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1/*
2 * Copyright (C) Maxime Coquelin 2015
3 * Author: Maxime Coquelin <mcoquelin.stm32@gmail.com>
4 * License terms: GNU General Public License (GPL), version 2
5 *
6 * Inspired by st-asc.c from STMicroelectronics (c)
7 */
8
9#if defined(CONFIG_SERIAL_STM32_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
10#define SUPPORT_SYSRQ
11#endif
12
13#include <linux/module.h>
14#include <linux/serial.h>
15#include <linux/console.h>
16#include <linux/sysrq.h>
17#include <linux/platform_device.h>
18#include <linux/io.h>
19#include <linux/irq.h>
20#include <linux/tty.h>
21#include <linux/tty_flip.h>
22#include <linux/delay.h>
23#include <linux/spinlock.h>
24#include <linux/pm_runtime.h>
25#include <linux/of.h>
26#include <linux/of_platform.h>
27#include <linux/serial_core.h>
28#include <linux/clk.h>
29
30#define DRIVER_NAME "stm32-usart"
31
32/* Register offsets */
33#define USART_SR 0x00
34#define USART_DR 0x04
35#define USART_BRR 0x08
36#define USART_CR1 0x0c
37#define USART_CR2 0x10
38#define USART_CR3 0x14
39#define USART_GTPR 0x18
40
41/* USART_SR */
42#define USART_SR_PE BIT(0)
43#define USART_SR_FE BIT(1)
44#define USART_SR_NF BIT(2)
45#define USART_SR_ORE BIT(3)
46#define USART_SR_IDLE BIT(4)
47#define USART_SR_RXNE BIT(5)
48#define USART_SR_TC BIT(6)
49#define USART_SR_TXE BIT(7)
50#define USART_SR_LBD BIT(8)
51#define USART_SR_CTS BIT(9)
52#define USART_SR_ERR_MASK (USART_SR_LBD | USART_SR_ORE | \
53 USART_SR_FE | USART_SR_PE)
54/* Dummy bits */
55#define USART_SR_DUMMY_RX BIT(16)
56
57/* USART_DR */
58#define USART_DR_MASK GENMASK(8, 0)
59
60/* USART_BRR */
61#define USART_BRR_DIV_F_MASK GENMASK(3, 0)
62#define USART_BRR_DIV_M_MASK GENMASK(15, 4)
63#define USART_BRR_DIV_M_SHIFT 4
64
65/* USART_CR1 */
66#define USART_CR1_SBK BIT(0)
67#define USART_CR1_RWU BIT(1)
68#define USART_CR1_RE BIT(2)
69#define USART_CR1_TE BIT(3)
70#define USART_CR1_IDLEIE BIT(4)
71#define USART_CR1_RXNEIE BIT(5)
72#define USART_CR1_TCIE BIT(6)
73#define USART_CR1_TXEIE BIT(7)
74#define USART_CR1_PEIE BIT(8)
75#define USART_CR1_PS BIT(9)
76#define USART_CR1_PCE BIT(10)
77#define USART_CR1_WAKE BIT(11)
78#define USART_CR1_M BIT(12)
79#define USART_CR1_UE BIT(13)
80#define USART_CR1_OVER8 BIT(15)
81#define USART_CR1_IE_MASK GENMASK(8, 4)
82
83/* USART_CR2 */
84#define USART_CR2_ADD_MASK GENMASK(3, 0)
85#define USART_CR2_LBDL BIT(5)
86#define USART_CR2_LBDIE BIT(6)
87#define USART_CR2_LBCL BIT(8)
88#define USART_CR2_CPHA BIT(9)
89#define USART_CR2_CPOL BIT(10)
90#define USART_CR2_CLKEN BIT(11)
91#define USART_CR2_STOP_2B BIT(13)
92#define USART_CR2_STOP_MASK GENMASK(13, 12)
93#define USART_CR2_LINEN BIT(14)
94
95/* USART_CR3 */
96#define USART_CR3_EIE BIT(0)
97#define USART_CR3_IREN BIT(1)
98#define USART_CR3_IRLP BIT(2)
99#define USART_CR3_HDSEL BIT(3)
100#define USART_CR3_NACK BIT(4)
101#define USART_CR3_SCEN BIT(5)
102#define USART_CR3_DMAR BIT(6)
103#define USART_CR3_DMAT BIT(7)
104#define USART_CR3_RTSE BIT(8)
105#define USART_CR3_CTSE BIT(9)
106#define USART_CR3_CTSIE BIT(10)
107#define USART_CR3_ONEBIT BIT(11)
108
109/* USART_GTPR */
110#define USART_GTPR_PSC_MASK GENMASK(7, 0)
111#define USART_GTPR_GT_MASK GENMASK(15, 8)
112
113#define DRIVER_NAME "stm32-usart"
114#define STM32_SERIAL_NAME "ttyS"
115#define STM32_MAX_PORTS 6
116
117struct stm32_port {
118 struct uart_port port;
119 struct clk *clk;
120 bool hw_flow_control;
121};
122
