[Feature]add MT2731_MP2_MR2_SVN388 baseline version
Change-Id: Ief04314834b31e27effab435d3ca8ba33b499059
diff --git a/src/kernel/linux/v4.14/drivers/usb/serial/ark3116.c b/src/kernel/linux/v4.14/drivers/usb/serial/ark3116.c
new file mode 100644
index 0000000..0adbd38
--- /dev/null
+++ b/src/kernel/linux/v4.14/drivers/usb/serial/ark3116.c
@@ -0,0 +1,790 @@
+/*
+ * Copyright (C) 2009 by Bart Hartgers (bart.hartgers+ark3116@gmail.com)
+ * Original version:
+ * Copyright (C) 2006
+ * Simon Schulz (ark3116_driver <at> auctionant.de)
+ *
+ * ark3116
+ * - implements a driver for the arkmicro ark3116 chipset (vendor=0x6547,
+ * productid=0x0232) (used in a datacable called KQ-U8A)
+ *
+ * Supports full modem status lines, break, hardware flow control. Does not
+ * support software flow control, since I do not know how to enable it in hw.
+ *
+ * This driver is a essentially new implementation. I initially dug
+ * into the old ark3116.c driver and suddenly realized the ark3116 is
+ * a 16450 with a USB interface glued to it. See comments at the
+ * bottom of this file.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/ioctl.h>
+#include <linux/tty.h>
+#include <linux/slab.h>
+#include <linux/tty_flip.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+#include <linux/serial.h>
+#include <linux/serial_reg.h>
+#include <linux/uaccess.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+
+#define DRIVER_AUTHOR "Bart Hartgers <bart.hartgers+ark3116@gmail.com>"
+#define DRIVER_DESC "USB ARK3116 serial/IrDA driver"
+#define DRIVER_DEV_DESC "ARK3116 RS232/IrDA"
+#define DRIVER_NAME "ark3116"
+
+/* usb timeout of 1 second */
+#define ARK_TIMEOUT 1000
+
+static const struct usb_device_id id_table[] = {
+ { USB_DEVICE(0x6547, 0x0232) },
+ { USB_DEVICE(0x18ec, 0x3118) }, /* USB to IrDA adapter */
+ { },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+static int is_irda(struct usb_serial *serial)
+{
+ struct usb_device *dev = serial->dev;
+ if (le16_to_cpu(dev->descriptor.idVendor) == 0x18ec &&
+ le16_to_cpu(dev->descriptor.idProduct) == 0x3118)
+ return 1;
+ return 0;
+}
+
+struct ark3116_private {
+ int irda; /* 1 for irda device */
+
+ /* protects hw register updates */
+ struct mutex hw_lock;
+
+ int quot; /* baudrate divisor */
+ __u32 lcr; /* line control register value */
+ __u32 hcr; /* handshake control register (0x8)
+ * value */
+ __u32 mcr; /* modem control register value */
+
+ /* protects the status values below */
+ spinlock_t status_lock;
+ __u32 msr; /* modem status register value */
+ __u32 lsr; /* line status register value */
+};
+
+static int ark3116_write_reg(struct usb_serial *serial,
+ unsigned reg, __u8 val)
+{
+ int result;
+ /* 0xfe 0x40 are magic values taken from original driver */
+ result = usb_control_msg(serial->dev,
+ usb_sndctrlpipe(serial->dev, 0),
+ 0xfe, 0x40, val, reg,
+ NULL, 0, ARK_TIMEOUT);
+ return result;
+}
+
+static int ark3116_read_reg(struct usb_serial *serial,
+ unsigned reg, unsigned char *buf)
+{
+ int result;
+ /* 0xfe 0xc0 are magic values taken from original driver */
+ result = usb_control_msg(serial->dev,
+ usb_rcvctrlpipe(serial->dev, 0),
+ 0xfe, 0xc0, 0, reg,
+ buf, 1, ARK_TIMEOUT);
+ if (result < 1) {
+ dev_err(&serial->interface->dev,
+ "failed to read register %u: %d\n",
+ reg, result);
+ if (result >= 0)
+ result = -EIO;
+
+ return result;
+ }
+
+ return buf[0];
+}
+
+static inline int calc_divisor(int bps)
+{
+ /* Original ark3116 made some exceptions in rounding here
+ * because windows did the same. Assume that is not really
+ * necessary.
