1/* 2 * Copyright (C) 2009 by Bart Hartgers (bart.hartgers+ark3116@gmail.com) 3 * Original version: 4 * Copyright (C) 2006 5 * Simon Schulz (ark3116_driver <at> auctionant.de) 6 * 7 * ark3116 8 * - implements a driver for the arkmicro ark3116 chipset (vendor=0x6547, 9 * productid=0x0232) (used in a datacable called KQ-U8A) 10 * 11 * Supports full modem status lines, break, hardware flow control. Does not 12 * support software flow control, since I do not know how to enable it in hw. 13 * 14 * This driver is a essentially new implementation. I initially dug 15 * into the old ark3116.c driver and suddenly realized the ark3116 is 16 * a 16450 with a USB interface glued to it. See comments at the 17 * bottom of this file. 18 * 19 * This program is free software; you can redistribute it and/or modify it 20 * under the terms of the GNU General Public License as published by the 21 * Free Software Foundation; either version 2 of the License, or (at your 22 * option) any later version. 23 */ 24 25#include <linux/kernel.h> 26#include <linux/ioctl.h> 27#include <linux/tty.h> 28#include <linux/slab.h> 29#include <linux/tty_flip.h> 30#include <linux/module.h> 31#include <linux/usb.h> 32#include <linux/usb/serial.h> 33#include <linux/serial.h> 34#include <linux/serial_reg.h> 35#include <linux/uaccess.h> 36#include <linux/mutex.h> 37#include <linux/spinlock.h> 38 39#define DRIVER_AUTHOR "Bart Hartgers <bart.hartgers+ark3116@gmail.com>" 40#define DRIVER_DESC "USB ARK3116 serial/IrDA driver" 41#define DRIVER_DEV_DESC "ARK3116 RS232/IrDA" 42#define DRIVER_NAME "ark3116" 43 44/* usb timeout of 1 second */ 45#define ARK_TIMEOUT 1000 46 47static const struct usb_device_id id_table[] = { 48 { USB_DEVICE(0x6547, 0x0232) }, 49 { USB_DEVICE(0x18ec, 0x3118) }, /* USB to IrDA adapter */ 50 { }, 51}; 52MODULE_DEVICE_TABLE(usb, id_table); 53 54static int is_irda(struct usb_serial *serial) 55{ 56 struct usb_device *dev = serial->dev; 57 if (le16_to_cpu(dev->descriptor.idVendor) == 0x18ec && 58 le16_to_cpu(dev->descriptor.idProduct) == 0x3118) 59 return 1; 60 return 0; 61} 62 63struct ark3116_private { 64 int irda; /* 1 for irda device */ 65 66 /* protects hw register updates */ 67 struct mutex hw_lock; 68 69 int quot; /* baudrate divisor */ 70 __u32 lcr; /* line control register value */ 71 __u32 hcr; /* handshake control register (0x8) 72 * value */ 73 __u32 mcr; /* modem control register value */ 74 75 /* protects the status values below */ 76 spinlock_t status_lock; 77 __u32 msr; /* modem status register value */ 78 __u32 lsr; /* line status register value */ 79}; 80 81static int ark3116_write_reg(struct usb_serial *serial, 82 unsigned reg, __u8 val) 83{ 84 int result; 85 /* 0xfe 0x40 are magic values taken from original driver */ 86 result = usb_control_msg(serial->dev, 87 usb_sndctrlpipe(serial->dev, 0), 88 0xfe, 0x40, val, reg, 89 NULL, 0, ARK_TIMEOUT); 90 return result; 91} 92 93static int ark3116_read_reg(struct usb_serial *serial, 94 unsigned reg, unsigned char *buf) 95{ 96 int result; 97 /* 0xfe 0xc0 are magic values taken from original driver */ 98 result = usb_control_msg(serial->dev, 99 usb_rcvctrlpipe(serial->dev, 0), 100 0xfe, 0xc0, 0, reg, 101 buf, 1, ARK_TIMEOUT); 102 if (result < 0) 103 return result; 104 else 105 return buf[0]; 106} 107 108static inline int calc_divisor(int bps) 109{ 110 /* Original ark3116 made some exceptions in rounding here 111 * because windows did the same. Assume that is not really 112 * necessary. 