diff options
Diffstat (limited to 'drivers/usb/serial/ark3116.c')
| -rw-r--r-- | drivers/usb/serial/ark3116.c | 791 |
1 files changed, 791 insertions, 0 deletions
diff --git a/drivers/usb/serial/ark3116.c b/drivers/usb/serial/ark3116.c new file mode 100644 index 000000000..1532cde8a --- /dev/null +++ b/drivers/usb/serial/ark3116.c @@ -0,0 +1,791 @@ +/* + * 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 < 0) + return result; + else + 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_attach(struct usb_serial *serial) +{ + /* make sure we have our end-points */ + if ((serial->num_bulk_in == 0) || + (serial->num_bulk_out == 0) || + (serial->num_interrupt_in == 0)) { + dev_err(&serial->dev->dev, + "%s - missing endpoint - " + "bulk in: %d, bulk out: %d, int in %d\n", + KBUILD_MODNAME, + serial->num_bulk_in, + serial->num_bulk_out, + serial->num_interrupt_in); + return -EINVAL; + } + + return 0; +} + +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(&serial->dev->dev, + "%s using %s mode\n", + KBUILD_MODNAME, + 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(&serial->dev->dev, + "%s: don't know how to do software flow control\n", + KBUILD_MODNAME); + } + + /* 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); + if (serial->num_interrupt_in) + 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_out; + } + + /* remove any data still left: also clears error state */ + ark3116_read_reg(serial, UART_RX, buf); + + /* read modem status */ + priv->msr = ark3116_read_reg(serial, UART_MSR, buf); + /* read line status */ + priv->lsr = ark3116_read_reg(serial, UART_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); + ark3116_close(port); + goto err_out; + } + + /* 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); + +err_out: + 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(&urb->dev->dev, + "%s - Error %d submitting interrupt urb\n", + __func__, 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, + .attach = ark3116_attach, + .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 + */ |