--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/5.10/0002-USB-serial-ftdi_sio-add-support-for-FreeCalypso-DUAR.patch	Mon Dec 11 06:27:14 2023 +0000
@@ -0,0 +1,163 @@
+From b62f7547c226b12c85254079ee7a4289fc506be3 Mon Sep 17 00:00:00 2001
+From: "Mychaela N. Falconia" <falcon@freecalypso.org>
+Date: Fri, 2 Oct 2020 18:01:12 +0000
+Subject: [PATCH 2/2] USB: serial: ftdi_sio: add support for FreeCalypso
+ DUART28C adapter
+
+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     | 61 +++++++++++++++++++++++++++++++++++----
+ drivers/usb/serial/ftdi_sio_ids.h |  1 +
+ 2 files changed, 57 insertions(+), 5 deletions(-)
+
+diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
+index b69032c9ec2b..6bf92836ea23 100644
+--- a/drivers/usb/serial/ftdi_sio.c
++++ b/drivers/usb/serial/ftdi_sio.c
+@@ -69,6 +69,8 @@ struct ftdi_private {
+ 				   this value */
+ 	int force_rtscts;	/* if non-zero, force RTS-CTS to always
+ 				   be enabled */
++	int no_auto_dtr_rts;	/* if non-zero, suppress automatic assertion
++				   of DTR & RTS on device open */
+ 
+ 	unsigned int latency;		/* latency setting in use */
+ 	unsigned short max_packet_size;
+@@ -97,6 +99,7 @@ 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 +125,10 @@ 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:
+@@ -1042,6 +1049,8 @@ 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 */
+ };
+ 
+@@ -2386,6 +2395,39 @@ 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
++ * 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 must be applied only to FT2232D Channel B:
++ * Channel A is wired normally, with the chip's ADBUS2 and ADBUS4 outputs
++ * actually being RTS and DTR rather than something else.
++ */
++static void ftdi_duart28c_setup(struct usb_serial_port *port)
++{
++	struct ftdi_private *priv = usb_get_serial_port_data(port);
++	struct usb_serial *serial = port->serial;
++	struct usb_interface *intf = serial->interface;
++	int ifnum = intf->cur_altsetting->desc.bInterfaceNumber;
++
++	if (ifnum == 1)
++		priv->no_auto_dtr_rts = 1;
++}
++
+ static int ftdi_sio_port_remove(struct usb_serial_port *port)
+ {
+ 	struct ftdi_private *priv = usb_get_serial_port_data(port);
+@@ -2437,10 +2479,18 @@ static void ftdi_dtr_rts(struct usb_serial_port *port, int on)
+ 			dev_err(&port->dev, "error from flowcontrol urb\n");
+ 		}
+ 	}
+-	/* drop RTS and DTR */
+-	if (on)
+-		set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
+-	else
++	/*
++	 * Assert or negate RTS and DTR as requested.  When DUART28C
++	 * quirk is applied, we suppress automatic assertion, but
++	 * automatic negation on device close is retained - these
++	 * special control signals are meant to be pulsed, and leaving
++	 * either of them stuck on when the responsible userspace
++	 * program has terminated unexpectedly is undesirable.
++	 */
++	if (on) {
++		if (!priv->no_auto_dtr_rts)
++			set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
++	} else
+ 		clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
+ }
+ 
+@@ -2788,7 +2838,8 @@ static void ftdi_set_termios(struct tty_struct *tty,
+ 			dev_err(ddev, "%s urb failed to set baudrate\n", __func__);
+ 		mutex_unlock(&priv->cfg_lock);
+ 		/* Ensure RTS and DTR are raised when baudrate changed from 0 */
+-		if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
++		if (old_termios && (old_termios->c_cflag & CBAUD) == B0
++		    && !priv->no_auto_dtr_rts)
+ 			set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
+ 	}
+ 
+diff --git a/drivers/usb/serial/ftdi_sio_ids.h b/drivers/usb/serial/ftdi_sio_ids.h
+index 3d47c6d72256..3081b8916a0a 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
+