xref: /linux/drivers/tty/serial/sprd_serial.c (revision e3b3d0f549c1d19b94e6ac55c66643166ea649ef) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2012-2015 Spreadtrum Communications Inc.
4  *
5  * This software is licensed under the terms of the GNU General Public
6  * License version 2, as published by the Free Software Foundation, and
7  * may be copied, distributed, and modified under those terms.
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  */
14 
15 #if defined(CONFIG_SERIAL_SPRD_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
16 #define SUPPORT_SYSRQ
17 #endif
18 
19 #include <linux/clk.h>
20 #include <linux/console.h>
21 #include <linux/delay.h>
22 #include <linux/io.h>
23 #include <linux/ioport.h>
24 #include <linux/kernel.h>
25 #include <linux/module.h>
26 #include <linux/of.h>
27 #include <linux/platform_device.h>
28 #include <linux/serial_core.h>
29 #include <linux/serial.h>
30 #include <linux/slab.h>
31 #include <linux/tty.h>
32 #include <linux/tty_flip.h>
33 
34 /* device name */
35 #define UART_NR_MAX		8
36 #define SPRD_TTY_NAME		"ttyS"
37 #define SPRD_FIFO_SIZE		128
38 #define SPRD_DEF_RATE		26000000
39 #define SPRD_BAUD_IO_LIMIT	3000000
40 #define SPRD_TIMEOUT		256000
41 
42 /* the offset of serial registers and BITs for them */
43 /* data registers */
44 #define SPRD_TXD		0x0000
45 #define SPRD_RXD		0x0004
46 
47 /* line status register and its BITs  */
48 #define SPRD_LSR		0x0008
49 #define SPRD_LSR_OE		BIT(4)
50 #define SPRD_LSR_FE		BIT(3)
51 #define SPRD_LSR_PE		BIT(2)
52 #define SPRD_LSR_BI		BIT(7)
53 #define SPRD_LSR_TX_OVER	BIT(15)
54 
55 /* data number in TX and RX fifo */
56 #define SPRD_STS1		0x000C
57 
58 /* interrupt enable register and its BITs */
59 #define SPRD_IEN		0x0010
60 #define SPRD_IEN_RX_FULL	BIT(0)
61 #define SPRD_IEN_TX_EMPTY	BIT(1)
62 #define SPRD_IEN_BREAK_DETECT	BIT(7)
63 #define SPRD_IEN_TIMEOUT	BIT(13)
64 
65 /* interrupt clear register */
66 #define SPRD_ICLR		0x0014
67 #define SPRD_ICLR_TIMEOUT	BIT(13)
68 
69 /* line control register */
70 #define SPRD_LCR		0x0018
71 #define SPRD_LCR_STOP_1BIT	0x10
72 #define SPRD_LCR_STOP_2BIT	0x30
73 #define SPRD_LCR_DATA_LEN	(BIT(2) | BIT(3))
74 #define SPRD_LCR_DATA_LEN5	0x0
75 #define SPRD_LCR_DATA_LEN6	0x4
76 #define SPRD_LCR_DATA_LEN7	0x8
77 #define SPRD_LCR_DATA_LEN8	0xc
78 #define SPRD_LCR_PARITY	(BIT(0) | BIT(1))
79 #define SPRD_LCR_PARITY_EN	0x2
80 #define SPRD_LCR_EVEN_PAR	0x0
81 #define SPRD_LCR_ODD_PAR	0x1
82 
83 /* control register 1 */
84 #define SPRD_CTL1			0x001C
85 #define RX_HW_FLOW_CTL_THLD	BIT(6)
86 #define RX_HW_FLOW_CTL_EN	BIT(7)
87 #define TX_HW_FLOW_CTL_EN	BIT(8)
88 #define RX_TOUT_THLD_DEF	0x3E00
89 #define RX_HFC_THLD_DEF	0x40
90 
91 /* fifo threshold register */
92 #define SPRD_CTL2		0x0020
93 #define THLD_TX_EMPTY	0x40
94 #define THLD_RX_FULL	0x40
95 
96 /* config baud rate register */
97 #define SPRD_CLKD0		0x0024
98 #define SPRD_CLKD1		0x0028
99 
100 /* interrupt mask status register */
101 #define SPRD_IMSR			0x002C
102 #define SPRD_IMSR_RX_FIFO_FULL		BIT(0)
