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 <linux/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, 0x5523) },
  85         { USB_DEVICE(0x1a86, 0x7522) },
  86         { USB_DEVICE(0x1a86, 0x7523) },
  87         { USB_DEVICE(0x2184, 0x0057) },
  88         { USB_DEVICE(0x4348, 0x5523) },
  89         { USB_DEVICE(0x9986, 0x7523) },
  90         { },
  91 };
  92 MODULE_DEVICE_TABLE(usb, id_table);
  93
  94 struct ch341_private {
  95         spinlock_t lock; /* access lock */
  96         unsigned baud_rate; /* set baud rate */
  97         u8 mcr;
  98         u8 msr;
  99         u8 lcr;
 100
 101         unsigned long quirks;
 102         u8 version;
 103
 104         unsigned long break_end;
 105 };
 106
 107 static void ch341_set_termios(struct tty_struct *tty,
 108                               struct usb_serial_port *port,
 109                               const struct ktermios *old_termios);
 110
 111 static int ch341_control_out(struct usb_device *dev, u8 request,
 112                              u16 value, u16 index)
 113 {
 114         int r;
 115
 116         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__,
 117                 request, value, index);
 118
 119         r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
 120                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
 121                             value, index, NULL, 0, DEFAULT_TIMEOUT);
 122         if (r < 0)
 123                 dev_err(&dev->dev, "failed to send control message: %d\n", r);
 124
 125         return r;
 126 }
 127
 128 static int ch341_control_in(struct usb_device *dev,
 129                             u8 request, u16 value, u16 index,
 130                             char *buf, unsigned bufsize)
 131 {
 132         int r;
 133
 134         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
 135                 request, value, index, bufsize);
 136
 137         r = usb_control_msg_recv(dev, 0, request,
 138                                  USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 139                                  value, index, buf, bufsize, DEFAULT_TIMEOUT,
 140                                  GFP_KERNEL);
 141         if (r) {
 142                 dev_err(&dev->dev, "failed to receive control message: %d\n",
 143                         r);
 144                 return r;
 145         }
 146
 147         return 0;
 148 }
 149
 150 #define CH341_CLKRATE           48000000
 151 #define CH341_CLK_DIV(ps, fact) (1 << (12 - 3 * (ps) - (fact)))
 152 #define CH341_MIN_RATE(ps)      (CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512))
 153
 154 static const speed_t ch341_min_rates[] = {
 155         CH341_MIN_RATE(0),
 156         CH341_MIN_RATE(1),
 157         CH341_MIN_RATE(2),
 158         CH341_MIN_RATE(3),
 159 };
 160
 161 /* Supported range is 46 to 3000000 bps. */
 162 #define CH341_MIN_BPS   DIV_ROUND_UP(CH341_CLKRATE, CH341_CLK_DIV(0, 0) * 256)
 163 #define CH341_MAX_BPS   (CH341_CLKRATE / (CH341_CLK_DIV(3, 0) * 2))
 164
 165 /*
 166  * The device line speed is given by the following equation:
 167  *
 168  *      baudrate = 48000000 / (2^(12 - 3 * ps - fact) * div), where
 169  *
 170  *              0 <= ps <= 3,
 171  *              0 <= fact <= 1,
 172  *              2 <= div <= 256 if fact = 0, or
 173  *              9 <= div <= 256 if fact = 1
 174  */
 175 static int ch341_get_divisor(struct ch341_private *priv, speed_t speed)
 176 {
 177         unsigned int fact, div, clk_div;
 178         bool force_fact0 = false;
 179         int ps;
 180
 181         /*
 182          * Clamp to supported range, this makes the (ps < 0) and (div < 2)
 183          * sanity checks below redundant.
 184          */
 185         speed = clamp_val(speed, CH341_MIN_BPS, CH341_MAX_BPS);
 186
 187         /*
 188          * Start with highest possible base clock (fact = 1) that will give a
 189          * divisor strictly less than 512.
