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_LCR          0x18
  63 #define CH341_NBREAK_BITS      0x01
  64
  65 #define CH341_LCR_ENABLE_RX    0x80
  66 #define CH341_LCR_ENABLE_TX    0x40
  67 #define CH341_LCR_MARK_SPACE   0x20
  68 #define CH341_LCR_PAR_EVEN     0x10
  69 #define CH341_LCR_ENABLE_PAR   0x08
  70 #define CH341_LCR_STOP_BITS_2  0x04
  71 #define CH341_LCR_CS8          0x03
  72 #define CH341_LCR_CS7          0x02
  73 #define CH341_LCR_CS6          0x01
  74 #define CH341_LCR_CS5          0x00
  75
  76 static const struct usb_device_id id_table[] = {
  77         { USB_DEVICE(0x4348, 0x5523) },
  78         { USB_DEVICE(0x1a86, 0x7523) },
  79         { USB_DEVICE(0x1a86, 0x5523) },
  80         { },
  81 };
  82 MODULE_DEVICE_TABLE(usb, id_table);
  83
  84 struct ch341_private {
  85         spinlock_t lock; /* access lock */
  86         unsigned baud_rate; /* set baud rate */
  87         u8 mcr;
  88         u8 msr;
  89         u8 lcr;
  90 };
  91
  92 static void ch341_set_termios(struct tty_struct *tty,
  93                               struct usb_serial_port *port,
  94                               struct ktermios *old_termios);
  95
  96 static int ch341_control_out(struct usb_device *dev, u8 request,
  97                              u16 value, u16 index)
  98 {
  99         int r;
 100
 101         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__,
 102                 request, value, index);
 103
 104         r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
 105                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
 106                             value, index, NULL, 0, DEFAULT_TIMEOUT);
 107         if (r < 0)
 108                 dev_err(&dev->dev, "failed to send control message: %d\n", r);
 109
 110         return r;
 111 }
 112
 113 static int ch341_control_in(struct usb_device *dev,
 114                             u8 request, u16 value, u16 index,
 115                             char *buf, unsigned bufsize)
 116 {
 117         int r;
 118
 119         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
 120                 request, value, index, bufsize);
 121
 122         r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
 123                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 124                             value, index, buf, bufsize, DEFAULT_TIMEOUT);
 125         if (r < (int)bufsize) {
 126                 if (r >= 0) {
 127                         dev_err(&dev->dev,
 128                                 "short control message received (%d < %u)\n",
 129                                 r, bufsize);
 130                         r = -EIO;
 131                 }
 132
 133                 dev_err(&dev->dev, "failed to receive control message: %d\n",
 134                         r);
 135                 return r;
 136         }
 137
 138         return 0;
 139 }
 140
 141 #define CH341_CLKRATE           48000000
 142 #define CH341_CLK_DIV(ps, fact) (1 << (12 - 3 * (ps) - (fact)))
 143 #define CH341_MIN_RATE(ps)      (CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512))
 144
 145 static const speed_t ch341_min_rates[] = {
 146         CH341_MIN_RATE(0),
 147         CH341_MIN_RATE(1),
 148         CH341_MIN_RATE(2),
 149         CH341_MIN_RATE(3),
 150 };
 151
 152 /*
 153  * The device line speed is given by the following equation:
 154  *
 155  *      baudrate = 48000000 / (2^(12 - 3 * ps - fact) * div), where
 156  *
 157  *              0 <= ps <= 3,
 158  *              0 <= fact <= 1,
 159  *              2 <= div <= 256 if fact = 0, or
 160  *              9 <= div <= 256 if fact = 1
 161  */
 162 static int ch341_get_divisor(speed_t speed)
 163 {
 164         unsigned int fact, div, clk_div;
 165         int ps;
 166
 167         /*
 168          * Clamp to supported range, this makes the (ps < 0) and (div < 2)
 169          * sanity checks below redundant.
 170          */
 171         speed = clamp(speed, 46U, 3000000U);
 172
 173         /*
 174          * Start with highest possible base clock (fact = 1) that will give a
 175          * divisor strictly less than 512.
