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

Ilpo Järvinen
2025-06-11T12:08:00Z

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On Wed, 11 Jun 2025, Jiri Slaby (SUSE) wrote:

> 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.

At this point of series I was already expecting this will come. :-)
Another nice cleanup.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

--
i.

> 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))
>