 190          */
 191         fact = 1;
 192         for (ps = 3; ps >= 0; ps--) {
 193                 if (speed > ch341_min_rates[ps])
 194                         break;
 195         }
 196
 197         if (ps < 0)
 198                 return -EINVAL;
 199
 200         /* Determine corresponding divisor, rounding down. */
 201         clk_div = CH341_CLK_DIV(ps, fact);
 202         div = CH341_CLKRATE / (clk_div * speed);
 203
 204         /* Some devices require a lower base clock if ps < 3. */
 205         if (ps < 3 && (priv->quirks & CH341_QUIRK_LIMITED_PRESCALER))
 206                 force_fact0 = true;
 207
 208         /* Halve base clock (fact = 0) if required. */
 209         if (div < 9 || div > 255 || force_fact0) {
 210                 div /= 2;
 211                 clk_div *= 2;
 212                 fact = 0;
 213         }
 214
 215         if (div < 2)
 216                 return -EINVAL;
 217
 218         /*
 219          * Pick next divisor if resulting rate is closer to the requested one,
 220          * scale up to avoid rounding errors on low rates.
 221          */
 222         if (16 * CH341_CLKRATE / (clk_div * div) - 16 * speed >=
 223                         16 * speed - 16 * CH341_CLKRATE / (clk_div * (div + 1)))
 224                 div++;
 225
 226         /*
 227          * Prefer lower base clock (fact = 0) if even divisor.
 228          *
 229          * Note that this makes the receiver more tolerant to errors.
 230          */
 231         if (fact == 1 && div % 2 == 0) {
 232                 div /= 2;
 233                 fact = 0;
 234         }
 235
 236         return (0x100 - div) << 8 | fact << 2 | ps;
 237 }
 238
 239 static int ch341_set_baudrate_lcr(struct usb_device *dev,
 240                                   struct ch341_private *priv,
 241                                   speed_t baud_rate, u8 lcr)
 242 {
 243         int val;
 244         int r;
 245
 246         if (!baud_rate)
 247                 return -EINVAL;
 248
 249         val = ch341_get_divisor(priv, baud_rate);
 250         if (val < 0)
 251                 return -EINVAL;
 252
 253         /*
 254          * CH341A buffers data until a full endpoint-size packet (32 bytes)
 255          * has been received unless bit 7 is set.
 256          *
 257          * At least one device with version 0x27 appears to have this bit
 258          * inverted.
 259          */
 260         if (priv->version > 0x27)
 261                 val |= BIT(7);
 262
 263         r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
 264                               CH341_REG_DIVISOR << 8 | CH341_REG_PRESCALER,
 265                               val);
 266         if (r)
 267                 return r;
 268
 269         /*
 270          * Chip versions before version 0x30 as read using
 271          * CH341_REQ_READ_VERSION used separate registers for line control
 272          * (stop bits, parity and word length). Version 0x30 and above use
 273          * CH341_REG_LCR only and CH341_REG_LCR2 is always set to zero.
