1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Copyright (C) 2009 by Bart Hartgers (bart.hartgers+ark3116@gmail.com) 4 * Original version: 5 * Copyright (C) 2006 6 * Simon Schulz (ark3116_driver <at> auctionant.de) 7 * 8 * ark3116 9 * - implements a driver for the arkmicro ark3116 chipset (vendor=0x6547, 10 * productid=0x0232) (used in a datacable called KQ-U8A) 11 * 12 * Supports full modem status lines, break, hardware flow control. Does not 13 * support software flow control, since I do not know how to enable it in hw. 14 * 15 * This driver is a essentially new implementation. I initially dug 16 * into the old ark3116.c driver and suddenly realized the ark3116 is 17 * a 16450 with a USB interface glued to it. See comments at the 18 * bottom of this file. 19 * 20 * This program is free software; you can redistribute it and/or modify it 21 * under the terms of the GNU General Public License as published by the 22 * Free Software Foundation; either version 2 of the License, or (at your 23 * option) any later version. 24 */ 25 26 #include <linux/kernel.h> 27 #include <linux/ioctl.h> 28 #include <linux/tty.h> 29 #include <linux/slab.h> 30 #include <linux/tty_flip.h> 31 #include <linux/module.h> 32 #include <linux/usb.h> 33 #include <linux/usb/serial.h> 34 #include <linux/serial.h> 35 #include <linux/serial_reg.h> 36 #include <linux/uaccess.h> 37 #include <linux/mutex.h> 38 #include <linux/spinlock.h> 39 40 #define DRIVER_AUTHOR "Bart Hartgers <bart.hartgers+ark3116@gmail.com>" 41 #define DRIVER_DESC "USB ARK3116 serial/IrDA driver" 42 #define DRIVER_DEV_DESC "ARK3116 RS232/IrDA" 43 #define DRIVER_NAME "ark3116" 44 45 /* usb timeout of 1 second */ 46 #define ARK_TIMEOUT 1000 47 48 static const struct usb_device_id id_table[] = { 49 { USB_DEVICE(0x6547, 0x0232) }, 50 { USB_DEVICE(0x18ec, 0x3118) }, /* USB to IrDA adapter */ 51 { }, 52 }; 53 MODULE_DEVICE_TABLE(usb, id_table); 54 55 static int is_irda(struct usb_serial *serial) 56 { 57 struct usb_device *dev = serial->dev; 58 if (le16_to_cpu(dev->descriptor.idVendor) == 0x18ec && 59 le16_to_cpu(dev->descriptor.idProduct) == 0x3118) 60 return 1; 61 return 0; 62 } 63 64 struct ark3116_private { 65 int irda; /* 1 for irda device */ 66 67 /* protects hw register updates */ 68 struct mutex hw_lock; 69 70 int quot; /* baudrate divisor */ 71 __u32 lcr; /* line control register value */ 72 __u32 hcr; /* handshake control register (0x8) 73 * value */ 74 __u32 mcr; /* modem control register value */ 75 76 /* protects the status values below */ 77 spinlock_t status_lock; 78 __u32 msr; /* modem status register value */ 79 __u32 lsr; /* line status register value */ 80 }; 81 82 static int ark3116_write_reg(struct usb_serial *serial, 83 unsigned reg, __u8 val) 84 { 85 int result; 86 /* 0xfe 0x40 are magic values taken from original driver */ 87 result = usb_control_msg(serial->dev, 88 usb_sndctrlpipe(serial->dev, 0), 89 0xfe, 0x40, val, reg, 90 NULL, 0, ARK_TIMEOUT); 91 return result; 92 } 93 94 static int ark3116_read_reg(struct usb_serial *serial, 95 unsigned reg, unsigned char *buf) 96 { 97 int result; 98 /* 0xfe 0xc0 are magic values taken from original driver */ 99 result = usb_control_msg(serial->dev, 100 usb_rcvctrlpipe(serial->dev, 0), 101 0xfe, 0xc0, 0, reg, 102 buf, 1, ARK_TIMEOUT); 103 if (result < 1) { 104 dev_err(&serial->interface->dev, 105 "failed to read register %u: %d\n", 106 reg, result); 107 if (result >= 0) 108 result = -EIO; 109 110 return result; 111 } 112 113 return buf[0]; 114 } 115 116 static inline int calc_divisor(int bps) 117 { 118 /* Original ark3116 made some exceptions in rounding here 119 * because windows did the same. Assume that is not really 120 * necessary. 121 * Crystal is 12MHz, probably because of USB, but we divide by 4? 122 */ 123 return (12000000 + 2*bps) / (4*bps); 124 } 125 126 static int ark3116_port_probe(struct usb_serial_port *port) 127 { 128 struct usb_serial *serial = port->serial; 129 struct ark3116_private *priv; 130 131 priv = kzalloc(sizeof(*priv), GFP_KERNEL); 132 if (!priv) 133 return -ENOMEM; 134 135 mutex_init(&priv->hw_lock); 136 spin_lock_init(&priv->status_lock); 137 138 priv->irda = is_irda(serial); 139 140 usb_set_serial_port_data(port, priv); 141 142 /* setup the hardware */ 143 ark3116_write_reg(serial, UART_IER, 0); 144 /* disable DMA */ 145 ark3116_write_reg(serial, UART_FCR, 0); 146 /* handshake control */ 147 priv->hcr = 0; 148 ark3116_write_reg(serial, 0x8 , 0); 149 /* modem control */ 150 priv->mcr = 0; 151 ark3116_write_reg(serial, UART_MCR, 0); 152 153 if (!(priv->irda)) { 154 ark3116_write_reg(serial, 0xb , 0); 155 } else { 156 ark3116_write_reg(serial, 0xb , 1); 157 ark3116_write_reg(serial, 0xc , 0); 158 ark3116_write_reg(serial, 0xd , 0x41); 159 ark3116_write_reg(serial, 0xa , 1); 160 } 161 162 /* setup baudrate */ 163 ark3116_write_reg(serial, UART_LCR, UART_LCR_DLAB); 164 165 /* setup for 9600 8N1 */ 166 priv->quot = calc_divisor(9600); 167 ark3116_write_reg(serial, UART_DLL, priv->quot & 0xff); 168 ark3116_write_reg(serial, UART_DLM, (priv->quot>>8) & 0xff); 169 170 priv->lcr = UART_LCR_WLEN8; 171 ark3116_write_reg(serial, UART_LCR, UART_LCR_WLEN8); 172 173 ark3116_write_reg(serial, 0xe, 0); 174 175 if (priv->irda) 176 ark3116_write_reg(serial, 0x9, 0); 177 178 dev_info(&port->dev, "using %s mode\n", priv->irda ? "IrDA" : "RS232"); 179 180 return 0; 181 } 182 183 static int ark3116_port_remove(struct usb_serial_port *port) 184 { 185 struct ark3116_private *priv = usb_get_serial_port_data(port); 186 187 /* device is closed, so URBs and DMA should be down */ 188 mutex_destroy(&priv->hw_lock); 189 kfree(priv); 190 191 return 0; 192 } 193 194 static void ark3116_init_termios(struct tty_struct *tty) 195 { 196 struct ktermios *termios = &tty->termios; 197 *termios = tty_std_termios; 198 termios->c_cflag = B9600 | CS8 199 | CREAD | HUPCL | CLOCAL; 200 termios->c_ispeed = 9600; 201 termios->c_ospeed = 9600; 202 } 203 204 static void ark3116_set_termios(struct tty_struct *tty, 205 struct usb_serial_port *port, 206 struct ktermios *old_termios) 207 { 208 struct usb_serial *serial = port->serial; 209 struct ark3116_private *priv = usb_get_serial_port_data(port); 210 struct ktermios *termios = &tty->termios; 211 unsigned int cflag = termios->c_cflag; 212 int bps = tty_get_baud_rate(tty); 213 int quot; 214 __u8 lcr, hcr, eval; 215 216 /* set data bit count */ 217 switch (cflag & CSIZE) { 218 case CS5: 219 lcr = UART_LCR_WLEN5; 220 break; 221 case CS6: 222 lcr = UART_LCR_WLEN6; 223 break; 224 case CS7: 225 lcr = UART_LCR_WLEN7; 226 break; 227 default: 228 case CS8: 229 lcr = UART_LCR_WLEN8; 230 break; 231 } 232 if (cflag & CSTOPB) 233 lcr |= UART_LCR_STOP; 234 if (cflag & PARENB) 235 lcr |= UART_LCR_PARITY; 236 if (!