5 Jul 2023 21:18:28 +0300
Subject: [PATCH] tty: serial: meson: redesign the module to platform_driver

References: bsc#1214683 (PREEMPT_RT prerequisite backports)
Patch-mainline: v6.6-rc1
Git-commit: bcb5645f99ef93b3cad3cdb7937eb4b2cecfd560

Actually, the meson_uart module is already a platform_driver, but it is
currently registered manually and the uart core registration is run
outside the probe() scope, which results in some restrictions. For
instance, it is not possible to communicate with the OF subsystem
because it requires an initialized device object.

To address this issue, apply module_platform_driver() instead of direct
module init/exit routines. Additionally, move uart_register_driver() to
the driver probe(), and destroy manual console registration because it's
already run in the uart_register_driver() flow.

Signed-off-by: Dmitry Rokosov <ddrokosov@sberdevices.ru>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20230705181833.16137-3-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 | 51 ++++++++++++-----------------------------
 1 file changed, 15 insertions(+), 36 deletions(-)

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 0f6157c8be89..523361569cb3 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -625,12 +625,6 @@ static struct console meson_serial_console = {
 	.data		= &meson_uart_driver,
 };
 
-static int __init meson_serial_console_init(void)
-{
-	register_console(&meson_serial_console);
-	return 0;
-}
-
 static void meson_serial_early_console_write(struct console *co,
 					     const char *s,
 					     u_int count)
@@ -656,9 +650,6 @@ OF_EARLYCON_DECLARE(meson, "amlogic,meson-ao-uart",
 
 #define MESON_SERIAL_CONSOLE	(&meson_serial_console)
 #else
-static int __init meson_serial_console_init(void) {
-	return 0;
-}
 #define MESON_SERIAL_CONSOLE	NULL
 #endif
 
@@ -744,6 +735,13 @@ 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);
+		if (ret)
+			return dev_err_probe(&pdev->dev, ret,
+					     "can't register uart driver\n");
+	}
+
 	port->iotype = UPIO_MEM;
 	port->mapbase = res_mem->start;
 	port->mapsize = resource_size(res_mem);
@@ -784,6 +782,13 @@ static int meson_uart_remove(struct platform_device *pdev)
 	uart_remove_one_port(&meson_uart_driver, port);
 	meson_ports[pdev->id] = NULL;
 
+	for (int id = 0; id < AML_UART_PORT_NUM; id++)
+		if (meson_ports[id])
+			return 0;
+
+	/* No more available uart ports, unregister uart driver */
+	uart_unregister_driver(&meson_uart_driver);
+
 	return 0;
 }
 
@@ -817,33 +822,7 @@ static  struct platform_driver meson_uart_platform_driver = {
 	},
 };
 
-static int __init meson_uart_init(void)
-{
-	int ret;
-
-	ret = meson_serial_console_init();
-	if (ret)
-		return ret;
-	
-	ret = uart_register_driver(&meson_uart_driver);
-	if (ret)
-		return ret;
-
-	ret = platform_driver_register(&meson_uart_platform_driver);
-	if (ret)
-		uart_unregister_driver(&meson_uart_driver);
-
-	return ret;
-}
-
-static void __exit meson_uart_exit(void)
-{
-	platform_driver_unregister(&meson_uart_platform_driver);
-	uart_unregister_driver(&meson_uart_driver);
-}
-
-module_init(meson_uart_init);
-module_exit(meson_uart_exit);
+module_platform_driver(meson_uart_platform_driver);
 
 MODULE_AUTHOR("Carlo Caione <carlo@caione.org>");
 MODULE_DESCRIPTION("Amlogic Meson serial port driver");