 274          */
 275         if (priv->version < 0x30)
 276                 return 0;
 277
 278         r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
 279                               CH341_REG_LCR2 << 8 | CH341_REG_LCR, lcr);
 280         if (r)
 281                 return r;
 282
 283         return r;
 284 }
 285
 286 static int ch341_set_handshake(struct usb_device *dev, u8 control)
 287 {
 288         return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0);
 289 }
 290
 291 static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
 292 {
 293         const unsigned int size = 2;
 294         u8 buffer[2];
 295         int r;
 296         unsigned long flags;
 297
 298         r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
 299         if (r)
 300                 return r;
 301
 302         spin_lock_irqsave(&priv->lock, flags);
 303         priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
 304         spin_unlock_irqrestore(&priv->lock, flags);
 305
 306         return 0;
 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         u8 buffer[2];
 315         int r;
 316
 317         /* expect two bytes 0x27 0x00 */
 318         r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
 319         if (r)
 320                 return r;
 321
 322         priv->version = buffer[0];
 323         dev_dbg(&dev->dev, "Chip version: 0x%02x\n", priv->version);
 324
 325         r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
 326         if (r < 0)
 327                 return r;
 328
 329         r = ch341_set_baudrate_lcr(dev, priv, priv->baud_rate, priv->lcr);
 330         if (r < 0)
 331                 return r;
 332
 333         r = ch341_set_handshake(dev, priv->mcr);
 334         if (r < 0)
 335                 return r;
 336
 337         return 0;
 338 }
 339
 340 static int ch341_detect_quirks(struct usb_serial_port *port)
 341 {
 342         struct ch341_private *priv = usb_get_serial_port_data(port);
 343         struct usb_device *udev = port->serial->dev;
 344         const unsigned int size = 2;
 345         unsigned long quirks = 0;
 346         u8 buffer[2];
 347         int r;
 348
 349         /*
 350          * A subset of CH34x devices does not support all features. The
 351          * prescaler is limited and there is no support for sending a RS232
 352          * break condition. A read failure when trying to set up the latter is
 353          * used to detect these devices.
 354          */
 355         r = usb_control_msg_recv(udev, 0, CH341_REQ_READ_REG,
 356                                  USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 357                                  CH341_REG_BREAK, 0, &buffer, size,
 358                                  DEFAULT_TIMEOUT, GFP_KERNEL);
 359         if (r == -EPIPE) {
 360                 dev_info(&port->dev, "break control not supported, using simulated break\n");
 361                 quirks = CH341_QUIRK_LIMITED_PRESCALER | CH341_QUIRK_SIMULATE_BREAK;
 362                 r = 0;
 363         } else if (r) {
 364                 dev_err(&port->dev, "failed to read break control: %d\n", r);
 365         }
 366
 367         if (quirks) {
 368                 dev_dbg(&port->dev, "enabling quirk flags: 0x%02lx\n", quirks);
 369                 priv->quirks |= quirks;
 370         }
 371
 372         return r;
 373 }
 374
 375 static int ch341_port_probe(struct usb_serial_port *port)
 376 {
 377         struct ch341_private *priv;
 378         int r;
 379
 380         priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
 381         if (!priv)
 382                 return -ENOMEM;
 383
 384         spin_lock_init(&priv->lock);
 385         priv->baud_rate = DEFAULT_BAUD_RATE;
 386         /*
 387          * Some CH340 devices appear unable to change the initial LCR
 388          * settings, so set a sane 8N1 default.
 389          */
 390         priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
 391
 392         r = ch341_configure(port->serial->dev, priv);
 393         if (r < 0)
 394                 goto error;
 395
 396         usb_set_serial_port_data(port, priv);
 397
 398         r = ch341_detect_quirks(port);
 399         if (r < 0)
 400                 goto error;
 401
 402         return 0;
 403
 404 error:  kfree(priv);
 405         return r;
 406 }
 407
 408 static void ch341_port_remove(struct usb_serial_port *port)
 409 {
 410         struct ch341_private *priv;
 411
 412         priv = usb_get_serial_port_data(port);
 413         kfree(priv);
 414 }
 415
 416 static int ch341_carrier_raised(struct usb_serial_port *port)
 417 {
 418         struct ch341_private *priv = usb_get_serial_port_data(port);
 419         if (priv->msr & CH341_BIT_DCD)
 420                 return 1;
 421         return 0;
 422 }
 423
 424 static void ch341_dtr_rts(struct usb_serial_port *port, int on)
