linux-kernel - [PATCH] serial: core: Fix probing serial_base

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Message-Id: <20230601141445.11321-1-tony@atomide.com>
Date:   Thu,  1 Jun 2023 17:14:44 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] serial: core: Fix probing serial_base_bus devices

If a physical serial port device driver uses arch_initcall() we fail to
probe the serial_base_bus devices and the serial port tx fails. This is
because as serial_base_bus uses module_initcall().

Let's fix the issue by changing serial_base_bus to use arch_initcall().

Let's also return an error if a driver attempts to call uart_add_one_port()
too early.

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Closes: https://lore.kernel.org/linux-serial/20230601132012.GB14287@atomide.com/T/#m6a40440fc04d551d27b147da8602e065c982a115
Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
Signed-off-by: Tony Lindgren <tony@...mide.com>
---
 drivers/tty/serial/serial_base_bus.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_base_bus.c b/drivers/tty/serial/serial_base_bus.c
--- a/drivers/tty/serial/serial_base_bus.c
+++ b/drivers/tty/serial/serial_base_bus.c
@@ -17,6 +17,8 @@
 
 #include "serial_base.h"
 
+static bool serial_base_initialized;
+
 static int serial_base_match(struct device *dev, struct device_driver *drv)
 {
 	int len = strlen(drv->name);
@@ -48,6 +50,11 @@ static int serial_base_device_init(struct uart_port *port,
 				   void (*release)(struct device *dev),
 				   int id)
 {
+	if (!serial_base_initialized) {
+		dev_err(port->dev, "uart_add_one_port() called before arch_initcall()?\n");
+		return -EPROBE_DEFER;
+	}
+
 	device_initialize(dev);
 	dev->type = type;
 	dev->parent = parent_dev;
@@ -175,6 +182,8 @@ static int serial_base_init(void)
 	if (ret)
 		goto err_ctrl_exit;
 
+	serial_base_initialized = true;
+
 	return 0;
 
 err_ctrl_exit:
@@ -185,7 +194,7 @@ static int serial_base_init(void)
 
 	return ret;
 }
-module_init(serial_base_init);
+arch_initcall(serial_base_init);
 
 static void serial_base_exit(void)
 {
-- 
2.40.1