xref: /openbmc/linux/drivers/tty/serial/sprd_serial.c (revision 612a462a) 
1 /*
2  * Copyright (C) 2012-2015 Spreadtrum Communications Inc.
3  *
4  * This software is licensed under the terms of the GNU General Public
5  * License version 2, as published by the Free Software Foundation, and
6  * may be copied, distributed, and modified under those terms.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11  * GNU General Public License for more details.
12  */
13 
14 #if defined(CONFIG_SERIAL_SPRD_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
15 #define SUPPORT_SYSRQ
16 #endif
17 
18 #include <linux/clk.h>
19 #include <linux/console.h>
20 #include <linux/delay.h>
21 #include <linux/io.h>
22 #include <linux/ioport.h>
23 #include <linux/kernel.h>
24 #include <linux/module.h>
25 #include <linux/of.h>
26 #include <linux/platform_device.h>
27 #include <linux/serial_core.h>
28 #include <linux/serial.h>
29 #include <linux/slab.h>
30 #include <linux/tty.h>
31 #include <linux/tty_flip.h>
32 
33 /* device name */
34 #define UART_NR_MAX		8
35 #define SPRD_TTY_NAME		"ttyS"
36 #define SPRD_FIFO_SIZE		128
37 #define SPRD_DEF_RATE		26000000
38 #define SPRD_BAUD_IO_LIMIT	3000000
39 #define SPRD_TIMEOUT		256000
40 
41 /* the offset of serial registers and BITs for them */
42 /* data registers */
43 #define SPRD_TXD		0x0000
44 #define SPRD_RXD		0x0004
45 
46 /* line status register and its BITs  */
47 #define SPRD_LSR		0x0008
48 #define SPRD_LSR_OE		BIT(4)
49 #define SPRD_LSR_FE		BIT(3)
50 #define SPRD_LSR_PE		BIT(2)
51 #define SPRD_LSR_BI		BIT(7)
52 #define SPRD_LSR_TX_OVER	BIT(15)
53 
54 /* data number in TX and RX fifo */
55 #define SPRD_STS1		0x000C
56 
57 /* interrupt enable register and its BITs */
58 #define SPRD_IEN		0x0010
59 #define SPRD_IEN_RX_FULL	BIT(0)
60 #define SPRD_IEN_TX_EMPTY	BIT(1)
61 #define SPRD_IEN_BREAK_DETECT	BIT(7)
62 #define SPRD_IEN_TIMEOUT	BIT(13)
63 
64 /* interrupt clear register */
65 #define SPRD_ICLR		0x0014
66 #define SPRD_ICLR_TIMEOUT	BIT(13)
67 
68 /* line control register */
69 #define SPRD_LCR		0x0018
70 #define SPRD_LCR_STOP_1BIT	0x10
71 #define SPRD_LCR_STOP_2BIT	0x30
72 #define SPRD_LCR_DATA_LEN	(BIT(2) | BIT(3))
73 #define SPRD_LCR_DATA_LEN5	0x0
74 #define SPRD_LCR_DATA_LEN6	0x4
75 #define SPRD_LCR_DATA_LEN7	0x8
76 #define SPRD_LCR_DATA_LEN8	0xc
77 #define SPRD_LCR_PARITY	(BIT(0) | BIT(1))
78 #define SPRD_LCR_PARITY_EN	0x2
79 #define SPRD_LCR_EVEN_PAR	0x0
80 #define SPRD_LCR_ODD_PAR	0x1
81 
82 /* control register 1 */
83 #define SPRD_CTL1			0x001C
84 #define RX_HW_FLOW_CTL_THLD	BIT(6)
85 #define RX_HW_FLOW_CTL_EN	BIT(7)
86 #define TX_HW_FLOW_CTL_EN	BIT(8)
87 #define RX_TOUT_THLD_DEF	0x3E00
88 #define RX_HFC_THLD_DEF	0x40
89 
90 /* fifo threshold register */
91 #define SPRD_CTL2		0x0020
92 #define THLD_TX_EMPTY	0x40
93 #define THLD_RX_FULL	0x40
94 
95 /* config baud rate register */
96 #define SPRD_CLKD0		0x0024
97 #define SPRD_CLKD1		0x0028
98 
99 /* interrupt mask status register */
100 #define SPRD_IMSR			0x002C
101 #define SPRD_IMSR_RX_FIFO_FULL		BIT(0)