 425 {
 426         struct ch341_private *priv = usb_get_serial_port_data(port);
 427         unsigned long flags;
 428
 429         /* drop DTR and RTS */
 430         spin_lock_irqsave(&priv->lock, flags);
 431         if (on)
 432                 priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
 433         else
 434                 priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
 435         spin_unlock_irqrestore(&priv->lock, flags);
 436         ch341_set_handshake(port->serial->dev, priv->mcr);
 437 }
 438
 439 static void ch341_close(struct usb_serial_port *port)
 440 {
 441         usb_serial_generic_close(port);
 442         usb_kill_urb(port->interrupt_in_urb);
 443 }
 444
 445
 446 /* open this device, set default parameters */
 447 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
 448 {
 449         struct ch341_private *priv = usb_get_serial_port_data(port);
 450         int r;
 451
 452         if (tty)
 453                 ch341_set_termios(tty, port, NULL);
 454
 455         dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
 456         r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 457         if (r) {
 458                 dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n",
 459                         __func__, r);
 460                 return r;
 461         }
 462
 463         r = ch341_get_status(port->serial->dev, priv);
 464         if (r < 0) {
 465                 dev_err(&port->dev, "failed to read modem status: %d\n", r);
 466                 goto err_kill_interrupt_urb;
 467         }
 468
 469         r = usb_serial_generic_open(tty, port);
 470         if (r)
 471                 goto err_kill_interrupt_urb;
 472
 473         return 0;
 474
 475 err_kill_interrupt_urb:
 476         usb_kill_urb(port->interrupt_in_urb);
 477
 478         return r;
 479 }
 480
 481 /* Old_termios contains the original termios settings and
 482  * tty->termios contains the new setting to be used.
 483  */
 484 static void ch341_set_termios(struct tty_struct *tty,
 485                               struct usb_serial_port *port,
 486                               const struct ktermios *old_termios)
 487 {
 488         struct ch341_private *priv = usb_get_serial_port_data(port);
 489         unsigned baud_rate;
 490         unsigned long flags;
 491         u8 lcr;
 492         int r;
 493
 494         /* redundant changes may cause the chip to lose bytes */
 495         if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
 496                 return;
 497
 498         baud_rate = tty_get_baud_rate(tty);
 499
 500         lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
 501
 502         switch (C_CSIZE(tty)) {
 503         case CS5:
 504                 lcr |= CH341_LCR_CS5;
 505                 break;
 506         case CS6:
 507                 lcr |= CH341_LCR_CS6;
 508                 break;
 509         case CS7:
 510                 lcr |= CH341_LCR_CS7;
 511                 break;
 512         case CS8:
 513                 lcr |= CH341_LCR_CS8;
 514                 break;
 515         }
 516
 517         if (C_PARENB(tty)) {
 518                 lcr |= CH341_LCR_ENABLE_PAR;
 519                 if (C_PARODD(tty) == 0)
 520                         lcr |= CH341_LCR_PAR_EVEN;
 521                 if (C_CMSPAR(tty))
 522                         lcr |= CH341_LCR_MARK_SPACE;
 523         }
 524
 525         if (C_CSTOPB(tty))
 526                 lcr |= CH341_LCR_STOP_BITS_2;
 527
 528         if (baud_rate) {
 529                 priv->baud_rate = baud_rate;
 530
 531                 r = ch341_set_baudrate_lcr(port->serial->dev, priv,
 532                                            priv->baud_rate, lcr);
 533                 if (r < 0 && old_termios) {
 534                         priv->baud_rate = tty_termios_baud_rate(old_termios);
 535                         tty_termios_copy_hw(&tty->termios, old_termios);
 536                 } else if (r == 0) {
 537                         priv->lcr = lcr;
 538                 }
 539         }
 540
 541         spin_lock_irqsave(&priv->lock, flags);
 542         if (C_BAUD(tty) == B0)
 543                 priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
 544         else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
 545                 priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
 546         spin_unlock_irqrestore(&priv->lock, flags);
 547
 548         ch341_set_handshake(port->serial->dev, priv->mcr);
 549 }
 550
 551 /*
 552  * A subset of all CH34x devices don't support a real break condition and
 553  * reading CH341_REG_BREAK fails (see also ch341_detect_quirks). This function
 554  * simulates a break condition by lowering the baud rate to the minimum
 555  * supported by the hardware upon enabling the break condition and sending
 556  * a NUL byte.