123static struct stm32_port stm32_ports[STM32_MAX_PORTS];
124static struct uart_driver stm32_usart_driver;
125
126static void stm32_stop_tx(struct uart_port *port);
127
128static inline struct stm32_port *to_stm32_port(struct uart_port *port)
129{
130 return container_of(port, struct stm32_port, port);
131}
132
133static void stm32_set_bits(struct uart_port *port, u32 reg, u32 bits)
134{
135 u32 val;
136
137 val = readl_relaxed(port->membase + reg);
138 val |= bits;
139 writel_relaxed(val, port->membase + reg);
140}
141
142static void stm32_clr_bits(struct uart_port *port, u32 reg, u32 bits)
143{
144 u32 val;
145
146 val = readl_relaxed(port->membase + reg);
147 val &= ~bits;
148 writel_relaxed(val, port->membase + reg);
149}
150
151static void stm32_receive_chars(struct uart_port *port)
152{
153 struct tty_port *tport = &port->state->port;
154 unsigned long c;
155 u32 sr;
156 char flag;
157
158 if (port->irq_wake)
159 pm_wakeup_event(tport->tty->dev, 0);
160
161 while ((sr = readl_relaxed(port->membase + USART_SR)) & USART_SR_RXNE) {
162 sr |= USART_SR_DUMMY_RX;
163 c = readl_relaxed(port->membase + USART_DR);
164 flag = TTY_NORMAL;
165 port->icount.rx++;
166
167 if (sr & USART_SR_ERR_MASK) {
168 if (sr & USART_SR_LBD) {
169 port->icount.brk++;
170 if (uart_handle_break(port))
171 continue;
172 } else if (sr & USART_SR_ORE) {
173 port->icount.overrun++;
174 } else if (sr & USART_SR_PE) {
175 port->icount.parity++;
176 } else if (sr & USART_SR_FE) {
177 port->icount.frame++;
178 }
179
180 sr &= port->read_status_mask;
181
182 if (sr & USART_SR_LBD)
183 flag = TTY_BREAK;
184 else if (sr & USART_SR_PE)
185 flag = TTY_PARITY;
186 else if (sr & USART_SR_FE)
187 flag = TTY_FRAME;
188 }
189
190 if (uart_handle_sysrq_char(port, c))
191 continue;
192 uart_insert_char(port, sr, USART_SR_ORE, c, flag);
193 }
194
195 spin_unlock(&port->lock);
196 tty_flip_buffer_push(tport);
197 spin_lock(&port->lock);
198}
199
200static void stm32_transmit_chars(struct uart_port *port)
201{
202 struct circ_buf *xmit = &port->state->xmit;
203
204 if (port->x_char) {
205 writel_relaxed(port->x_char, port->membase + USART_DR);
206 port->x_char = 0;
207 port->icount.tx++;
208 return;
209 }
210
211 if (uart_tx_stopped(port)) {
212 stm32_stop_tx(port);
213 return;
214 }
215
216 if (uart_circ_empty(xmit)) {
217 stm32_stop_tx(port);
218 return;
219 }
220
221 writel_relaxed(xmit->buf[xmit->tail], port->membase + USART_DR);
222 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
223 port->icount.tx++;
224
225 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
226 uart_write_wakeup(port);
227
228 if (uart_circ_empty(xmit))
229 stm32_stop_tx(port);
230}
231
232static irqreturn_t stm32_interrupt(int irq, void *ptr)
233{
234 struct uart_port *port = ptr;
235 u32 sr;
236
237 spin_lock(&port->lock);
238
239 sr = readl_relaxed(port->membase + USART_SR);
240
241 if (sr & USART_SR_RXNE)
242 stm32_receive_chars(port);
243
244 if (sr & USART_SR_TXE)
245 stm32_transmit_chars(port);
246
247 spin_unlock(&port->lock);
248
249 return IRQ_HANDLED;
250}
251
252static unsigned int stm32_tx_empty(struct uart_port *port)
253{
254 return readl_relaxed(port->membase + USART_SR) & USART_SR_TXE;
255}
256
257static void stm32_set_mctrl(struct uart_port *port, unsigned int mctrl)
258{
259 if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
260 stm32_set_bits(port, USART_CR3, USART_CR3_RTSE);
261 else
262 stm32_clr_bits(port, USART_CR3, USART_CR3_RTSE);