102 #define SPRD_IMSR_TX_FIFO_EMPTY	BIT(1)
103 #define SPRD_IMSR_BREAK_DETECT		BIT(7)
104 #define SPRD_IMSR_TIMEOUT		BIT(13)
105 
106 struct reg_backup {
107 	u32 ien;
108 	u32 ctrl0;
109 	u32 ctrl1;
110 	u32 ctrl2;
111 	u32 clkd0;
112 	u32 clkd1;
113 	u32 dspwait;
114 };
115 
116 struct sprd_uart_port {
117 	struct uart_port port;
118 	struct reg_backup reg_bak;
119 	char name[16];
120 };
121 
122 static struct sprd_uart_port *sprd_port[UART_NR_MAX];
123 static int sprd_ports_num;
124 
125 static inline unsigned int serial_in(struct uart_port *port, int offset)
126 {
127 	return readl_relaxed(port->membase + offset);
128 }
129 
130 static inline void serial_out(struct uart_port *port, int offset, int value)
131 {
132 	writel_relaxed(value, port->membase + offset);
133 }
134 
135 static unsigned int sprd_tx_empty(struct uart_port *port)
136 {
137 	if (serial_in(port, SPRD_STS1) & 0xff00)
138 		return 0;
139 	else
140 		return TIOCSER_TEMT;
141 }
142 
143 static unsigned int sprd_get_mctrl(struct uart_port *port)
144 {
145 	return TIOCM_DSR | TIOCM_CTS;
146 }
147 
148 static void sprd_set_mctrl(struct uart_port *port, unsigned int mctrl)
149 {
150 	/* nothing to do */
151 }
152 
153 static void sprd_stop_tx(struct uart_port *port)
154 {
155 	unsigned int ien, iclr;
156 
157 	iclr = serial_in(port, SPRD_ICLR);
158 	ien = serial_in(port, SPRD_IEN);
159 
160 	iclr |= SPRD_IEN_TX_EMPTY;
161 	ien &= ~SPRD_IEN_TX_EMPTY;
162 
163 	serial_out(port, SPRD_ICLR, iclr);
164 	serial_out(port, SPRD_IEN, ien);
165 }
166 
167 static void sprd_start_tx(struct uart_port *port)
168 {
169 	unsigned int ien;
170 
171 	ien = serial_in(port, SPRD_IEN);
172 	if (!(ien & SPRD_IEN_TX_EMPTY)) {
173 		ien |= SPRD_IEN_TX_EMPTY;
174 		serial_out(port, SPRD_IEN, ien);
175 	}
176 }
177 
178 static void sprd_stop_rx(struct uart_port *port)
179 {
180 	unsigned int ien, iclr;
181 
182 	iclr = serial_in(port, SPRD_ICLR);
183 	ien = serial_in(port, SPRD_IEN);
184 
185 	ien &= ~(SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT);
186 	iclr |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT;
187 
188 	serial_out(port, SPRD_IEN, ien);
189 	serial_out(port, SPRD_ICLR, iclr);
190 }
191 
192 /* The Sprd serial does not support this function. */
193 static void sprd_break_ctl(struct uart_port *port, int break_state)
194 {
195 	/* nothing to do */
196 }
197 
198 static int handle_lsr_errors(struct uart_port *port,
199 			     unsigned int *flag,
200 			     unsigned int *lsr)
201 {
202 	int ret = 0;
203 
204 	/* statistics */
205 	if (*lsr & SPRD_LSR_BI) {
206 		*lsr &= ~(SPRD_LSR_FE | SPRD_LSR_PE);
207 		port->icount.brk++;
208 		ret = uart_handle_break(port);
209 		if (ret)
210 			return ret;
211 	} else if (*lsr & SPRD_LSR_PE)
212 		port->icount.parity++;
213 	else if (*lsr & SPRD_LSR_FE)
214 		port->icount.frame++;
215 	if (*lsr & SPRD_LSR_OE)
216 		port->icount.overrun++;
217 
218 	/* mask off conditions which should be ignored */
219 	*lsr &= port->read_status_mask;
220 	if (*lsr & SPRD_LSR_BI)
221 		*flag = TTY_BREAK;