 176          */
 177         fact = 1;
 178         for (ps = 3; ps >= 0; ps--) {
 179                 if (speed > ch341_min_rates[ps])
 180                         break;
 181         }
 182
 183         if (ps < 0)
 184                 return -EINVAL;
 185
 186         /* Determine corresponding divisor, rounding down. */
 187         clk_div = CH341_CLK_DIV(ps, fact);
 188         div = CH341_CLKRATE / (clk_div * speed);
 189
 190         /* Halve base clock (fact = 0) if required. */
 191         if (div < 9 || div > 255) {
 192                 div /= 2;
 193                 clk_div *= 2;
 194                 fact = 0;
 195         }
 196
 197         if (div < 2)
 198                 return -EINVAL;
 199
 200         /*
 201          * Pick next divisor if resulting rate is closer to the requested one,
 202          * scale up to avoid rounding errors on low rates.
 203          */
 204         if (16 * CH341_CLKRATE / (clk_div * div) - 16 * speed >=
 205                         16 * speed - 16 * CH341_CLKRATE / (clk_div * (div + 1)))
 206                 div++;
 207
 208         /*
 209          * Prefer lower base clock (fact = 0) if even divisor.
 210          *
 211          * Note that this makes the receiver more tolerant to errors.
 212          */
 213         if (fact == 1 && div % 2 == 0) {
 214                 div /= 2;
 215                 fact = 0;
 216         }
 217
 218         return (0x100 - div) << 8 | fact << 2 | ps;
 219 }
 220
 221 static int ch341_set_baudrate_lcr(struct usb_device *dev,
 222                                   struct ch341_private *priv, u8 lcr)
 223 {
 224         int val;
 225         int r;
 226
 227         if (!priv->baud_rate)
 228                 return -EINVAL;
 229
 230         val = ch341_get_divisor(priv->baud_rate);
 231         if (val < 0)
 232                 return -EINVAL;
 233
 234         /*
 235          * CH341A buffers data until a full endpoint-size packet (32 bytes)
 236          * has been received unless bit 7 is set.
 237          */
 238         val |= BIT(7);
 239
 240         r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x1312, val);
 241         if (r)
 242                 return r;
 243
 244         r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x2518, lcr);
 245         if (r)
 246                 return r;
 247
 248         return r;
 249 }
 250
 251 static int ch341_set_handshake(struct usb_device *dev, u8 control)
 252 {
 253         return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0);
 254 }
 255
 256 static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
 257 {
 258         const unsigned int size = 2;
 259         char *buffer;
 260         int r;
 261         unsigned long flags;
 262
 263         buffer = kmalloc(size, GFP_KERNEL);
 264         if (!buffer)
 265                 return -ENOMEM;
 266
 267         r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
 268         if (r < 0)
 269                 goto out;
 270
 271         spin_lock_irqsave(&priv->lock, flags);
 272         priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
 273         spin_unlock_irqrestore(&priv->lock, flags);
 274
 275 out:    kfree(buffer);
 276         return r;
 277 }
 278
 279 /* -------------------------------------------------------------------------- */
 280
 281 static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
 282 {
 283         const unsigned int size = 2;
 284         char *buffer;
 285         int r;
 286
 287         buffer = kmalloc(size, GFP_KERNEL);
 288         if (!buffer)
 289                 return -ENOMEM;
 290
 291         /* expect two bytes 0x27 0x00 */
 292         r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
 293         if (r < 0)
 294                 goto out;
 295         dev_dbg(&dev->dev, "Chip version: 0x%02x\n", buffer[0]);
 296
 297         r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
 298         if (r < 0)
 299                 goto out;
 300
 301         r = ch341_set_baudrate_lcr(dev, priv, priv->lcr);
 302         if (r < 0)
 303                 goto out;
 304
 305         r = ch341_set_handshake(dev, priv->mcr);
 306
 307 out:    kfree(buffer);
 308         return r;
 309 }
 310
 311 static int ch341_port_probe(struct usb_serial_port *port)
 312 {
 313         struct ch341_private *priv;
 314         int r;
 315
 316         priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
 317         if (!priv)
 318                 return -ENOMEM;
 319
 320         spin_lock_init(&priv->lock);
 321         priv->baud_rate = DEFAULT_BAUD_RATE;
 322         /*
 323          * Some CH340 devices appear unable to change the initial LCR
 324          * settings, so set a sane 8N1 default.