+ * Crystal is 12MHz, probably because of USB, but we divide by 4?
+ */
+ return (12000000 + 2*bps) / (4*bps);
+}
+
+static int ark3116_port_probe(struct usb_serial_port *port)
+{
+ struct usb_serial *serial = port->serial;
+ struct ark3116_private *priv;
+
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ mutex_init(&priv->hw_lock);
+ spin_lock_init(&priv->status_lock);
+
+ priv->irda = is_irda(serial);
+
+ usb_set_serial_port_data(port, priv);
+
+ /* setup the hardware */
+ ark3116_write_reg(serial, UART_IER, 0);
+ /* disable DMA */
+ ark3116_write_reg(serial, UART_FCR, 0);
+ /* handshake control */
+ priv->hcr = 0;
+ ark3116_write_reg(serial, 0x8 , 0);
+ /* modem control */
+ priv->mcr = 0;
+ ark3116_write_reg(serial, UART_MCR, 0);
+
+ if (!(priv->irda)) {
+ ark3116_write_reg(serial, 0xb , 0);
+ } else {
+ ark3116_write_reg(serial, 0xb , 1);
+ ark3116_write_reg(serial, 0xc , 0);
+ ark3116_write_reg(serial, 0xd , 0x41);
+ ark3116_write_reg(serial, 0xa , 1);
+ }
+
+ /* setup baudrate */
+ ark3116_write_reg(serial, UART_LCR, UART_LCR_DLAB);
+
+ /* setup for 9600 8N1 */
+ priv->quot = calc_divisor(9600);
+ ark3116_write_reg(serial, UART_DLL, priv->quot & 0xff);
+ ark3116_write_reg(serial, UART_DLM, (priv->quot>>8) & 0xff);
+
+ priv->lcr = UART_LCR_WLEN8;
+ ark3116_write_reg(serial, UART_LCR, UART_LCR_WLEN8);
+
+ ark3116_write_reg(serial, 0xe, 0);
+
+ if (priv->irda)
+ ark3116_write_reg(serial, 0x9, 0);
+
+ dev_info(&port->dev, "using %s mode\n", priv->irda ? "IrDA" : "RS232");
+
+ return 0;
+}
+
+static int ark3116_port_remove(struct usb_serial_port *port)
+{
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+
+ /* device is closed, so URBs and DMA should be down */
+ mutex_destroy(&priv->hw_lock);
+ kfree(priv);
+
+ return 0;
+}
+
+static void ark3116_init_termios(struct tty_struct *tty)
+{
+ struct ktermios *termios = &tty->termios;
+ *termios = tty_std_termios;
+ termios->c_cflag = B9600 | CS8
+ | CREAD | HUPCL | CLOCAL;
+ termios->c_ispeed = 9600;
+ termios->c_ospeed = 9600;
+}
+
+static void ark3116_set_termios(struct tty_struct *tty,
+ struct usb_serial_port *port,
+ struct ktermios *old_termios)
+{
+ struct usb_serial *serial = port->serial;
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+ struct ktermios *termios = &tty->termios;
+ unsigned int cflag = termios->c_cflag;
+ int bps = tty_get_baud_rate(tty);
+ int quot;
+ __u8 lcr, hcr, eval;
+
+ /* set data bit count */
+ switch (cflag & CSIZE) {
+ case CS5:
+ lcr = UART_LCR_WLEN5;
+ break;
+ case CS6:
+ lcr = UART_LCR_WLEN6;
+ break;
+ case CS7:
+ lcr = UART_LCR_WLEN7;
+ break;
+ default:
+ case CS8:
+ lcr = UART_LCR_WLEN8;
+ break;
+ }
+ if (cflag & CSTOPB)
+ lcr |= UART_LCR_STOP;
+ if (cflag & PARENB)
+ lcr |= UART_LCR_PARITY;
+ if (!(cflag & PARODD))
+ lcr |= UART_LCR_EPAR;
+#ifdef CMSPAR
+ if (cflag & CMSPAR)
+ lcr |= UART_LCR_SPAR;
+#endif
+ /* handshake control */