222 	else if (*lsr & SPRD_LSR_PE)
223 		*flag = TTY_PARITY;
224 	else if (*lsr & SPRD_LSR_FE)
225 		*flag = TTY_FRAME;
226 
227 	return ret;
228 }
229 
230 static inline void sprd_rx(struct uart_port *port)
231 {
232 	struct tty_port *tty = &port->state->port;
233 	unsigned int ch, flag, lsr, max_count = SPRD_TIMEOUT;
234 
235 	while ((serial_in(port, SPRD_STS1) & 0x00ff) && max_count--) {
236 		lsr = serial_in(port, SPRD_LSR);
237 		ch = serial_in(port, SPRD_RXD);
238 		flag = TTY_NORMAL;
239 		port->icount.rx++;
240 
241 		if (lsr & (SPRD_LSR_BI | SPRD_LSR_PE |
242 			SPRD_LSR_FE | SPRD_LSR_OE))
243 			if (handle_lsr_errors(port, &lsr, &flag))
244 				continue;
245 		if (uart_handle_sysrq_char(port, ch))
246 			continue;
247 
248 		uart_insert_char(port, lsr, SPRD_LSR_OE, ch, flag);
249 	}
250 
251 	tty_flip_buffer_push(tty);
252 }
253 
254 static inline void sprd_tx(struct uart_port *port)
255 {
256 	struct circ_buf *xmit = &port->state->xmit;
257 	int count;
258 
259 	if (port->x_char) {
260 		serial_out(port, SPRD_TXD, port->x_char);
261 		port->icount.tx++;
262 		port->x_char = 0;
263 		return;
264 	}
265 
266 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
267 		sprd_stop_tx(port);
268 		return;
269 	}
270 
271 	count = THLD_TX_EMPTY;
272 	do {
273 		serial_out(port, SPRD_TXD, xmit->buf[xmit->tail]);
274 		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
275 		port->icount.tx++;
276 		if (uart_circ_empty(xmit))
277 			break;
278 	} while (--count > 0);
279 
280 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
281 		uart_write_wakeup(port);
282 
283 	if (uart_circ_empty(xmit))
284 		sprd_stop_tx(port);
285 }
286 
287 /* this handles the interrupt from one port */
288 static irqreturn_t sprd_handle_irq(int irq, void *dev_id)
289 {
290 	struct uart_port *port = dev_id;
291 	unsigned int ims;
292 
293 	spin_lock(&port->lock);
294 
295 	ims = serial_in(port, SPRD_IMSR);
296 
297 	if (!ims) {
298 		spin_unlock(&port->lock);
299 		return IRQ_NONE;
300 	}
301 
302 	if (ims & SPRD_IMSR_TIMEOUT)
303 		serial_out(port, SPRD_ICLR, SPRD_ICLR_TIMEOUT);
304 
305 	if (ims & (SPRD_IMSR_RX_FIFO_FULL |
306 		SPRD_IMSR_BREAK_DETECT | SPRD_IMSR_TIMEOUT))
307 		sprd_rx(port);
308 
309 	if (ims & SPRD_IMSR_TX_FIFO_EMPTY)
310 		sprd_tx(port);
311 
312 	spin_unlock(&port->lock);
313 
314 	return IRQ_HANDLED;
315 }
316 
317 static int sprd_startup(struct uart_port *port)
318 {
319 	int ret = 0;
320 	unsigned int ien, fc;
321 	unsigned int timeout;
322 	struct sprd_uart_port *sp;
323 	unsigned long flags;
324 
325 	serial_out(port, SPRD_CTL2, ((THLD_TX_EMPTY << 8) | THLD_RX_FULL));
326 
327 	/* clear rx fifo */
328 	timeout = SPRD_TIMEOUT;
329 	while (timeout-- && serial_in(port, SPRD_STS1) & 0x00ff)
330 		serial_in(port, SPRD_RXD);
331 
332 	/* clear tx fifo */
333 	timeout = SPRD_TIMEOUT;
334 	while (timeout-- && serial_in(port, SPRD_STS1) & 0xff00)
335 		cpu_relax();
336 
337 	/* clear interrupt */
338 	serial_out(port, SPRD_IEN, 0);
339 	serial_out(port, SPRD_ICLR, ~0);
340 
341 	/* allocate irq */
