drivers/serial/bfin_sport_uart.c

   1 /*
   2  * File:        linux/drivers/serial/bfin_sport_uart.c
   3  *
   4  * Based on:    drivers/serial/bfin_5xx.c by Aubrey Li.
   5  * Author:      Roy Huang <roy.huang@analog.com>
   6  *
   7  * Created:     Nov 22, 2006
   8  * Copyright:   (c) 2006-2007 Analog Devices Inc.
   9  * Description: this driver enable SPORTs on Blackfin emulate UART.
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, see the file COPYING, or write
  23  * to the Free Software Foundation, Inc.,
  24  * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  25  */
  26
  27 /*
  28  * This driver and the hardware supported are in term of EE-191 of ADI.
  29  * http://www.analog.com/UploadedFiles/Application_Notes/399447663EE191.pdf
  30  * This application note describe how to implement a UART on a Sharc DSP,
  31  * but this driver is implemented on Blackfin Processor.
  32  */
  33
  34 /* After reset, there is a prelude of low level pulse when transmit data first
  35  * time. No addtional pulse in following transmit.
  36  * According to document:
  37  * The SPORTs are ready to start transmitting or receiving data no later than
  38  * three serial clock cycles after they are enabled in the SPORTx_TCR1 or
  39  * SPORTx_RCR1 register. No serial clock cycles are lost from this point on.
  40  * The first internal frame sync will occur one frame sync delay after the
  41  * SPORTs are ready. External frame syncs can occur as soon as the SPORT is
  42  * ready.
  43  */
  44
  45 /* Thanks to Axel Alatalo <axel@rubico.se> for fixing sport rx bug. Sometimes
  46  * sport receives data incorrectly. The following is Axel's words.
  47  * As EE-191, sport rx samples 3 times of the UART baudrate and takes the
  48  * middle smaple of every 3 samples as the data bit. For a 8-N-1 UART setting,
  49  * 30 samples will be required for a byte. If transmitter sends a 1/3 bit short
  50  * byte due to buadrate drift, then the 30th sample of a byte, this sample is
  51  * also the third sample of the stop bit, will happens on the immediately
  52  * following start bit which will be thrown away and missed. Thus since parts
  53  * of the startbit will be missed and the receiver will begin to drift, the
  54  * effect accumulates over time until synchronization is lost.
  55  * If only require 2 samples of the stopbit (by sampling in total 29 samples),
  56  * then a to short byte as in the case above will be tolerated. Then the 1/3
  57  * early startbit will trigger a framesync since the last read is complete
  58  * after only 2/3 stopbit and framesync is active during the last 1/3 looking
  59  * for a possible early startbit. */
  60
  61 //#define DEBUG
  62
  63 #include <linux/module.h>
  64 #include <linux/ioport.h>
  65 #include <linux/init.h>
  66 #include <linux/console.h>
  67 #include <linux/sysrq.h>
  68 #include <linux/platform_device.h>
  69 #include <linux/tty.h>
  70 #include <linux/tty_flip.h>
  71 #include <linux/serial_core.h>
  72
  73 #include <asm/delay.h>
  74 #include <asm/portmux.h>
  75
  76 #include "bfin_sport_uart.h"
  77
  78 unsigned short bfin_uart_pin_req_sport0[] =
  79         {P_SPORT0_TFS, P_SPORT0_DTPRI, P_SPORT0_TSCLK, P_SPORT0_RFS, \
  80          P_SPORT0_DRPRI, P_SPORT0_RSCLK, P_SPORT0_DRSEC, P_SPORT0_DTSEC, 0};
  81
  82 unsigned short bfin_uart_pin_req_sport1[] =
  83         {P_SPORT1_TFS, P_SPORT1_DTPRI, P_SPORT1_TSCLK, P_SPORT1_RFS, \
  84         P_SPORT1_DRPRI, P_SPORT1_RSCLK, P_SPORT1_DRSEC, P_SPORT1_DTSEC, 0};
  85
  86 #define DRV_NAME "bfin-sport-uart"
  87
  88 struct sport_uart_port {
  89         struct uart_port        port;
  90         char                    *name;
  91
  92         int                     tx_irq;
