drivers/usb/serial/ch341.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
   4  * Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
   5  * Copyright 2009, Boris Hajduk <boris@hajduk.org>
   6  *
   7  * ch341.c implements a serial port driver for the Winchiphead CH341.
   8  *
   9  * The CH341 device can be used to implement an RS232 asynchronous
  10  * serial port, an IEEE-1284 parallel printer port or a memory-like
  11  * interface. In all cases the CH341 supports an I2C interface as well.
  12  * This driver only supports the asynchronous serial interface.
  13  */
  14
  15 #include <linux/kernel.h>
  16 #include <linux/tty.h>
  17 #include <linux/module.h>
  18 #include <linux/slab.h>
  19 #include <linux/usb.h>
  20 #include <linux/usb/serial.h>
  21 #include <linux/serial.h>
  22 #include <asm/unaligned.h>
  23
  24 #define DEFAULT_BAUD_RATE 9600
  25 #define DEFAULT_TIMEOUT   1000
  26
  27 /* flags for IO-Bits */
  28 #define CH341_BIT_RTS (1 << 6)
  29 #define CH341_BIT_DTR (1 << 5)
  30
  31 /******************************/
  32 /* interrupt pipe definitions */
  33 /******************************/
  34 /* always 4 interrupt bytes */
  35 /* first irq byte normally 0x08 */
  36 /* second irq byte base 0x7d + below */
  37 /* third irq byte base 0x94 + below */
  38 /* fourth irq byte normally 0xee */
  39
  40 /* second interrupt byte */
  41 #define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */
  42
  43 /* status returned in third interrupt answer byte, inverted in data
  44    from irq */
  45 #define CH341_BIT_CTS 0x01
  46 #define CH341_BIT_DSR 0x02
  47 #define CH341_BIT_RI  0x04
  48 #define CH341_BIT_DCD 0x08
  49 #define CH341_BITS_MODEM_STAT 0x0f /* all bits */
  50
  51 /* Break support - the information used to implement this was gleaned from
  52  * the Net/FreeBSD uchcom.c driver by Takanori Watanabe.  Domo arigato.
  53  */
  54
  55 #define CH341_REQ_READ_VERSION 0x5F
  56 #define CH341_REQ_WRITE_REG    0x9A
  57 #define CH341_REQ_READ_REG     0x95
  58 #define CH341_REQ_SERIAL_INIT  0xA1
  59 #define CH341_REQ_MODEM_CTRL   0xA4
  60
  61 #define CH341_REG_BREAK        0x05
  62 #define CH341_REG_PRESCALER    0x12
  63 #define CH341_REG_DIVISOR      0x13
  64 #define CH341_REG_LCR          0x18
  65 #define CH341_REG_LCR2         0x25
  66
  67 #define CH341_NBREAK_BITS      0x01
  68
  69 #define CH341_LCR_ENABLE_RX    0x80
  70 #define CH341_LCR_ENABLE_TX    0x40
  71 #define CH341_LCR_MARK_SPACE   0x20
  72 #define CH341_LCR_PAR_EVEN     0x10
  73 #define CH341_LCR_ENABLE_PAR   0x08
  74 #define CH341_LCR_STOP_BITS_2  0x04
  75 #define CH341_LCR_CS8          0x03
  76 #define CH341_LCR_CS7          0x02
  77 #define CH341_LCR_CS6          0x01
  78 #define CH341_LCR_CS5          0x00
  79
  80 #define CH341_QUIRK_LIMITED_PRESCALER   BIT(0)
  81 #define CH341_QUIRK_SIMULATE_BREAK      BIT(1)
  82
  83 static const struct usb_device_id id_table[] = {
  84         { USB_DEVICE(0x1a86, 0x5512) },
  85         { USB_DEVICE(0x1a86, 0x5523) },
  86         { USB_DEVICE(0x1a86, 0x7522) },
  87         { USB_DEVICE(0x1a86, 0x7523) },
  88         { USB_DEVICE(0x4348, 0x5523) },
  89         { },
  90 };
  91 MODULE_DEVICE_TABLE(usb, id_table);
  92
  93 struct ch341_private {
  94         spinlock_t lock; /* access lock */
  95         unsigned baud_rate; /* set baud rate */
  96         u8 mcr;
  97         u8 msr;
  98         u8 lcr;
  99         unsigned long quirks;