342 	sp = container_of(port, struct sprd_uart_port, port);
343 	snprintf(sp->name, sizeof(sp->name), "sprd_serial%d", port->line);
344 	ret = devm_request_irq(port->dev, port->irq, sprd_handle_irq,
345 				IRQF_SHARED, sp->name, port);
346 	if (ret) {
347 		dev_err(port->dev, "fail to request serial irq %d, ret=%d\n",
348 			port->irq, ret);
349 		return ret;
350 	}
351 	fc = serial_in(port, SPRD_CTL1);
352 	fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
353 	serial_out(port, SPRD_CTL1, fc);
354 
355 	/* enable interrupt */
356 	spin_lock_irqsave(&port->lock, flags);
357 	ien = serial_in(port, SPRD_IEN);
358 	ien |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT | SPRD_IEN_TIMEOUT;
359 	serial_out(port, SPRD_IEN, ien);
360 	spin_unlock_irqrestore(&port->lock, flags);
361 
362 	return 0;
363 }
364 
365 static void sprd_shutdown(struct uart_port *port)
366 {
367 	serial_out(port, SPRD_IEN, 0);
368 	serial_out(port, SPRD_ICLR, ~0);
369 	devm_free_irq(port->dev, port->irq, port);
370 }
371 
372 static void sprd_set_termios(struct uart_port *port,
373 				    struct ktermios *termios,
374 				    struct ktermios *old)
375 {
376 	unsigned int baud, quot;
377 	unsigned int lcr = 0, fc;
378 	unsigned long flags;
379 
380 	/* ask the core to calculate the divisor for us */
381 	baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
382 
383 	quot = (unsigned int)((port->uartclk + baud / 2) / baud);
384 
385 	/* set data length */
386 	switch (termios->c_cflag & CSIZE) {
387 	case CS5:
388 		lcr |= SPRD_LCR_DATA_LEN5;
389 		break;
390 	case CS6:
391 		lcr |= SPRD_LCR_DATA_LEN6;
392 		break;
393 	case CS7:
394 		lcr |= SPRD_LCR_DATA_LEN7;
395 		break;
396 	case CS8:
397 	default:
398 		lcr |= SPRD_LCR_DATA_LEN8;
399 		break;
400 	}
401 
402 	/* calculate stop bits */
403 	lcr &= ~(SPRD_LCR_STOP_1BIT | SPRD_LCR_STOP_2BIT);
404 	if (termios->c_cflag & CSTOPB)
405 		lcr |= SPRD_LCR_STOP_2BIT;
406 	else
407 		lcr |= SPRD_LCR_STOP_1BIT;
408 
409 	/* calculate parity */
410 	lcr &= ~SPRD_LCR_PARITY;
411 	termios->c_cflag &= ~CMSPAR;	/* no support mark/space */
412 	if (termios->c_cflag & PARENB) {
413 		lcr |= SPRD_LCR_PARITY_EN;
414 		if (termios->c_cflag & PARODD)
415 			lcr |= SPRD_LCR_ODD_PAR;
416 		else
417 			lcr |= SPRD_LCR_EVEN_PAR;
418 	}
419 
420 	spin_lock_irqsave(&port->lock, flags);
421 
422 	/* update the per-port timeout */
423 	uart_update_timeout(port, termios->c_cflag, baud);
424 
425 	port->read_status_mask = SPRD_LSR_OE;
426 	if (termios->c_iflag & INPCK)
427 		port->read_status_mask |= SPRD_LSR_FE | SPRD_LSR_PE;
428 	if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
429 		port->read_status_mask |= SPRD_LSR_BI;
430 
431 	/* characters to ignore */
432 	port->ignore_status_mask = 0;
433 	if (termios->c_iflag & IGNPAR)
434 		port->ignore_status_mask |= SPRD_LSR_PE | SPRD_LSR_FE;
435 	if (termios->c_iflag & IGNBRK) {
436 		port->ignore_status_mask |= SPRD_LSR_BI;
437 		/*
438 		 * If we're ignoring parity and break indicators,
439 		 * ignore overruns too (for real raw support).
