[PATCH v2 6.12.y 04/10] serial: 8250: convert serial8250_do_shutdown() to scoped_guard()

["Ionut Nechita (Wind River)" <ionut.nechita@windriver.com>]

From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>

This is a partial backport of upstream commit b339809edda1 ("serial:
8250: use guard()s"). Only the serial8250_do_shutdown() hunks of
drivers/tty/serial/8250/8250_port.c are taken; the rest of the
upstream commit is not needed for the BUSY deassert series.

This conversion is a textual prerequisite for applying
commit 59a33d83bbe6 ("serial: 8250: Protect LCR write in shutdown")
without conflicts, because that commit moves the LCR write into a
scoped_guard(uart_port_lock_irqsave) block that does not yet exist
in 6.12.y.

This depends on commit 0fd60b689b0d ("serial: introduce
uart_port_lock() guard()s") (also backported in this series) which
introduces DEFINE_LOCK_GUARD_1(uart_port_lock_irqsave, ...).

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250814072456.182853-10-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[Ionut: partial backport - only the serial8250_do_shutdown() hunks
 from b339809edda1, per Ilpo's guidance to take "8250_port.c shutdown
 hunks" from that commit; the remaining hunks are not required for
 the BUSY deassert series.]
Signed-off-by: Ionut Nechita <ionut.nechita@windriver.com>
---
 drivers/tty/serial/8250/8250_port.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index b4c8388ea6fc..21fa7907c0d6 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2461,7 +2461,6 @@ static int serial8250_startup(struct uart_port *port)
 void serial8250_do_shutdown(struct uart_port *port)
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
-	unsigned long flags;
 
 	serial8250_rpm_get(up);
 	/*
@@ -2469,26 +2468,26 @@ void serial8250_do_shutdown(struct uart_port *port)
 	 *
 	 * Synchronize UART_IER access against the console.
 	 */
-	uart_port_lock_irqsave(port, &flags);
-	up->ier = 0;
-	serial_port_out(port, UART_IER, 0);
-	uart_port_unlock_irqrestore(port, flags);
+	scoped_guard(uart_port_lock_irqsave, port) {
+		up->ier = 0;
+		serial_port_out(port, UART_IER, 0);
+	}
 
 	synchronize_irq(port->irq);
 
 	if (up->dma)
 		serial8250_release_dma(up);
 
-	uart_port_lock_irqsave(port, &flags);
-	if (port->flags & UPF_FOURPORT) {
-		/* reset interrupts on the AST Fourport board */
-		inb((port->iobase & 0xfe0) | 0x1f);
-		port->mctrl |= TIOCM_OUT1;
-	} else
-		port->mctrl &= ~TIOCM_OUT2;
+	scoped_guard(uart_port_lock_irqsave, port) {
+		if (port->flags & UPF_FOURPORT) {
+			/* reset interrupts on the AST Fourport board */
+			inb((port->iobase & 0xfe0) | 0x1f);
+			port->mctrl |= TIOCM_OUT1;
+		} else
+			port->mctrl &= ~TIOCM_OUT2;
 
-	serial8250_set_mctrl(port, port->mctrl);
-	uart_port_unlock_irqrestore(port, flags);
+		serial8250_set_mctrl(port, port->mctrl);
+	}
 
 	/*
 	 * Disable break condition and FIFOs
-- 
2.54.0