(cflag & PARODD)) 237 lcr |= UART_LCR_EPAR; 238 #ifdef CMSPAR 239 if (cflag & CMSPAR) 240 lcr |= UART_LCR_SPAR; 241 #endif 242 /* handshake control */ 243 hcr = (cflag & CRTSCTS) ? 0x03 : 0x00; 244 245 /* calc baudrate */ 246 dev_dbg(&port->dev, "%s - setting bps to %d\n", __func__, bps); 247 eval = 0; 248 switch (bps) { 249 case 0: 250 quot = calc_divisor(9600); 251 break; 252 default: 253 if ((bps < 75) || (bps > 3000000)) 254 bps = 9600; 255 quot = calc_divisor(bps); 256 break; 257 case 460800: 258 eval = 1; 259 quot = calc_divisor(bps); 260 break; 261 case 921600: 262 eval = 2; 263 quot = calc_divisor(bps); 264 break; 265 } 266 267 /* Update state: synchronize */ 268 mutex_lock(&priv->hw_lock); 269 270 /* keep old LCR_SBC bit */ 271 lcr |= (priv->lcr & UART_LCR_SBC); 272 273 dev_dbg(&port->dev, "%s - setting hcr:0x%02x,lcr:0x%02x,quot:%d\n", 274 __func__, hcr, lcr, quot); 275 276 /* handshake control */ 277 if (priv->hcr != hcr) { 278 priv->hcr = hcr; 279 ark3116_write_reg(serial, 0x8, hcr); 280 } 281 282 /* baudrate */ 283 if (priv->quot != quot) { 284 priv->quot = quot; 285 priv->lcr = lcr; /* need to write lcr anyway */ 286 287 /* disable DMA since transmit/receive is 288 * shadowed by UART_DLL 289 */ 290 ark3116_write_reg(serial, UART_FCR, 0); 291 292 ark3116_write_reg(serial, UART_LCR, 293 lcr|UART_LCR_DLAB); 294 ark3116_write_reg(serial, UART_DLL, quot & 0xff); 295 ark3116_write_reg(serial, UART_DLM, (quot>>8) & 0xff); 296 297 /* restore lcr */ 298 ark3116_write_reg(serial, UART_LCR, lcr); 299 /* magic baudrate thingy: not sure what it does, 300 * but windows does this as well. 301 */ 302 ark3116_write_reg(serial, 0xe, eval); 303 304 /* enable DMA */ 305 ark3116_write_reg(serial, UART_FCR, UART_FCR_DMA_SELECT); 306 } else if (priv->lcr != lcr) { 307 priv->lcr = lcr; 308 ark3116_write_reg(serial, UART_LCR, lcr); 309 } 310 311 mutex_unlock(&priv->hw_lock); 312 313 /* check for software flow control */ 314 if (I_IXOFF(tty) || I_IXON(tty)) { 315 dev_warn(&port->dev, 316 "software flow control not implemented\n"); 317 } 318 319 /* Don't rewrite B0 */ 320 if (tty_termios_baud_rate(termios)) 321 tty_termios_encode_baud_rate(termios, bps, bps); 322 } 323 324 static void ark3116_close(struct usb_serial_port *port) 325 { 326 struct usb_serial *serial = port->serial; 327 328 /* disable DMA */ 329 ark3116_write_reg(serial, UART_FCR, 0); 330 331 /* deactivate interrupts */ 332 ark3116_write_reg(serial, UART_IER, 0); 333 334 usb_serial_generic_close(port); 335 336 usb_kill_urb(port->interrupt_in_urb); 337 } 338 339 static int ark3116_open(struct tty_struct *tty, struct usb_serial_port *port) 340 { 341 struct ark3116_private *priv = usb_get_serial_port_data(port); 342 struct usb_serial *serial = port->serial; 343 unsigned char *buf; 344 int result; 345 346 buf = kmalloc(1, GFP_KERNEL); 347 if (buf == NULL) 348 return -ENOMEM; 349 350 result = usb_serial_generic_open(tty, port); 351 if (result) { 352 dev_dbg(&port->dev, 353 "%s - usb_serial_generic_open failed: %d\n", 354 __func__, result); 355 goto err_free; 356 } 357 358 /* remove any data still left: also clears error state */ 359 ark3116_read_reg(serial, UART_RX, buf); 360 361 /* read modem status */ 362 result = ark3116_read_reg(serial, UART_MSR, buf); 363 if (result < 0) 364 goto err_close; 365 priv->msr = *buf; 366 367 /* read line status */ 368 result = ark3116_read_reg(serial, UART_LSR, buf); 369 if (result < 0) 370 goto err_close; 371 priv->lsr = *buf; 372 373 result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL); 374 if (result) { 375 dev_err(&port->dev, "submit irq_in urb failed %d\n", 376 result); 377 goto err_close; 378 } 379 380 /* activate interrupts */ 381 ark3116_write_reg(port->serial, UART_IER, UART_IER_MSI|UART_IER_RLSI); 382 383 /* enable DMA */ 384 ark3116_write_reg(port->serial, UART_FCR, UART_FCR_DMA_SELECT); 385 386 /* setup termios */ 387 if (tty) 388 ark3116_set_termios(tty, port, NULL); 389 390 kfree(buf); 391 392 return 0; 393 394 err_close: 395 usb_serial_generic_close(port); 396 err_free: 397 kfree(buf); 398 399 return result; 400 } 401 402 static int ark3116_ioctl(struct tty_struct *tty, 403 unsigned int cmd, unsigned long arg) 404 { 405 struct usb_serial_port *port = tty->driver_data; 406 struct serial_struct serstruct; 407 void __user *user_arg = (void __user *)arg; 408 409 switch (cmd) { 410 case TIOCGSERIAL: 411 /* XXX: Some of these values are probably wrong. */ 412 memset(&serstruct, 0, sizeof(serstruct)); 413 serstruct.type = PORT_16654; 414 serstruct.line = port->minor; 415 serstruct.port = port->port_number; 416 serstruct.custom_divisor = 0; 417 serstruct.baud_base = 460800; 418 419 if (copy_to_user(user_arg, &serstruct, sizeof(serstruct))) 420 return -EFAULT; 421 422 return 0; 423 case TIOCSSERIAL: 424 if (copy_from_user(&serstruct, user_arg, sizeof(serstruct))) 425 return -EFAULT; 426 return 0; 427 } 428 429 return -ENOIOCTLCMD; 430 } 431 432 static int ark3116_tiocmget(struct tty_struct *tty) 433 { 434 struct usb_serial_port *port = tty->driver_data; 435 struct ark3116_private *priv = usb_get_serial_port_data(port); 436 __u32 status; 437 __u32 ctrl; 438 unsigned long flags; 439 440 mutex_lock(&priv->hw_lock); 441 ctrl = priv->mcr; 442 mutex_unlock(&priv->hw_lock); 443 444 spin_lock_irqsave(&priv->status_lock, flags); 445 status = priv->msr; 446 spin_unlock_irqrestore(&priv->status_lock, flags); 447 448 return (status & UART_MSR_DSR ? TIOCM_DSR : 0) | 449 (status & UART_MSR_CTS ? TIOCM_CTS : 0) | 450 (status & UART_MSR_RI ? TIOCM_RI : 0) | 451 (status & UART_MSR_DCD ? TIOCM_CD : 0) | 452 (ctrl & UART_MCR_DTR ? TIOCM_DTR : 0) | 453 (ctrl & UART_MCR_RTS ? TIOCM_RTS : 0) | 454 (ctrl & UART_MCR_OUT1 ? TIOCM_OUT1 : 0) | 455 (ctrl & UART_MCR_OUT2 ? TIOCM_OUT2 : 0); 456 } 457 458 static int ark3116_tiocmset(struct tty_struct *tty, 459 unsigned set, unsigned clr) 460 { 461 struct usb_serial_port *port = tty->driver_data; 462 struct ark3116_private *priv = usb_get_serial_port_data(port); 463 464 /* we need to take the mutex here, to make sure that the value 465 * in priv->mcr is actually the one that is in the hardware 466 */ 467 468 mutex_lock(&priv->hw_lock); 469 470 if (set & TIOCM_RTS) 471 priv->mcr |= UART_MCR_RTS; 472 if (set & TIOCM_DTR) 473 priv->mcr |= UART_MCR_DTR; 474 if (set & TIOCM_OUT1) 475 priv->mcr |= UART_MCR_OUT1; 476 if (set & TIOCM_OUT2) 477 priv->mcr |= UART_MCR_OUT2; 478 if (clr & TIOCM_RTS) 479 priv->mcr &= ~UART_MCR_RTS; 480 if (clr & TIOCM_DTR) 481 priv->mcr &= ~UART_MCR_DTR; 482 if (clr & TIOCM_OUT1) 483 priv->mcr &= ~UART_MCR_OUT1; 484 if (clr & TIOCM_OUT2) 485 priv->mcr &= ~UART_MCR_OUT2; 486 487 ark3116_write_reg(port->serial, UART_MCR, priv->mcr); 488 489 mutex_unlock(&priv->hw_lock); 490 491 return 0; 492 } 493 494 static void ark3116_break_ctl(struct tty_struct *tty, int break_state) 495 { 496 struct usb_serial_port *port = tty->driver_data; 497 struct ark3116_private *priv = usb_get_serial_port_data(port); 498 499 /* LCR is also used for other things: protect access */ 500 mutex_lock(&priv->hw_lock); 501 502 if (break_state) 503 priv->lcr |= UART_LCR_SBC; 504 else 505 priv->lcr &= ~UART_LCR_SBC; 506 507 ark3116_write_reg(port->serial, UART_LCR, priv->lcr); 508 509 mutex_unlock(&priv->hw_lock); 510 } 511 512 static void ark3116_update_msr(struct usb_serial_port *port, __u8 msr) 513 { 514 struct ark3116_private *priv = usb_get_serial_port_data(port); 515 unsigned long flags; 516 517 spin_lock_irqsave(&priv->status_lock, flags); 518 priv->msr = msr; 519 spin_unlock_irqrestore(&priv->status_lock, flags); 520 521 if (msr & UART_MSR_ANY_DELTA) { 522 /* update input line counters */ 523 if (msr & UART_MSR_DCTS) 524 port->icount.cts++; 525 if (msr & UART_MSR_DDSR) 526 port->icount.dsr++; 527 if (msr & UART_MSR_DDCD) 528 port->icount.dcd++; 529 if (msr & UART_MSR_TERI) 530 port->icount.rng++; 531 wake_up_interruptible(&port->port.delta_msr_wait); 532 } 533 } 534 535 static void ark3116_update_lsr(struct usb_serial_port *port, __u8 lsr) 536 { 537 struct ark3116_private *priv = usb_get_serial_port_data(port); 538 unsigned long flags; 539 540 spin_lock_irqsave(&priv->status_lock, flags); 541 /* combine bits */ 542 priv->lsr |= lsr; 543 spin_unlock_irqrestore(&priv->status_lock, flags); 544 545 if (lsr&UART_LSR_BRK_ERROR_BITS) { 546 if (lsr & UART_LSR_BI) 547 port->icount.brk++; 548 if (lsr & UART_LSR_FE) 549 port->icount.frame++; 550 if (lsr & UART_LSR_PE) 551 port->icount.parity++; 552 if (lsr & UART_LSR_OE) 553 port->icount.overrun++; 554 } 555 } 556 557 static void ark3116_read_int_callback(struct urb *urb) 558 { 559 struct usb_serial_port *port = urb->context; 560 int status = urb->status; 561 const __u8 *data = urb->transfer_buffer; 562 int result; 563 564 switch (status) { 565 case -ECONNRESET: 566 case -ENOENT: 567 case -ESHUTDOWN: 568 /* this urb is terminated, clean up */ 569 dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n", 570 __func__, status); 571 return; 572 default: 573 dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n", 574 __func__, status); 575 