103 #define SPRD_IMSR_TX_FIFO_EMPTY	BIT(1)
104 #define SPRD_IMSR_BREAK_DETECT		BIT(7)
105 #define SPRD_IMSR_TIMEOUT		BIT(13)
106 
107 struct reg_backup {
108 	u32 ien;
109 	u32 ctrl0;
110 	u32 ctrl1;
111 	u32 ctrl2;
112 	u32 clkd0;
113 	u32 clkd1;
114 	u32 dspwait;
115 };
116 
117 struct sprd_uart_port {
118 	struct uart_port port;
119 	struct reg_backup reg_bak;
120 	char name[16];
121 };
122 
123 static struct sprd_uart_port *sprd_port[UART_NR_MAX];
124 static int sprd_ports_num;
125 
126 static inline unsigned int serial_in(struct uart_port *port, int offset)
127 {
128 	return readl_relaxed(port->membase + offset);
129 }
130 
131 static inline void serial_out(struct uart_port *port, int offset, int value)
132 {
133 	writel_relaxed(value, port->membase + offset);
134 }
135 
136 static unsigned int sprd_tx_empty(struct uart_port *port)
137 {
138 	if (serial_in(port, SPRD_STS1) & 0xff00)
139 		return 0;
140 	else
141 		return TIOCSER_TEMT;
142 }
143 
144 static unsigned int sprd_get_mctrl(struct uart_port *port)
145 {
146 	return TIOCM_DSR | TIOCM_CTS;
147 }
148 
149 static void sprd_set_mctrl(struct uart_port *port, unsigned int mctrl)
150 {
151 	/* nothing to do */
152 }
153 
154 static void sprd_stop_tx(struct uart_port *port)
155 {
156 	unsigned int ien, iclr;
157 
158 	iclr = serial_in(port, SPRD_ICLR);
159 	ien = serial_in(port, SPRD_IEN);
160 
161 	iclr |= SPRD_IEN_TX_EMPTY;
162 	ien &= ~SPRD_IEN_TX_EMPTY;
163 
164 	serial_out(port, SPRD_ICLR, iclr);
165 	serial_out(port, SPRD_IEN, ien);
166 }
167 
168 static void sprd_start_tx(struct uart_port *port)
169 {
170 	unsigned int ien;
171 
172 	ien = serial_in(port, SPRD_IEN);
173 	if (!(ien & SPRD_IEN_TX_EMPTY)) {
174 		ien |= SPRD_IEN_TX_EMPTY;
175 		serial_out(port, SPRD_IEN, ien);
176 	}
177 }
178 
179 static void sprd_stop_rx(struct uart_port *port)
180 {
181 	unsigned int ien, iclr;
182 
183 	iclr = serial_in(port, SPRD_ICLR);
184 	ien = serial_in(port, SPRD_IEN);
185 
186 	ien &= ~(SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT);
187 	iclr |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT;
188 
189 	serial_out(port, SPRD_IEN, ien);
190 	serial_out(port, SPRD_ICLR, iclr);
191 }
192 
193 /* The Sprd serial does not support this function. */
194 static void sprd_break_ctl(struct uart_port *port, int break_state)
195 {
196 	/* nothing to do */
197 }
198 
199 static int handle_lsr_errors(struct uart_port *port,
200 			     unsigned int *flag,
201 			     unsigned int *lsr)
202 {
203 	int ret = 0;
204 
205 	/* statistics */
206 	if (*lsr & SPRD_LSR_BI) {
207 		*lsr &= ~(SPRD_LSR_FE | SPRD_LSR_PE);
208 		port->icount.brk++;
209 		ret = uart_handle_break(port);
210 		if (ret)
211 			return ret;
212 	} else if (*lsr & SPRD_LSR_PE)
213 		port->icount.parity++;
214 	else if (*lsr & SPRD_LSR_FE)
215 		port->icount.frame++;
216 	if (*lsr & SPRD_LSR_OE)
217 		port->icount.overrun++;
218 
219 	/* mask off conditions which should be ignored */
220 	*lsr &= port->read_status_mask;
221 	if (*lsr & SPRD_LSR_BI)
222 		*flag = TTY_BREAK;