  93         int                     rx_irq;
  94         int                     err_irq;
  95 };
  96
  97 static void sport_uart_tx_chars(struct sport_uart_port *up);
  98 static void sport_stop_tx(struct uart_port *port);
  99
 100 static inline void tx_one_byte(struct sport_uart_port *up, unsigned int value)
 101 {
 102         pr_debug("%s value:%x\n", __func__, value);
 103         /* Place a Start and Stop bit */
 104         __asm__ __volatile__ (
 105                 "R2 = b#01111111100;"
 106                 "R3 = b#10000000001;"
 107                 "%0 <<= 2;"
 108                 "%0 = %0 & R2;"
 109                 "%0 = %0 | R3;"
 110                 : "=d"(value)
 111                 : "d"(value)
 112                 : "ASTAT", "R2", "R3"
 113         );
 114         pr_debug("%s value:%x\n", __func__, value);
 115
 116         SPORT_PUT_TX(up, value);
 117 }
 118
 119 static inline unsigned int rx_one_byte(struct sport_uart_port *up)
 120 {
 121         unsigned int value, extract;
 122         u32 tmp_mask1, tmp_mask2, tmp_shift, tmp;
 123
 124         value = SPORT_GET_RX32(up);
 125         pr_debug("%s value:%x\n", __func__, value);
 126
 127         /* Extract 8 bits data */
 128         __asm__ __volatile__ (
 129                 "%[extr] = 0;"
 130                 "%[mask1] = 0x1801(Z);"
 131                 "%[mask2] = 0x0300(Z);"
 132                 "%[shift] = 0;"
 133                 "LSETUP(.Lloop_s, .Lloop_e) LC0 = %[lc];"
 134                 ".Lloop_s:"
 135                 "%[tmp] = extract(%[val], %[mask1].L)(Z);"
 136                 "%[tmp] <<= %[shift];"
 137                 "%[extr] = %[extr] | %[tmp];"
 138                 "%[mask1] = %[mask1] - %[mask2];"
 139                 ".Lloop_e:"
 140                 "%[shift] += 1;"
 141                 : [val]"=d"(value), [extr]"=d"(extract), [shift]"=d"(tmp_shift), [tmp]"=d"(tmp),
 142                   [mask1]"=d"(tmp_mask1), [mask2]"=d"(tmp_mask2)
 143                 : "d"(value), [lc]"a"(8)
 144                 : "ASTAT", "LB0", "LC0", "LT0"
 145         );
 146
 147         pr_debug("      extract:%x\n", extract);
 148         return extract;
 149 }
 150
 151 static int sport_uart_setup(struct sport_uart_port *up, int sclk, int baud_rate)
 152 {
 153         int tclkdiv, tfsdiv, rclkdiv;
 154
 155         /* Set TCR1 and TCR2 */
 156         SPORT_PUT_TCR1(up, (LATFS | ITFS | TFSR | TLSBIT | ITCLK));
 157         SPORT_PUT_TCR2(up, 10);
 158         pr_debug("%s TCR1:%x, TCR2:%x\n", __func__, SPORT_GET_TCR1(up), SPORT_GET_TCR2(up));
 159
 160         /* Set RCR1 and RCR2 */
 161         SPORT_PUT_RCR1(up, (RCKFE | LARFS | LRFS | RFSR | IRCLK));
 162         SPORT_PUT_RCR2(up, 28);
 163         pr_debug("%s RCR1:%x, RCR2:%x\n", __func__, SPORT_GET_RCR1(up), SPORT_GET_RCR2(up));
 164
 165         tclkdiv = sclk/(2 * baud_rate) - 1;
 166         tfsdiv = 12;
 167         rclkdiv = sclk/(2 * baud_rate * 3) - 1;
 168         SPORT_PUT_TCLKDIV(up, tclkdiv);
 169         SPORT_PUT_TFSDIV(up, tfsdiv);
 170         SPORT_PUT_RCLKDIV(up, rclkdiv);
 171         SSYNC();
 172         pr_debug("%s sclk:%d, baud_rate:%d, tclkdiv:%d, tfsdiv:%d, rclkdiv:%d\n",
 173                         __func__, sclk, baud_rate, tclkdiv, tfsdiv, rclkdiv);
 174
 175         return 0;
 176 }
 177
 178 static irqreturn_t sport_uart_rx_irq(int irq, void *dev_id)
 179 {
 180         struct sport_uart_port *up = dev_id;
 181         struct tty_struct *tty = up->port.info->port.tty;
 182         unsigned int ch;
 183
 184         do {
 185                 ch = rx_one_byte(up);
 186                 up->port.icount.rx++;
 187
 188                 if (uart_handle_sysrq_char(&up->port, ch))
 189                         ;
 190                 else