 100         unsigned long break_end;
 101 };
 102
 103 static void ch341_set_termios(struct tty_struct *tty,
 104                               struct usb_serial_port *port,
 105                               struct ktermios *old_termios);
 106
 107 static int ch341_control_out(struct usb_device *dev, u8 request,
 108                              u16 value, u16 index)
 109 {
 110         int r;
 111
 112         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__,
 113                 request, value, index);
 114
 115         r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
 116                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
 117                             value, index, NULL, 0, DEFAULT_TIMEOUT);
 118         if (r < 0)
 119                 dev_err(&dev->dev, "failed to send control message: %d\n", r);
 120
 121         return r;
 122 }
 123
 124 static int ch341_control_in(struct usb_device *dev,
 125                             u8 request, u16 value, u16 index,
 126                             char *buf, unsigned bufsize)
 127 {
 128         int r;
 129
 130         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
 131                 request, value, index, bufsize);
 132
 133         r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
 134                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 135                             value, index, buf, bufsize, DEFAULT_TIMEOUT);
 136         if (r < (int)bufsize) {
 137                 if (r >= 0) {
 138                         dev_err(&dev->dev,
 139                                 "short control message received (%d < %u)\n",
 140                                 r, bufsize);
 141                         r = -EIO;
 142                 }
 143
 144                 dev_err(&dev->dev, "failed to receive control message: %d\n",
 145                         r);
 146                 return r;
 147         }
 148
 149         return 0;
 150 }
 151
 152 #define CH341_CLKRATE           48000000
 153 #define CH341_CLK_DIV(ps, fact) (1 << (12 - 3 * (ps) - (fact)))
 154 #define CH341_MIN_RATE(ps)      (CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512))
 155
 156 static const speed_t ch341_min_rates[] = {
 157         CH341_MIN_RATE(0),
 158         CH341_MIN_RATE(1),
 159         CH341_MIN_RATE(2),
 160         CH341_MIN_RATE(3),
 161 };
 162
 163 /* Supported range is 46 to 3000000 bps. */
 164 #define CH341_MIN_BPS   DIV_ROUND_UP(CH341_CLKRATE, CH341_CLK_DIV(0, 0) * 256)
 165 #define CH341_MAX_BPS   (CH341_CLKRATE / (CH341_CLK_DIV(3, 0) * 2))
 166
 167 /*
 168  * The device line speed is given by the following equation:
 169  *
 170  *      baudrate = 48000000 / (2^(12 - 3 * ps - fact) * div), where
 171  *
 172  *              0 <= ps <= 3,
 173  *              0 <= fact <= 1,
 174  *              2 <= div <= 256 if fact = 0, or
 175  *              9 <= div <= 256 if fact = 1
 176  */
 177 static int ch341_get_divisor(struct ch341_private *priv, speed_t speed)
 178 {
 179         unsigned int fact, div, clk_div;
 180         bool force_fact0 = false;
 181         int ps;
 182
 183         /*
 184          * Clamp to supported range, this makes the (ps < 0) and (div < 2)
 185          * sanity checks below redundant.
 186          */
 187         speed = clamp_val(speed, CH341_MIN_BPS, CH341_MAX_BPS);
 188
 189         /*
 190          * Start with highest possible base clock (fact = 1) that will give a
 191          * divisor strictly less than 512.