440 		 */
441 		if (termios->c_iflag & IGNPAR)
442 			port->ignore_status_mask |= SPRD_LSR_OE;
443 	}
444 
445 	/* flow control */
446 	fc = serial_in(port, SPRD_CTL1);
447 	fc &= ~(RX_HW_FLOW_CTL_THLD | RX_HW_FLOW_CTL_EN | TX_HW_FLOW_CTL_EN);
448 	if (termios->c_cflag & CRTSCTS) {
449 		fc |= RX_HW_FLOW_CTL_THLD;
450 		fc |= RX_HW_FLOW_CTL_EN;
451 		fc |= TX_HW_FLOW_CTL_EN;
452 	}
453 
454 	/* clock divider bit0~bit15 */
455 	serial_out(port, SPRD_CLKD0, quot & 0xffff);
456 
457 	/* clock divider bit16~bit20 */
458 	serial_out(port, SPRD_CLKD1, (quot & 0x1f0000) >> 16);
459 	serial_out(port, SPRD_LCR, lcr);
460 	fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
461 	serial_out(port, SPRD_CTL1, fc);
462 
463 	spin_unlock_irqrestore(&port->lock, flags);
464 
465 	/* Don't rewrite B0 */
466 	if (tty_termios_baud_rate(termios))
467 		tty_termios_encode_baud_rate(termios, baud, baud);
468 }
469 
470 static const char *sprd_type(struct uart_port *port)
471 {
472 	return "SPX";
473 }
474 
475 static void sprd_release_port(struct uart_port *port)
476 {
477 	/* nothing to do */
478 }
479 
480 static int sprd_request_port(struct uart_port *port)
481 {
482 	return 0;
483 }
484 
485 static void sprd_config_port(struct uart_port *port, int flags)
486 {
487 	if (flags & UART_CONFIG_TYPE)
488 		port->type = PORT_SPRD;
489 }
490 
491 static int sprd_verify_port(struct uart_port *port,
492 				   struct serial_struct *ser)
493 {
494 	if (ser->type != PORT_SPRD)
495 		return -EINVAL;
496 	if (port->irq != ser->irq)
497 		return -EINVAL;
498 	if (port->iotype != ser->io_type)
499 		return -EINVAL;
500 	return 0;
501 }
502 
503 static const struct uart_ops serial_sprd_ops = {
504 	.tx_empty = sprd_tx_empty,
505 	.get_mctrl = sprd_get_mctrl,
506 	.set_mctrl = sprd_set_mctrl,
507 	.stop_tx = sprd_stop_tx,
508 	.start_tx = sprd_start_tx,
509 	.stop_rx = sprd_stop_rx,
510 	.break_ctl = sprd_break_ctl,
511 	.startup = sprd_startup,
512 	.shutdown = sprd_shutdown,
513 	.set_termios = sprd_set_termios,
514 	.type = sprd_type,
515 	.release_port = sprd_release_port,
516 	.request_port = sprd_request_port,
517 	.config_port = sprd_config_port,
518 	.verify_port = sprd_verify_port,
519 };
520 
521 #ifdef CONFIG_SERIAL_SPRD_CONSOLE
522 static void wait_for_xmitr(struct uart_port *port)
523 {
524 	unsigned int status, tmout = 10000;
525 
526 	/* wait up to 10ms for the character(s) to be sent */
527 	do {
528 		status = serial_in(port, SPRD_STS1);
529 		if (--tmout == 0)
530 			break;
531 		udelay(1);
532 	} while (status & 0xff00);
533 }
534 
535 static void sprd_console_putchar(struct uart_port *port, int ch)
536 {
537 	wait_for_xmitr(port);
538 	serial_out(port, SPRD_TXD, ch);
539 }
540 
541 static void sprd_console_write(struct console *co, const char *s,
542 				      unsigned int count)
543 {
544 	struct uart_port *port = &sprd_port[co->index]->port;
545 	int locked = 1;
546 	unsigned long flags;
547 
548 	if (port->sysrq)
549 		locked = 0;
550 	else if (oops_in_progress)
551 		locked = spin_trylock_irqsave(&port->lock, flags);
552 	else
553 		spin_lock_irqsave(&port->lock, flags);
554 