+ hcr = (cflag & CRTSCTS) ? 0x03 : 0x00;
+
+ /* calc baudrate */
+ dev_dbg(&port->dev, "%s - setting bps to %d\n", __func__, bps);
+ eval = 0;
+ switch (bps) {
+ case 0:
+ quot = calc_divisor(9600);
+ break;
+ default:
+ if ((bps < 75) || (bps > 3000000))
+ bps = 9600;
+ quot = calc_divisor(bps);
+ break;
+ case 460800:
+ eval = 1;
+ quot = calc_divisor(bps);
+ break;
+ case 921600:
+ eval = 2;
+ quot = calc_divisor(bps);
+ break;
+ }
+
+ /* Update state: synchronize */
+ mutex_lock(&priv->hw_lock);
+
+ /* keep old LCR_SBC bit */
+ lcr |= (priv->lcr & UART_LCR_SBC);
+
+ dev_dbg(&port->dev, "%s - setting hcr:0x%02x,lcr:0x%02x,quot:%d\n",
+ __func__, hcr, lcr, quot);
+
+ /* handshake control */
+ if (priv->hcr != hcr) {
+ priv->hcr = hcr;
+ ark3116_write_reg(serial, 0x8, hcr);
+ }
+
+ /* baudrate */
+ if (priv->quot != quot) {
+ priv->quot = quot;
+ priv->lcr = lcr; /* need to write lcr anyway */
+
+ /* disable DMA since transmit/receive is
+ * shadowed by UART_DLL
+ */
+ ark3116_write_reg(serial, UART_FCR, 0);
+
+ ark3116_write_reg(serial, UART_LCR,
+ lcr|UART_LCR_DLAB);
+ ark3116_write_reg(serial, UART_DLL, quot & 0xff);
+ ark3116_write_reg(serial, UART_DLM, (quot>>8) & 0xff);
+
+ /* restore lcr */
+ ark3116_write_reg(serial, UART_LCR, lcr);
+ /* magic baudrate thingy: not sure what it does,
+ * but windows does this as well.
+ */
+ ark3116_write_reg(serial, 0xe, eval);
+
+ /* enable DMA */
+ ark3116_write_reg(serial, UART_FCR, UART_FCR_DMA_SELECT);
+ } else if (priv->lcr != lcr) {
+ priv->lcr = lcr;
+ ark3116_write_reg(serial, UART_LCR, lcr);
+ }
+
+ mutex_unlock(&priv->hw_lock);
+
+ /* check for software flow control */
+ if (I_IXOFF(tty) || I_IXON(tty)) {
+ dev_warn(&port->dev,
+ "software flow control not implemented\n");
+ }
+
+ /* Don't rewrite B0 */
+ if (tty_termios_baud_rate(termios))
+ tty_termios_encode_baud_rate(termios, bps, bps);
+}
+
+static void ark3116_close(struct usb_serial_port *port)
+{
+ struct usb_serial *serial = port->serial;
+
+ /* disable DMA */
+ ark3116_write_reg(serial, UART_FCR, 0);
+
+ /* deactivate interrupts */
+ ark3116_write_reg(serial, UART_IER, 0);
+
+ usb_serial_generic_close(port);
+
+ usb_kill_urb(port->interrupt_in_urb);
+}
+
+static int ark3116_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+ struct usb_serial *serial = port->serial;
+ unsigned char *buf;
+ int result;
+
+ buf = kmalloc(1, GFP_KERNEL);
+ if (buf == NULL)
+ return -ENOMEM;
+
+ result = usb_serial_generic_open(tty, port);
+ if (result) {
+ dev_dbg(&port->dev,
+ "%s - usb_serial_generic_open failed: %d\n",
+ __func__, result);
+ goto err_free;
+ }
+
+ /* remove any data still left: also clears error state */
+ ark3116_read_reg(serial, UART_RX, buf);
+
+ /* read modem status */
+ result = ark3116_read_reg(serial, UART_MSR, buf);
+ if (result < 0)
+ goto err_close;
+ priv->msr = *buf;
+
+ /* read line status */