 192          */
 193         fact = 1;
 194         for (ps = 3; ps >= 0; ps--) {
 195                 if (speed > ch341_min_rates[ps])
 196                         break;
 197         }
 198
 199         if (ps < 0)
 200                 return -EINVAL;
 201
 202         /* Determine corresponding divisor, rounding down. */
 203         clk_div = CH341_CLK_DIV(ps, fact);
 204         div = CH341_CLKRATE / (clk_div * speed);
 205
 206         /* Some devices require a lower base clock if ps < 3. */
 207         if (ps < 3 && (priv->quirks & CH341_QUIRK_LIMITED_PRESCALER))
 208                 force_fact0 = true;
 209
 210         /* Halve base clock (fact = 0) if required. */
 211         if (div < 9 || div > 255 || force_fact0) {
 212                 div /= 2;
 213                 clk_div *= 2;
 214                 fact = 0;
 215         }
 216
 217         if (div < 2)
 218                 return -EINVAL;
 219
 220         /*
 221          * Pick next divisor if resulting rate is closer to the requested one,
 222          * scale up to avoid rounding errors on low rates.
 223          */
 224         if (16 * CH341_CLKRATE / (clk_div * div) - 16 * speed >=
 225                         16 * speed - 16 * CH341_CLKRATE / (clk_div * (div + 1)))
 226                 div++;
 227
 228         /*
 229          * Prefer lower base clock (fact = 0) if even divisor.
 230          *
 231          * Note that this makes the receiver more tolerant to errors.
 232          */
 233         if (fact == 1 && div % 2 == 0) {
 234                 div /= 2;
 235                 fact = 0;
 236         }
 237
 238         return (0x100 - div) << 8 | fact << 2 | ps;
 239 }
 240
 241 static int ch341_set_baudrate_lcr(struct usb_device *dev,
 242                                   struct ch341_private *priv,
 243                                   speed_t baud_rate, u8 lcr)
 244 {
 245         int val;
 246         int r;
 247
 248         if (!baud_rate)
 249                 return -EINVAL;
 250
 251         val = ch341_get_divisor(priv, baud_rate);
 252         if (val < 0)
 253                 return -EINVAL;
 254
 255         /*
 256          * CH341A buffers data until a full endpoint-size packet (32 bytes)
 257          * has been received unless bit 7 is set.
 258          */
 259         val |= BIT(7);
 260
 261         r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
 262                               CH341_REG_DIVISOR << 8 | CH341_REG_PRESCALER,
 263                               val);
 264         if (r)
 265                 return r;
 266
 267         /*
 268          * Chip versions before version 0x30 as read using
 269          * CH341_REQ_READ_VERSION used separate registers for line control
 270          * (stop bits, parity and word length). Version 0x30 and above use
 271          * CH341_REG_LCR only and CH341_REG_LCR2 is always set to zero.
 272          */
 273         r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
 274                               CH341_REG_LCR2 << 8 | CH341_REG_LCR, lcr);
 275         if (r)
 276                 return r;
 277
 278         return r;
 279 }
 280
 281 static int ch341_set_handshake(struct usb_device *dev, u8 control)
 282 {
 283         return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0);
 284 }
 285
 286 static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
 287 {
 288         const unsigned int size = 2;
 289         char *buffer;
 290         int r;
 291         unsigned long flags;
 292
 293         buffer = kmalloc(size, GFP_KERNEL);
 294         if (!buffer)
 295                 return -ENOMEM;
 296
 297         r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
 298         if (r < 0)
 299                 goto out;
 300
 301         spin_lock_irqsave(&priv->lock, flags);
 302         priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
 303         spin_unlock_irqrestore(&priv->lock, flags);
 304
 305 out:    kfree(buffer);
 306         return r;
 307 }
 308
 309 /* -------------------------------------------------------------------------- */
 310
 311 static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
 312 {
 313         const unsigned int size = 2;
 314         char *buffer;
 315         int r;
 316
 317         buffer = kmalloc(size, GFP_KERNEL);
 318         if (!buffer)
 319                 return -ENOMEM;
 320