 557  *
 558  * Incoming data is corrupted while the break condition is being simulated.
 559  *
 560  * Normally the duration of the break condition can be controlled individually
 561  * by userspace using TIOCSBRK and TIOCCBRK or by passing an argument to
 562  * TCSBRKP. Due to how the simulation is implemented the duration can't be
 563  * controlled. The duration is always about (1s / 46bd * 9bit) = 196ms.
 564  */
 565 static int ch341_simulate_break(struct tty_struct *tty, int break_state)
 566 {
 567         struct usb_serial_port *port = tty->driver_data;
 568         struct ch341_private *priv = usb_get_serial_port_data(port);
 569         unsigned long now, delay;
 570         int r, r2;
 571
 572         if (break_state != 0) {
 573                 dev_dbg(&port->dev, "enter break state requested\n");
 574
 575                 r = ch341_set_baudrate_lcr(port->serial->dev, priv,
 576                                 CH341_MIN_BPS,
 577                                 CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8);
 578                 if (r < 0) {
 579                         dev_err(&port->dev,
 580                                 "failed to change baud rate to %u: %d\n",
 581                                 CH341_MIN_BPS, r);
 582                         goto restore;
 583                 }
 584
 585                 r = tty_put_char(tty, '\0');
 586                 if (r < 0) {
 587                         dev_err(&port->dev,
 588                                 "failed to write NUL byte for simulated break condition: %d\n",
 589                                 r);
 590                         goto restore;
 591                 }
 592
 593                 /*
 594                  * Compute expected transmission duration including safety
 595                  * margin. The original baud rate is only restored after the
 596                  * computed point in time.
 597                  *
 598                  * 11 bits = 1 start, 8 data, 1 stop, 1 margin
 599                  */
 600                 priv->break_end = jiffies + (11 * HZ / CH341_MIN_BPS);
 601
 602                 return 0;
 603         }
 604
 605         dev_dbg(&port->dev, "leave break state requested\n");
 606
 607         now = jiffies;
 608
 609         if (time_before(now, priv->break_end)) {
 610                 /* Wait until NUL byte is written */
 611                 delay = priv->break_end - now;
 612                 dev_dbg(&port->dev,
 613                         "wait %d ms while transmitting NUL byte at %u baud\n",
 614                         jiffies_to_msecs(delay), CH341_MIN_BPS);
 615                 schedule_timeout_interruptible(delay);
 616         }
 617
 618         r = 0;
 619 restore:
 620         /* Restore original baud rate */
 621         r2 = ch341_set_baudrate_lcr(port->serial->dev, priv, priv->baud_rate,
 622                         priv->lcr);
 623         if (r2 < 0) {
 624                 dev_err(&port->dev,
 625                         "restoring original baud rate of %u failed: %d\n",
 626                         priv->baud_rate, r2);
 627                 return r2;
 628         }
 629
 630         return r;
 631 }
 632
 633 static int ch341_break_ctl(struct tty_struct *tty, int break_state)
 634 {
 635         const uint16_t ch341_break_reg =
 636                         ((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK;
 637         struct usb_serial_port *port = tty->driver_data;
 638         struct ch341_private *priv = usb_get_serial_port_data(port);
 639         int r;
 640         uint16_t reg_contents;
 641         uint8_t break_reg[2];
 642
 643         if (priv->quirks & CH341_QUIRK_SIMULATE_BREAK)
 644                 return ch341_simulate_break(tty, break_state);
 645
 646         r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
 647                         ch341_break_reg, 0, break_reg, 2);
 648         if (r) {
 649                 dev_err(&port->dev, "%s - USB control read error (%d)\n",
 650                                 __func__, r);
 651                 if (r > 0)
 652                         r = -EIO;
