summaryrefslogtreecommitdiff
path: root/drivers/tty/serial/arc_uart.c
blob: 03ebe401fff7483c269778f4f57ce923c1282267 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
/*
 * ARC On-Chip(fpga) UART Driver
 *
 * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * vineetg: July 10th 2012
 *  -Decoupled the driver from arch/arc
 *    +Using platform_get_resource() for irq/membase (thx to bfin_uart.c)
 *    +Using early_platform_xxx() for early console (thx to mach-shmobile/xxx)
 *
 * Vineetg: Aug 21st 2010
 *  -Is uart_tx_stopped() not done in tty write path as it has already been
 *   taken care of, in serial core
 *
 * Vineetg: Aug 18th 2010
 *  -New Serial Core based ARC UART driver
 *  -Derived largely from blackfin driver albiet with some major tweaks
 *
 * TODO:
 *  -check if sysreq works
 */

#if defined(CONFIG_SERIAL_ARC_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/module.h>
#include <linux/serial.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/platform_device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/io.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>

/*************************************
 * ARC UART Hardware Specs
 ************************************/
#define ARC_UART_TX_FIFO_SIZE  1

/*
 * UART Register set (this is not a Standards Compliant IP)
 * Also each reg is Word aligned, but only 8 bits wide
 */
#define R_ID0	0
#define R_ID1	4
#define R_ID2	8
#define R_ID3	12
#define R_DATA	16
#define R_STS	20
#define R_BAUDL	24
#define R_BAUDH	28

/* Bits for UART Status Reg (R/W) */
#define RXIENB  0x04	/* Receive Interrupt Enable */
#define TXIENB  0x40	/* Transmit Interrupt Enable */

#define RXEMPTY 0x20	/* Receive FIFO Empty: No char receivede */
#define TXEMPTY 0x80	/* Transmit FIFO Empty, thus char can be written into */

#define RXFULL  0x08	/* Receive FIFO full */
#define RXFULL1 0x10	/* Receive FIFO has space for 1 char (tot space=4) */

#define RXFERR  0x01	/* Frame Error: Stop Bit not detected */
#define RXOERR  0x02	/* OverFlow Err: Char recv but RXFULL still set */

/* Uart bit fiddling helpers: lowest level */
#define RBASE(port, reg)      (port->membase + reg)
#define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
#define UART_REG_GET(u, r)    readb(RBASE(u, r))

#define UART_REG_OR(u, r, v)  UART_REG_SET(u, r, UART_REG_GET(u, r) | (v))
#define UART_REG_CLR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) & ~(v))

/* Uart bit fiddling helpers: API level */
#define UART_SET_DATA(uart, val)   UART_REG_SET(uart, R_DATA, val)
#define UART_GET_DATA(uart)        UART_REG_GET(uart, R_DATA)

#define UART_SET_BAUDH(uart, val)  UART_REG_SET(uart, R_BAUDH, val)
#define UART_SET_BAUDL(uart, val)  UART_REG_SET(uart, R_BAUDL, val)

#define UART_CLR_STATUS(uart, val) UART_REG_CLR(uart, R_STS, val)
#define UART_GET_STATUS(uart)      UART_REG_GET(uart, R_STS)

#define UART_ALL_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB|TXIENB)
#define UART_RX_IRQ_DISABLE(uart)  UART_REG_CLR(uart, R_STS, RXIENB)
#define UART_TX_IRQ_DISABLE(uart)  UART_REG_CLR(uart, R_STS, TXIENB)

#define UART_ALL_IRQ_ENABLE(uart)  UART_REG_OR(uart, R_STS, RXIENB|TXIENB)
#define UART_RX_IRQ_ENABLE(uart)   UART_REG_OR(uart, R_STS, RXIENB)
#define UART_TX_IRQ_ENABLE(uart)   UART_REG_OR(uart, R_STS, TXIENB)

#define ARC_SERIAL_DEV_NAME	"ttyARC"

struct arc_uart_port {
	struct uart_port port;
	unsigned long baud;
};

#define to_arc_port(uport)  container_of(uport, struct arc_uart_port, port)

static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];