223 	else if (*lsr & SPRD_LSR_PE)
224 		*flag = TTY_PARITY;
225 	else if (*lsr & SPRD_LSR_FE)
226 		*flag = TTY_FRAME;
227 
228 	return ret;
229 }
230 
231 static inline void sprd_rx(struct uart_port *port)
232 {
233 	struct tty_port *tty = &port->state->port;
234 	unsigned int ch, flag, lsr, max_count = SPRD_TIMEOUT;
235 
236 	while ((serial_in(port, SPRD_STS1) & 0x00ff) && max_count--) {
237 		lsr = serial_in(port, SPRD_LSR);
238 		ch = serial_in(port, SPRD_RXD);
239 		flag = TTY_NORMAL;
240 		port->icount.rx++;
241 
242 		if (lsr & (SPRD_LSR_BI | SPRD_LSR_PE |
243 			SPRD_LSR_FE | SPRD_LSR_OE))
244 			if (handle_lsr_errors(port, &lsr, &flag))
245 				continue;
246 		if (uart_handle_sysrq_char(port, ch))
247 			continue;
248 
249 		uart_insert_char(port, lsr, SPRD_LSR_OE, ch, flag);
250 	}
251 
252 	tty_flip_buffer_push(tty);
253 }
254 
255 static inline void sprd_tx(struct uart_port *port)
256 {
257 	struct circ_buf *xmit = &port->state->xmit;
258 	int count;
259 
260 	if (port->x_char) {
261 		serial_out(port, SPRD_TXD, port->x_char);
262 		port->icount.tx++;
263 		port->x_char = 0;
264 		return;
265 	}
266 
267 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
268 		sprd_stop_tx(port);
269 		return;
270 	}
271 
272 	count = THLD_TX_EMPTY;
273 	do {
274 		serial_out(port, SPRD_TXD, xmit->buf[xmit->tail]);
275 		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
276 		port->icount.tx++;
277 		if (uart_circ_empty(xmit))
278 			break;
279 	} while (--count > 0);
280 
281 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
282 		uart_write_wakeup(port);
283 
284 	if (uart_circ_empty(xmit))
285 		sprd_stop_tx(port);
286 }
287 
288 /* this handles the interrupt from one port */
289 static irqreturn_t sprd_handle_irq(int irq, void *dev_id)
290 {
291 	struct uart_port *port = dev_id;
292 	unsigned int ims;
293 
294 	spin_lock(&port->lock);
295 
296 	ims = serial_in(port, SPRD_IMSR);
297 
298 	if (!ims) {
299 		spin_unlock(&port->lock);
300 		return IRQ_NONE;
301 	}
302 
303 	if (ims & SPRD_IMSR_TIMEOUT)
304 		serial_out(port, SPRD_ICLR, SPRD_ICLR_TIMEOUT);
305 
306 	if (ims & (SPRD_IMSR_RX_FIFO_FULL |
307 		SPRD_IMSR_BREAK_DETECT | SPRD_IMSR_TIMEOUT))
308 		sprd_rx(port);
309 
310 	if (ims & SPRD_IMSR_TX_FIFO_EMPTY)
311 		sprd_tx(port);
312 
313 	spin_unlock(&port->lock);
314 
315 	return IRQ_HANDLED;
316 }
317 
318 static int sprd_startup(struct uart_port *port)
319 {
320 	int ret = 0;
321 	unsigned int ien, fc;
322 	unsigned int timeout;
323 	struct sprd_uart_port *sp;
324 	unsigned long flags;
325 
326 	serial_out(port, SPRD_CTL2, ((THLD_TX_EMPTY << 8) | THLD_RX_FULL));
327 
328 	/* clear rx fifo */
329 	timeout = SPRD_TIMEOUT;
330 	while (timeout-- && serial_in(port, SPRD_STS1) & 0x00ff)
331 		serial_in(port, SPRD_RXD);
332 
333 	/* clear tx fifo */
334 	timeout = SPRD_TIMEOUT;
335 	while (timeout-- && serial_in(port, SPRD_STS1) & 0xff00)
336 		cpu_relax();
337 
338 	/* clear interrupt */
339 	serial_out(port, SPRD_IEN, 0);
340 	serial_out(port, SPRD_ICLR, ~0);
341 
342 	/* allocate irq */