263}
264
265static unsigned int stm32_get_mctrl(struct uart_port *port)
266{
267 /* This routine is used to get signals of: DCD, DSR, RI, and CTS */
268 return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
269}
270
271/* Transmit stop */
272static void stm32_stop_tx(struct uart_port *port)
273{
274 stm32_clr_bits(port, USART_CR1, USART_CR1_TXEIE);
275}
276
277/* There are probably characters waiting to be transmitted. */
278static void stm32_start_tx(struct uart_port *port)
279{
280 struct circ_buf *xmit = &port->state->xmit;
281
282 if (uart_circ_empty(xmit))
283 return;
284
285 stm32_set_bits(port, USART_CR1, USART_CR1_TXEIE | USART_CR1_TE);
286}
287
288/* Throttle the remote when input buffer is about to overflow. */
289static void stm32_throttle(struct uart_port *port)
290{
291 unsigned long flags;
292
293 spin_lock_irqsave(&port->lock, flags);
294 stm32_clr_bits(port, USART_CR1, USART_CR1_RXNEIE);
295 spin_unlock_irqrestore(&port->lock, flags);
296}
297
298/* Unthrottle the remote, the input buffer can now accept data. */
299static void stm32_unthrottle(struct uart_port *port)
300{
301 unsigned long flags;
302
303 spin_lock_irqsave(&port->lock, flags);
304 stm32_set_bits(port, USART_CR1, USART_CR1_RXNEIE);
305 spin_unlock_irqrestore(&port->lock, flags);
306}
307
308/* Receive stop */
309static void stm32_stop_rx(struct uart_port *port)
310{
311 stm32_clr_bits(port, USART_CR1, USART_CR1_RXNEIE);
312}
313
314/* Handle breaks - ignored by us */
315static void stm32_break_ctl(struct uart_port *port, int break_state)
316{
317}
318
319static int stm32_startup(struct uart_port *port)
320{
321 const char *name = to_platform_device(port->dev)->name;
322 u32 val;
323 int ret;
324
325 ret = request_irq(port->irq, stm32_interrupt, 0, name, port);
326 if (ret)
327 return ret;
328
329 val = USART_CR1_RXNEIE | USART_CR1_TE | USART_CR1_RE;
330 stm32_set_bits(port, USART_CR1, val);
331
332 return 0;
333}
334
335static void stm32_shutdown(struct uart_port *port)
336{
337 u32 val;
338
339 val = USART_CR1_TXEIE | USART_CR1_RXNEIE | USART_CR1_TE | USART_CR1_RE;
340 stm32_set_bits(port, USART_CR1, val);
341
342 free_irq(port->irq, port);
343}
344
345static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
346 struct ktermios *old)
347{
348 struct stm32_port *stm32_port = to_stm32_port(port);
349 unsigned int baud;
350 u32 usartdiv, mantissa, fraction, oversampling;
351 tcflag_t cflag = termios->c_cflag;
352 u32 cr1, cr2, cr3;
353 unsigned long flags;
354
355 if (!stm32_port->hw_flow_control)
356 cflag &= ~CRTSCTS;
357
358 baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 8);
359
360 spin_lock_irqsave(&port->lock, flags);
361
362 /* Stop serial port and reset value */
363 writel_relaxed(0, port->membase + USART_CR1);
364
365 cr1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_UE | USART_CR1_RXNEIE;
366 cr2 = 0;
367 cr3 = 0;
368
369 if (cflag & CSTOPB)
370 cr2 |= USART_CR2_STOP_2B;
371
372 if (cflag & PARENB) {
373 cr1 |= USART_CR1_PCE;
374 if ((cflag & CSIZE) == CS8)
375 cr1 |= USART_CR1_M;
376 }
377
378 if (cflag & PARODD)
379 cr1 |= USART_CR1_PS;
380
381 port->status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS);
382 if (cflag & CRTSCTS) {
383 port->status |= UPSTAT_AUTOCTS | UPSTAT_AUTORTS;
384 cr3 |= USART_CR3_CTSE;
385 }
386
387 usartdiv = DIV_ROUND_CLOSEST(port->uartclk, baud);
388
389 /*
390 * The USART supports 16 or 8 times oversampling.
