[PATCH 14/33] serial: 8250: extract serial8250_set_TRG_levels()

Jiri Slaby (SUSE)
2025-06-11T10:03:52Z

serial8250_do_startup() contains peculiar trigger levels setup for
special ports (16850, ALTR_16550_*). Move this away to a separate
function: serial8250_set_TRG_levels().

And use switch-case instead of 'if's.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
drivers/tty/serial/8250/8250_port.c | 77 +++++++++++++++--------------
1 file changed, 41 insertions(+), 36 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 21ff56a31b56..c09a90b38d8f 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2159,6 +2159,46 @@ static void serial8250_startup_special(struct uart_port *port)
}
}

+static void serial8250_set_TRG_levels(struct uart_port *port)
+{
+ struct uart_8250_port *up = up_to_u8250p(port);
+
+ switch (port->type) {
+ /* For a XR16C850, we need to set the trigger levels */
+ case PORT_16850: {
+ u8 fctr;
+
+ serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+
+ fctr = serial_in(up, UART_FCTR) & ~(UART_FCTR_RX|UART_FCTR_TX);
+ fctr |= UART_FCTR_TRGD;
+ serial_port_out(port, UART_FCTR, fctr | UART_FCTR_RX);
+ serial_port_out(port, UART_TRG, UART_TRG_96);
+ serial_port_out(port, UART_FCTR, fctr | UART_FCTR_TX);
+ serial_port_out(port, UART_TRG, UART_TRG_96);
+
+ serial_port_out(port, UART_LCR, 0);
+ break;
+ }
+ /* For the Altera 16550 variants, set TX threshold trigger level. */
+ case PORT_ALTR_16550_F32:
+ case PORT_ALTR_16550_F64:
+ case PORT_ALTR_16550_F128:
+ if (port->fifosize <= 1)
+ return;
+
+ /* Bounds checking of TX threshold (valid 0 to fifosize-2) */
+ if (up->tx_loadsz < 2 || up->tx_loadsz > port->fifosize) {
+ dev_err(port->dev, "TX FIFO Threshold errors, skipping\n");
+ return;
+ }
+ serial_port_out(port, UART_ALTR_AFR, UART_ALTR_EN_TXFIFO_LW);
+ serial_port_out(port, UART_ALTR_TX_LOW, port->fifosize - up->tx_loadsz);
+ port->handle_irq = serial8250_tx_threshold_handle_irq;
+ break;
+ }
+}
+
int serial8250_do_startup(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
@@ -2208,42 +2248,7 @@ int serial8250_do_startup(struct uart_port *port)
goto out;
}

- /*
- * For a XR16C850, we need to set the trigger levels
- */
- if (port->type == PORT_16850) {
- unsigned char fctr;
-
- serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
-
- fctr = serial_in(up, UART_FCTR) & ~(UART_FCTR_RX|UART_FCTR_TX);
- serial_port_out(port, UART_FCTR,
- fctr | UART_FCTR_TRGD | UART_FCTR_RX);
- serial_port_out(port, UART_TRG, UART_TRG_96);
- serial_port_out(port, UART_FCTR,
- fctr | UART_FCTR_TRGD | UART_FCTR_TX);
- serial_port_out(port, UART_TRG, UART_TRG_96);
-
- serial_port_out(port, UART_LCR, 0);
- }
-
- /*
- * For the Altera 16550 variants, set TX threshold trigger level.
- */
- if (((port->type == PORT_ALTR_16550_F32) ||
- (port->type == PORT_ALTR_16550_F64) ||
- (port->type == PORT_ALTR_16550_F128)) && (port->fifosize > 1)) {
- /* Bounds checking of TX threshold (valid 0 to fifosize-2) */
- if ((up->tx_loadsz < 2) || (up->tx_loadsz > port->fifosize)) {
- dev_err(port->dev, "TX FIFO Threshold errors, skipping\n");
- } else {
- serial_port_out(port, UART_ALTR_AFR,
- UART_ALTR_EN_TXFIFO_LW);
- serial_port_out(port, UART_ALTR_TX_LOW,
- port->fifosize - up->tx_loadsz);
- port->handle_irq = serial8250_tx_threshold_handle_irq;
- }
- }
+ serial8250_set_TRG_levels(port);

/* Check if we need to have shared IRQs */
if (port->irq && (up->port.flags & UPF_SHARE_IRQ))
--
2.49.0