343 	sp = container_of(port, struct sprd_uart_port, port);
344 	snprintf(sp->name, sizeof(sp->name), "sprd_serial%d", port->line);
345 	ret = devm_request_irq(port->dev, port->irq, sprd_handle_irq,
346 				IRQF_SHARED, sp->name, port);
347 	if (ret) {
348 		dev_err(port->dev, "fail to request serial irq %d, ret=%d\n",
349 			port->irq, ret);
350 		return ret;
351 	}
352 	fc = serial_in(port, SPRD_CTL1);
353 	fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
354 	serial_out(port, SPRD_CTL1, fc);
355 
356 	/* enable interrupt */
357 	spin_lock_irqsave(&port->lock, flags);
358 	ien = serial_in(port, SPRD_IEN);
359 	ien |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT | SPRD_IEN_TIMEOUT;
360 	serial_out(port, SPRD_IEN, ien);
361 	spin_unlock_irqrestore(&port->lock, flags);
362 
363 	return 0;
364 }
365 
366 static void sprd_shutdown(struct uart_port *port)
367 {
368 	serial_out(port, SPRD_IEN, 0);
369 	serial_out(port, SPRD_ICLR, ~0);
370 	devm_free_irq(port->dev, port->irq, port);
371 }
372 
373 static void sprd_set_termios(struct uart_port *port,
374 				    struct ktermios *termios,
375 				    struct ktermios *old)
376 {
377 	unsigned int baud, quot;
378 	unsigned int lcr = 0, fc;
379 	unsigned long flags;
380 
381 	/* ask the core to calculate the divisor for us */
382 	baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
383 
384 	quot = (unsigned int)((port->uartclk + baud / 2) / baud);
385 
386 	/* set data length */
387 	switch (termios->c_cflag & CSIZE) {
388 	case CS5:
389 		lcr |= SPRD_LCR_DATA_LEN5;
390 		break;
391 	case CS6:
392 		lcr |= SPRD_LCR_DATA_LEN6;
393 		break;
394 	case CS7:
395 		lcr |= SPRD_LCR_DATA_LEN7;
396 		break;
397 	case CS8:
398 	default:
399 		lcr |= SPRD_LCR_DATA_LEN8;
400 		break;
401 	}
402 
403 	/* calculate stop bits */
404 	lcr &= ~(SPRD_LCR_STOP_1BIT | SPRD_LCR_STOP_2BIT);
405 	if (termios->c_cflag & CSTOPB)
406 		lcr |= SPRD_LCR_STOP_2BIT;
407 	else
408 		lcr |= SPRD_LCR_STOP_1BIT;
409 
410 	/* calculate parity */
411 	lcr &= ~SPRD_LCR_PARITY;
412 	termios->c_cflag &= ~CMSPAR;	/* no support mark/space */
413 	if (termios->c_cflag & PARENB) {
414 		lcr |= SPRD_LCR_PARITY_EN;
415 		if (termios->c_cflag & PARODD)
416 			lcr |= SPRD_LCR_ODD_PAR;
417 		else
418 			lcr |= SPRD_LCR_EVEN_PAR;
419 	}
420 
421 	spin_lock_irqsave(&port->lock, flags);
422 
423 	/* update the per-port timeout */
424 	uart_update_timeout(port, termios->c_cflag, baud);
425 
426 	port->read_status_mask = SPRD_LSR_OE;
427 	if (termios->c_iflag & INPCK)
428 		port->read_status_mask |= SPRD_LSR_FE | SPRD_LSR_PE;
429 	if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
430 		port->read_status_mask |= SPRD_LSR_BI;
431 
432 	/* characters to ignore */
433 	port->ignore_status_mask = 0;
434 	if (termios->c_iflag & IGNPAR)
435 		port->ignore_status_mask |= SPRD_LSR_PE | SPRD_LSR_FE;
436 	if (termios->c_iflag & IGNBRK) {
437 		port->ignore_status_mask |= SPRD_LSR_BI;
438 		/*
439 		 * If we're ignoring parity and break indicators,
440 		 * ignore overruns too (for real raw support).