+ result = ark3116_read_reg(serial, UART_LSR, buf);
+ if (result < 0)
+ goto err_close;
+ priv->lsr = *buf;
+
+ result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+ if (result) {
+ dev_err(&port->dev, "submit irq_in urb failed %d\n",
+ result);
+ goto err_close;
+ }
+
+ /* activate interrupts */
+ ark3116_write_reg(port->serial, UART_IER, UART_IER_MSI|UART_IER_RLSI);
+
+ /* enable DMA */
+ ark3116_write_reg(port->serial, UART_FCR, UART_FCR_DMA_SELECT);
+
+ /* setup termios */
+ if (tty)
+ ark3116_set_termios(tty, port, NULL);
+
+ kfree(buf);
+
+ return 0;
+
+err_close:
+ usb_serial_generic_close(port);
+err_free:
+ kfree(buf);
+
+ return result;
+}
+
+static int ark3116_ioctl(struct tty_struct *tty,
+ unsigned int cmd, unsigned long arg)
+{
+ struct usb_serial_port *port = tty->driver_data;
+ struct serial_struct serstruct;
+ void __user *user_arg = (void __user *)arg;
+
+ switch (cmd) {
+ case TIOCGSERIAL:
+ /* XXX: Some of these values are probably wrong. */
+ memset(&serstruct, 0, sizeof(serstruct));
+ serstruct.type = PORT_16654;
+ serstruct.line = port->minor;
+ serstruct.port = port->port_number;
+ serstruct.custom_divisor = 0;
+ serstruct.baud_base = 460800;
+
+ if (copy_to_user(user_arg, &serstruct, sizeof(serstruct)))
+ return -EFAULT;
+
+ return 0;
+ case TIOCSSERIAL:
+ if (copy_from_user(&serstruct, user_arg, sizeof(serstruct)))
+ return -EFAULT;
+ return 0;
+ }
+
+ return -ENOIOCTLCMD;
+}
+
+static int ark3116_tiocmget(struct tty_struct *tty)
+{
+ struct usb_serial_port *port = tty->driver_data;
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+ __u32 status;
+ __u32 ctrl;
+ unsigned long flags;
+
+ mutex_lock(&priv->hw_lock);
+ ctrl = priv->mcr;
+ mutex_unlock(&priv->hw_lock);
+
+ spin_lock_irqsave(&priv->status_lock, flags);
+ status = priv->msr;
+ spin_unlock_irqrestore(&priv->status_lock, flags);
+
+ return (status & UART_MSR_DSR ? TIOCM_DSR : 0) |
+ (status & UART_MSR_CTS ? TIOCM_CTS : 0) |
+ (status & UART_MSR_RI ? TIOCM_RI : 0) |
+ (status & UART_MSR_DCD ? TIOCM_CD : 0) |
+ (ctrl & UART_MCR_DTR ? TIOCM_DTR : 0) |
+ (ctrl & UART_MCR_RTS ? TIOCM_RTS : 0) |
+ (ctrl & UART_MCR_OUT1 ? TIOCM_OUT1 : 0) |
+ (ctrl & UART_MCR_OUT2 ? TIOCM_OUT2 : 0);
+}
+
+static int ark3116_tiocmset(struct tty_struct *tty,
+ unsigned set, unsigned clr)
+{
+ struct usb_serial_port *port = tty->driver_data;
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+
+ /* we need to take the mutex here, to make sure that the value
+ * in priv->mcr is actually the one that is in the hardware
+ */
+
+ mutex_lock(&priv->hw_lock);
+
+ if (set & TIOCM_RTS)
+ priv->mcr |= UART_MCR_RTS;
+ if (set & TIOCM_DTR)
+ priv->mcr |= UART_MCR_DTR;
+ if (set & TIOCM_OUT1)
+ priv->mcr |= UART_MCR_OUT1;
+ if (set & TIOCM_OUT2)
+ priv->mcr |= UART_MCR_OUT2;
+ if (clr & TIOCM_RTS)
+ priv->mcr &= ~UART_MCR_RTS;
+ if (clr & TIOCM_DTR)
+ priv->mcr &= ~UART_MCR_DTR;