391 * By default we prefer 16 times oversampling, so that the receiver
392 * has a better tolerance to clock deviations.
393 * 8 times oversampling is only used to achieve higher speeds.
394 */
395 if (usartdiv < 16) {
396 oversampling = 8;
397 stm32_set_bits(port, USART_CR1, USART_CR1_OVER8);
398 } else {
399 oversampling = 16;
400 stm32_clr_bits(port, USART_CR1, USART_CR1_OVER8);
401 }
402
403 mantissa = (usartdiv / oversampling) << USART_BRR_DIV_M_SHIFT;
404 fraction = usartdiv % oversampling;
405 writel_relaxed(mantissa | fraction, port->membase + USART_BRR);
406
407 uart_update_timeout(port, cflag, baud);
408
409 port->read_status_mask = USART_SR_ORE;
410 if (termios->c_iflag & INPCK)
411 port->read_status_mask |= USART_SR_PE | USART_SR_FE;
412 if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
413 port->read_status_mask |= USART_SR_LBD;
414
415 /* Characters to ignore */
416 port->ignore_status_mask = 0;
417 if (termios->c_iflag & IGNPAR)
418 port->ignore_status_mask = USART_SR_PE | USART_SR_FE;
419 if (termios->c_iflag & IGNBRK) {
420 port->ignore_status_mask |= USART_SR_LBD;
421 /*
422 * If we're ignoring parity and break indicators,
423 * ignore overruns too (for real raw support).
424 */
425 if (termios->c_iflag & IGNPAR)
426 port->ignore_status_mask |= USART_SR_ORE;
427 }
428
429 /* Ignore all characters if CREAD is not set */
430 if ((termios->c_cflag & CREAD) == 0)
431 port->ignore_status_mask |= USART_SR_DUMMY_RX;
432
433 writel_relaxed(cr3, port->membase + USART_CR3);
434 writel_relaxed(cr2, port->membase + USART_CR2);
435 writel_relaxed(cr1, port->membase + USART_CR1);
436
437 spin_unlock_irqrestore(&port->lock, flags);
438}
439
440static const char *stm32_type(struct uart_port *port)
441{
442 return (port->type == PORT_STM32) ? DRIVER_NAME : NULL;
443}
444
445static void stm32_release_port(struct uart_port *port)
446{
447}
448
449static int stm32_request_port(struct uart_port *port)
450{
451 return 0;
452}
453
454static void stm32_config_port(struct uart_port *port, int flags)
455{
456 if (flags & UART_CONFIG_TYPE)
457 port->type = PORT_STM32;
458}
459
460static int
461stm32_verify_port(struct uart_port *port, struct serial_struct *ser)
462{
463 /* No user changeable parameters */
464 return -EINVAL;
465}
466
467static void stm32_pm(struct uart_port *port, unsigned int state,
468 unsigned int oldstate)
469{
470 struct stm32_port *stm32port = container_of(port,
471 struct stm32_port, port);
472 unsigned long flags = 0;
473
474 switch (state) {
475 case UART_PM_STATE_ON:
476 clk_prepare_enable(stm32port->clk);
477 break;
478 case UART_PM_STATE_OFF:
479 spin_lock_irqsave(&port->lock, flags);
480 stm32_clr_bits(port, USART_CR1, USART_CR1_UE);
481 spin_unlock_irqrestore(&port->lock, flags);
482 clk_disable_unprepare(stm32port->clk);
483 break;
484 }
485}
486
487static const struct uart_ops stm32_uart_ops = {
488 .tx_empty = stm32_tx_empty,
489 .set_mctrl = stm32_set_mctrl,
490 .get_mctrl = stm32_get_mctrl,
491 .stop_tx = stm32_stop_tx,
492 .start_tx = stm32_start_tx,
493 .throttle = stm32_throttle,
494 .unthrottle = stm32_unthrottle,
495 .stop_rx = stm32_stop_rx,
496 .break_ctl = stm32_break_ctl,