break; 576 case 0: /* success */ 577 /* discovered this by trail and error... */ 578 if ((urb->actual_length == 4) && (data[0] == 0xe8)) { 579 const __u8 id = data[1]&UART_IIR_ID; 580 dev_dbg(&port->dev, "%s: iir=%02x\n", __func__, data[1]); 581 if (id == UART_IIR_MSI) { 582 dev_dbg(&port->dev, "%s: msr=%02x\n", 583 __func__, data[3]); 584 ark3116_update_msr(port, data[3]); 585 break; 586 } else if (id == UART_IIR_RLSI) { 587 dev_dbg(&port->dev, "%s: lsr=%02x\n", 588 __func__, data[2]); 589 ark3116_update_lsr(port, data[2]); 590 break; 591 } 592 } 593 /* 594 * Not sure what this data meant... 595 */ 596 usb_serial_debug_data(&port->dev, __func__, 597 urb->actual_length, 598 urb->transfer_buffer); 599 break; 600 } 601 602 result = usb_submit_urb(urb, GFP_ATOMIC); 603 if (result) 604 dev_err(&port->dev, "failed to resubmit interrupt urb: %d\n", 605 result); 606 } 607 608 609 /* Data comes in via the bulk (data) URB, errors/interrupts via the int URB. 610 * This means that we cannot be sure which data byte has an associated error 611 * condition, so we report an error for all data in the next bulk read. 612 * 613 * Actually, there might even be a window between the bulk data leaving the 614 * ark and reading/resetting the lsr in the read_bulk_callback where an 615 * interrupt for the next data block could come in. 616 * Without somekind of ordering on the ark, we would have to report the 617 * error for the next block of data as well... 618 * For now, let's pretend this can't happen. 619 */ 620 static void ark3116_process_read_urb(struct urb *urb) 621 { 622 struct usb_serial_port *port = urb->context; 623 struct ark3116_private *priv = usb_get_serial_port_data(port); 624 unsigned char *data = urb->transfer_buffer; 625 char tty_flag = TTY_NORMAL; 626 unsigned long flags; 627 __u32 lsr; 628 629 /* update line status */ 630 spin_lock_irqsave(&priv->status_lock, flags); 631 lsr = priv->lsr; 632 priv->lsr &= ~UART_LSR_BRK_ERROR_BITS; 633 spin_unlock_irqrestore(&priv->status_lock, flags); 634 635 if (!urb->actual_length) 636 return; 637 638 if (lsr & UART_LSR_BRK_ERROR_BITS) { 639 if (lsr & UART_LSR_BI) 640 tty_flag = TTY_BREAK; 641 else if (lsr & UART_LSR_PE) 642 tty_flag = TTY_PARITY; 643 else if (lsr & UART_LSR_FE) 644 tty_flag = TTY_FRAME; 645 646 /* overrun is special, not associated with a char */ 647 if (lsr & UART_LSR_OE) 648 tty_insert_flip_char(&port->port, 0, TTY_OVERRUN); 649 } 650 tty_insert_flip_string_fixed_flag(&port->port, data, tty_flag, 651 urb->actual_length); 652 tty_flip_buffer_push(&port->port); 653 } 654 655 static struct usb_serial_driver ark3116_device = { 656 .driver = { 657 .owner = THIS_MODULE, 658 .name = "ark3116", 659 }, 660 .id_table = id_table, 661 .num_ports = 1, 662 .num_bulk_in = 1, 663 .num_bulk_out = 1, 664 .num_interrupt_in = 1, 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 }; 680 681 static struct usb_serial_driver * const serial_drivers[] = { 682 &ark3116_device, NULL 683 }; 684 685 module_usb_serial_driver(serial_drivers, id_table); 686 687 MODULE_LICENSE("GPL"); 688 689 MODULE_AUTHOR(DRIVER_AUTHOR); 690 MODULE_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