 191                         tty_insert_flip_char(tty, ch, TTY_NORMAL);
 192         } while (SPORT_GET_STAT(up) & RXNE);
 193         tty_flip_buffer_push(tty);
 194
 195         return IRQ_HANDLED;
 196 }
 197
 198 static irqreturn_t sport_uart_tx_irq(int irq, void *dev_id)
 199 {
 200         sport_uart_tx_chars(dev_id);
 201
 202         return IRQ_HANDLED;
 203 }
 204
 205 static irqreturn_t sport_uart_err_irq(int irq, void *dev_id)
 206 {
 207         struct sport_uart_port *up = dev_id;
 208         struct tty_struct *tty = up->port.info->port.tty;
 209         unsigned int stat = SPORT_GET_STAT(up);
 210
 211         /* Overflow in RX FIFO */
 212         if (stat & ROVF) {
 213                 up->port.icount.overrun++;
 214                 tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 215                 SPORT_PUT_STAT(up, ROVF); /* Clear ROVF bit */
 216         }
 217         /* These should not happen */
 218         if (stat & (TOVF | TUVF | RUVF)) {
 219                 printk(KERN_ERR "SPORT Error:%s %s %s\n",
 220                                 (stat & TOVF)?"TX overflow":"",
 221                                 (stat & TUVF)?"TX underflow":"",
 222                                 (stat & RUVF)?"RX underflow":"");
 223                 SPORT_PUT_TCR1(up, SPORT_GET_TCR1(up) & ~TSPEN);
 224                 SPORT_PUT_RCR1(up, SPORT_GET_RCR1(up) & ~RSPEN);
 225         }
 226         SSYNC();
 227
 228         return IRQ_HANDLED;
 229 }
 230
 231 /* Reqeust IRQ, Setup clock */
 232 static int sport_startup(struct uart_port *port)
 233 {
 234         struct sport_uart_port *up = (struct sport_uart_port *)port;
 235         char buffer[20];
 236         int retval;
 237
 238         pr_debug("%s enter\n", __func__);
 239         memset(buffer, 20, '\0');
 240         snprintf(buffer, 20, "%s rx", up->name);
 241         retval = request_irq(up->rx_irq, sport_uart_rx_irq, IRQF_SAMPLE_RANDOM, buffer, up);
 242         if (retval) {
 243                 printk(KERN_ERR "Unable to request interrupt %s\n", buffer);
 244                 return retval;
 245         }
 246
 247         snprintf(buffer, 20, "%s tx", up->name);
 248         retval = request_irq(up->tx_irq, sport_uart_tx_irq, IRQF_SAMPLE_RANDOM, buffer, up);
 249         if (retval) {
 250                 printk(KERN_ERR "Unable to request interrupt %s\n", buffer);
 251                 goto fail1;
 252         }
 253
 254         snprintf(buffer, 20, "%s err", up->name);
 255         retval = request_irq(up->err_irq, sport_uart_err_irq, IRQF_SAMPLE_RANDOM, buffer, up);
 256         if (retval) {
 257                 printk(KERN_ERR "Unable to request interrupt %s\n", buffer);
 258                 goto fail2;
 259         }
 260
 261         if (port->line) {
 262                 if (peripheral_request_list(bfin_uart_pin_req_sport1, DRV_NAME))
 263                         goto fail3;
 264         } else {
 265                 if (peripheral_request_list(bfin_uart_pin_req_sport0, DRV_NAME))
 266                         goto fail3;
 267         }
 268
 269         sport_uart_setup(up, get_sclk(), port->uartclk);
 270
 271         /* Enable receive interrupt */
 272         SPORT_PUT_RCR1(up, (SPORT_GET_RCR1(up) | RSPEN));
 273         SSYNC();
 274
 275         return 0;
 276
 277
 278 fail3:
 279         printk(KERN_ERR DRV_NAME
 280                 ": Requesting Peripherals failed\n");
 281
 282         free_irq(up->err_irq, up);
 283 fail2:
 284         free_irq(up->tx_irq, up);
 285 fail1:
 286         free_irq(up->rx_irq, up);
 287
 288         return retval;
 289
 290 }
 291
 292 static void sport_uart_tx_chars(struct sport_uart_port *up)
 293 {
 294         struct circ_buf *xmit = &up->port.info->xmit;
 295
 296         if (SPORT_GET_STAT(up) & TXF)