 325          */
 326         priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
 327
 328         r = ch341_configure(port->serial->dev, priv);
 329         if (r < 0)
 330                 goto error;
 331
 332         usb_set_serial_port_data(port, priv);
 333         return 0;
 334
 335 error:  kfree(priv);
 336         return r;
 337 }
 338
 339 static int ch341_port_remove(struct usb_serial_port *port)
 340 {
 341         struct ch341_private *priv;
 342
 343         priv = usb_get_serial_port_data(port);
 344         kfree(priv);
 345
 346         return 0;
 347 }
 348
 349 static int ch341_carrier_raised(struct usb_serial_port *port)
 350 {
 351         struct ch341_private *priv = usb_get_serial_port_data(port);
 352         if (priv->msr & CH341_BIT_DCD)
 353                 return 1;
 354         return 0;
 355 }
 356
 357 static void ch341_dtr_rts(struct usb_serial_port *port, int on)
 358 {
 359         struct ch341_private *priv = usb_get_serial_port_data(port);
 360         unsigned long flags;
 361
 362         /* drop DTR and RTS */
 363         spin_lock_irqsave(&priv->lock, flags);
 364         if (on)
 365                 priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
 366         else
 367                 priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
 368         spin_unlock_irqrestore(&priv->lock, flags);
 369         ch341_set_handshake(port->serial->dev, priv->mcr);
 370 }
 371
 372 static void ch341_close(struct usb_serial_port *port)
 373 {
 374         usb_serial_generic_close(port);
 375         usb_kill_urb(port->interrupt_in_urb);
 376 }
 377
 378
 379 /* open this device, set default parameters */
 380 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
 381 {
 382         struct ch341_private *priv = usb_get_serial_port_data(port);
 383         int r;
 384
 385         if (tty)
 386                 ch341_set_termios(tty, port, NULL);
 387
 388         dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
 389         r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 390         if (r) {
 391                 dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n",
 392                         __func__, r);
 393                 return r;
 394         }
 395
 396         r = ch341_get_status(port->serial->dev, priv);
 397         if (r < 0) {
 398                 dev_err(&port->dev, "failed to read modem status: %d\n", r);
 399                 goto err_kill_interrupt_urb;
 400         }
 401
 402         r = usb_serial_generic_open(tty, port);
 403         if (r)
 404                 goto err_kill_interrupt_urb;
 405
 406         return 0;
 407
 408 err_kill_interrupt_urb:
 409         usb_kill_urb(port->interrupt_in_urb);
 410
 411         return r;
 412 }
 413
 414 /* Old_termios contains the original termios settings and
 415  * tty->termios contains the new setting to be used.
 416  */
 417 static void ch341_set_termios(struct tty_struct *tty,
 418                 struct usb_serial_port *port, struct ktermios *old_termios)
 419 {
 420         struct ch341_private *priv = usb_get_serial_port_data(port);
 421         unsigned baud_rate;
 422         unsigned long flags;
 423         u8 lcr;
 424         int r;
 425
 426         /* redundant changes may cause the chip to lose bytes */
 427         if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
 428                 return;
 429
 430         baud_rate = tty_get_baud_rate(tty);
 431
 432         lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
 433
 434         switch (C_CSIZE(tty)) {
 435         case CS5:
 436                 lcr |= CH341_LCR_CS5;
 437                 break;
 438         case CS6:
 439                 lcr |= CH341_LCR_CS6;
 440                 break;
 441         case CS7:
 442                 lcr |= CH341_LCR_CS7;
 443                 break;
 444         case CS8:
 445                 lcr |= CH341_LCR_CS8;
 446                 break;
 447         }
 448
 449         if (C_PARENB(tty)) {
 450                 lcr |= CH341_LCR_ENABLE_PAR;
 451                 if (C_PARODD(tty) == 0)
 452                         lcr |= CH341_LCR_PAR_EVEN;
 453                 if (C_CMSPAR(tty))
 454                         lcr |= CH341_LCR_MARK_SPACE;
 455         }
 456
 457         if (C_CSTOPB(tty))
 458                 lcr |= CH341_LCR_STOP_BITS_2;
 459
 460         if (baud_rate) {
 461                 priv->baud_rate = baud_rate;
 462
 463                 r = ch341_set_baudrate_lcr(port->serial->dev, priv, lcr);
 464                 if (r < 0 && old_termios) {
 465                         priv->baud_rate = tty_termios_baud_rate(old_termios);
 466                         tty_termios_copy_hw(&tty->termios, old_termios);
 467                 } else if (r == 0) {