497 .startup = stm32_startup,
498 .shutdown = stm32_shutdown,
499 .set_termios = stm32_set_termios,
500 .pm = stm32_pm,
501 .type = stm32_type,
502 .release_port = stm32_release_port,
503 .request_port = stm32_request_port,
504 .config_port = stm32_config_port,
505 .verify_port = stm32_verify_port,
506};
507
508static int stm32_init_port(struct stm32_port *stm32port,
509 struct platform_device *pdev)
510{
511 struct uart_port *port = &stm32port->port;
512 struct resource *res;
513 int ret;
514
515 port->iotype = UPIO_MEM;
516 port->flags = UPF_BOOT_AUTOCONF;
517 port->ops = &stm32_uart_ops;
518 port->dev = &pdev->dev;
519 port->irq = platform_get_irq(pdev, 0);
520
521 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
522 port->membase = devm_ioremap_resource(&pdev->dev, res);
523 if (IS_ERR(port->membase))
524 return PTR_ERR(port->membase);
525 port->mapbase = res->start;
526
527 spin_lock_init(&port->lock);
528
529 stm32port->clk = devm_clk_get(&pdev->dev, NULL);
530 if (IS_ERR(stm32port->clk))
531 return PTR_ERR(stm32port->clk);
532
533 /* Ensure that clk rate is correct by enabling the clk */
534 ret = clk_prepare_enable(stm32port->clk);
535 if (ret)
536 return ret;
537
538 stm32port->port.uartclk = clk_get_rate(stm32port->clk);
539 if (!stm32port->port.uartclk)
540 ret = -EINVAL;
541
542 clk_disable_unprepare(stm32port->clk);
543
544 return ret;
545}
546
547static struct stm32_port *stm32_of_get_stm32_port(struct platform_device *pdev)
548{
549 struct device_node *np = pdev->dev.of_node;
550 int id;
551
552 if (!np)
553 return NULL;
554
555 id = of_alias_get_id(np, "serial");
556 if (id < 0)
557 id = 0;
558
559 if (WARN_ON(id >= STM32_MAX_PORTS))
560 return NULL;
561
562 stm32_ports[id].hw_flow_control = of_property_read_bool(np,
563 "auto-flow-control");
564 stm32_ports[id].port.line = id;
565 return &stm32_ports[id];
566}
567
568#ifdef CONFIG_OF
569static const struct of_device_id stm32_match[] = {
570 { .compatible = "st,stm32-usart", },
571 { .compatible = "st,stm32-uart", },
572 {},
573};
574
575MODULE_DEVICE_TABLE(of, stm32_match);
576#endif
577
578static int stm32_serial_probe(struct platform_device *pdev)
579{
580 int ret;
581 struct stm32_port *stm32port;
582
583 stm32port = stm32_of_get_stm32_port(pdev);
584 if (!stm32port)
585 return -ENODEV;
586
587 ret = stm32_init_port(stm32port, pdev);
588 if (ret)
589 return ret;
590
591 ret = uart_add_one_port(&stm32_usart_driver, &stm32port->port);
592 if (ret)
593 return ret;
594
595 platform_set_drvdata(pdev, &stm32port->port);
596
597 return 0;
598}
599
600static int stm32_serial_remove(struct platform_device *pdev)
601{
602 struct uart_port *port = platform_get_drvdata(pdev);
603
604 return uart_remove_one_port(&stm32_usart_driver, port);
605}
606
607
608#ifdef CONFIG_SERIAL_STM32_CONSOLE
609static void stm32_console_putchar(struct uart_port *port, int ch)
610{
611 while (!(readl_relaxed(port->membase + USART_SR) & USART_SR_TXE))
612 cpu_relax();
613
614 writel_relaxed(ch, port->membase + USART_DR);
615}
616
617static void stm32_console_write(struct console *co, const char *s, unsigned cnt)
618{
619 struct uart_port *port = &stm32_ports[co->index].port;