 297                 return;
 298
 299         if (up->port.x_char) {
 300                 tx_one_byte(up, up->port.x_char);
 301                 up->port.icount.tx++;
 302                 up->port.x_char = 0;
 303                 return;
 304         }
 305
 306         if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
 307                 sport_stop_tx(&up->port);
 308                 return;
 309         }
 310
 311         while(!(SPORT_GET_STAT(up) & TXF) && !uart_circ_empty(xmit)) {
 312                 tx_one_byte(up, xmit->buf[xmit->tail]);
 313                 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE -1);
 314                 up->port.icount.tx++;
 315         }
 316
 317         if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 318                 uart_write_wakeup(&up->port);
 319 }
 320
 321 static unsigned int sport_tx_empty(struct uart_port *port)
 322 {
 323         struct sport_uart_port *up = (struct sport_uart_port *)port;
 324         unsigned int stat;
 325
 326         stat = SPORT_GET_STAT(up);
 327         pr_debug("%s stat:%04x\n", __func__, stat);
 328         if (stat & TXHRE) {
 329                 return TIOCSER_TEMT;
 330         } else
 331                 return 0;
 332 }
 333
 334 static unsigned int sport_get_mctrl(struct uart_port *port)
 335 {
 336         pr_debug("%s enter\n", __func__);
 337         return (TIOCM_CTS | TIOCM_CD | TIOCM_DSR);
 338 }
 339
 340 static void sport_set_mctrl(struct uart_port *port, unsigned int mctrl)
 341 {
 342         pr_debug("%s enter\n", __func__);
 343 }
 344
 345 static void sport_stop_tx(struct uart_port *port)
 346 {
 347         struct sport_uart_port *up = (struct sport_uart_port *)port;
 348         unsigned int stat;
 349
 350         pr_debug("%s enter\n", __func__);
 351
 352         stat = SPORT_GET_STAT(up);
 353         while(!(stat & TXHRE)) {
 354                 udelay(1);
 355                 stat = SPORT_GET_STAT(up);
 356         }
 357         /* Although the hold register is empty, last byte is still in shift
 358          * register and not sent out yet. If baud rate is lower than default,
 359          * delay should be longer. For example, if the baud rate is 9600,
 360          * the delay must be at least 2ms by experience */
 361         udelay(500);
 362
 363         SPORT_PUT_TCR1(up, (SPORT_GET_TCR1(up) & ~TSPEN));
 364         SSYNC();
 365
 366         return;
 367 }
 368
 369 static void sport_start_tx(struct uart_port *port)
 370 {
 371         struct sport_uart_port *up = (struct sport_uart_port *)port;
 372
 373         pr_debug("%s enter\n", __func__);
 374         /* Write data into SPORT FIFO before enable SPROT to transmit */
 375         sport_uart_tx_chars(up);
 376
 377         /* Enable transmit, then an interrupt will generated */
 378         SPORT_PUT_TCR1(up, (SPORT_GET_TCR1(up) | TSPEN));
 379         SSYNC();
 380         pr_debug("%s exit\n", __func__);
 381 }
 382
 383 static void sport_stop_rx(struct uart_port *port)
 384 {
 385         struct sport_uart_port *up = (struct sport_uart_port *)port;
 386
 387         pr_debug("%s enter\n", __func__);
 388         /* Disable sport to stop rx */
 389         SPORT_PUT_RCR1(up, (SPORT_GET_RCR1(up) & ~RSPEN));
 390         SSYNC();
 391 }
 392
 393 static void sport_enable_ms(struct uart_port *port)
 394 {
 395         pr_debug("%s enter\n", __func__);
 396 }
 397
 398 static void sport_break_ctl(struct uart_port *port, int break_state)
 399 {
 400         pr_debug("%s enter\n", __func__);
 401 }
 402
 403 static void sport_shutdown(struct uart_port *port)
 404 {
 405         struct sport_uart_port *up = (struct sport_uart_port *)port;
 406
 407         pr_debug("%s enter\n", __func__);
 408
