linux-kernel - [PATCH v2 1/1] tty: serial: 8250: Fix another runtime PM usage counter underflow

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Message-Id: <20241210170120.2231-1-ilpo.jarvinen@linux.intel.com>
Date: Tue, 10 Dec 2024 19:01:20 +0200
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Arnd Bergmann <arnd@...nel.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	stable@...r.kernel.org
Subject: [PATCH v2 1/1] tty: serial: 8250: Fix another runtime PM usage counter underflow

The commit f9b11229b79c ("serial: 8250: Fix PM usage_count for console
handover") fixed one runtime PM usage counter balance problem that
occurs because .dev is not set during univ8250 setup preventing call to
pm_runtime_get_sync(). Later, univ8250_console_exit() will trigger the
runtime PM usage counter underflow as .dev is already set at that time.

Call pm_runtime_get_sync() to balance the RPM usage counter also in
serial8250_register_8250_port() before trying to add the port.

Reported-by: Borislav Petkov (AMD) <bp@...en8.de>
Fixes: bedb404e91bb ("serial: 8250_port: Don't use power management for kernel console")
Cc: <stable@...r.kernel.org>
Tested-by: Borislav Petkov (AMD) <bp@...en8.de>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
v2:
- Added tags

 drivers/tty/serial/8250/8250_core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 5f9f06911795..68baf75bdadc 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -812,6 +812,9 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
 			uart->dl_write = up->dl_write;
 
 		if (uart->port.type != PORT_8250_CIR) {
+			if (uart_console_registered(&uart->port))
+				pm_runtime_get_sync(uart->port.dev);
+
 			if (serial8250_isa_config != NULL)
 				serial8250_isa_config(0, &uart->port,
 						&uart->capabilities);
-- 
2.39.5