On Wed, 18 Oct 2023, Crescent CY Hsieh wrote:
> MOXA PCIe boards have 4 serial interfaces and don't require additional
> stuff to switch between interfaces:
>
> - RS232
> - RS422
> - RS485_2W (half-duplex)
> - RS485_4W (full-duplex)
>
> By using ioctl command "TIOCRS485", it can switch between default
> interface and RS485 if supported.
>
> That means, for RS422/RS485 board, it can switch between RS422 and
> RS485 by setting the flags within struct serial_rs485.
>
> However, for the RS232/RS422/RS485 board, it can only switch between
> RS232 and RS485, there's no flag for switching interface into RS422.
>
> This patch uses "SER_RS485_TERMINATE_BUS" to represent RS422 as a
> workaround solution:
>
> - RS232 = (no flags are set)
> - RS422 = SER_RS485_ENABLED | SER_RS485_TERMINATE_BUS
> - RS485_2W (half-duplex) = SER_RS485_ENABLED
> - RS485_4W (full-duplex) = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX
>
> Signed-off-by: Crescent CY Hsieh <crescentcy.hsieh@xxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_pci.c | 58 ++++++++++++++++++++++++++++++
> 1 file changed, 58 insertions(+)
>
> diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
> index 29a28e72b..098ac466b 100644
> --- a/drivers/tty/serial/8250/8250_pci.c
> +++ b/drivers/tty/serial/8250/8250_pci.c
> @@ -1974,6 +1974,10 @@ pci_sunix_setup(struct serial_private *priv,
> #define MOXA_RS485_2W 0x0F
> #define MOXA_UIR_OFFSET 0x04
>
> +static const struct serial_rs485 pci_moxa_rs485_supported = {
> + .flags = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
As recently discussed on linux-serial list, one of the RTS flags should be
enabled (the one the HW uses even if it's not configurable).
> +};
> +
> static bool pci_moxa_is_mini_pcie(unsigned short device)
> {
> if (device == PCI_DEVICE_ID_MOXA_CP102N ||
> @@ -2024,6 +2028,46 @@ static int pci_moxa_set_interface(const struct pci_dev *dev,
> return 0;
> }
>
> +/*
> + * MOXA PCIe boards support switching the serial interface using the ioctl
> + * command "TIOCSRS485", but there is currently no dedicated flag for switching
> + * to RS422. As a workaround, we utilize the "SER_RS485_TERMINATE_BUS" flag to
> + * represent RS422.
> + *
> + * RS232 = (no flags are set)
> + * RS422 = SER_RS485_ENABLED | SER_RS485_TERMINATE_BUS
> + * RS485_2W (half-duplex) = SER_RS485_ENABLED
> + * RS485_4W (full-duplex) = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX
> + */
> +static int pci_moxa_rs485_config(struct uart_port *port,
> + struct ktermios *termios,
> + struct serial_rs485 *rs485)
> +{
> + struct pci_dev *dev = to_pci_dev(port->dev);
> + unsigned short device = dev->device;
> + u8 mode = MOXA_RS232;
> +
> + if (rs485->flags & SER_RS485_ENABLED) {
> + if (rs485->flags & SER_RS485_TERMINATE_BUS) {
> + mode = MOXA_RS422;
> + } else {
> + if (rs485->flags & SER_RS485_RX_DURING_TX)
> + mode = MOXA_RS485_4W;
> + else
> + mode = MOXA_RS485_2W;
> + }
> + } else {
> + /*
> + * RS232 is not supported for MOXA PCIe boards with device IDs
> + * matching the pattern 0x*3**.
> + */
> + if (pci_moxa_match_second_digit(device, 0x0300))
> + return -EOPNOTSUPP;
This is not the correct error code I think. Maybe return -ENXIO instead.
> + }
> +
> + return pci_moxa_set_interface(dev, port->port_id, mode);
> +}
> +
> static int pci_moxa_init(struct pci_dev *dev)
> {
> unsigned short device = dev->device;
> @@ -2063,9 +2107,23 @@ pci_moxa_setup(struct serial_private *priv,
> const struct pciserial_board *board,
> struct uart_8250_port *port, int idx)
> {
> + struct pci_dev *dev = priv->dev;
> + unsigned short device = dev->device;
> unsigned int bar = FL_GET_BASE(board->flags);
> int offset;
>
> + /*
> + * For the device IDs of MOXA PCIe boards match the pattern 0x*1** and 0x*3**,
> + * these boards support switching interface between RS422/RS485 using TIOCSRS485.
> + */
> + if (pci_moxa_match_second_digit(device, 0x0100) ||
> + pci_moxa_match_second_digit(device, 0x0300)) {
As mentioned in the other patch, all these literals must be named.
> + port->port.rs485_config = pci_moxa_rs485_config;
> + port->port.rs485_supported = pci_moxa_rs485_supported;
> +
> + if (pci_moxa_match_second_digit(device, 0x0300))
> + port->port.rs485.flags |= SER_RS485_ENABLED | SER_RS485_TERMINATE_BUS;
> + }
> if (board->num_ports == 4 && idx == 3)
> offset = 7 * board->uart_offset;
> else
>
--
i.