 409         /* Disable sport */
 410         SPORT_PUT_TCR1(up, (SPORT_GET_TCR1(up) & ~TSPEN));
 411         SPORT_PUT_RCR1(up, (SPORT_GET_RCR1(up) & ~RSPEN));
 412         SSYNC();
 413
 414         if (port->line) {
 415                 peripheral_free_list(bfin_uart_pin_req_sport1);
 416         } else {
 417                 peripheral_free_list(bfin_uart_pin_req_sport0);
 418         }
 419
 420         free_irq(up->rx_irq, up);
 421         free_irq(up->tx_irq, up);
 422         free_irq(up->err_irq, up);
 423 }
 424
 425 static void sport_set_termios(struct uart_port *port,
 426                 struct ktermios *termios, struct ktermios *old)
 427 {
 428         pr_debug("%s enter, c_cflag:%08x\n", __func__, termios->c_cflag);
 429         uart_update_timeout(port, CS8 ,port->uartclk);
 430 }
 431
 432 static const char *sport_type(struct uart_port *port)
 433 {
 434         struct sport_uart_port *up = (struct sport_uart_port *)port;
 435
 436         pr_debug("%s enter\n", __func__);
 437         return up->name;
 438 }
 439
 440 static void sport_release_port(struct uart_port *port)
 441 {
 442         pr_debug("%s enter\n", __func__);
 443 }
 444
 445 static int sport_request_port(struct uart_port *port)
 446 {
 447         pr_debug("%s enter\n", __func__);
 448         return 0;
 449 }
 450
 451 static void sport_config_port(struct uart_port *port, int flags)
 452 {
 453         struct sport_uart_port *up = (struct sport_uart_port *)port;
 454
 455         pr_debug("%s enter\n", __func__);
 456         up->port.type = PORT_BFIN_SPORT;
 457 }
 458
 459 static int sport_verify_port(struct uart_port *port, struct serial_struct *ser)
 460 {
 461         pr_debug("%s enter\n", __func__);
 462         return 0;
 463 }
 464
 465 struct uart_ops sport_uart_ops = {
 466         .tx_empty       = sport_tx_empty,
 467         .set_mctrl      = sport_set_mctrl,
 468         .get_mctrl      = sport_get_mctrl,
 469         .stop_tx        = sport_stop_tx,
 470         .start_tx       = sport_start_tx,
 471         .stop_rx        = sport_stop_rx,
 472         .enable_ms      = sport_enable_ms,
 473         .break_ctl      = sport_break_ctl,
 474         .startup        = sport_startup,
 475         .shutdown       = sport_shutdown,
 476         .set_termios    = sport_set_termios,
 477         .type           = sport_type,
 478         .release_port   = sport_release_port,
 479         .request_port   = sport_request_port,
 480         .config_port    = sport_config_port,
 481         .verify_port    = sport_verify_port,
 482 };
 483
 484 static struct sport_uart_port sport_uart_ports[] = {
 485         { /* SPORT 0 */
 486                 .name   = "SPORT0",
 487                 .tx_irq = IRQ_SPORT0_TX,
 488                 .rx_irq = IRQ_SPORT0_RX,
 489                 .err_irq= IRQ_SPORT0_ERROR,
 490                 .port   = {
 491                         .type           = PORT_BFIN_SPORT,
 492                         .iotype         = UPIO_MEM,
 493                         .membase        = (void __iomem *)SPORT0_TCR1,
 494                         .mapbase        = SPORT0_TCR1,
 495                         .irq            = IRQ_SPORT0_RX,
 496                         .uartclk        = CONFIG_SPORT_BAUD_RATE,
 497                         .fifosize       = 8,
 498                         .ops            = &sport_uart_ops,
 499                         .line           = 0,
 500                 },
 501         }, { /* SPORT 1 */
 502                 .name   = "SPORT1",
 503                 .tx_irq = IRQ_SPORT1_TX,
 504                 .rx_irq = IRQ_SPORT1_RX,
 505                 .err_irq= IRQ_SPORT1_ERROR,
 506                 .port   = {
 507                         .type           = PORT_BFIN_SPORT,