+ if (clr & TIOCM_OUT1)
+ priv->mcr &= ~UART_MCR_OUT1;
+ if (clr & TIOCM_OUT2)
+ priv->mcr &= ~UART_MCR_OUT2;
+
+ ark3116_write_reg(port->serial, UART_MCR, priv->mcr);
+
+ mutex_unlock(&priv->hw_lock);
+
+ return 0;
+}
+
+static void ark3116_break_ctl(struct tty_struct *tty, int break_state)
+{
+ struct usb_serial_port *port = tty->driver_data;
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+
+ /* LCR is also used for other things: protect access */
+ mutex_lock(&priv->hw_lock);
+
+ if (break_state)
+ priv->lcr |= UART_LCR_SBC;
+ else
+ priv->lcr &= ~UART_LCR_SBC;
+
+ ark3116_write_reg(port->serial, UART_LCR, priv->lcr);
+
+ mutex_unlock(&priv->hw_lock);
+}
+
+static void ark3116_update_msr(struct usb_serial_port *port, __u8 msr)
+{
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+ unsigned long flags;
+
+ spin_lock_irqsave(&priv->status_lock, flags);
+ priv->msr = msr;
+ spin_unlock_irqrestore(&priv->status_lock, flags);
+
+ if (msr & UART_MSR_ANY_DELTA) {
+ /* update input line counters */
+ if (msr & UART_MSR_DCTS)
+ port->icount.cts++;
+ if (msr & UART_MSR_DDSR)
+ port->icount.dsr++;
+ if (msr & UART_MSR_DDCD)
+ port->icount.dcd++;
+ if (msr & UART_MSR_TERI)
+ port->icount.rng++;
+ wake_up_interruptible(&port->port.delta_msr_wait);
+ }
+}
+
+static void ark3116_update_lsr(struct usb_serial_port *port, __u8 lsr)
+{
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+ unsigned long flags;
+
+ spin_lock_irqsave(&priv->status_lock, flags);
+ /* combine bits */
+ priv->lsr |= lsr;
+ spin_unlock_irqrestore(&priv->status_lock, flags);
+
+ if (lsr&UART_LSR_BRK_ERROR_BITS) {
+ if (lsr & UART_LSR_BI)
+ port->icount.brk++;
+ if (lsr & UART_LSR_FE)
+ port->icount.frame++;
+ if (lsr & UART_LSR_PE)
+ port->icount.parity++;
+ if (lsr & UART_LSR_OE)
+ port->icount.overrun++;
+ }
+}
+
+static void ark3116_read_int_callback(struct urb *urb)
+{
+ struct usb_serial_port *port = urb->context;
+ int status = urb->status;
+ const __u8 *data = urb->transfer_buffer;
+ int result;
+
+ switch (status) {
+ case -ECONNRESET:
+ case -ENOENT:
+ case -ESHUTDOWN:
+ /* this urb is terminated, clean up */
+ dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n",
+ __func__, status);
+ return;
+ default:
+ dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n",
+ __func__, status);
+ break;
+ case 0: /* success */
+ /* discovered this by trail and error... */
+ if ((urb->actual_length == 4) && (data[0] == 0xe8)) {
+ const __u8 id = data[1]&UART_IIR_ID;
+ dev_dbg(&port->dev, "%s: iir=%02x\n", __func__, data[1]);
+ if (id == UART_IIR_MSI) {
+ dev_dbg(&port->dev, "%s: msr=%02x\n",
+ __func__, data[3]);
+ ark3116_update_msr(port, data[3]);
+ break;
+ } else if (id == UART_IIR_RLSI) {
+ dev_dbg(&port->dev, "%s: lsr=%02x\n",
+ __func__, data[2]);
+ ark3116_update_lsr(port, data[2]);
+ break;
+ }
+ }
+ /*
+ * Not sure what this data meant...