 321         /* expect two bytes 0x27 0x00 */
 322         r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
 323         if (r < 0)
 324                 goto out;
 325         dev_dbg(&dev->dev, "Chip version: 0x%02x\n", buffer[0]);
 326
 327         r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
 328         if (r < 0)
 329                 goto out;
 330
 331         r = ch341_set_baudrate_lcr(dev, priv, priv->baud_rate, priv->lcr);
 332         if (r < 0)
 333                 goto out;
 334
 335         r = ch341_set_handshake(dev, priv->mcr);
 336
 337 out:    kfree(buffer);
 338         return r;
 339 }
 340
 341 static int ch341_detect_quirks(struct usb_serial_port *port)
 342 {
 343         struct ch341_private *priv = usb_get_serial_port_data(port);
 344         struct usb_device *udev = port->serial->dev;
 345         const unsigned int size = 2;
 346         unsigned long quirks = 0;
 347         char *buffer;
 348         int r;
 349
 350         buffer = kmalloc(size, GFP_KERNEL);
 351         if (!buffer)
 352                 return -ENOMEM;
 353
 354         /*
 355          * A subset of CH34x devices does not support all features. The
 356          * prescaler is limited and there is no support for sending a RS232
 357          * break condition. A read failure when trying to set up the latter is
 358          * used to detect these devices.
 359          */
 360         r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0), CH341_REQ_READ_REG,
 361                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 362                             CH341_REG_BREAK, 0, buffer, size, DEFAULT_TIMEOUT);
 363         if (r == -EPIPE) {
 364                 dev_info(&port->dev, "break control not supported, using simulated break\n");
 365                 quirks = CH341_QUIRK_LIMITED_PRESCALER | CH341_QUIRK_SIMULATE_BREAK;
 366                 r = 0;
 367                 goto out;
 368         }
 369
 370         if (r != size) {
 371                 if (r >= 0)
 372                         r = -EIO;
 373                 dev_err(&port->dev, "failed to read break control: %d\n", r);
 374                 goto out;
 375         }
 376
 377         r = 0;
 378 out:
 379         kfree(buffer);
 380
 381         if (quirks) {
 382                 dev_dbg(&port->dev, "enabling quirk flags: 0x%02lx\n", quirks);
 383                 priv->quirks |= quirks;
 384         }
 385
 386         return r;
 387 }
 388
 389 static int ch341_port_probe(struct usb_serial_port *port)
 390 {
 391         struct ch341_private *priv;
 392         int r;
 393
 394         priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
 395         if (!priv)
 396                 return -ENOMEM;
 397
 398         spin_lock_init(&priv->lock);
 399         priv->baud_rate = DEFAULT_BAUD_RATE;
 400         /*
 401          * Some CH340 devices appear unable to change the initial LCR
 402          * settings, so set a sane 8N1 default.
 403          */
 404         priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
 405
 406         r = ch341_configure(port->serial->dev, priv);
 407         if (r < 0)
 408                 goto error;
 409
 410         usb_set_serial_port_data(port, priv);
 411
 412         r = ch341_detect_quirks(port);
 413         if (r < 0)
 414                 goto error;
 415
 416         return 0;
 417
 418 error:  kfree(priv);
 419         return r;
 420 }
 421
 422 static int ch341_port_remove(struct usb_serial_port *port)
 423 {
 424         struct ch341_private *priv;
 425
 426         priv = usb_get_serial_port_data(port);
 427         kfree(priv);
 428
 429         return 0;
 430 }
 431
 432 static int ch341_carrier_raised(struct usb_serial_port *port)
 433 {
 434         struct ch341_private *priv = usb_get_serial_port_data(port);
 435         if (priv->msr & CH341_BIT_DCD)
 436                 return 1;
 437         return 0;
 438 }
 439
 440 static void ch341_dtr_rts(struct usb_serial_port *port, int on)
 441 {
 442         struct ch341_private *priv = usb_get_serial_port_data(port);
 443         unsigned long flags;
 444
 445         /* drop DTR and RTS */
 446         spin_lock_irqsave(&priv->lock, flags);
 447         if (on)
 448                 priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
 449         else
 450                 priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