#ifdef CONFIG_SERIAL_ARC_CONSOLE
static struct console arc_console;
#endif

#define DRIVER_NAME	"arc-uart"

static struct uart_driver arc_uart_driver = {
	.owner		= THIS_MODULE,
	.driver_name	= DRIVER_NAME,
	.dev_name	= ARC_SERIAL_DEV_NAME,
	.major		= 0,
	.minor		= 0,
	.nr		= CONFIG_SERIAL_ARC_NR_PORTS,
#ifdef CONFIG_SERIAL_ARC_CONSOLE
	.cons		= &arc_console,
#endif
};

static void arc_serial_stop_rx(struct uart_port *port)
{
	UART_RX_IRQ_DISABLE(port);
}

static void arc_serial_stop_tx(struct uart_port *port)
{
	while (!(UART_GET_STATUS(port) & TXEMPTY))
		cpu_relax();

	UART_TX_IRQ_DISABLE(port);
}

/*
 * Return TIOCSER_TEMT when transmitter is not busy.
 */
static unsigned int arc_serial_tx_empty(struct uart_port *port)
{
	unsigned int stat;

	stat = UART_GET_STATUS(port);
	if (stat & TXEMPTY)
		return TIOCSER_TEMT;

	return 0;
}

/*
 * Driver internal routine, used by both tty(serial core) as well as tx-isr
 *  -Called under spinlock in either cases
 *  -also tty->stopped has already been checked
 *     = by uart_start( ) before calling us
 *     = tx_ist checks that too before calling
 */
static void arc_serial_tx_chars(struct uart_port *port)
{
	struct circ_buf *xmit = &port->state->xmit;
	int sent = 0;
	unsigned char ch;

	if (unlikely(port->x_char)) {
		UART_SET_DATA(port, port->x_char);
		port->icount.tx++;
		port->x_char = 0;
		sent = 1;
	} else if (!uart_circ_empty(xmit)) {
		ch = xmit->buf[xmit->tail];
		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
		port->icount.tx++;
		while (!(UART_GET_STATUS(port) & TXEMPTY))
			cpu_relax();
		UART_SET_DATA(port, ch);
		sent = 1;
	}

	/*
	 * If num chars in xmit buffer are too few, ask tty layer for more.
	 * By Hard ISR to schedule processing in software interrupt part
	 */
	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
		uart_write_wakeup(port);

	if (sent)
		UART_TX_IRQ_ENABLE(port);
}

/*
 * port is locked and interrupts are disabled
 * uart_start( ) calls us under the port spinlock irqsave
 */
static void arc_serial_start_tx(struct uart_port *port)
{
	arc_serial_tx_chars(port);
}

static void arc_serial_rx_chars(struct uart_port *port, unsigned int status)
{
	unsigned int ch, flg = 0;

	/*
	 * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
	 * is very subtle. Here's how ...
	 * Upon getting a RX-Intr, such that RX-EMPTY=0, meaning data available,
	 * driver reads the DATA Reg and keeps doing that in a loop, until
	 * RX-EMPTY=1. Multiple chars being avail, with a single Interrupt,
	 * before RX-EMPTY=0, implies some sort of buffering going on in the
	 * controller, which is indeed the Rx-FIFO.
	 */
	do {
		/*
		 * This could be an Rx Intr for err (no data),
		 * so check err and clear that Intr first
		 */
		if (unlikely(status & (RXOERR | RXFERR))) {
			if (status & RXOERR) {
				port->icount.overrun++;
				flg = TTY_OVERRUN;
				UART_CLR_STATUS(port, RXOERR);
			}

			if (status & RXFERR) {
				port->icount.frame++;
				flg = TTY_FRAME;
				UART_CLR_STATUS(port, RXFERR);
			}
		} else
			flg = TTY_NORMAL;

		if (status & RXEMPTY)
			continue;

		ch = UART_GET_DATA(port);
		port->icount.rx++;

		if (!(uart_handle_sysrq_char(port, ch)))
			uart_insert_char(port, status, RXOERR, ch, flg);

		spin_unlock(&port->lock);
		tty_flip_buffer_push(&port->state->port);
		spin_lock(&port->lock);
	} while (!((status = UART_GET_STATUS(port)) & RXEMPTY));
}