620 unsigned long flags;
621 u32 old_cr1, new_cr1;
622 int locked = 1;
623
624 local_irq_save(flags);
625 if (port->sysrq)
626 locked = 0;
627 else if (oops_in_progress)
628 locked = spin_trylock(&port->lock);
629 else
630 spin_lock(&port->lock);
631
632 /* Save and disable interrupts */
633 old_cr1 = readl_relaxed(port->membase + USART_CR1);
634 new_cr1 = old_cr1 & ~USART_CR1_IE_MASK;
635 writel_relaxed(new_cr1, port->membase + USART_CR1);
636
637 uart_console_write(port, s, cnt, stm32_console_putchar);
638
639 /* Restore interrupt state */
640 writel_relaxed(old_cr1, port->membase + USART_CR1);
641
642 if (locked)
643 spin_unlock(&port->lock);
644 local_irq_restore(flags);
645}
646
647static int stm32_console_setup(struct console *co, char *options)
648{
649 struct stm32_port *stm32port;
650 int baud = 9600;
651 int bits = 8;
652 int parity = 'n';
653 int flow = 'n';
654
655 if (co->index >= STM32_MAX_PORTS)
656 return -ENODEV;
657
658 stm32port = &stm32_ports[co->index];
659
660 /*
661 * This driver does not support early console initialization
662 * (use ARM early printk support instead), so we only expect
663 * this to be called during the uart port registration when the
664 * driver gets probed and the port should be mapped at that point.
665 */
666 if (stm32port->port.mapbase == 0 || stm32port->port.membase == NULL)
667 return -ENXIO;
668
669 if (options)
670 uart_parse_options(options, &baud, &parity, &bits, &flow);
671
672 return uart_set_options(&stm32port->port, co, baud, parity, bits, flow);
673}
674
675static struct console stm32_console = {
676 .name = STM32_SERIAL_NAME,
677 .device = uart_console_device,
678 .write = stm32_console_write,
679 .setup = stm32_console_setup,
680 .flags = CON_PRINTBUFFER,
681 .index = -1,
682 .data = &stm32_usart_driver,
683};
684
685#define STM32_SERIAL_CONSOLE (&stm32_console)
686
687#else
688#define STM32_SERIAL_CONSOLE NULL
689#endif /* CONFIG_SERIAL_STM32_CONSOLE */
690
691static struct uart_driver stm32_usart_driver = {
692 .driver_name = DRIVER_NAME,
693 .dev_name = STM32_SERIAL_NAME,
694 .major = 0,
695 .minor = 0,
696 .nr = STM32_MAX_PORTS,
697 .cons = STM32_SERIAL_CONSOLE,
698};
699
700static struct platform_driver stm32_serial_driver = {
701 .probe = stm32_serial_probe,
702 .remove = stm32_serial_remove,
703 .driver = {
704 .name = DRIVER_NAME,
705 .of_match_table = of_match_ptr(stm32_match),
706 },
707};
708
709static int __init usart_init(void)
710{
711 static char banner[] __initdata = "STM32 USART driver initialized";
712 int ret;
713
714 pr_info("%s\n", banner);
715
716 ret = uart_register_driver(&stm32_usart_driver);
717 if (ret)
718 return ret;
719
720 ret = platform_driver_register(&stm32_serial_driver);
721 if (ret)
722 uart_unregister_driver(&stm32_usart_driver);
723
724 return ret;
725}
726
727static void __exit usart_exit(void)
728{
729 platform_driver_unregister(&stm32_serial_driver);
730 uart_unregister_driver(&stm32_usart_driver);
731}
732
733module_init(usart_init);
734module_exit(usart_exit);
735
736MODULE_ALIAS("platform:" DRIVER_NAME);
737MODULE_DESCRIPTION("STMicroelectronics STM32 serial port driver");
738MODULE_LICENSE("GPL v2");