 468                         priv->lcr = lcr;
 469                 }
 470         }
 471
 472         spin_lock_irqsave(&priv->lock, flags);
 473         if (C_BAUD(tty) == B0)
 474                 priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
 475         else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
 476                 priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
 477         spin_unlock_irqrestore(&priv->lock, flags);
 478
 479         ch341_set_handshake(port->serial->dev, priv->mcr);
 480 }
 481
 482 static void ch341_break_ctl(struct tty_struct *tty, int break_state)
 483 {
 484         const uint16_t ch341_break_reg =
 485                         ((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK;
 486         struct usb_serial_port *port = tty->driver_data;
 487         int r;
 488         uint16_t reg_contents;
 489         uint8_t *break_reg;
 490
 491         break_reg = kmalloc(2, GFP_KERNEL);
 492         if (!break_reg)
 493                 return;
 494
 495         r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
 496                         ch341_break_reg, 0, break_reg, 2);
 497         if (r < 0) {
 498                 dev_err(&port->dev, "%s - USB control read error (%d)\n",
 499                                 __func__, r);
 500                 goto out;
 501         }
 502         dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
 503                 __func__, break_reg[0], break_reg[1]);
 504         if (break_state != 0) {
 505                 dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
 506                 break_reg[0] &= ~CH341_NBREAK_BITS;
 507                 break_reg[1] &= ~CH341_LCR_ENABLE_TX;
 508         } else {
 509                 dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
 510                 break_reg[0] |= CH341_NBREAK_BITS;
 511                 break_reg[1] |= CH341_LCR_ENABLE_TX;
 512         }
 513         dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
 514                 __func__, break_reg[0], break_reg[1]);
 515         reg_contents = get_unaligned_le16(break_reg);
 516         r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
 517                         ch341_break_reg, reg_contents);
 518         if (r < 0)
 519                 dev_err(&port->dev, "%s - USB control write error (%d)\n",
 520                                 __func__, r);
 521 out:
 522         kfree(break_reg);
 523 }
 524
 525 static int ch341_tiocmset(struct tty_struct *tty,
 526                           unsigned int set, unsigned int clear)
 527 {
 528         struct usb_serial_port *port = tty->driver_data;
 529         struct ch341_private *priv = usb_get_serial_port_data(port);
 530         unsigned long flags;
 531         u8 control;
 532
 533         spin_lock_irqsave(&priv->lock, flags);
 534         if (set & TIOCM_RTS)
 535                 priv->mcr |= CH341_BIT_RTS;
 536         if (set & TIOCM_DTR)
 537                 priv->mcr |= CH341_BIT_DTR;
 538         if (clear & TIOCM_RTS)
 539                 priv->mcr &= ~CH341_BIT_RTS;
 540         if (clear & TIOCM_DTR)
 541                 priv->mcr &= ~CH341_BIT_DTR;
 542         control = priv->mcr;
 543         spin_unlock_irqrestore(&priv->lock, flags);
 544
 545         return ch341_set_handshake(port->serial->dev, control);
 546 }
 547
 548 static void ch341_update_status(struct usb_serial_port *port,
 549                                         unsigned char *data, size_t len)
 550 {
 551         struct ch341_private *priv = usb_get_serial_port_data(port);
 552         struct tty_struct *tty;
 553         unsigned long flags;
 554         u8 status;
 555         u8 delta;
 556
 557         if (len < 4)
 558                 return;
 559
 560         status = ~data[2] & CH341_BITS_MODEM_STAT;
 561
 562         spin_lock_irqsave(&priv->lock, flags);
 563         delta = status ^ priv->msr;
 564         priv->msr = status;
 565         spin_unlock_irqrestore(&priv->lock, flags);
 566
 567         if (data[1] & CH341_MULT_STAT)
 568                 dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
 569
 570         if (!delta)
 571                 return;
 572
 573         if (delta & CH341_BIT_CTS)
 574                 port->icount.cts++;
 575         if (delta & CH341_BIT_DSR)
 576                 port->icount.dsr++;
 577         if (delta & CH341_BIT_RI)
 578                 port->icount.rng++;
 579         if (delta & CH341_BIT_DCD) {
 580                 port->icount.dcd++;
 581                 tty = tty_port_tty_get(&port->port);
 582                 if (tty) {
 583                         usb_serial_handle_dcd_change(port, tty,
 584                                                 status & CH341_BIT_DCD);