/*
 * A note on the Interrupt handling state machine of this driver
 *
 * kernel printk writes funnel thru the console driver framework and in order
 * to keep things simple as well as efficient, it writes to UART in polled
 * mode, in one shot, and exits.
 *
 * OTOH, Userland output (via tty layer), uses interrupt based writes as there
 * can be undeterministic delay between char writes.
 *
 * Thus Rx-interrupts are always enabled, while tx-interrupts are by default
 * disabled.
 *
 * When tty has some data to send out, serial core calls driver's start_tx
 * which
 *   -checks-if-tty-buffer-has-char-to-send
 *   -writes-data-to-uart
 *   -enable-tx-intr
 *
 * Once data bits are pushed out, controller raises the Tx-room-avail-Interrupt.
 * The first thing Tx ISR does is disable further Tx interrupts (as this could
 * be the last char to send, before settling down into the quiet polled mode).
 * It then calls the exact routine used by tty layer write to send out any
 * more char in tty buffer. In case of sending, it re-enables Tx-intr. In case
 * of no data, it remains disabled.
 * This is how the transmit state machine is dynamically switched on/off
 */

static irqreturn_t arc_serial_isr(int irq, void *dev_id)
{
	struct uart_port *port = dev_id;
	unsigned int status;

	status = UART_GET_STATUS(port);

	/*
	 * Single IRQ for both Rx (data available) Tx (room available) Interrupt
	 * notifications from the UART Controller.
	 * To demultiplex between the two, we check the relevant bits
	 */
	if (status & RXIENB) {

		/* already in ISR, no need of xx_irqsave */
		spin_lock(&port->lock);
		arc_serial_rx_chars(port, status);
		spin_unlock(&port->lock);
	}

	if ((status & TXIENB) && (status & TXEMPTY)) {

		/* Unconditionally disable further Tx-Interrupts.
		 * will be enabled by tx_chars() if needed.
		 */
		UART_TX_IRQ_DISABLE(port);

		spin_lock(&port->lock);

		if (!uart_tx_stopped(port))
			arc_serial_tx_chars(port);

		spin_unlock(&port->lock);
	}

	return IRQ_HANDLED;
}

static unsigned int arc_serial_get_mctrl(struct uart_port *port)
{
	/*
	 * Pretend we have a Modem status reg and following bits are
	 *  always set, to satify the serial core state machine
	 *  (DSR) Data Set Ready
	 *  (CTS) Clear To Send
	 *  (CAR) Carrier Detect
	 */
	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
}

static void arc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
	/* MCR not present */
}

static void arc_serial_break_ctl(struct uart_port *port, int break_state)
{
	/* ARC UART doesn't support sending Break signal */
}

static int arc_serial_startup(struct uart_port *port)
{
	/* Before we hook up the ISR, Disable all UART Interrupts */
	UART_ALL_IRQ_DISABLE(port);

	if (request_irq(port->irq, arc_serial_isr, 0, "arc uart rx-tx", port)) {
		dev_warn(port->dev, "Unable to attach ARC UART intr\n");
		return -EBUSY;
	}

	UART_RX_IRQ_ENABLE(port); /* Only Rx IRQ enabled to begin with */

	return 0;
}

/* This is not really needed */
static void arc_serial_shutdown(struct uart_port *port)
{
	free_irq(port->irq, port);
}

static void
arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
		       struct ktermios *old)
{
	struct arc_uart_port *uart = to_arc_port(port);
	unsigned int baud, uartl, uarth, hw_val;
	unsigned long flags;

	/*
	 * Use the generic handler so that any specially encoded baud rates
	 * such as SPD_xx flags or "%B0" can be handled
	 * Max Baud I suppose will not be more than current 115K * 4
	 * Formula for ARC UART is: hw-val = ((CLK/(BAUD*4)) -1)
	 * spread over two 8-bit registers
	 */
	baud = uart_get_baud_rate(port, new, old, 0, 460800);

	hw_val = port->uartclk / (uart->baud * 4) - 1;
	uartl = hw_val & 0xFF;
	uarth = (hw_val >> 8) & 0xFF;

	spin_lock_irqsave(&port->lock, flags);

	UART_ALL_IRQ_DISABLE(port);

	UART_SET_BAUDL(port, uartl);
	UART_SET_BAUDH(port, uarth);

	UART_RX_IRQ_ENABLE(port);