 451         spin_unlock_irqrestore(&priv->lock, flags);
 452         ch341_set_handshake(port->serial->dev, priv->mcr);
 453 }
 454
 455 static void ch341_close(struct usb_serial_port *port)
 456 {
 457         usb_serial_generic_close(port);
 458         usb_kill_urb(port->interrupt_in_urb);
 459 }
 460
 461
 462 /* open this device, set default parameters */
 463 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
 464 {
 465         struct ch341_private *priv = usb_get_serial_port_data(port);
 466         int r;
 467
 468         if (tty)
 469                 ch341_set_termios(tty, port, NULL);
 470
 471         dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
 472         r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 473         if (r) {
 474                 dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n",
 475                         __func__, r);
 476                 return r;
 477         }
 478
 479         r = ch341_get_status(port->serial->dev, priv);
 480         if (r < 0) {
 481                 dev_err(&port->dev, "failed to read modem status: %d\n", r);
 482                 goto err_kill_interrupt_urb;
 483         }
 484
 485         r = usb_serial_generic_open(tty, port);
 486         if (r)
 487                 goto err_kill_interrupt_urb;
 488
 489         return 0;
 490
 491 err_kill_interrupt_urb:
 492         usb_kill_urb(port->interrupt_in_urb);
 493
 494         return r;
 495 }
 496
 497 /* Old_termios contains the original termios settings and
 498  * tty->termios contains the new setting to be used.
 499  */
 500 static void ch341_set_termios(struct tty_struct *tty,
 501                 struct usb_serial_port *port, struct ktermios *old_termios)
 502 {
 503         struct ch341_private *priv = usb_get_serial_port_data(port);
 504         unsigned baud_rate;
 505         unsigned long flags;
 506         u8 lcr;
 507         int r;
 508
 509         /* redundant changes may cause the chip to lose bytes */
 510         if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
 511                 return;
 512
 513         baud_rate = tty_get_baud_rate(tty);
 514
 515         lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
 516
 517         switch (C_CSIZE(tty)) {
 518         case CS5:
 519                 lcr |= CH341_LCR_CS5;
 520                 break;
 521         case CS6:
 522                 lcr |= CH341_LCR_CS6;
 523                 break;
 524         case CS7:
 525                 lcr |= CH341_LCR_CS7;
 526                 break;
 527         case CS8:
 528                 lcr |= CH341_LCR_CS8;
 529                 break;
 530         }
 531
 532         if (C_PARENB(tty)) {
 533                 lcr |= CH341_LCR_ENABLE_PAR;
 534                 if (C_PARODD(tty) == 0)
 535                         lcr |= CH341_LCR_PAR_EVEN;
 536                 if (C_CMSPAR(tty))
 537                         lcr |= CH341_LCR_MARK_SPACE;
 538         }
 539
 540         if (C_CSTOPB(tty))
 541                 lcr |= CH341_LCR_STOP_BITS_2;
 542
 543         if (baud_rate) {
 544                 priv->baud_rate = baud_rate;
 545
 546                 r = ch341_set_baudrate_lcr(port->serial->dev, priv,
 547                                            priv->baud_rate, lcr);
 548                 if (r < 0 && old_termios) {
 549                         priv->baud_rate = tty_termios_baud_rate(old_termios);
 550                         tty_termios_copy_hw(&tty->termios, old_termios);
 551                 } else if (r == 0) {
 552                         priv->lcr = lcr;
 553                 }
 554         }
 555
 556         spin_lock_irqsave(&priv->lock, flags);
 557         if (C_BAUD(tty) == B0)
 558                 priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
 559         else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
 560                 priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
 561         spin_unlock_irqrestore(&priv->lock, flags);
 562
 563         ch341_set_handshake(port->serial->dev, priv->mcr);
 564 }
 565
 566 /*
 567  * A subset of all CH34x devices don't support a real break condition and
 568  * reading CH341_REG_BREAK fails (see also ch341_detect_quirks). This function
 569  * simulates a break condition by lowering the baud rate to the minimum
 570  * supported by the hardware upon enabling the break condition and sending
 571  * a NUL byte.
