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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * ARC On-Chip(fpga) UART Driver
4 *
5 * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.com)
6 *
7 * vineetg: July 10th 2012
8 * -Decoupled the driver from arch/arc
9 * +Using platform_get_resource() for irq/membase (thx to bfin_uart.c)
10 * +Using early_platform_xxx() for early console (thx to mach-shmobile/xxx)
11 *
12 * Vineetg: Aug 21st 2010
13 * -Is uart_tx_stopped() not done in tty write path as it has already been
14 * taken care of, in serial core
15 *
16 * Vineetg: Aug 18th 2010
17 * -New Serial Core based ARC UART driver
18 * -Derived largely from blackfin driver albiet with some major tweaks
19 *
20 * TODO:
21 * -check if sysreq works
22 */
23
24#include <linux/module.h>
25#include <linux/serial.h>
26#include <linux/console.h>
27#include <linux/sysrq.h>
28#include <linux/platform_device.h>
29#include <linux/tty.h>
30#include <linux/tty_flip.h>
31#include <linux/serial_core.h>
32#include <linux/io.h>
33#include <linux/of_irq.h>
34#include <linux/of_address.h>
35
36/*************************************
37 * ARC UART Hardware Specs
38 ************************************/
39#define ARC_UART_TX_FIFO_SIZE 1
40
41/*
42 * UART Register set (this is not a Standards Compliant IP)
43 * Also each reg is Word aligned, but only 8 bits wide
44 */
45#define R_ID0 0
46#define R_ID1 4
47#define R_ID2 8
48#define R_ID3 12
49#define R_DATA 16
50#define R_STS 20
51#define R_BAUDL 24
52#define R_BAUDH 28
53
54/* Bits for UART Status Reg (R/W) */
55#define RXIENB 0x04 /* Receive Interrupt Enable */
56#define TXIENB 0x40 /* Transmit Interrupt Enable */
57
58#define RXEMPTY 0x20 /* Receive FIFO Empty: No char receivede */
59#define TXEMPTY 0x80 /* Transmit FIFO Empty, thus char can be written into */
60
61#define RXFULL 0x08 /* Receive FIFO full */
62#define RXFULL1 0x10 /* Receive FIFO has space for 1 char (tot space=4) */
63
64#define RXFERR 0x01 /* Frame Error: Stop Bit not detected */
65#define RXOERR 0x02 /* OverFlow Err: Char recv but RXFULL still set */
66
67/* Uart bit fiddling helpers: lowest level */
68#define RBASE(port, reg) (port->membase + reg)
69#define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
70#define UART_REG_GET(u, r) readb(RBASE(u, r))
71
72#define UART_REG_OR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) | (v))
73#define UART_REG_CLR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) & ~(v))
74
75/* Uart bit fiddling helpers: API level */
76#define UART_SET_DATA(uart, val) UART_REG_SET(uart, R_DATA, val)
77#define UART_GET_DATA(uart) UART_REG_GET(uart, R_DATA)
78
79#define UART_SET_BAUDH(uart, val) UART_REG_SET(uart, R_BAUDH, val)
80#define UART_SET_BAUDL(uart, val) UART_REG_SET(uart, R_BAUDL, val)
81
82#define UART_CLR_STATUS(uart, val) UART_REG_CLR(uart, R_STS, val)
83#define UART_GET_STATUS(uart) UART_REG_GET(uart, R_STS)
84
85#define UART_ALL_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB|TXIENB)
86#define UART_RX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB)
87#define UART_TX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, TXIENB)
88
89#define UART_ALL_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB|TXIENB)
90#define UART_RX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB)
91#define UART_TX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, TXIENB)
92
93#define ARC_SERIAL_DEV_NAME "ttyARC"
94
95struct arc_uart_port {
96 struct uart_port port;
97 unsigned long baud;
98};
99
100#define to_arc_port(uport) container_of(uport, struct arc_uart_port, port)
101
102static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];
103
104#ifdef CONFIG_SERIAL_ARC_CONSOLE
105static struct console arc_console;
106#endif
107
108#define DRIVER_NAME "arc-uart"
109
110static struct uart_driver arc_uart_driver = {
111 .owner = THIS_MODULE,
112 .driver_name = DRIVER_NAME,
113 .dev_name = ARC_SERIAL_DEV_NAME,
114 .major = 0,
115 .minor = 0,
116 .nr = CONFIG_SERIAL_ARC_NR_PORTS,
117#ifdef CONFIG_SERIAL_ARC_CONSOLE
118 .cons = &arc_console,
119#endif
120};
121
122static void arc_serial_stop_rx(struct uart_port *port)
123{
124 UART_RX_IRQ_DISABLE(port);
125}
126
127static void arc_serial_stop_tx(struct uart_port *port)
128{
129 while (!(UART_GET_STATUS(port) & TXEMPTY))
130 cpu_relax();
131
132 UART_TX_IRQ_DISABLE(port);
133}
134
135/*
136 * Return TIOCSER_TEMT when transmitter is not busy.