441 		 */
442 		if (termios->c_iflag & IGNPAR)
443 			port->ignore_status_mask |= SPRD_LSR_OE;
444 	}
445 
446 	/* flow control */
447 	fc = serial_in(port, SPRD_CTL1);
448 	fc &= ~(RX_HW_FLOW_CTL_THLD | RX_HW_FLOW_CTL_EN | TX_HW_FLOW_CTL_EN);
449 	if (termios->c_cflag & CRTSCTS) {
450 		fc |= RX_HW_FLOW_CTL_THLD;
451 		fc |= RX_HW_FLOW_CTL_EN;
452 		fc |= TX_HW_FLOW_CTL_EN;
453 	}
454 
455 	/* clock divider bit0~bit15 */
456 	serial_out(port, SPRD_CLKD0, quot & 0xffff);
457 
458 	/* clock divider bit16~bit20 */
459 	serial_out(port, SPRD_CLKD1, (quot & 0x1f0000) >> 16);
460 	serial_out(port, SPRD_LCR, lcr);
461 	fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
462 	serial_out(port, SPRD_CTL1, fc);
463 
464 	spin_unlock_irqrestore(&port->lock, flags);
465 
466 	/* Don't rewrite B0 */
467 	if (tty_termios_baud_rate(termios))
468 		tty_termios_encode_baud_rate(termios, baud, baud);
469 }
470 
471 static const char *sprd_type(struct uart_port *port)
472 {
473 	return "SPX";
474 }
475 
476 static void sprd_release_port(struct uart_port *port)
477 {
478 	/* nothing to do */
479 }
480 
481 static int sprd_request_port(struct uart_port *port)
482 {
483 	return 0;
484 }
485 
486 static void sprd_config_port(struct uart_port *port, int flags)
487 {
488 	if (flags & UART_CONFIG_TYPE)
489 		port->type = PORT_SPRD;
490 }
491 
492 static int sprd_verify_port(struct uart_port *port,
493 				   struct serial_struct *ser)
494 {
495 	if (ser->type != PORT_SPRD)
496 		return -EINVAL;
497 	if (port->irq != ser->irq)
498 		return -EINVAL;
499 	if (port->iotype != ser->io_type)
500 		return -EINVAL;
501 	return 0;
502 }
503 
504 static const struct uart_ops serial_sprd_ops = {
505 	.tx_empty = sprd_tx_empty,
506 	.get_mctrl = sprd_get_mctrl,
507 	.set_mctrl = sprd_set_mctrl,
508 	.stop_tx = sprd_stop_tx,
509 	.start_tx = sprd_start_tx,
510 	.stop_rx = sprd_stop_rx,
511 	.break_ctl = sprd_break_ctl,
512 	.startup = sprd_startup,
513 	.shutdown = sprd_shutdown,
514 	.set_termios = sprd_set_termios,
515 	.type = sprd_type,
516 	.release_port = sprd_release_port,
517 	.request_port = sprd_request_port,
518 	.config_port = sprd_config_port,
519 	.verify_port = sprd_verify_port,
520 };
521 
522 #ifdef CONFIG_SERIAL_SPRD_CONSOLE
523 static void wait_for_xmitr(struct uart_port *port)
524 {
525 	unsigned int status, tmout = 10000;
526 
527 	/* wait up to 10ms for the character(s) to be sent */
528 	do {
529 		status = serial_in(port, SPRD_STS1);
530 		if (--tmout == 0)
531 			break;
532 		udelay(1);
533 	} while (status & 0xff00);
534 }
535 
536 static void sprd_console_putchar(struct uart_port *port, int ch)
537 {
538 	wait_for_xmitr(port);
539 	serial_out(port, SPRD_TXD, ch);
540 }
541 
542 static void sprd_console_write(struct console *co, const char *s,
543 				      unsigned int count)
544 {
545 	struct uart_port *port = &sprd_port[co->index]->port;
546 	int locked = 1;
547 	unsigned long flags;
548 
549 	if (port->sysrq)
550 		locked = 0;
551 	else if (oops_in_progress)
552 		locked = spin_trylock_irqsave(&port->lock, flags);
553 	else
554 		spin_lock_irqsave(&port->lock, flags);
555 
