[PATCH 6.18 072/212] serial: 8250: Add serial8250_handle_irq_locked()

Greg Kroah-Hartman
2026-03-23T14:04:40Z

From: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

commit 8324a54f604da18f21070702a8ad82ab2062787b upstream.

8250_port exports serial8250_handle_irq() to HW specific 8250 drivers.
It takes port's lock within but a HW specific 8250 driver may want to
take port's lock itself, do something, and then call the generic
handler in 8250_port but to do that, the caller has to release port's
lock for no good reason.

Introduce serial8250_handle_irq_locked() which a HW specific driver can
call while already holding port's lock.

As this is new export, put it straight into a namespace (where all 8250
exports should eventually be moved).

Tested-by: Bandal, Shankar <shankar.bandal@intel.com>
Tested-by: Murthy, Shanth <shanth.murthy@intel.com>
Cc: stable <stable@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/20260203171049.4353-4-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/8250/8250_port.c | 24 ++++++++++++++++--------
include/linux/serial_8250.h | 1 +
2 files changed, 17 insertions(+), 8 deletions(-)

--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -18,6 +18,7 @@
#include <linux/irq.h>
#include <linux/console.h>
#include <linux/gpio/consumer.h>
+#include <linux/lockdep.h>
#include <linux/sysrq.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
@@ -1782,20 +1783,16 @@ static bool handle_rx_dma(struct uart_82
}

/*
- * This handles the interrupt from one port.
+ * Context: port's lock must be held by the caller.
*/
-int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
+void serial8250_handle_irq_locked(struct uart_port *port, unsigned int iir)
{
struct uart_8250_port *up = up_to_u8250p(port);
struct tty_port *tport = &port->state->port;
bool skip_rx = false;
- unsigned long flags;
u16 status;

- if (iir & UART_IIR_NO_INT)
- return 0;
-
- uart_port_lock_irqsave(port, &flags);
+ lockdep_assert_held_once(&port->lock);

status = serial_lsr_in(up);

@@ -1828,8 +1825,19 @@ int serial8250_handle_irq(struct uart_po
else if (!up->dma->tx_running)
__stop_tx(up);
}
+}
+EXPORT_SYMBOL_NS_GPL(serial8250_handle_irq_locked, "SERIAL_8250");
+
+/*
+ * This handles the interrupt from one port.
+ */
+int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
+{
+ if (iir & UART_IIR_NO_INT)
+ return 0;

- uart_unlock_and_check_sysrq_irqrestore(port, flags);
+ guard(uart_port_lock_irqsave)(port);
+ serial8250_handle_irq_locked(port, iir);

return 1;
}
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -195,6 +195,7 @@ void serial8250_do_set_mctrl(struct uart
void serial8250_do_set_divisor(struct uart_port *port, unsigned int baud,
unsigned int quot);
int fsl8250_handle_irq(struct uart_port *port);
+void serial8250_handle_irq_locked(struct uart_port *port, unsigned int iir);
int serial8250_handle_irq(struct uart_port *port, unsigned int iir);
u16 serial8250_rx_chars(struct uart_8250_port *up, u16 lsr);
void serial8250_read_char(struct uart_8250_port *up, u16 lsr);