	/*
	 * UART doesn't support Parity/Hardware Flow Control;
	 * Only supports 8N1 character size
	 */
	new->c_cflag &= ~(CMSPAR|CRTSCTS|CSIZE);
	new->c_cflag |= CS8;

	if (old)
		tty_termios_copy_hw(new, old);

	/* Don't rewrite B0 */
	if (tty_termios_baud_rate(new))
		tty_termios_encode_baud_rate(new, baud, baud);

	uart_update_timeout(port, new->c_cflag, baud);

	spin_unlock_irqrestore(&port->lock, flags);
}

static const char *arc_serial_type(struct uart_port *port)
{
	return port->type == PORT_ARC ? DRIVER_NAME : NULL;
}

static void arc_serial_release_port(struct uart_port *port)
{
}

static int arc_serial_request_port(struct uart_port *port)
{
	return 0;
}

/*
 * Verify the new serial_struct (for TIOCSSERIAL).
 */
static int
arc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
{
	if (port->type != PORT_UNKNOWN && ser->type != PORT_ARC)
		return -EINVAL;

	return 0;
}

/*
 * Configure/autoconfigure the port.
 */
static void arc_serial_config_port(struct uart_port *port, int flags)
{
	if (flags & UART_CONFIG_TYPE)
		port->type = PORT_ARC;
}

#ifdef CONFIG_CONSOLE_POLL

static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
{
	while (!(UART_GET_STATUS(port) & TXEMPTY))
		cpu_relax();

	UART_SET_DATA(port, chr);
}

static int arc_serial_poll_getchar(struct uart_port *port)
{
	unsigned char chr;

	while (!(UART_GET_STATUS(port) & RXEMPTY))
		cpu_relax();

	chr = UART_GET_DATA(port);
	return chr;
}
#endif

static struct uart_ops arc_serial_pops = {
	.tx_empty	= arc_serial_tx_empty,
	.set_mctrl	= arc_serial_set_mctrl,
	.get_mctrl	= arc_serial_get_mctrl,
	.stop_tx	= arc_serial_stop_tx,
	.start_tx	= arc_serial_start_tx,
	.stop_rx	= arc_serial_stop_rx,
	.break_ctl	= arc_serial_break_ctl,
	.startup	= arc_serial_startup,
	.shutdown	= arc_serial_shutdown,
	.set_termios	= arc_serial_set_termios,
	.type		= arc_serial_type,
	.release_port	= arc_serial_release_port,
	.request_port	= arc_serial_request_port,
	.config_port	= arc_serial_config_port,
	.verify_port	= arc_serial_verify_port,
#ifdef CONFIG_CONSOLE_POLL
	.poll_put_char = arc_serial_poll_putchar,
	.poll_get_char = arc_serial_poll_getchar,
#endif
};

#ifdef CONFIG_SERIAL_ARC_CONSOLE

static int arc_serial_console_setup(struct console *co, char *options)
{
	struct uart_port *port;
	int baud = 115200;
	int bits = 8;
	int parity = 'n';
	int flow = 'n';

	if (co->index < 0 || co->index >= CONFIG_SERIAL_ARC_NR_PORTS)
		return -ENODEV;

	/*
	 * The uart port backing the console (e.g. ttyARC1) might not have been
	 * init yet. If so, defer the console setup to after the port.
	 */
	port = &arc_uart_ports[co->index].port;
	if (!port->membase)
		return -ENODEV;

	if (options)
		uart_parse_options(options, &baud, &parity, &bits, &flow);

	/*
	 * Serial core will call port->ops->set_termios( )
	 * which will set the baud reg
	 */
	return uart_set_options(port, co, baud, parity, bits, flow);
}

static void arc_serial_console_putchar(struct uart_port *port, int ch)
{
	while (!(UART_GET_STATUS(port) & TXEMPTY))
		cpu_relax();