113 * Crystal is 12MHz, probably because of USB, but we divide by 4? 114 */ 115 return (12000000 + 2*bps) / (4*bps); 116} 117 118static int ark3116_attach(struct usb_serial *serial) 119{ 120 /* make sure we have our end-points */ 121 if ((serial->num_bulk_in == 0) || 122 (serial->num_bulk_out == 0) || 123 (serial->num_interrupt_in == 0)) { 124 dev_err(&serial->dev->dev, 125 "%s - missing endpoint - " 126 "bulk in: %d, bulk out: %d, int in %d\n", 127 KBUILD_MODNAME, 128 serial->num_bulk_in, 129 serial->num_bulk_out, 130 serial->num_interrupt_in); 131 return -EINVAL; 132 } 133 134 return 0; 135} 136 137static int ark3116_port_probe(struct usb_serial_port *port) 138{ 139 struct usb_serial *serial = port->serial; 140 struct ark3116_private *priv; 141 142 priv = kzalloc(sizeof(*priv), GFP_KERNEL); 143 if (!priv) 144 return -ENOMEM; 145 146 mutex_init(&priv->hw_lock); 147 spin_lock_init(&priv->status_lock); 148 149 priv->irda = is_irda(serial); 150 151 usb_set_serial_port_data(port, priv); 152 153 /* setup the hardware */ 154 ark3116_write_reg(serial, UART_IER, 0); 155 /* disable DMA */ 156 ark3116_write_reg(serial, UART_FCR, 0); 157 /* handshake control */ 158 priv->hcr = 0; 159 ark3116_write_reg(serial, 0x8 , 0); 160 /* modem control */ 161 priv->mcr = 0; 162 ark3116_write_reg(serial, UART_MCR, 0); 163 164 if (!(priv->irda)) { 165 ark3116_write_reg(serial, 0xb , 0); 166 } else { 167 ark3116_write_reg(serial, 0xb , 1); 168 ark3116_write_reg(serial, 0xc , 0); 169 ark3116_write_reg(serial, 0xd , 0x41); 170 ark3116_write_reg(serial, 0xa , 1); 171 } 172 173 /* setup baudrate */ 174 ark3116_write_reg(serial, UART_LCR, UART_LCR_DLAB); 175 176 /* setup for 9600 8N1 */ 177 priv->quot = calc_divisor(9600); 178 ark3116_write_reg(serial, UART_DLL, priv->quot & 0xff); 179 ark3116_write_reg(serial, UART_DLM, (priv->quot>>8) & 0xff); 180 181 priv->lcr = UART_LCR_WLEN8; 182 ark3116_write_reg(serial, UART_LCR, UART_LCR_WLEN8); 183 184 ark3116_write_reg(serial, 0xe, 0); 185 186 if (priv->irda) 187 ark3116_write_reg(serial, 0x9, 0); 188 189 dev_info(&serial->dev->dev, 190 "%s using %s mode\n", 191 KBUILD_MODNAME, 192 priv->irda ? "IrDA" : "RS232"); 193 return 0; 194} 195 196static int ark3116_port_remove(struct usb_serial_port *port) 197{ 198 struct ark3116_private *priv = usb_get_serial_port_data(port); 199 200 /* device is closed, so URBs and DMA should be down */ 201 mutex_destroy(&priv->hw_lock); 202 kfree(priv); 203 204 return 0; 205} 206 207static void ark3116_init_termios(struct tty_struct *tty) 208{ 209 struct ktermios *termios = &tty->termios; 210 *termios = tty_std_termios; 211 termios->c_cflag = B9600 | CS8 212 | CREAD | HUPCL | CLOCAL; 213 termios->c_ispeed = 9600; 214 termios->c_ospeed = 9600; 215} 216 217static void ark3116_set_termios(struct tty_struct *tty, 218 struct usb_serial_port *port, 219 struct ktermios *old_termios) 220{ 221 struct usb_serial *serial = port->serial; 222 struct ark3116_private *priv = usb_get_serial_port_data(port); 223 struct ktermios *termios = &tty->termios; 224 unsigned int cflag = termios->c_cflag; 225 int bps = tty_get_baud_rate(tty); 226 int quot; 227 __u8 lcr, hcr, eval; 228 229 /* set data bit count */ 230 switch (cflag & CSIZE) { 231 case CS5: 232 lcr = UART_LCR_WLEN5; 233 break; 234 case CS6: 235 lcr = UART_LCR_WLEN6; 236 break; 237 case CS7: 238 lcr = UART_LCR_WLEN7; 239 break; 240 default: 241 case CS8: 242 lcr = UART_LCR_WLEN8; 243 break; 244 } 245 if (cflag & CSTOPB) 246 lcr |= UART_LCR_STOP; 247 if (cflag & PARENB) 248 lcr |= UART_LCR_PARITY; 249 if (!