tty: serial: 8250: Set RS422 interface by default to fix Moxa RS422/RS485 PCIe boards

MOXA PCIe RS422/RS485 boards will not function by default because of the
initial default serial interface of all MOXA PCIe boards is set to
RS232.

This patch fixes the problem above by setting the initial default serial
interface to RS422 for those MOXA RS422/RS485 PCIe boards.

Signed-off-by: Crescent CY Hsieh <crescentcy.hsieh@moxa.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20231214060234.6147-1-crescentcy.hsieh@moxa.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 614be0f13a31348642619bb0350b3dbf96785a69..8ccf691935b75330092588dbc35bd745dde8d557 100644 (file)
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -19,6 +19,7 @@
 #include <linux/serial_core.h>
 #include <linux/8250_pci.h>
 #include <linux/bitops.h>
+#include <linux/bitfield.h>
 
 #include <asm/byteorder.h>
 #include <asm/io.h>
@@ -1970,6 +1971,20 @@ pci_sunix_setup(struct serial_private *priv,
 
 #define MOXA_GPIO_PIN2 BIT(2)
 
+#define MOXA_RS232     0x00
+#define MOXA_RS422     0x01
+#define MOXA_RS485_4W  0x0B
+#define MOXA_RS485_2W  0x0F
+#define MOXA_UIR_OFFSET        0x04
+#define MOXA_EVEN_RS_MASK      GENMASK(3, 0)
+#define MOXA_ODD_RS_MASK       GENMASK(7, 4)
+
+enum {
+       MOXA_SUPP_RS232 = BIT(0),
+       MOXA_SUPP_RS422 = BIT(1),
+       MOXA_SUPP_RS485 = BIT(2),
+};
+
 static bool pci_moxa_is_mini_pcie(unsigned short device)
 {
        if (device == PCI_DEVICE_ID_MOXA_CP102N ||
@@ -1983,13 +1998,54 @@ static bool pci_moxa_is_mini_pcie(unsigned short device)
        return false;
 }
 
+static unsigned int pci_moxa_supported_rs(struct pci_dev *dev)
+{
+       switch (dev->device & 0x0F00) {
+       case 0x0000:
+       case 0x0600:
+               return MOXA_SUPP_RS232;
+       case 0x0100:
+               return MOXA_SUPP_RS232 | MOXA_SUPP_RS422 | MOXA_SUPP_RS485;
+       case 0x0300:
+               return MOXA_SUPP_RS422 | MOXA_SUPP_RS485;
+       }
+       return 0;
+}
+
+static int pci_moxa_set_interface(const struct pci_dev *dev,
+                                 unsigned int port_idx,
+                                 u8 mode)
+{
+       resource_size_t iobar_addr = pci_resource_start(dev, 2);
+       resource_size_t UIR_addr = iobar_addr + MOXA_UIR_OFFSET + port_idx / 2;
+       u8 val;
+
+       val = inb(UIR_addr);
+
+       if (port_idx % 2) {
+               val &= ~MOXA_ODD_RS_MASK;
+               val |= FIELD_PREP(MOXA_ODD_RS_MASK, mode);
+       } else {
+               val &= ~MOXA_EVEN_RS_MASK;
+               val |= FIELD_PREP(MOXA_EVEN_RS_MASK, mode);
+       }
+       outb(val, UIR_addr);
+
+       return 0;
+}
+
 static int pci_moxa_init(struct pci_dev *dev)
 {
        unsigned short device = dev->device;
        resource_size_t iobar_addr = pci_resource_start(dev, 2);
-       unsigned int num_ports = (device & 0x00F0) >> 4;
+       unsigned int num_ports = (device & 0x00F0) >> 4, i;
        u8 val;
 
+       if (!(pci_moxa_supported_rs(dev) & MOXA_SUPP_RS232)) {
+               for (i = 0; i < num_ports; ++i)
+                       pci_moxa_set_interface(dev, i, MOXA_RS422);
+       }
+
        /*
         * Enable hardware buffer to prevent break signal output when system boots up.
         * This hardware buffer is only supported on Mini PCIe series.