555 	uart_console_write(port, s, count, sprd_console_putchar);
556 
557 	/* wait for transmitter to become empty */
558 	wait_for_xmitr(port);
559 
560 	if (locked)
561 		spin_unlock_irqrestore(&port->lock, flags);
562 }
563 
564 static int __init sprd_console_setup(struct console *co, char *options)
565 {
566 	struct uart_port *port;
567 	int baud = 115200;
568 	int bits = 8;
569 	int parity = 'n';
570 	int flow = 'n';
571 
572 	if (co->index >= UART_NR_MAX || co->index < 0)
573 		co->index = 0;
574 
575 	port = &sprd_port[co->index]->port;
576 	if (port == NULL) {
577 		pr_info("serial port %d not yet initialized\n", co->index);
578 		return -ENODEV;
579 	}
580 	if (options)
581 		uart_parse_options(options, &baud, &parity, &bits, &flow);
582 
583 	return uart_set_options(port, co, baud, parity, bits, flow);
584 }
585 
586 static struct uart_driver sprd_uart_driver;
587 static struct console sprd_console = {
588 	.name = SPRD_TTY_NAME,
589 	.write = sprd_console_write,
590 	.device = uart_console_device,
591 	.setup = sprd_console_setup,
592 	.flags = CON_PRINTBUFFER,
593 	.index = -1,
594 	.data = &sprd_uart_driver,
595 };
596 
597 #define SPRD_CONSOLE	(&sprd_console)
598 
599 /* Support for earlycon */
600 static void sprd_putc(struct uart_port *port, int c)
601 {
602 	unsigned int timeout = SPRD_TIMEOUT;
603 
604 	while (timeout-- &&
605 		   !(readl(port->membase + SPRD_LSR) & SPRD_LSR_TX_OVER))
606 		cpu_relax();
607 
608 	writeb(c, port->membase + SPRD_TXD);
609 }
610 
611 static void sprd_early_write(struct console *con, const char *s,
612 				    unsigned n)
613 {
614 	struct earlycon_device *dev = con->data;
615 
616 	uart_console_write(&dev->port, s, n, sprd_putc);
617 }
618 
619 static int __init sprd_early_console_setup(
620 				struct earlycon_device *device,
621 				const char *opt)
622 {
623 	if (!device->port.membase)
624 		return -ENODEV;
625 
626 	device->con->write = sprd_early_write;
627 	return 0;
628 }
629 OF_EARLYCON_DECLARE(sprd_serial, "sprd,sc9836-uart",
630 		    sprd_early_console_setup);
631 
632 #else /* !CONFIG_SERIAL_SPRD_CONSOLE */
633 #define SPRD_CONSOLE		NULL
634 #endif
635 
636 static struct uart_driver sprd_uart_driver = {
637 	.owner = THIS_MODULE,
638 	.driver_name = "sprd_serial",
639 	.dev_name = SPRD_TTY_NAME,
640 	.major = 0,
641 	.minor = 0,
642 	.nr = UART_NR_MAX,
643 	.cons = SPRD_CONSOLE,
644 };
645 
646 static int sprd_probe_dt_alias(int index, struct device *dev)
647 {
648 	struct device_node *np;
649 	int ret = index;
650 
651 	if (!IS_ENABLED(CONFIG_OF))
652 		return ret;
653 
654 	np = dev->of_node;
655 	if (!np)
656 		return ret;
657 
658 	ret = of_alias_get_id(np, "serial");
659 	if (ret < 0)
660 		ret = index;
661 	else if (ret >= ARRAY_SIZE(sprd_port) || sprd_port[ret] != NULL) {
662 		dev_warn(dev, "requested serial port %d not available.\n", ret);
663 		ret = index;
664 	}
665 
666 	return ret;
667 }
668 
669 static int sprd_remove(struct platform_device *dev)
670 {
671 	struct sprd_uart_port *sup = platform_get_drvdata(dev);
672 
673 	if (sup) {
674 		uart_remove_one_port(&sprd_uart_driver, &sup->port);
675 		sprd_port[sup->port.line] = NULL;