+ */
+ usb_serial_debug_data(&port->dev, __func__,
+ urb->actual_length,
+ urb->transfer_buffer);
+ break;
+ }
+
+ result = usb_submit_urb(urb, GFP_ATOMIC);
+ if (result)
+ dev_err(&port->dev, "failed to resubmit interrupt urb: %d\n",
+ result);
+}
+
+
+/* Data comes in via the bulk (data) URB, errors/interrupts via the int URB.
+ * This means that we cannot be sure which data byte has an associated error
+ * condition, so we report an error for all data in the next bulk read.
+ *
+ * Actually, there might even be a window between the bulk data leaving the
+ * ark and reading/resetting the lsr in the read_bulk_callback where an
+ * interrupt for the next data block could come in.
+ * Without somekind of ordering on the ark, we would have to report the
+ * error for the next block of data as well...
+ * For now, let's pretend this can't happen.
+ */
+static void ark3116_process_read_urb(struct urb *urb)
+{
+ struct usb_serial_port *port = urb->context;
+ struct ark3116_private *priv = usb_get_serial_port_data(port);
+ unsigned char *data = urb->transfer_buffer;
+ char tty_flag = TTY_NORMAL;
+ unsigned long flags;
+ __u32 lsr;
+
+ /* update line status */
+ spin_lock_irqsave(&priv->status_lock, flags);
+ lsr = priv->lsr;
+ priv->lsr &= ~UART_LSR_BRK_ERROR_BITS;
+ spin_unlock_irqrestore(&priv->status_lock, flags);
+
+ if (!urb->actual_length)
+ return;
+
+ if (lsr & UART_LSR_BRK_ERROR_BITS) {
+ if (lsr & UART_LSR_BI)
+ tty_flag = TTY_BREAK;
+ else if (lsr & UART_LSR_PE)
+ tty_flag = TTY_PARITY;
+ else if (lsr & UART_LSR_FE)
+ tty_flag = TTY_FRAME;
+
+ /* overrun is special, not associated with a char */
+ if (lsr & UART_LSR_OE)
+ tty_insert_flip_char(&port->port, 0, TTY_OVERRUN);
+ }
+ tty_insert_flip_string_fixed_flag(&port->port, data, tty_flag,
+ urb->actual_length);
+ tty_flip_buffer_push(&port->port);
+}
+
+static struct usb_serial_driver ark3116_device = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "ark3116",
+ },
+ .id_table = id_table,
+ .num_ports = 1,
+ .num_bulk_in = 1,
+ .num_bulk_out = 1,
+ .num_interrupt_in = 1,
+ .port_probe = ark3116_port_probe,
+ .port_remove = ark3116_port_remove,
+ .set_termios = ark3116_set_termios,
+ .init_termios = ark3116_init_termios,
+ .ioctl = ark3116_ioctl,
+ .tiocmget = ark3116_tiocmget,
+ .tiocmset = ark3116_tiocmset,
+ .tiocmiwait = usb_serial_generic_tiocmiwait,
+ .get_icount = usb_serial_generic_get_icount,
+ .open = ark3116_open,
+ .close = ark3116_close,
+ .break_ctl = ark3116_break_ctl,
+ .read_int_callback = ark3116_read_int_callback,
+ .process_read_urb = ark3116_process_read_urb,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+ &ark3116_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_LICENSE("GPL");
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+
+/*
+ * The following describes what I learned from studying the old
+ * ark3116.c driver, disassembling the windows driver, and some lucky
+ * guesses. Since I do not have any datasheet or other
+ * documentation, inaccuracies are almost guaranteed.
