[PATCH v2 6/6] USB: serial: ftdi_sio: add support for FreeCalypso DUART28C adapter

Mychaela N. Falconia
2022-05-31T04:37:54Z

FreeCalypso DUART28C is an FT2232D-based USB to dual UART adapter
with a special quirk: Channel B RTS and DTR outputs (BDBUS2 and BDBUS4
on the chip) have been repurposed to drive PWON and RESET controls
on Calypso targets. The circuit is wired such that BDBUS[24] high
(RTS/DTR inactive) is the normal state with Iota VRPC controls
NOT activated, whereas BDBUS[24] low (RTS or DTR active) turn ON
the corresponding open drain control signal drivers.

A special ftdi_sio driver quirk is needed in order to suppress
automatic assertion of DTR & RTS on device open: this device's
special PWON and RESET control drivers MUST NOT be activated
when the port is ordinarily opened for plain serial communication,
instead they must only be activated when a special userspace
application explicitly requests such activation with a TIOCMBIS ioctl.
These special userspace applications are responsible for making the
needed pulse with a TIOCMBIS, delay, TIOCMBIC sequence.

The special quirk is conditionalized on the DUART28C adapter's custom
USB ID, and is further limited to FT2232D Channel B only: Channel A
is wired normally, with the chip's ADBUS2 and ADBUS4 outputs
actually being RTS and DTR rather than something else.

Signed-off-by: Mychaela N. Falconia <falcon@freecalypso.org>
---
drivers/usb/serial/ftdi_sio.c | 25 +++++++++++++++++++++++++
drivers/usb/serial/ftdi_sio_ids.h | 1 +
2 files changed, 26 insertions(+)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 6523a36dcc45..f62d9f804c73 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -97,6 +97,7 @@ static int ftdi_stmclite_probe(struct usb_serial *serial);
static int ftdi_8u2232c_probe(struct usb_serial *serial);
static void ftdi_USB_UIRT_setup(struct usb_serial_port *port);
static void ftdi_HE_TIRA1_setup(struct usb_serial_port *port);
+static void ftdi_duart28c_setup(struct usb_serial_port *port);

static const struct ftdi_sio_quirk ftdi_jtag_quirk = {
.probe = ftdi_jtag_probe,
@@ -122,6 +123,10 @@ static const struct ftdi_sio_quirk ftdi_8u2232c_quirk = {
.probe = ftdi_8u2232c_probe,
};

+static const struct ftdi_sio_quirk ftdi_duart28c_quirk = {
+ .port_probe = ftdi_duart28c_setup,
+};
+
/*
* The 8U232AM has the same API as the sio except for:
* - it can support MUCH higher baudrates; up to:
@@ -1050,6 +1055,8 @@ static const struct usb_device_id id_table_combined[] = {
.driver_info = (kernel_ulong_t)&ftdi_jtag_quirk },
{ USB_DEVICE(FTDI_VID, FTDI_FALCONIA_JTAG_UNBUF_PID),
.driver_info = (kernel_ulong_t)&ftdi_jtag_quirk },
+ { USB_DEVICE(FTDI_VID, FTDI_FALCONIA_DUART28C_PID),
+ .driver_info = (kernel_ulong_t)&ftdi_duart28c_quirk },
{ } /* Terminating entry */
};

@@ -2372,6 +2379,24 @@ static int ftdi_stmclite_probe(struct usb_serial *serial)
return 0;
}

+/*
+ * FreeCalypso DUART28C is an FT2232D-based USB to dual UART adapter
+ * with a special quirk: Channel B RTS and DTR outputs (BDBUS2 and BDBUS4
+ * on the chip) have been repurposed to drive PWON and RESET controls.
+ *
+ * Only Channel B is subject to the quirk - Channel A needs to retain
+ * standard POSIX/SUS behaviour.
+ */
+static void ftdi_duart28c_setup(struct usb_serial_port *port)
+{
+ struct usb_serial *serial = port->serial;
+ struct usb_interface *intf = serial->interface;
+ int ifnum = intf->cur_altsetting->desc.bInterfaceNumber;
+
+ if (ifnum == 1)
+ tty_port_set_nordy(&port->port, true);
+}
+
static void ftdi_sio_port_remove(struct usb_serial_port *port)
{
struct ftdi_private *priv = usb_get_serial_port_data(port);
diff --git a/drivers/usb/serial/ftdi_sio_ids.h b/drivers/usb/serial/ftdi_sio_ids.h
index d1a9564697a4..6ff2509e54a2 100644
--- a/drivers/usb/serial/ftdi_sio_ids.h
+++ b/drivers/usb/serial/ftdi_sio_ids.h
@@ -45,6 +45,7 @@
*/
#define FTDI_FALCONIA_JTAG_BUF_PID 0x7150
#define FTDI_FALCONIA_JTAG_UNBUF_PID 0x7151
+#define FTDI_FALCONIA_DUART28C_PID 0x7152

/* Sienna Serial Interface by Secyourit GmbH */
#define FTDI_SIENNA_PID 0x8348
--
2.9.0