[tip: sched/rt] serial: core: Provide low-level functions to lock port

[tip-bot2 for John Ogness]

The following commit has been merged into the sched/rt branch of tip:

Commit-ID:     77e73c0687f5bc884fa1b0cb97aca912bcc01957
Gitweb:        https://git.kernel.org/tip/77e73c0687f5bc884fa1b0cb97aca912bcc01957
Author:        John Ogness <john.ogness@xxxxxxxxxxxxx>
AuthorDate:    Tue, 20 Aug 2024 08:35:36 +02:06
Committer:     Petr Mladek <pmladek@xxxxxxxx>
CommitterDate: Wed, 21 Aug 2024 14:56:23 +02:00

serial: core: Provide low-level functions to lock port

It will be necessary at times for the uart nbcon console
drivers to acquire the port lock directly (without the
additional nbcon functionality of the port lock wrappers).
These are special cases such as the implementation of the
device_lock()/device_unlock() callbacks or for internal
port lock wrapper synchronization.

Provide low-level variants __uart_port_lock_irqsave() and
__uart_port_unlock_irqrestore() for this purpose.

Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx>
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240820063001.36405-11-john.ogness@xxxxxxxxxxxxx
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
---
 include/linux/serial_core.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index aea25ee..8872cd2 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -590,6 +590,24 @@ struct uart_port {
 	void			*private_data;		/* generic platform data pointer */
 };
 
+/*
+ * Only for console->device_lock()/_unlock() callbacks and internal
+ * port lock wrapper synchronization.
+ */
+static inline void __uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
+{
+	spin_lock_irqsave(&up->lock, *flags);
+}
+
+/*
+ * Only for console->device_lock()/_unlock() callbacks and internal
+ * port lock wrapper synchronization.
+ */
+static inline void __uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
+{
+	spin_unlock_irqrestore(&up->lock, flags);
+}
+
 /**
  * uart_port_lock - Lock the UART port
  * @up:		Pointer to UART port structure