(cflag & PARODD)) 250 lcr |= UART_LCR_EPAR; 251#ifdef CMSPAR 252 if (cflag & CMSPAR) 253 lcr |= UART_LCR_SPAR; 254#endif 255 /* handshake control */ 256 hcr = (cflag & CRTSCTS) ? 0x03 : 0x00; 257 258 /* calc baudrate */ 259 dev_dbg(&port->dev, "%s - setting bps to %d\n", __func__, bps); 260 eval = 0; 261 switch (bps) { 262 case 0: 263 quot = calc_divisor(9600); 264 break; 265 default: 266 if ((bps < 75) || (bps > 3000000)) 267 bps = 9600; 268 quot = calc_divisor(bps); 269 break; 270 case 460800: 271 eval = 1; 272 quot = calc_divisor(bps); 273 break; 274 case 921600: 275 eval = 2; 276 quot = calc_divisor(bps); 277 break; 278 } 279 280 /* Update state: synchronize */ 281 mutex_lock(&priv->hw_lock); 282 283 /* keep old LCR_SBC bit */ 284 lcr |= (priv->lcr & UART_LCR_SBC); 285 286 dev_dbg(&port->dev, "%s - setting hcr:0x%02x,lcr:0x%02x,quot:%d\n", 287 __func__, hcr, lcr, quot); 288 289 /* handshake control */ 290 if (priv->hcr != hcr) { 291 priv->hcr = hcr; 292 ark3116_write_reg(serial, 0x8, hcr); 293 } 294 295 /* baudrate */ 296 if (priv->quot != quot) { 297 priv->quot = quot; 298 priv->lcr = lcr; /* need to write lcr anyway */ 299 300 /* disable DMA since transmit/receive is 301 * shadowed by UART_DLL 302 */ 303 ark3116_write_reg(serial, UART_FCR, 0); 304 305 ark3116_write_reg(serial, UART_LCR, 306 lcr|UART_LCR_DLAB); 307 ark3116_write_reg(serial, UART_DLL, quot & 0xff); 308 ark3116_write_reg(serial, UART_DLM, (quot>>8) & 0xff); 309 310 /* restore lcr */ 311 ark3116_write_reg(serial, UART_LCR, lcr); 312 /* magic baudrate thingy: not sure what it does, 313 * but windows does this as well. 314 */ 315 ark3116_write_reg(serial, 0xe, eval); 316 317 /* enable DMA */ 318 ark3116_write_reg(serial, UART_FCR, UART_FCR_DMA_SELECT); 319 } else if (priv->lcr != lcr) { 320 priv->lcr = lcr; 321 ark3116_write_reg(serial, UART_LCR, lcr); 322 } 323 324 mutex_unlock(&priv->hw_lock); 325 326 /* check for software flow control */ 327 if (I_IXOFF(tty) || I_IXON(tty)) { 328 dev_warn(&serial->dev->dev, 329 "%s: don't know how to do software flow control\n", 330 KBUILD_MODNAME); 331 } 332 333 /* Don't rewrite B0 */ 334 if (tty_termios_baud_rate(termios)) 335 tty_termios_encode_baud_rate(termios, bps, bps); 336} 337 338static void ark3116_close(struct usb_serial_port *port) 339{ 340 struct usb_serial *serial = port->serial; 341 342 /* disable DMA */ 343 ark3116_write_reg(serial, UART_FCR, 0); 344 345 /* deactivate interrupts */ 346 ark3116_write_reg(serial, UART_IER, 0); 347 348 usb_serial_generic_close(port); 349 if (serial->num_interrupt_in) 350 usb_kill_urb(port->interrupt_in_urb); 351} 352 353static int ark3116_open(struct tty_struct *tty, struct usb_serial_port *port) 354{ 355 struct ark3116_private *priv = usb_get_serial_port_data(port); 356 struct usb_serial *serial = port->serial; 357 unsigned char *buf; 358 int result; 359 360 buf = kmalloc(1, GFP_KERNEL); 361 if (buf == NULL) 362 return -ENOMEM; 363 364 result = usb_serial_generic_open(tty, port); 365 if (result) { 366 dev_dbg(&port->dev, 367 "%s - usb_serial_generic_open failed: %d\n", 368 __func__, result); 