556 	uart_console_write(port, s, count, sprd_console_putchar);
557 
558 	/* wait for transmitter to become empty */
559 	wait_for_xmitr(port);
560 
561 	if (locked)
562 		spin_unlock_irqrestore(&port->lock, flags);
563 }
564 
565 static int __init sprd_console_setup(struct console *co, char *options)
566 {
567 	struct uart_port *port;
568 	int baud = 115200;
569 	int bits = 8;
570 	int parity = 'n';
571 	int flow = 'n';
572 
573 	if (co->index >= UART_NR_MAX || co->index < 0)
574 		co->index = 0;
575 
576 	port = &sprd_port[co->index]->port;
577 	if (port == NULL) {
578 		pr_info("serial port %d not yet initialized\n", co->index);
579 		return -ENODEV;
580 	}
581 	if (options)
582 		uart_parse_options(options, &baud, &parity, &bits, &flow);
583 
584 	return uart_set_options(port, co, baud, parity, bits, flow);
585 }
586 
587 static struct uart_driver sprd_uart_driver;
588 static struct console sprd_console = {
589 	.name = SPRD_TTY_NAME,
590 	.write = sprd_console_write,
591 	.device = uart_console_device,
592 	.setup = sprd_console_setup,
593 	.flags = CON_PRINTBUFFER,
594 	.index = -1,
595 	.data = &sprd_uart_driver,
596 };
597 
598 #define SPRD_CONSOLE	(&sprd_console)
599 
600 /* Support for earlycon */
601 static void sprd_putc(struct uart_port *port, int c)
602 {
603 	unsigned int timeout = SPRD_TIMEOUT;
604 
605 	while (timeout-- &&
606 		   !(readl(port->membase + SPRD_LSR) & SPRD_LSR_TX_OVER))
607 		cpu_relax();
608 
609 	writeb(c, port->membase + SPRD_TXD);
610 }
611 
612 static void sprd_early_write(struct console *con, const char *s,
613 				    unsigned n)
614 {
615 	struct earlycon_device *dev = con->data;
616 
617 	uart_console_write(&dev->port, s, n, sprd_putc);
618 }
619 
620 static int __init sprd_early_console_setup(
621 				struct earlycon_device *device,
622 				const char *opt)
623 {
624 	if (!device->port.membase)
625 		return -ENODEV;
626 
627 	device->con->write = sprd_early_write;
628 	return 0;
629 }
630 OF_EARLYCON_DECLARE(sprd_serial, "sprd,sc9836-uart",
631 		    sprd_early_console_setup);
632 
633 #else /* !CONFIG_SERIAL_SPRD_CONSOLE */
634 #define SPRD_CONSOLE		NULL
635 #endif
636 
637 static struct uart_driver sprd_uart_driver = {
638 	.owner = THIS_MODULE,
639 	.driver_name = "sprd_serial",
640 	.dev_name = SPRD_TTY_NAME,
641 	.major = 0,
642 	.minor = 0,
643 	.nr = UART_NR_MAX,
644 	.cons = SPRD_CONSOLE,
645 };
646 
647 static int sprd_probe_dt_alias(int index, struct device *dev)
648 {
649 	struct device_node *np;
650 	int ret = index;
651 
652 	if (!IS_ENABLED(CONFIG_OF))
653 		return ret;
654 
655 	np = dev->of_node;
656 	if (!np)
657 		return ret;
658 
659 	ret = of_alias_get_id(np, "serial");
660 	if (ret < 0)
661 		ret = index;
662 	else if (ret >= ARRAY_SIZE(sprd_port) || sprd_port[ret] != NULL) {
663 		dev_warn(dev, "requested serial port %d not available.\n", ret);
664 		ret = index;
665 	}
666 
667 	return ret;
668 }
669 
670 static int sprd_remove(struct platform_device *dev)
671 {
672 	struct sprd_uart_port *sup = platform_get_drvdata(dev);
673 
674 	if (sup) {
675 		uart_remove_one_port(&sprd_uart_driver, &sup->port);
676 		sprd_port[sup->port.line] = NULL;
