[PATCH 24/33] serial: 8250: extract serial8250_set_fcr()

Jiri Slaby (SUSE)
2025-06-11T10:04:07Z

serial8250_do_set_termios() consists of many registers and up flags
settings. Extract all these into separate functions. This time, setting
of FCR.

serial8250_do_set_termios() looks sane at this point.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
drivers/tty/serial/8250/8250_port.c | 41 ++++++++++++++++++-----------
1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 0f16398cc86f..85b75ff0699e 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2792,6 +2792,30 @@ static void serial8250_set_efr(struct uart_port *port, struct ktermios *termios)
serial_port_out(port, efr_reg, efr);
}

+static void serial8250_set_fcr(struct uart_port *port, struct ktermios *termios)
+{
+ struct uart_8250_port *up = up_to_u8250p(port);
+ bool is_16750 = port->type == PORT_16750;
+
+ if (is_16750)
+ serial_port_out(port, UART_FCR, up->fcr);
+
+ /*
+ * LCR DLAB must be reset to enable 64-byte FIFO mode. If the FCR is written without DLAB
+ * set, this mode will be disabled.
+ */
+ serial_port_out(port, UART_LCR, up->lcr);
+
+ if (is_16750)
+ return;
+
+ /* emulated UARTs (Lucent Venus 167x) need two steps */
+ if (up->fcr & UART_FCR_ENABLE_FIFO)
+ serial_port_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
+
+ serial_port_out(port, UART_FCR, up->fcr);
+}
+
void
serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
const struct ktermios *old)
@@ -2823,22 +2847,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
serial8250_set_ier(port, termios);
serial8250_set_efr(port, termios);
serial8250_set_divisor(port, baud, quot, frac);
-
- /*
- * LCR DLAB must be set to enable 64-byte FIFO mode. If the FCR
- * is written without DLAB set, this mode will be disabled.
- */
- if (port->type == PORT_16750)
- serial_port_out(port, UART_FCR, up->fcr);
-
- serial_port_out(port, UART_LCR, up->lcr); /* reset DLAB */
- if (port->type != PORT_16750) {
- /* emulated UARTs (Lucent Venus 167x) need two steps */
- if (up->fcr & UART_FCR_ENABLE_FIFO)
- serial_port_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
- serial_port_out(port, UART_FCR, up->fcr); /* set fcr */
- }
+ serial8250_set_fcr(port, termios);
serial8250_set_mctrl(port, port->mctrl);
+
uart_port_unlock_irqrestore(port, flags);
serial8250_rpm_put(up);

--
2.49.0