369 goto err_out; 370 } 371 372 /* remove any data still left: also clears error state */ 373 ark3116_read_reg(serial, UART_RX, buf); 374 375 /* read modem status */ 376 priv->msr = ark3116_read_reg(serial, UART_MSR, buf); 377 /* read line status */ 378 priv->lsr = ark3116_read_reg(serial, UART_LSR, buf); 379 380 result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL); 381 if (result) { 382 dev_err(&port->dev, "submit irq_in urb failed %d\n", 383 result); 384 ark3116_close(port); 385 goto err_out; 386 } 387 388 /* activate interrupts */ 389 ark3116_write_reg(port->serial, UART_IER, UART_IER_MSI|UART_IER_RLSI); 390 391 /* enable DMA */ 392 ark3116_write_reg(port->serial, UART_FCR, UART_FCR_DMA_SELECT); 393 394 /* setup termios */ 395 if (tty) 396 ark3116_set_termios(tty, port, NULL); 397 398err_out: 399 kfree(buf); 400 return result; 401} 402 403static int ark3116_ioctl(struct tty_struct *tty, 404 unsigned int cmd, unsigned long arg) 405{ 406 struct usb_serial_port *port = tty->driver_data; 407 struct serial_struct serstruct; 408 void __user *user_arg = (void __user *)arg; 409 410 switch (cmd) { 411 case TIOCGSERIAL: 412 /* XXX: Some of these values are probably wrong. */ 413 memset(&serstruct, 0, sizeof(serstruct)); 414 serstruct.type = PORT_16654; 415 serstruct.line = port->minor; 416 serstruct.port = port->port_number; 417 serstruct.custom_divisor = 0; 418 serstruct.baud_base = 460800; 419 420 if (copy_to_user(user_arg, &serstruct, sizeof(serstruct))) 421 return -EFAULT; 422 423 return 0; 424 case TIOCSSERIAL: 425 if (copy_from_user(&serstruct, user_arg, sizeof(serstruct))) 426 return -EFAULT; 427 return 0; 428 } 429 430 return -ENOIOCTLCMD; 431} 432 433static int ark3116_tiocmget(struct tty_struct *tty) 434{ 435 struct usb_serial_port *port = tty->driver_data; 436 struct ark3116_private *priv = usb_get_serial_port_data(port); 437 __u32 status; 438 __u32 ctrl; 439 unsigned long flags; 440 441 mutex_lock(&priv->hw_lock); 442 ctrl = priv->mcr; 443 mutex_unlock(&priv->hw_lock); 444 445 spin_lock_irqsave(&priv->status_lock, flags); 446 status = priv->msr; 447 spin_unlock_irqrestore(&priv->status_lock, flags); 448 449 return (status & UART_MSR_DSR ? TIOCM_DSR : 0) | 450 (status & UART_MSR_CTS ? TIOCM_CTS : 0) | 451 (status & UART_MSR_RI ? TIOCM_RI : 0) | 452 (status & UART_MSR_DCD ? TIOCM_CD : 0) | 453 (ctrl & UART_MCR_DTR ? TIOCM_DTR : 0) | 454 (ctrl & UART_MCR_RTS ? TIOCM_RTS : 0) | 455 (ctrl & UART_MCR_OUT1 ? TIOCM_OUT1 : 0) | 456 (ctrl & UART_MCR_OUT2 ? TIOCM_OUT2 : 0); 457} 458 459static int ark3116_tiocmset(struct tty_struct *tty, 460 unsigned set, unsigned clr) 461{ 462 struct usb_serial_port *port = tty->driver_data; 463 struct ark3116_private *priv = usb_get_serial_port_data(port); 464 465 /* we need to take the mutex here, to make sure that the value 466 * in priv->mcr is actually the one that is in the hardware 467 */ 468 469 mutex_lock(&priv->hw_lock); 470 471 if (set & TIOCM_RTS) 472 priv->mcr |= UART_MCR_RTS; 473 if (set & TIOCM_DTR) 474 priv->mcr |= UART_MCR_DTR; 475 if (set & TIOCM_OUT1) 476 priv->mcr |= UART_MCR_OUT1; 477 if (set & TIOCM_OUT2) 478 priv->mcr |= UART_MCR_OUT2; 479 if (clr & TIOCM_RTS) 480 priv->mcr &= ~UART_MCR_RTS; 481 if (clr & TIOCM_DTR) 482 priv->mcr &= ~UART_MCR_DTR; 483 if (clr & TIOCM_OUT1) 484 priv->mcr &= ~UART_MCR_OUT1; 485 if (clr & TIOCM_OUT2) 486 priv->mcr &= ~UART_MCR_OUT2; 487 488 ark3116_write_reg(port->serial, UART_MCR, priv->mcr); 489 490 mutex_unlock(&priv->hw_lock); 491 492 return 0; 493} 494 495static void ark3116_break_ctl(struct tty_struct *tty, int break_state) 496{ 497 struct usb_serial_port *port = tty->driver_data; 498 struct ark3116_private *priv = usb_get_serial_port_data(port); 499 500 /* LCR is also used for other things: protect access */ 501 mutex_lock(&priv->hw_lock); 502 503 if (break_state) 504 priv->lcr |= UART_LCR_SBC; 505 else 506 priv->lcr &= ~UART_LCR_SBC; 507 508 ark3116_write_reg(port->serial, UART_LCR, priv->lcr); 509 510 mutex_unlock(&priv->hw_lock); 511} 512 513static void ark3116_update_msr(struct usb_serial_port *port, __u8 msr) 514{ 515 struct ark3116_private *priv = usb_get_serial_port_data(port); 516 unsigned long flags; 517 518 spin_lock_irqsave(&priv->status_lock, flags); 519 priv->msr = msr; 520 spin_unlock_irqrestore(&priv->status_lock, flags); 521 522 if (msr & UART_MSR_ANY_DELTA) { 523 /* update input line counters */ 524 if (msr & UART_MSR_DCTS) 525 port->icount.cts++; 526 if (msr & UART_MSR_DDSR) 527 port->icount.dsr++; 528 if (msr & UART_MSR_DDCD) 529 port->icount.dcd++; 530 if (msr & UART_MSR_TERI) 531 port->icount.rng++; 532 wake_up_interruptible(&port->port.delta_msr_wait); 533 } 534} 535 536static void ark3116_update_lsr(struct usb_serial_port *port, __u8 lsr) 537{ 538 struct ark3116_private *priv = usb_get_serial_port_data(port); 539 unsigned long flags; 540 541 spin_lock_irqsave(&priv->status_lock, flags); 542 /* combine bits */ 543 priv->lsr |= lsr; 544 spin_unlock_irqrestore(&priv->status_lock, flags); 545 546 if (lsr&UART_LSR_BRK_ERROR_BITS) { 547 if (lsr & UART_LSR_BI) 548 port->icount.brk++; 549 if (lsr & UART_LSR_FE) 550 port->icount.frame++; 551 if (lsr & UART_LSR_PE) 552 port->icount.parity++; 553 if (lsr & UART_LSR_OE) 554 port->icount.overrun++; 555 } 556} 557 558static void ark3116_read_int_callback(struct urb *urb) 559{ 560 struct usb_serial_port *port = urb->context; 561 int status = urb->status; 562 const __u8 *data = urb->transfer_buffer; 563 int result; 564 565 switch (status) { 566 case -ECONNRESET: 567 case -ENOENT: 568 case -ESHUTDOWN: 569 /* this urb is terminated, clean up */ 570 dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n", 571 __func__, status); 572 return; 573 default: 574 dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n", 575 __func__, status); 576 break; 577 case 0: /* success */ 578 /* discovered this by trail and error... */ 579 if ((urb->actual_length == 4) && (data[0] == 0xe8)) { 580 const __u8 id = data[1]&UART_IIR_ID; 581 dev_dbg(&port->dev, "%s: iir=%02x\n", __func__, data[1]); 582 if (id == UART_IIR_MSI) { 583 dev_dbg(&port->dev, "%s: msr=%02x\n", 584 __func__, data[3]); 585 ark3116_update_msr(port, data[3]); 586 break; 587 } else if (id == UART_IIR_RLSI) { 588 dev_dbg(&port->dev, "%s: lsr=%02x\n", 589 __func__, data[2]); 590 ark3116_update_lsr(port, data[2]); 591 break; 592 } 593 } 594 /* 595 * Not sure what this data meant... 