 572  *
 573  * Incoming data is corrupted while the break condition is being simulated.
 574  *
 575  * Normally the duration of the break condition can be controlled individually
 576  * by userspace using TIOCSBRK and TIOCCBRK or by passing an argument to
 577  * TCSBRKP. Due to how the simulation is implemented the duration can't be
 578  * controlled. The duration is always about (1s / 46bd * 9bit) = 196ms.
 579  */
 580 static void ch341_simulate_break(struct tty_struct *tty, int break_state)
 581 {
 582         struct usb_serial_port *port = tty->driver_data;
 583         struct ch341_private *priv = usb_get_serial_port_data(port);
 584         unsigned long now, delay;
 585         int r;
 586
 587         if (break_state != 0) {
 588                 dev_dbg(&port->dev, "enter break state requested\n");
 589
 590                 r = ch341_set_baudrate_lcr(port->serial->dev, priv,
 591                                 CH341_MIN_BPS,
 592                                 CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8);
 593                 if (r < 0) {
 594                         dev_err(&port->dev,
 595                                 "failed to change baud rate to %u: %d\n",
 596                                 CH341_MIN_BPS, r);
 597                         goto restore;
 598                 }
 599
 600                 r = tty_put_char(tty, '\0');
 601                 if (r < 0) {
 602                         dev_err(&port->dev,
 603                                 "failed to write NUL byte for simulated break condition: %d\n",
 604                                 r);
 605                         goto restore;
 606                 }
 607
 608                 /*
 609                  * Compute expected transmission duration including safety
 610                  * margin. The original baud rate is only restored after the
 611                  * computed point in time.
 612                  *
 613                  * 11 bits = 1 start, 8 data, 1 stop, 1 margin
 614                  */
 615                 priv->break_end = jiffies + (11 * HZ / CH341_MIN_BPS);
 616
 617                 return;
 618         }
 619
 620         dev_dbg(&port->dev, "leave break state requested\n");
 621
 622         now = jiffies;
 623
 624         if (time_before(now, priv->break_end)) {
 625                 /* Wait until NUL byte is written */
 626                 delay = priv->break_end - now;
 627                 dev_dbg(&port->dev,
 628                         "wait %d ms while transmitting NUL byte at %u baud\n",
 629                         jiffies_to_msecs(delay), CH341_MIN_BPS);
 630                 schedule_timeout_interruptible(delay);
 631         }
 632
 633 restore:
 634         /* Restore original baud rate */
 635         r = ch341_set_baudrate_lcr(port->serial->dev, priv, priv->baud_rate,
 636                                    priv->lcr);
 637         if (r < 0)
 638                 dev_err(&port->dev,
 639                         "restoring original baud rate of %u failed: %d\n",
 640                         priv->baud_rate, r);
 641 }
 642
 643 static void ch341_break_ctl(struct tty_struct *tty, int break_state)
 644 {
 645         const uint16_t ch341_break_reg =
 646                         ((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK;
 647         struct usb_serial_port *port = tty->driver_data;
 648         struct ch341_private *priv = usb_get_serial_port_data(port);
 649         int r;
 650         uint16_t reg_contents;
 651         uint8_t *break_reg;
 652
 653         if (priv->quirks & CH341_QUIRK_SIMULATE_BREAK) {
 654                 ch341_simulate_break(tty, break_state);
 655                 return;
 656         }
 657
 658         break_reg = kmalloc(2, GFP_KERNEL);
 659         if (!break_reg)
 660                 return;
 661
 662         r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
 663                         ch341_break_reg, 0, break_reg, 2);
 664         if (r < 0) {
 665                 dev_err(&port->dev, "%s - USB control read error (%d)\n",
 666                                 __func__, r);