 653                 return r;
 654         }
 655         dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
 656                 __func__, break_reg[0], break_reg[1]);
 657         if (break_state != 0) {
 658                 dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
 659                 break_reg[0] &= ~CH341_NBREAK_BITS;
 660                 break_reg[1] &= ~CH341_LCR_ENABLE_TX;
 661         } else {
 662                 dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
 663                 break_reg[0] |= CH341_NBREAK_BITS;
 664                 break_reg[1] |= CH341_LCR_ENABLE_TX;
 665         }
 666         dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
 667                 __func__, break_reg[0], break_reg[1]);
 668         reg_contents = get_unaligned_le16(break_reg);
 669         r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
 670                         ch341_break_reg, reg_contents);
 671         if (r < 0) {
 672                 dev_err(&port->dev, "%s - USB control write error (%d)\n",
 673                                 __func__, r);
 674                 return r;
 675         }
 676
 677         return 0;
 678 }
 679
 680 static int ch341_tiocmset(struct tty_struct *tty,
 681                           unsigned int set, unsigned int clear)
 682 {
 683         struct usb_serial_port *port = tty->driver_data;
 684         struct ch341_private *priv = usb_get_serial_port_data(port);
 685         unsigned long flags;
 686         u8 control;
 687
 688         spin_lock_irqsave(&priv->lock, flags);
 689         if (set & TIOCM_RTS)
 690                 priv->mcr |= CH341_BIT_RTS;
 691         if (set & TIOCM_DTR)
 692                 priv->mcr |= CH341_BIT_DTR;
 693         if (clear & TIOCM_RTS)
 694                 priv->mcr &= ~CH341_BIT_RTS;
 695         if (clear & TIOCM_DTR)
 696                 priv->mcr &= ~CH341_BIT_DTR;
 697         control = priv->mcr;
 698         spin_unlock_irqrestore(&priv->lock, flags);
 699
 700         return ch341_set_handshake(port->serial->dev, control);
 701 }
 702
 703 static void ch341_update_status(struct usb_serial_port *port,
 704                                         unsigned char *data, size_t len)
 705 {
 706         struct ch341_private *priv = usb_get_serial_port_data(port);
 707         struct tty_struct *tty;
 708         unsigned long flags;
 709         u8 status;
 710         u8 delta;
 711
 712         if (len < 4)
 713                 return;
 714
 715         status = ~data[2] & CH341_BITS_MODEM_STAT;
 716
 717         spin_lock_irqsave(&priv->lock, flags);
 718         delta = status ^ priv->msr;
 719         priv->msr = status;
 720         spin_unlock_irqrestore(&priv->lock, flags);
 721
 722         if (data[1] & CH341_MULT_STAT)
 723                 dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
 724
 725         if (!delta)
 726                 return;
 727
 728         if (delta & CH341_BIT_CTS)
 729                 port->icount.cts++;
 730         if (delta & CH341_BIT_DSR)
 731                 port->icount.dsr++;
 732         if (delta & CH341_BIT_RI)
 733                 port->icount.rng++;
 734         if (delta & CH341_BIT_DCD) {
 735                 port->icount.dcd++;
 736                 tty = tty_port_tty_get(&port->port);
 737                 if (tty) {
 738                         usb_serial_handle_dcd_change(port, tty,
 739                                                 status & CH341_BIT_DCD);
 740                         tty_kref_put(tty);
 741                 }
 742         }
 743
 744         wake_up_interruptible(&port->port.delta_msr_wait);
 745 }
 746
 747 static void ch341_read_int_callback(struct urb *urb)
 748 {
 749         struct usb_serial_port *port = urb->context;
 750         unsigned char *data = urb->transfer_buffer;
 751         unsigned int len = urb->actual_length;
 752         int status;
 753
 754         switch (urb->status) {
 755         case 0:
 756                 /* success */
 757                 break;
 758         case -ECONNRESET:
 759         case -ENOENT:
 760         case -ESHUTDOWN:
