[PATCH 16/33] serial: 8250: extract serial8250_initialize()

Jiri Slaby (SUSE)
2025-06-11T10:03:55Z

serial8250_do_startup() initializes the ports in the middle of the
function. This code can be separated to serial8250_initialize(), so that
serial8250_do_startup() can be readable again.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
drivers/tty/serial/8250/8250_port.c | 103 ++++++++++++++--------------
1 file changed, 50 insertions(+), 53 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 5466286bb44f..6851c197b31d 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2247,13 +2247,59 @@ static void serial8250_THRE_test(struct uart_port *port)
up->bugs |= UART_BUG_THRE;
}

-int serial8250_do_startup(struct uart_port *port)
+static void serial8250_initialize(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
unsigned long flags;
- unsigned char iir;
+ bool lsr_TEMT, iir_NOINT;
+
+ serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
+
+ uart_port_lock_irqsave(port, &flags);
+ if (port->flags & UPF_FOURPORT) {
+ if (!port->irq)
+ port->mctrl |= TIOCM_OUT1;
+ } else {
+ /* Most PC uarts need OUT2 raised to enable interrupts. */
+ if (port->irq)
+ port->mctrl |= TIOCM_OUT2;
+ }
+
+ serial8250_set_mctrl(port, port->mctrl);
+
+ /*
+ * Serial over Lan (SoL) hack:
+ * Intel 8257x Gigabit ethernet chips have a 16550 emulation, to be used for Serial Over
+ * Lan. Those chips take a longer time than a normal serial device to signalize that a
+ * transmission data was queued. Due to that, the above test generally fails. One solution
+ * would be to delay the reading of iir. However, this is not reliable, since the timeout is
+ * variable. So, let's just don't test if we receive TX irq. This way, we'll never enable
+ * UART_BUG_TXEN.
+ */
+ if (!(port->quirks & UPQ_NO_TXEN_TEST)) {
+ /* Do a quick test to see if we receive an interrupt when we enable the TX irq. */
+ serial_port_out(port, UART_IER, UART_IER_THRI);
+ lsr_TEMT = serial_port_in(port, UART_LSR) & UART_LSR_TEMT;
+ iir_NOINT = serial_port_in(port, UART_IIR) & UART_IIR_NO_INT;
+ serial_port_out(port, UART_IER, 0);
+
+ if (lsr_TEMT && iir_NOINT) {
+ if (!(up->bugs & UART_BUG_TXEN)) {
+ up->bugs |= UART_BUG_TXEN;
+ dev_dbg(port->dev, "enabling bad tx status workarounds\n");
+ }
+ } else {
+ up->bugs &= ~UART_BUG_TXEN;
+ }
+ }
+
+ uart_port_unlock_irqrestore(port, flags);
+}
+
+int serial8250_do_startup(struct uart_port *port)
+{
+ struct uart_8250_port *up = up_to_u8250p(port);
int retval;
- u16 lsr;

if (!port->fifosize)
port->fifosize = uart_config[port->type].fifo_size;
@@ -2310,56 +2356,7 @@ int serial8250_do_startup(struct uart_port *port)

up->ops->setup_timer(up);

- /*
- * Now, initialize the UART
- */
- serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
-
- uart_port_lock_irqsave(port, &flags);
- if (up->port.flags & UPF_FOURPORT) {
- if (!up->port.irq)
- up->port.mctrl |= TIOCM_OUT1;
- } else
- /*
- * Most PC uarts need OUT2 raised to enable interrupts.
- */
- if (port->irq)
- up->port.mctrl |= TIOCM_OUT2;
-
- serial8250_set_mctrl(port, port->mctrl);
-
- /*
- * Serial over Lan (SoL) hack:
- * Intel 8257x Gigabit ethernet chips have a 16550 emulation, to be
- * used for Serial Over Lan. Those chips take a longer time than a
- * normal serial device to signalize that a transmission data was
- * queued. Due to that, the above test generally fails. One solution
- * would be to delay the reading of iir. However, this is not
- * reliable, since the timeout is variable. So, let's just don't
- * test if we receive TX irq. This way, we'll never enable
- * UART_BUG_TXEN.
- */
- if (!(up->port.quirks & UPQ_NO_TXEN_TEST)) {
- /*
- * Do a quick test to see if we receive an interrupt when we
- * enable the TX irq.
- */
- serial_port_out(port, UART_IER, UART_IER_THRI);
- lsr = serial_port_in(port, UART_LSR);
- iir = serial_port_in(port, UART_IIR);
- serial_port_out(port, UART_IER, 0);
-
- if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT) {
- if (!(up->bugs & UART_BUG_TXEN)) {
- up->bugs |= UART_BUG_TXEN;
- dev_dbg(port->dev, "enabling bad tx status workarounds\n");
- }
- } else {
- up->bugs &= ~UART_BUG_TXEN;
- }
- }
-
- uart_port_unlock_irqrestore(port, flags);
+ serial8250_initialize(port);

/*
* Clear the interrupt registers again for luck, and clear the
--
2.49.0