 667                 goto out;
 668         }
 669         dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
 670                 __func__, break_reg[0], break_reg[1]);
 671         if (break_state != 0) {
 672                 dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
 673                 break_reg[0] &= ~CH341_NBREAK_BITS;
 674                 break_reg[1] &= ~CH341_LCR_ENABLE_TX;
 675         } else {
 676                 dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
 677                 break_reg[0] |= CH341_NBREAK_BITS;
 678                 break_reg[1] |= CH341_LCR_ENABLE_TX;
 679         }
 680         dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
 681                 __func__, break_reg[0], break_reg[1]);
 682         reg_contents = get_unaligned_le16(break_reg);
 683         r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
 684                         ch341_break_reg, reg_contents);
 685         if (r < 0)
 686                 dev_err(&port->dev, "%s - USB control write error (%d)\n",
 687                                 __func__, r);
 688 out:
 689         kfree(break_reg);
 690 }
 691
 692 static int ch341_tiocmset(struct tty_struct *tty,
 693                           unsigned int set, unsigned int clear)
 694 {
 695         struct usb_serial_port *port = tty->driver_data;
 696         struct ch341_private *priv = usb_get_serial_port_data(port);
 697         unsigned long flags;
 698         u8 control;
 699
 700         spin_lock_irqsave(&priv->lock, flags);
 701         if (set & TIOCM_RTS)
 702                 priv->mcr |= CH341_BIT_RTS;
 703         if (set & TIOCM_DTR)
 704                 priv->mcr |= CH341_BIT_DTR;
 705         if (clear & TIOCM_RTS)
 706                 priv->mcr &= ~CH341_BIT_RTS;
 707         if (clear & TIOCM_DTR)
 708                 priv->mcr &= ~CH341_BIT_DTR;
 709         control = priv->mcr;
 710         spin_unlock_irqrestore(&priv->lock, flags);
 711
 712         return ch341_set_handshake(port->serial->dev, control);
 713 }
 714
 715 static void ch341_update_status(struct usb_serial_port *port,
 716                                         unsigned char *data, size_t len)
 717 {
 718         struct ch341_private *priv = usb_get_serial_port_data(port);
 719         struct tty_struct *tty;
 720         unsigned long flags;
 721         u8 status;
 722         u8 delta;
 723
 724         if (len < 4)
 725                 return;
 726
 727         status = ~data[2] & CH341_BITS_MODEM_STAT;
 728
 729         spin_lock_irqsave(&priv->lock, flags);
 730         delta = status ^ priv->msr;
 731         priv->msr = status;
 732         spin_unlock_irqrestore(&priv->lock, flags);
 733
 734         if (data[1] & CH341_MULT_STAT)
 735                 dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
 736
 737         if (!delta)
 738                 return;
 739
 740         if (delta & CH341_BIT_CTS)
 741                 port->icount.cts++;
 742         if (delta & CH341_BIT_DSR)
 743                 port->icount.dsr++;
 744         if (delta & CH341_BIT_RI)
 745                 port->icount.rng++;
 746         if (delta & CH341_BIT_DCD) {
 747                 port->icount.dcd++;
 748                 tty = tty_port_tty_get(&port->port);
 749                 if (tty) {
 750                         usb_serial_handle_dcd_change(port, tty,
 751                                                 status & CH341_BIT_DCD);
 752                         tty_kref_put(tty);
 753                 }
 754         }
 755
 756         wake_up_interruptible(&port->port.delta_msr_wait);
 757 }
 758
 759 static void ch341_read_int_callback(struct urb *urb)
 760 {
 761         struct usb_serial_port *port = urb->context;
 762         unsigned char *data = urb->transfer_buffer;
 763         unsigned int len = urb->actual_length;
 764         int status;
 765
 766         switch (urb->status) {
 767         case 0:
 768                 /* success */
 769                 break;
 770         case -ECONNRESET:
 771         case -ENOENT:
 772         case -ESHUTDOWN:
 773                 /* this urb is terminated, clean up */
 774                 dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n",
 775                         __func__, urb->status);
 776                 return;
 777         default:
 778                 dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n",
 779                         __func__, urb->status);
 780                 goto exit;
 781         }
 782
 783         usb_serial_debug_data(&port->dev, __func__, len, data);
 784         ch341_update_status(port, data, len);
 785 exit:
 786         status = usb_submit_urb(urb, GFP_ATOMIC);
 787         if (status) {
 788                 dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n",
 789                         __func__, status);
 790         }
 791 }
 792
 793 static int ch341_tiocmget(struct tty_struct *tty)
 794 {
 795         struct usb_serial_port *port = tty->driver_data;
 796         struct ch341_private *priv = usb_get_serial_port_data(port);
 797         unsigned long flags;
 798         u8 mcr;
 799         u8 status;
 800         unsigned int result;
 801
 802         spin_lock_irqsave(&priv->lock, flags);
 803         mcr = priv->mcr;
 804         status = priv->msr;
 805         spin_unlock_irqrestore(&priv->lock, flags);
 806
 807         result = ((mcr & CH341_BIT_DTR)         ? TIOCM_DTR : 0)
 808                   | ((mcr & CH341_BIT_RTS)      ? TIOCM_RTS : 0)
 809                   | ((status & CH341_BIT_CTS)   ? TIOCM_CTS : 0)
 810                   | ((status & CH341_BIT_DSR)   ? TIOCM_DSR : 0)
 811                   | ((status & CH341_BIT_RI)    ? TIOCM_RI  : 0)
 812                   | ((status & CH341_BIT_DCD)   ? TIOCM_CD  : 0);
 813
 814         dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
 815
 816         return result;
 817 }
 818
 819 static int ch341_reset_resume(struct usb_serial *serial)
 820 {
 821         struct usb_serial_port *port = serial->port[0];
 822         struct ch341_private *priv;
 823         int ret;
 824
 825         priv = usb_get_serial_port_data(port);
 826         if (!priv)
 827                 return 0;
 828
 829         /* reconfigure ch341 serial port after bus-reset */
 830         ch341_configure(serial->dev, priv);
 831
 832         if (tty_port_initialized(&port->port)) {
 833                 ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
 834                 if (ret) {
 835                         dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
 836                                 ret);
 837                         return ret;
 838                 }
 839
 840                 ret = ch341_get_status(port->serial->dev, priv);
 841                 if (ret < 0) {
 842                         dev_err(&port->dev, "failed to read modem status: %d\n",
 843                                 ret);
 844                 }
 845         }
 846
 847         return usb_serial_generic_resume(serial);
 848 }
 849
 850 static struct usb_serial_driver ch341_device = {
 851         .driver = {
 852                 .owner  = THIS_MODULE,
 853                 .name   = "ch341-uart",
 854         },
 855         .id_table          = id_table,
 856         .num_ports         = 1,
 857         .open              = ch341_open,
 858         .dtr_rts           = ch341_dtr_rts,
 859         .carrier_raised    = ch341_carrier_raised,
 860         .close             = ch341_close,
 861         .set_termios       = ch341_set_termios,
 862         .break_ctl         = ch341_break_ctl,
 863         .tiocmget          = ch341_tiocmget,
 864         .tiocmset          = ch341_tiocmset,
 865         .tiocmiwait        = usb_serial_generic_tiocmiwait,
 866         .read_int_callback = ch341_read_int_callback,
 867         .port_probe        = ch341_port_probe,
 868         .port_remove       = ch341_port_remove,
 869         .reset_resume      = ch341_reset_resume,
 870 };
 871
 872 static struct usb_serial_driver * const serial_drivers[] = {
 873         &ch341_device, NULL
 874 };
 875
 876 module_usb_serial_driver(serial_drivers, id_table);
 877
 878 MODULE_LICENSE("GPL v2");