 761                 /* this urb is terminated, clean up */
 762                 dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n",
 763                         __func__, urb->status);
 764                 return;
 765         default:
 766                 dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n",
 767                         __func__, urb->status);
 768                 goto exit;
 769         }
 770
 771         usb_serial_debug_data(&port->dev, __func__, len, data);
 772         ch341_update_status(port, data, len);
 773 exit:
 774         status = usb_submit_urb(urb, GFP_ATOMIC);
 775         if (status) {
 776                 dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n",
 777                         __func__, status);
 778         }
 779 }
 780
 781 static int ch341_tiocmget(struct tty_struct *tty)
 782 {
 783         struct usb_serial_port *port = tty->driver_data;
 784         struct ch341_private *priv = usb_get_serial_port_data(port);
 785         unsigned long flags;
 786         u8 mcr;
 787         u8 status;
 788         unsigned int result;
 789
 790         spin_lock_irqsave(&priv->lock, flags);
 791         mcr = priv->mcr;
 792         status = priv->msr;
 793         spin_unlock_irqrestore(&priv->lock, flags);
 794
 795         result = ((mcr & CH341_BIT_DTR)         ? TIOCM_DTR : 0)
 796                   | ((mcr & CH341_BIT_RTS)      ? TIOCM_RTS : 0)
 797                   | ((status & CH341_BIT_CTS)   ? TIOCM_CTS : 0)
 798                   | ((status & CH341_BIT_DSR)   ? TIOCM_DSR : 0)
 799                   | ((status & CH341_BIT_RI)    ? TIOCM_RI  : 0)
 800                   | ((status & CH341_BIT_DCD)   ? TIOCM_CD  : 0);
 801
 802         dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
 803
 804         return result;
 805 }
 806
 807 static int ch341_reset_resume(struct usb_serial *serial)
 808 {
 809         struct usb_serial_port *port = serial->port[0];
 810         struct ch341_private *priv;
 811         int ret;
 812
 813         priv = usb_get_serial_port_data(port);
 814         if (!priv)
 815                 return 0;
 816
 817         /* reconfigure ch341 serial port after bus-reset */
 818         ch341_configure(serial->dev, priv);
 819
 820         if (tty_port_initialized(&port->port)) {
 821                 ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
 822                 if (ret) {
 823                         dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
 824                                 ret);
 825                         return ret;
 826                 }
 827
 828                 ret = ch341_get_status(port->serial->dev, priv);
 829                 if (ret < 0) {
 830                         dev_err(&port->dev, "failed to read modem status: %d\n",
 831                                 ret);
 832                 }
 833         }
 834
 835         return usb_serial_generic_resume(serial);
 836 }
 837
 838 static struct usb_serial_driver ch341_device = {
 839         .driver = {
 840                 .name   = "ch341-uart",
 841         },
 842         .id_table          = id_table,
 843         .num_ports         = 1,
 844         .open              = ch341_open,
 845         .dtr_rts           = ch341_dtr_rts,
 846         .carrier_raised    = ch341_carrier_raised,
 847         .close             = ch341_close,
 848         .set_termios       = ch341_set_termios,
 849         .break_ctl         = ch341_break_ctl,
 850         .tiocmget          = ch341_tiocmget,
 851         .tiocmset          = ch341_tiocmset,
 852         .tiocmiwait        = usb_serial_generic_tiocmiwait,
 853         .read_int_callback = ch341_read_int_callback,
 854         .port_probe        = ch341_port_probe,
 855         .port_remove       = ch341_port_remove,
 856         .reset_resume      = ch341_reset_resume,
 857 };
 858
 859 static struct usb_serial_driver * const serial_drivers[] = {
 860         &ch341_device, NULL
 861 };
 862
 863 module_usb_serial_driver(serial_drivers, id_table);
 864
 865 MODULE_DESCRIPTION("Winchiphead CH341 USB Serial driver");
 866 MODULE_LICENSE("GPL v2");