	UART_SET_DATA(port, (unsigned char)ch);
}

/*
 * Interrupts are disabled on entering
 */
static void arc_serial_console_write(struct console *co, const char *s,
				     unsigned int count)
{
	struct uart_port *port = &arc_uart_ports[co->index].port;
	unsigned long flags;

	spin_lock_irqsave(&port->lock, flags);
	uart_console_write(port, s, count, arc_serial_console_putchar);
	spin_unlock_irqrestore(&port->lock, flags);
}

static struct console arc_console = {
	.name	= ARC_SERIAL_DEV_NAME,
	.write	= arc_serial_console_write,
	.device	= uart_console_device,
	.setup	= arc_serial_console_setup,
	.flags	= CON_PRINTBUFFER,
	.index	= -1,
	.data	= &arc_uart_driver
};

static __init void arc_early_serial_write(struct console *con, const char *s,
					  unsigned int n)
{
	struct earlycon_device *dev = con->data;

	uart_console_write(&dev->port, s, n, arc_serial_console_putchar);
}

static int __init arc_early_console_setup(struct earlycon_device *dev,
					  const char *opt)
{
	struct uart_port *port = &dev->port;
	unsigned int l, h, hw_val;

	if (!dev->port.membase)
		return -ENODEV;

	hw_val = port->uartclk / (dev->baud * 4) - 1;
	l = hw_val & 0xFF;
	h = (hw_val >> 8) & 0xFF;

	UART_SET_BAUDL(port, l);
	UART_SET_BAUDH(port, h);

	dev->con->write = arc_early_serial_write;
	return 0;
}
EARLYCON_DECLARE(arc_uart, arc_early_console_setup);
OF_EARLYCON_DECLARE(arc_uart, "snps,arc-uart", arc_early_console_setup);

#endif	/* CONFIG_SERIAL_ARC_CONSOLE */

static int arc_serial_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct arc_uart_port *uart;
	struct uart_port *port;
	int dev_id;
	u32 val;

	/* no device tree device */
	if (!np)
		return -ENODEV;

	dev_id = of_alias_get_id(np, "serial");
	if (dev_id < 0)
		dev_id = 0;

	uart = &arc_uart_ports[dev_id];
	port = &uart->port;

	if (of_property_read_u32(np, "clock-frequency", &val)) {
		dev_err(&pdev->dev, "clock-frequency property NOTset\n");
		return -EINVAL;
	}
	port->uartclk = val;

	if (of_property_read_u32(np, "current-speed", &val)) {
		dev_err(&pdev->dev, "current-speed property NOT set\n");
		return -EINVAL;
	}
	uart->baud = val;

	port->membase = of_iomap(np, 0);
	if (!port->membase)
		/* No point of dev_err since UART itself is hosed here */
		return -ENXIO;

	port->irq = irq_of_parse_and_map(np, 0);

	port->dev = &pdev->dev;
	port->iotype = UPIO_MEM;
	port->flags = UPF_BOOT_AUTOCONF;
	port->line = dev_id;
	port->ops = &arc_serial_pops;

	port->fifosize = ARC_UART_TX_FIFO_SIZE;

	/*
	 * uart_insert_char( ) uses it in decideding whether to ignore a
	 * char or not. Explicitly setting it here, removes the subtelty
	 */
	port->ignore_status_mask = 0;

	return uart_add_one_port(&arc_uart_driver, &arc_uart_ports[dev_id].port);
}

static int arc_serial_remove(struct platform_device *pdev)
{
	/* This will never be called */
	return 0;
}

static const struct of_device_id arc_uart_dt_ids[] = {
	{ .compatible = "snps,arc-uart" },
	{ /* Sentinel */ }
};
MODULE_DEVICE_TABLE(of, arc_uart_dt_ids);

static struct platform_driver arc_platform_driver = {
	.probe = arc_serial_probe,
	.remove = arc_serial_remove,
	.driver = {
		.name = DRIVER_NAME,
		.of_match_table  = arc_uart_dt_ids,
	 },
};

static int __init arc_serial_init(void)
{
	int ret;

	ret = uart_register_driver(&arc_uart_driver);
	if (ret)
		return ret;

	ret = platform_driver_register(&arc_platform_driver);
	if (ret)
		uart_unregister_driver(&arc_uart_driver);

	return ret;
}

static void __exit arc_serial_exit(void)
{
	platform_driver_unregister(&arc_platform_driver);
	uart_unregister_driver(&arc_uart_driver);
}

module_init(arc_serial_init);
module_exit(arc_serial_exit);

MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRIVER_NAME);
MODULE_AUTHOR("Vineet Gupta");
MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");