137 */
138static unsigned int arc_serial_tx_empty(struct uart_port *port)
139{
140 unsigned int stat;
141
142 stat = UART_GET_STATUS(port);
143 if (stat & TXEMPTY)
144 return TIOCSER_TEMT;
145
146 return 0;
147}
148
149/*
150 * Driver internal routine, used by both tty(serial core) as well as tx-isr
151 * -Called under spinlock in either cases
152 * -also tty->flow.stopped has already been checked
153 * = by uart_start( ) before calling us
154 * = tx_ist checks that too before calling
155 */
156static void arc_serial_tx_chars(struct uart_port *port)
157{
158 struct tty_port *tport = &port->state->port;
159 int sent = 0;
160 unsigned char ch;
161
162 if (unlikely(port->x_char)) {
163 UART_SET_DATA(port, port->x_char);
164 port->icount.tx++;
165 port->x_char = 0;
166 sent = 1;
167 } else if (uart_fifo_get(port, &ch)) {
168 while (!(UART_GET_STATUS(port) & TXEMPTY))
169 cpu_relax();
170 UART_SET_DATA(port, ch);
171 sent = 1;
172 }
173
174 /*
175 * If num chars in xmit buffer are too few, ask tty layer for more.
176 * By Hard ISR to schedule processing in software interrupt part
177 */
178 if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
179 uart_write_wakeup(port);
180
181 if (sent)
182 UART_TX_IRQ_ENABLE(port);
183}
184
185/*
186 * port is locked and interrupts are disabled
187 * uart_start( ) calls us under the port spinlock irqsave
188 */
189static void arc_serial_start_tx(struct uart_port *port)
190{
191 arc_serial_tx_chars(port);
192}
193
194static void arc_serial_rx_chars(struct uart_port *port, unsigned int status)
195{
196 /*
197 * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
198 * is very subtle. Here's how ...
199 * Upon getting a RX-Intr, such that RX-EMPTY=0, meaning data available,
200 * driver reads the DATA Reg and keeps doing that in a loop, until
201 * RX-EMPTY=1. Multiple chars being avail, with a single Interrupt,
202 * before RX-EMPTY=0, implies some sort of buffering going on in the
203 * controller, which is indeed the Rx-FIFO.
204 */
205 do {
206 u8 ch, flg = TTY_NORMAL;
207
208 /*
209 * This could be an Rx Intr for err (no data),
210 * so check err and clear that Intr first
211 */
212 if (status & RXOERR) {
213 port->icount.overrun++;
214 flg = TTY_OVERRUN;
215 UART_CLR_STATUS(port, RXOERR);
216 }
217
218 if (status & RXFERR) {
219 port->icount.frame++;
220 flg = TTY_FRAME;
221 UART_CLR_STATUS(port, RXFERR);
222 }
223
224 if (status & RXEMPTY)
225 continue;
226
227 ch = UART_GET_DATA(port);
228 port->icount.rx++;
229
230 if (!(uart_handle_sysrq_char(port, ch)))
231 uart_insert_char(port, status, RXOERR, ch, flg);
232
233 tty_flip_buffer_push(&port->state->port);
234 } while (!((status = UART_GET_STATUS(port)) & RXEMPTY));
235}
236
237/*
238 * A note on the Interrupt handling state machine of this driver
239 *
240 * kernel printk writes funnel thru the console driver framework and in order
241 * to keep things simple as well as efficient, it writes to UART in polled
242 * mode, in one shot, and exits.
243 *
244 * OTOH, Userland output (via tty layer), uses interrupt based writes as there
245 * can be undeterministic delay between char writes.
246 *
247 * Thus Rx-interrupts are always enabled, while tx-interrupts are by default
248 * disabled.
249 *
250 * When tty has some data to send out, serial core calls driver's start_tx
251 * which
252 * -checks-if-tty-buffer-has-char-to-send
253 * -writes-data-to-uart
254 * -enable-tx-intr
255 *
256 * Once data bits are pushed out, controller raises the Tx-room-avail-Interrupt.
257 * The first thing Tx ISR does is disable further Tx interrupts (as this could
258 * be the last char to send, before settling down into the quiet polled mode).
