[PATCH 17/33] serial: 8250: extract serial8250_clear_interrupts()

Jiri Slaby (SUSE)
2025-06-11T10:03:57Z

On three places in 8250_port.c, the interrupts are cleared by reading 4
registers. Extract this to a separate function:
serial8250_clear_interrupts(). And call it from all the places.

Note autoconfig_irq() now uses serial_port_in() instead of serial_in().
But they are the same, in fact (modulo parameter).

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
drivers/tty/serial/8250/8250_port.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 6851c197b31d..a73f4db22feb 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -705,6 +705,15 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
serial8250_rpm_put(p);
}

+/* Clear the interrupt registers. */
+static void serial8250_clear_interrupts(struct uart_port *port)
+{
+ serial_port_in(port, UART_LSR);
+ serial_port_in(port, UART_RX);
+ serial_port_in(port, UART_IIR);
+ serial_port_in(port, UART_MSR);
+}
+
static void serial8250_clear_IER(struct uart_8250_port *up)
{
if (up->capabilities & UART_CAP_UUE)
@@ -1275,10 +1284,7 @@ static void autoconfig_irq(struct uart_8250_port *up)
uart_port_lock_irq(port);
serial_out(up, UART_IER, UART_IER_ALL_INTR);
uart_port_unlock_irq(port);
- serial_in(up, UART_LSR);
- serial_in(up, UART_RX);
- serial_in(up, UART_IIR);
- serial_in(up, UART_MSR);
+ serial8250_clear_interrupts(port);
serial_out(up, UART_TX, 0xFF);
udelay(20);
irq = probe_irq_off(irqs);
@@ -2322,13 +2328,7 @@ int serial8250_do_startup(struct uart_port *port)
*/
serial8250_clear_fifos(up);

- /*
- * Clear the interrupt registers.
- */
- serial_port_in(port, UART_LSR);
- serial_port_in(port, UART_RX);
- serial_port_in(port, UART_IIR);
- serial_port_in(port, UART_MSR);
+ serial8250_clear_interrupts(port);

/*
* At this point, there's no way the LSR could still be 0xff;
@@ -2363,10 +2363,7 @@ int serial8250_do_startup(struct uart_port *port)
* saved flags to avoid getting false values from polling
* routines or the previous session.
*/
- serial_port_in(port, UART_LSR);
- serial_port_in(port, UART_RX);
- serial_port_in(port, UART_IIR);
- serial_port_in(port, UART_MSR);
+ serial8250_clear_interrupts(port);
up->lsr_saved_flags = 0;
up->msr_saved_flags = 0;

--
2.49.0