1 files changed, 76 insertions, 0 deletions
diff --git a/debian/patches-rt/0018-serial-apb-Use-port-lock-wrappers.patch b/debian/patches-rt/0018-serial-apb-Use-port-lock-wrappers.patch
new file mode 100644
index 000000000..4dcf54a89
--- /dev/null
+++ b/debian/patches-rt/0018-serial-apb-Use-port-lock-wrappers.patch
@@ -0,0 +1,76 @@
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Thu, 14 Sep 2023 20:43:35 +0206
+Subject: [PATCH 018/134] serial: apb: Use port lock wrappers
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz
+
+When a serial port is used for kernel console output, then all
+modifications to the UART registers which are done from other contexts,
+e.g. getty, termios, are interference points for the kernel console.
+
+So far this has been ignored and the printk output is based on the
+principle of hope. The rework of the console infrastructure which aims to
+support threaded and atomic consoles, requires to mark sections which
+modify the UART registers as unsafe. This allows the atomic write function
+to make informed decisions and eventually to restore operational state. It
+also allows to prevent the regular UART code from modifying UART registers
+while printk output is in progress.
+
+All modifications of UART registers are guarded by the UART port lock,
+which provides an obvious synchronization point with the console
+infrastructure.
+
+To avoid adding this functionality to all UART drivers, wrap the
+spin_[un]lock*() invocations for uart_port::lock into helper functions
+which just contain the spin_[un]lock*() invocations for now. In a
+subsequent step these helpers will gain the console synchronization
+mechanisms.
+
+Converted with coccinelle. No functional change.
+
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Link: https://lore.kernel.org/r/20230914183831.587273-19-john.ogness@linutronix.de
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ drivers/tty/serial/apbuart.c |    8 ++++----
+ 1 file changed, 4 insertions(+), 4 deletions(-)
+
+--- a/drivers/tty/serial/apbuart.c
++++ b/drivers/tty/serial/apbuart.c
+@@ -133,7 +133,7 @@ static irqreturn_t apbuart_int(int irq,
+ 	struct uart_port *port = dev_id;
+ 	unsigned int status;
+ 
+-	spin_lock(&port->lock);
++	uart_port_lock(port);
+ 
+ 	status = UART_GET_STATUS(port);
+ 	if (status & UART_STATUS_DR)
+@@ -141,7 +141,7 @@ static irqreturn_t apbuart_int(int irq,
+ 	if (status & UART_STATUS_THE)
+ 		apbuart_tx_chars(port);
+ 
+-	spin_unlock(&port->lock);
++	uart_port_unlock(port);
+ 
+ 	return IRQ_HANDLED;
+ }
+@@ -228,7 +228,7 @@ static void apbuart_set_termios(struct u
+ 	if (termios->c_cflag & CRTSCTS)
+ 		cr |= UART_CTRL_FL;
+ 
+-	spin_lock_irqsave(&port->lock, flags);
++	uart_port_lock_irqsave(port, &flags);
+ 
+ 	/* Update the per-port timeout. */
+ 	uart_update_timeout(port, termios->c_cflag, baud);
+@@ -251,7 +251,7 @@ static void apbuart_set_termios(struct u
+ 	UART_PUT_SCAL(port, quot);
+ 	UART_PUT_CTRL(port, cr);
+ 
+-	spin_unlock_irqrestore(&port->lock, flags);
++	uart_port_unlock_irqrestore(port, flags);
+ }
+ 
+ static const char *apbuart_type(struct uart_port *port)