596 */ 597 usb_serial_debug_data(&port->dev, __func__, 598 urb->actual_length, 599 urb->transfer_buffer); 600 break; 601 } 602 603 result = usb_submit_urb(urb, GFP_ATOMIC); 604 if (result) 605 dev_err(&urb->dev->dev, 606 "%s - Error %d submitting interrupt urb\n", 607 __func__, result); 608} 609 610 611/* Data comes in via the bulk (data) URB, errors/interrupts via the int URB. 612 * This means that we cannot be sure which data byte has an associated error 613 * condition, so we report an error for all data in the next bulk read. 614 * 615 * Actually, there might even be a window between the bulk data leaving the 616 * ark and reading/resetting the lsr in the read_bulk_callback where an 617 * interrupt for the next data block could come in. 618 * Without somekind of ordering on the ark, we would have to report the 619 * error for the next block of data as well... 620 * For now, let's pretend this can't happen. 621 */ 622static void ark3116_process_read_urb(struct urb *urb) 623{ 624 struct usb_serial_port *port = urb->context; 625 struct ark3116_private *priv = usb_get_serial_port_data(port); 626 unsigned char *data = urb->transfer_buffer; 627 char tty_flag = TTY_NORMAL; 628 unsigned long flags; 629 __u32 lsr; 630 631 /* update line status */ 632 spin_lock_irqsave(&priv->status_lock, flags); 633 lsr = priv->lsr; 634 priv->lsr &= ~UART_LSR_BRK_ERROR_BITS; 635 spin_unlock_irqrestore(&priv->status_lock, flags); 636 637 if (!urb->actual_length) 638 return; 639 640 if (lsr & UART_LSR_BRK_ERROR_BITS) { 641 if (lsr & UART_LSR_BI) 642 tty_flag = TTY_BREAK; 643 else if (lsr & UART_LSR_PE) 644 tty_flag = TTY_PARITY; 645 else if (lsr & UART_LSR_FE) 646 tty_flag = TTY_FRAME; 647 648 /* overrun is special, not associated with a char */ 649 if (lsr & UART_LSR_OE) 650 tty_insert_flip_char(&port->port, 0, TTY_OVERRUN); 651 } 652 tty_insert_flip_string_fixed_flag(&port->port, data, tty_flag, 653 urb->actual_length); 654 tty_flip_buffer_push(&port->port); 655} 656 657static struct usb_serial_driver ark3116_device = { 658 .driver = { 659 .owner = THIS_MODULE, 660 .name = "ark3116", 661 }, 662 .id_table = id_table, 663 .num_ports = 1, 664 .attach = ark3116_attach, 665 .port_probe = ark3116_port_probe, 666 .port_remove = ark3116_port_remove, 667 .set_termios = ark3116_set_termios, 668 .init_termios = ark3116_init_termios, 669 .ioctl = ark3116_ioctl, 670 .tiocmget = ark3116_tiocmget, 671 .tiocmset = ark3116_tiocmset, 672 .tiocmiwait = usb_serial_generic_tiocmiwait, 673 .get_icount = usb_serial_generic_get_icount, 674 .open = ark3116_open, 675 .close = ark3116_close, 676 .break_ctl = ark3116_break_ctl, 677 .read_int_callback = ark3116_read_int_callback, 678 .process_read_urb = ark3116_process_read_urb, 679}; 680 681static struct usb_serial_driver * const serial_drivers[] = { 682 &ark3116_device, NULL 683}; 684 685module_usb_serial_driver(serial_drivers, id_table); 686 687MODULE_LICENSE("GPL"); 688 689MODULE_AUTHOR(DRIVER_AUTHOR); 690MODULE_DESCRIPTION(DRIVER_DESC); 691 692/* 693 * The following describes what I learned from studying the old 694 * ark3116.c driver, disassembling the windows driver, and some lucky 695 * guesses. Since I do not have any datasheet or other 696 * documentation, inaccuracies are almost guaranteed. 697 * 698 * Some specs for the ARK3116 can be found here: 699 * http://web.archive.org/web/20060318000438/ 700 * www.arkmicro.com/en/products/view.php?id=10 701 * On that page, 2 GPIO pins are mentioned: I assume these are the 702 * OUT1 and OUT2 pins of the UART, so I added support for those 703 * through the MCR. Since the pins are not available on my hardware, 704 * I could not verify this. 705 * Also, it states there is "on-chip hardware flow control". I have 706 * discovered how to enable that. Unfortunately, I do not know how to 707 * enable XON/XOFF (software) flow control, which would need support 708 * from the chip as well to work. Because of the wording on the web 709 * page there is a real possibility the chip simply does not support 710 * software flow control. 