+ *
+ * Some specs for the ARK3116 can be found here:
+ * http://web.archive.org/web/20060318000438/
+ * www.arkmicro.com/en/products/view.php?id=10
+ * On that page, 2 GPIO pins are mentioned: I assume these are the
+ * OUT1 and OUT2 pins of the UART, so I added support for those
+ * through the MCR. Since the pins are not available on my hardware,
+ * I could not verify this.
+ * Also, it states there is "on-chip hardware flow control". I have
+ * discovered how to enable that. Unfortunately, I do not know how to
+ * enable XON/XOFF (software) flow control, which would need support
+ * from the chip as well to work. Because of the wording on the web
+ * page there is a real possibility the chip simply does not support
+ * software flow control.
+ *
+ * I got my ark3116 as part of a mobile phone adapter cable. On the
+ * PCB, the following numbered contacts are present:
+ *
+ * 1:- +5V
+ * 2:o DTR
+ * 3:i RX
+ * 4:i DCD
+ * 5:o RTS
+ * 6:o TX
+ * 7:i RI
+ * 8:i DSR
+ * 10:- 0V
+ * 11:i CTS
+ *
+ * On my chip, all signals seem to be 3.3V, but 5V tolerant. But that
+ * may be different for the one you have ;-).
+ *
+ * The windows driver limits the registers to 0-F, so I assume there
+ * are actually 16 present on the device.
+ *
+ * On an UART interrupt, 4 bytes of data come in on the interrupt
+ * endpoint. The bytes are 0xe8 IIR LSR MSR.
+ *
+ * The baudrate seems to be generated from the 12MHz crystal, using
+ * 4-times subsampling. So quot=12e6/(4*baud). Also see description
+ * of register E.
+ *
+ * Registers 0-7:
+ * These seem to be the same as for a regular 16450. The FCR is set
+ * to UART_FCR_DMA_SELECT (0x8), I guess to enable transfers between
+ * the UART and the USB bridge/DMA engine.
+ *
+ * Register 8:
+ * By trial and error, I found out that bit 0 enables hardware CTS,
+ * stopping TX when CTS is +5V. Bit 1 does the same for RTS, making
+ * RTS +5V when the 3116 cannot transfer the data to the USB bus
+ * (verified by disabling the reading URB). Note that as far as I can
+ * tell, the windows driver does NOT use this, so there might be some
+ * hardware bug or something.
+ *
+ * According to a patch provided here
+ * (http://lkml.org/lkml/2009/7/26/56), the ARK3116 can also be used
+ * as an IrDA dongle. Since I do not have such a thing, I could not
+ * investigate that aspect. However, I can speculate ;-).
+ *
+ * - IrDA encodes data differently than RS232. Most likely, one of
+ * the bits in registers 9..E enables the IR ENDEC (encoder/decoder).
+ * - Depending on the IR transceiver, the input and output need to be
+ * inverted, so there are probably bits for that as well.
+ * - IrDA is half-duplex, so there should be a bit for selecting that.
+ *
+ * This still leaves at least two registers unaccounted for. Perhaps
+ * The chip can do XON/XOFF or CRC in HW?
+ *
+ * Register 9:
+ * Set to 0x00 for IrDA, when the baudrate is initialised.
+ *
+ * Register A:
+ * Set to 0x01 for IrDA, at init.
+ *
+ * Register B:
+ * Set to 0x01 for IrDA, 0x00 for RS232, at init.
+ *
+ * Register C:
+ * Set to 00 for IrDA, at init.
+ *
+ * Register D:
+ * Set to 0x41 for IrDA, at init.
+ *
+ * Register E:
+ * Somekind of baudrate override. The windows driver seems to set
+ * this to 0x00 for normal baudrates, 0x01 for 460800, 0x02 for 921600.
+ * Since 460800 and 921600 cannot be obtained by dividing 3MHz by an integer,
+ * it could be somekind of subdivisor thingy.
+ * However,it does not seem to do anything: selecting 921600 (divisor 3,
+ * reg E=2), still gets 1 MHz. I also checked if registers 9, C or F would
+ * work, but they don't.
+ *
+ * Register F: unknown
+ */