677 		sprd_ports_num--;
678 	}
679 
680 	if (!sprd_ports_num)
681 		uart_unregister_driver(&sprd_uart_driver);
682 
683 	return 0;
684 }
685 
686 static int sprd_probe(struct platform_device *pdev)
687 {
688 	struct resource *res;
689 	struct uart_port *up;
690 	struct clk *clk;
691 	int irq;
692 	int index;
693 	int ret;
694 
695 	for (index = 0; index < ARRAY_SIZE(sprd_port); index++)
696 		if (sprd_port[index] == NULL)
697 			break;
698 
699 	if (index == ARRAY_SIZE(sprd_port))
700 		return -EBUSY;
701 
702 	index = sprd_probe_dt_alias(index, &pdev->dev);
703 
704 	sprd_port[index] = devm_kzalloc(&pdev->dev,
705 		sizeof(*sprd_port[index]), GFP_KERNEL);
706 	if (!sprd_port[index])
707 		return -ENOMEM;
708 
709 	up = &sprd_port[index]->port;
710 	up->dev = &pdev->dev;
711 	up->line = index;
712 	up->type = PORT_SPRD;
713 	up->iotype = UPIO_MEM;
714 	up->uartclk = SPRD_DEF_RATE;
715 	up->fifosize = SPRD_FIFO_SIZE;
716 	up->ops = &serial_sprd_ops;
717 	up->flags = UPF_BOOT_AUTOCONF;
718 
719 	clk = devm_clk_get(&pdev->dev, NULL);
720 	if (!IS_ERR_OR_NULL(clk))
721 		up->uartclk = clk_get_rate(clk);
722 
723 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
724 	if (!res) {
725 		dev_err(&pdev->dev, "not provide mem resource\n");
726 		return -ENODEV;
727 	}
728 	up->mapbase = res->start;
729 	up->membase = devm_ioremap_resource(&pdev->dev, res);
730 	if (IS_ERR(up->membase))
731 		return PTR_ERR(up->membase);
732 
733 	irq = platform_get_irq(pdev, 0);
734 	if (irq < 0) {
735 		dev_err(&pdev->dev, "not provide irq resource: %d\n", irq);
736 		return irq;
737 	}
738 	up->irq = irq;
739 
740 	if (!sprd_ports_num) {
741 		ret = uart_register_driver(&sprd_uart_driver);
742 		if (ret < 0) {
743 			pr_err("Failed to register SPRD-UART driver\n");
744 			return ret;
745 		}
746 	}
747 	sprd_ports_num++;
748 
749 	ret = uart_add_one_port(&sprd_uart_driver, up);
750 	if (ret) {
751 		sprd_port[index] = NULL;
752 		sprd_remove(pdev);
753 	}
754 
755 	platform_set_drvdata(pdev, up);
756 
757 	return ret;
758 }
759 
760 #ifdef CONFIG_PM_SLEEP
761 static int sprd_suspend(struct device *dev)
762 {
763 	struct sprd_uart_port *sup = dev_get_drvdata(dev);
764 
765 	uart_suspend_port(&sprd_uart_driver, &sup->port);
766 
767 	return 0;
768 }
769 
770 static int sprd_resume(struct device *dev)
771 {
772 	struct sprd_uart_port *sup = dev_get_drvdata(dev);
773 
774 	uart_resume_port(&sprd_uart_driver, &sup->port);
775 
776 	return 0;
777 }
778 #endif
779 
780 static SIMPLE_DEV_PM_OPS(sprd_pm_ops, sprd_suspend, sprd_resume);
781 
782 static const struct of_device_id serial_ids[] = {
783 	{.compatible = "sprd,sc9836-uart",},
784 	{}
785 };
786 MODULE_DEVICE_TABLE(of, serial_ids);
787 
788 static struct platform_driver sprd_platform_driver = {
789 	.probe		= sprd_probe,
790 	.remove		= sprd_remove,
791 	.driver		= {
792 		.name	= "sprd_serial",
793 		.of_match_table = of_match_ptr(serial_ids),
794 		.pm	= &sprd_pm_ops,
795 	},
796 };
797 
798 module_platform_driver(sprd_platform_driver);
799 
800 MODULE_LICENSE("GPL v2");
801 MODULE_DESCRIPTION("Spreadtrum SoC serial driver series");
802