711 * 712 * I got my ark3116 as part of a mobile phone adapter cable. On the 713 * PCB, the following numbered contacts are present: 714 * 715 * 1:- +5V 716 * 2:o DTR 717 * 3:i RX 718 * 4:i DCD 719 * 5:o RTS 720 * 6:o TX 721 * 7:i RI 722 * 8:i DSR 723 * 10:- 0V 724 * 11:i CTS 725 * 726 * On my chip, all signals seem to be 3.3V, but 5V tolerant. But that 727 * may be different for the one you have ;-). 728 * 729 * The windows driver limits the registers to 0-F, so I assume there 730 * are actually 16 present on the device. 731 * 732 * On an UART interrupt, 4 bytes of data come in on the interrupt 733 * endpoint. The bytes are 0xe8 IIR LSR MSR. 734 * 735 * The baudrate seems to be generated from the 12MHz crystal, using 736 * 4-times subsampling. So quot=12e6/(4*baud). Also see description 737 * of register E. 738 * 739 * Registers 0-7: 740 * These seem to be the same as for a regular 16450. The FCR is set 741 * to UART_FCR_DMA_SELECT (0x8), I guess to enable transfers between 742 * the UART and the USB bridge/DMA engine. 743 * 744 * Register 8: 745 * By trial and error, I found out that bit 0 enables hardware CTS, 746 * stopping TX when CTS is +5V. Bit 1 does the same for RTS, making 747 * RTS +5V when the 3116 cannot transfer the data to the USB bus 748 * (verified by disabling the reading URB). Note that as far as I can 749 * tell, the windows driver does NOT use this, so there might be some 750 * hardware bug or something. 751 * 752 * According to a patch provided here 753 * (http://lkml.org/lkml/2009/7/26/56), the ARK3116 can also be used 754 * as an IrDA dongle. Since I do not have such a thing, I could not 755 * investigate that aspect. However, I can speculate ;-). 756 * 757 * - IrDA encodes data differently than RS232. Most likely, one of 758 * the bits in registers 9..E enables the IR ENDEC (encoder/decoder). 759 * - Depending on the IR transceiver, the input and output need to be 760 * inverted, so there are probably bits for that as well. 761 * - IrDA is half-duplex, so there should be a bit for selecting that. 762 * 763 * This still leaves at least two registers unaccounted for. Perhaps 764 * The chip can do XON/XOFF or CRC in HW? 765 * 766 * Register 9: 767 * Set to 0x00 for IrDA, when the baudrate is initialised. 768 * 769 * Register A: 770 * Set to 0x01 for IrDA, at init. 771 * 772 * Register B: 773 * Set to 0x01 for IrDA, 0x00 for RS232, at init. 774 * 775 * Register C: 776 * Set to 00 for IrDA, at init. 777 * 778 * Register D: 779 * Set to 0x41 for IrDA, at init. 780 * 781 * Register E: 782 * Somekind of baudrate override. The windows driver seems to set 783 * this to 0x00 for normal baudrates, 0x01 for 460800, 0x02 for 921600. 784 * Since 460800 and 921600 cannot be obtained by dividing 3MHz by an integer, 785 * it could be somekind of subdivisor thingy. 786 * However,it does not seem to do anything: selecting 921600 (divisor 3, 787 * reg E=2), still gets 1 MHz. I also checked if registers 9, C or F would 788 * work, but they don't. 789 * 790 * Register F: unknown 791 */ 792