676 		sprd_ports_num--;
677 	}
678 
679 	if (!sprd_ports_num)
680 		uart_unregister_driver(&sprd_uart_driver);
681 
682 	return 0;
683 }
684 
685 static int sprd_probe(struct platform_device *pdev)
686 {
687 	struct resource *res;
688 	struct uart_port *up;
689 	struct clk *clk;
690 	int irq;
691 	int index;
692 	int ret;
693 
694 	for (index = 0; index < ARRAY_SIZE(sprd_port); index++)
695 		if (sprd_port[index] == NULL)
696 			break;
697 
698 	if (index == ARRAY_SIZE(sprd_port))
699 		return -EBUSY;
700 
701 	index = sprd_probe_dt_alias(index, &pdev->dev);
702 
703 	sprd_port[index] = devm_kzalloc(&pdev->dev,
704 		sizeof(*sprd_port[index]), GFP_KERNEL);
705 	if (!sprd_port[index])
706 		return -ENOMEM;
707 
708 	up = &sprd_port[index]->port;
709 	up->dev = &pdev->dev;
710 	up->line = index;
711 	up->type = PORT_SPRD;
712 	up->iotype = UPIO_MEM;
713 	up->uartclk = SPRD_DEF_RATE;
714 	up->fifosize = SPRD_FIFO_SIZE;
715 	up->ops = &serial_sprd_ops;
716 	up->flags = UPF_BOOT_AUTOCONF;
717 
718 	clk = devm_clk_get(&pdev->dev, NULL);
719 	if (!IS_ERR_OR_NULL(clk))
720 		up->uartclk = clk_get_rate(clk);
721 
722 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
723 	if (!res) {
724 		dev_err(&pdev->dev, "not provide mem resource\n");
725 		return -ENODEV;
726 	}
727 	up->mapbase = res->start;
728 	up->membase = devm_ioremap_resource(&pdev->dev, res);
729 	if (IS_ERR(up->membase))
730 		return PTR_ERR(up->membase);
731 
732 	irq = platform_get_irq(pdev, 0);
733 	if (irq < 0) {
734 		dev_err(&pdev->dev, "not provide irq resource: %d\n", irq);
735 		return irq;
736 	}
737 	up->irq = irq;
738 
739 	if (!sprd_ports_num) {
740 		ret = uart_register_driver(&sprd_uart_driver);
741 		if (ret < 0) {
742 			pr_err("Failed to register SPRD-UART driver\n");
743 			return ret;
744 		}
745 	}
746 	sprd_ports_num++;
747 
748 	ret = uart_add_one_port(&sprd_uart_driver, up);
749 	if (ret) {
750 		sprd_port[index] = NULL;
751 		sprd_remove(pdev);
752 	}
753 
754 	platform_set_drvdata(pdev, up);
755 
756 	return ret;
757 }
758 
759 #ifdef CONFIG_PM_SLEEP
760 static int sprd_suspend(struct device *dev)
761 {
762 	struct sprd_uart_port *sup = dev_get_drvdata(dev);
763 
764 	uart_suspend_port(&sprd_uart_driver, &sup->port);
765 
766 	return 0;
767 }
768 
769 static int sprd_resume(struct device *dev)
770 {
771 	struct sprd_uart_port *sup = dev_get_drvdata(dev);
772 
773 	uart_resume_port(&sprd_uart_driver, &sup->port);
774 
775 	return 0;
776 }
777 #endif
778 
779 static SIMPLE_DEV_PM_OPS(sprd_pm_ops, sprd_suspend, sprd_resume);
780 
781 static const struct of_device_id serial_ids[] = {
782 	{.compatible = "sprd,sc9836-uart",},
783 	{}
784 };
785 MODULE_DEVICE_TABLE(of, serial_ids);
786 
787 static struct platform_driver sprd_platform_driver = {
788 	.probe		= sprd_probe,
789 	.remove		= sprd_remove,
790 	.driver		= {
791 		.name	= "sprd_serial",
792 		.of_match_table = of_match_ptr(serial_ids),
793 		.pm	= &sprd_pm_ops,
794 	},
795 };
796 
797 module_platform_driver(sprd_platform_driver);
798 
799 MODULE_LICENSE("GPL v2");
800 MODULE_DESCRIPTION("Spreadtrum SoC serial driver series");
801