 585                         tty_kref_put(tty);
 586                 }
 587         }
 588
 589         wake_up_interruptible(&port->port.delta_msr_wait);
 590 }
 591
 592 static void ch341_read_int_callback(struct urb *urb)
 593 {
 594         struct usb_serial_port *port = urb->context;
 595         unsigned char *data = urb->transfer_buffer;
 596         unsigned int len = urb->actual_length;
 597         int status;
 598
 599         switch (urb->status) {
 600         case 0:
 601                 /* success */
 602                 break;
 603         case -ECONNRESET:
 604         case -ENOENT:
 605         case -ESHUTDOWN:
 606                 /* this urb is terminated, clean up */
 607                 dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n",
 608                         __func__, urb->status);
 609                 return;
 610         default:
 611                 dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n",
 612                         __func__, urb->status);
 613                 goto exit;
 614         }
 615
 616         usb_serial_debug_data(&port->dev, __func__, len, data);
 617         ch341_update_status(port, data, len);
 618 exit:
 619         status = usb_submit_urb(urb, GFP_ATOMIC);
 620         if (status) {
 621                 dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n",
 622                         __func__, status);
 623         }
 624 }
 625
 626 static int ch341_tiocmget(struct tty_struct *tty)
 627 {
 628         struct usb_serial_port *port = tty->driver_data;
 629         struct ch341_private *priv = usb_get_serial_port_data(port);
 630         unsigned long flags;
 631         u8 mcr;
 632         u8 status;
 633         unsigned int result;
 634
 635         spin_lock_irqsave(&priv->lock, flags);
 636         mcr = priv->mcr;
 637         status = priv->msr;
 638         spin_unlock_irqrestore(&priv->lock, flags);
 639
 640         result = ((mcr & CH341_BIT_DTR)         ? TIOCM_DTR : 0)
 641                   | ((mcr & CH341_BIT_RTS)      ? TIOCM_RTS : 0)
 642                   | ((status & CH341_BIT_CTS)   ? TIOCM_CTS : 0)
 643                   | ((status & CH341_BIT_DSR)   ? TIOCM_DSR : 0)
 644                   | ((status & CH341_BIT_RI)    ? TIOCM_RI  : 0)
 645                   | ((status & CH341_BIT_DCD)   ? TIOCM_CD  : 0);
 646
 647         dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
 648
 649         return result;
 650 }
 651
 652 static int ch341_reset_resume(struct usb_serial *serial)
 653 {
 654         struct usb_serial_port *port = serial->port[0];
 655         struct ch341_private *priv;
 656         int ret;
 657
 658         priv = usb_get_serial_port_data(port);
 659         if (!priv)
 660                 return 0;
 661
 662         /* reconfigure ch341 serial port after bus-reset */
 663         ch341_configure(serial->dev, priv);
 664
 665         if (tty_port_initialized(&port->port)) {
 666                 ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
 667                 if (ret) {
 668                         dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
 669                                 ret);
 670                         return ret;
 671                 }
 672
 673                 ret = ch341_get_status(port->serial->dev, priv);
 674                 if (ret < 0) {
 675                         dev_err(&port->dev, "failed to read modem status: %d\n",
 676                                 ret);
 677                 }
 678         }
 679
 680         return usb_serial_generic_resume(serial);
 681 }
 682
 683 static struct usb_serial_driver ch341_device = {
 684         .driver = {
 685                 .owner  = THIS_MODULE,
 686                 .name   = "ch341-uart",
 687         },
 688         .id_table          = id_table,
 689         .num_ports         = 1,
 690         .open              = ch341_open,
 691         .dtr_rts           = ch341_dtr_rts,
 692         .carrier_raised    = ch341_carrier_raised,
 693         .close             = ch341_close,
 694         .set_termios       = ch341_set_termios,
 695         .break_ctl         = ch341_break_ctl,
 696         .tiocmget          = ch341_tiocmget,
 697         .tiocmset          = ch341_tiocmset,
 698         .tiocmiwait        = usb_serial_generic_tiocmiwait,
 699         .read_int_callback = ch341_read_int_callback,
 700         .port_probe        = ch341_port_probe,
 701         .port_remove       = ch341_port_remove,
 702         .reset_resume      = ch341_reset_resume,
 703 };
 704
 705 static struct usb_serial_driver * const serial_drivers[] = {
 706         &ch341_device, NULL
 707 };
 708
 709 module_usb_serial_driver(serial_drivers, id_table);
 710
 711 MODULE_LICENSE("GPL v2");