 508                         .iotype         = UPIO_MEM,
 509                         .membase        = (void __iomem *)SPORT1_TCR1,
 510                         .mapbase        = SPORT1_TCR1,
 511                         .irq            = IRQ_SPORT1_RX,
 512                         .uartclk        = CONFIG_SPORT_BAUD_RATE,
 513                         .fifosize       = 8,
 514                         .ops            = &sport_uart_ops,
 515                         .line           = 1,
 516                 },
 517         }
 518 };
 519
 520 static struct uart_driver sport_uart_reg = {
 521         .owner          = THIS_MODULE,
 522         .driver_name    = "SPORT-UART",
 523         .dev_name       = "ttySS",
 524         .major          = 204,
 525         .minor          = 84,
 526         .nr             = ARRAY_SIZE(sport_uart_ports),
 527         .cons           = NULL,
 528 };
 529
 530 static int sport_uart_suspend(struct platform_device *dev, pm_message_t state)
 531 {
 532         struct sport_uart_port *sport = platform_get_drvdata(dev);
 533
 534         pr_debug("%s enter\n", __func__);
 535         if (sport)
 536                 uart_suspend_port(&sport_uart_reg, &sport->port);
 537
 538         return 0;
 539 }
 540
 541 static int sport_uart_resume(struct platform_device *dev)
 542 {
 543         struct sport_uart_port *sport = platform_get_drvdata(dev);
 544
 545         pr_debug("%s enter\n", __func__);
 546         if (sport)
 547                 uart_resume_port(&sport_uart_reg, &sport->port);
 548
 549         return 0;
 550 }
 551
 552 static int sport_uart_probe(struct platform_device *dev)
 553 {
 554         pr_debug("%s enter\n", __func__);
 555         sport_uart_ports[dev->id].port.dev = &dev->dev;
 556         uart_add_one_port(&sport_uart_reg, &sport_uart_ports[dev->id].port);
 557         platform_set_drvdata(dev, &sport_uart_ports[dev->id]);
 558
 559         return 0;
 560 }
 561
 562 static int sport_uart_remove(struct platform_device *dev)
 563 {
 564         struct sport_uart_port *sport = platform_get_drvdata(dev);
 565
 566         pr_debug("%s enter\n", __func__);
 567         platform_set_drvdata(dev, NULL);
 568
 569         if (sport)
 570                 uart_remove_one_port(&sport_uart_reg, &sport->port);
 571
 572         return 0;
 573 }
 574
 575 static struct platform_driver sport_uart_driver = {
 576         .probe          = sport_uart_probe,
 577         .remove         = sport_uart_remove,
 578         .suspend        = sport_uart_suspend,
 579         .resume         = sport_uart_resume,
 580         .driver         = {
 581                 .name   = DRV_NAME,
 582         },
 583 };
 584
 585 static int __init sport_uart_init(void)
 586 {
 587         int ret;
 588
 589         pr_debug("%s enter\n", __func__);
 590         ret = uart_register_driver(&sport_uart_reg);
 591         if (ret != 0) {
 592                 printk(KERN_ERR "Failed to register %s:%d\n",
 593                                 sport_uart_reg.driver_name, ret);
 594                 return ret;
 595         }
 596
 597         ret = platform_driver_register(&sport_uart_driver);
 598         if (ret != 0) {
 599                 printk(KERN_ERR "Failed to register sport uart driver:%d\n", ret);
 600                 uart_unregister_driver(&sport_uart_reg);
 601         }
 602
 603
 604         pr_debug("%s exit\n", __func__);
 605         return ret;
 606 }
 607
 608 static void __exit sport_uart_exit(void)
 609 {
 610         pr_debug("%s enter\n", __func__);
 611         platform_driver_unregister(&sport_uart_driver);
 612         uart_unregister_driver(&sport_uart_reg);
 613 }
 614
 615 module_init(sport_uart_init);
 616 module_exit(sport_uart_exit);
 617
 618 MODULE_LICENSE("GPL");