259 * It then calls the exact routine used by tty layer write to send out any
260 * more char in tty buffer. In case of sending, it re-enables Tx-intr. In case
261 * of no data, it remains disabled.
262 * This is how the transmit state machine is dynamically switched on/off
263 */
264
265static irqreturn_t arc_serial_isr(int irq, void *dev_id)
266{
267 struct uart_port *port = dev_id;
268 unsigned int status;
269
270 status = UART_GET_STATUS(port);
271
272 /*
273 * Single IRQ for both Rx (data available) Tx (room available) Interrupt
274 * notifications from the UART Controller.
275 * To demultiplex between the two, we check the relevant bits
276 */
277 if (status & RXIENB) {
278
279 /* already in ISR, no need of xx_irqsave */
280 uart_port_lock(port);
281 arc_serial_rx_chars(port, status);
282 uart_port_unlock(port);
283 }
284
285 if ((status & TXIENB) && (status & TXEMPTY)) {
286
287 /* Unconditionally disable further Tx-Interrupts.
288 * will be enabled by tx_chars() if needed.
289 */
290 UART_TX_IRQ_DISABLE(port);
291
292 uart_port_lock(port);
293
294 if (!uart_tx_stopped(port))
295 arc_serial_tx_chars(port);
296
297 uart_port_unlock(port);
298 }
299
300 return IRQ_HANDLED;
301}
302
303static unsigned int arc_serial_get_mctrl(struct uart_port *port)
304{
305 /*
306 * Pretend we have a Modem status reg and following bits are
307 * always set, to satify the serial core state machine
308 * (DSR) Data Set Ready
309 * (CTS) Clear To Send
310 * (CAR) Carrier Detect
311 */
312 return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
313}
314
315static void arc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
316{
317 /* MCR not present */
318}
319
320static void arc_serial_break_ctl(struct uart_port *port, int break_state)
321{
322 /* ARC UART doesn't support sending Break signal */
323}
324
325static int arc_serial_startup(struct uart_port *port)
326{
327 /* Before we hook up the ISR, Disable all UART Interrupts */
328 UART_ALL_IRQ_DISABLE(port);
329
330 if (request_irq(port->irq, arc_serial_isr, 0, "arc uart rx-tx", port)) {
331 dev_warn(port->dev, "Unable to attach ARC UART intr\n");
332 return -EBUSY;
333 }
334
335 UART_RX_IRQ_ENABLE(port); /* Only Rx IRQ enabled to begin with */
336
337 return 0;
338}
339
340/* This is not really needed */
341static void arc_serial_shutdown(struct uart_port *port)
342{
343 free_irq(port->irq, port);
344}
345
346static void
347arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
348 const struct ktermios *old)
349{
350 struct arc_uart_port *uart = to_arc_port(port);
351 unsigned int baud, uartl, uarth, hw_val;
352 unsigned long flags;
353
354 /*
355 * Use the generic handler so that any specially encoded baud rates
356 * such as SPD_xx flags or "%B0" can be handled
357 * Max Baud I suppose will not be more than current 115K * 4
358 * Formula for ARC UART is: hw-val = ((CLK/(BAUD*4)) -1)
359 * spread over two 8-bit registers
360 */
361 baud = uart_get_baud_rate(port, new, old, 0, 460800);
362
363 hw_val = port->uartclk / (uart->baud * 4) - 1;
364 uartl = hw_val & 0xFF;
365 uarth = (hw_val >> 8) & 0xFF;
366
367 uart_port_lock_irqsave(port, &flags);
368
369 UART_ALL_IRQ_DISABLE(port);
370
371 UART_SET_BAUDL(port, uartl);
372 UART_SET_BAUDH(port, uarth);
373
374 UART_RX_IRQ_ENABLE(port);
375
376 /*
377 * UART doesn't support Parity/Hardware Flow Control;
378 * Only supports 8N1 character size
379 */
380 new->c_cflag &= ~(CMSPAR|CRTSCTS|CSIZE);
381 new->c_cflag |= CS8;
382
383 if (old)
384 tty_termios_copy_hw(new, old);
385
386 /* Don't rewrite B0 */
387 if (tty_termios_baud_rate(new))
388 tty_termios_encode_baud_rate(new, baud, baud);
389
390 uart_update_timeout(port, new->c_cflag, baud);
391
392 uart_port_unlock_irqrestore(port, flags);
393}
394
395static const char *arc_serial_type(struct uart_port *port)
396{
397 return port->type == PORT_ARC ? DRIVER_NAME : NULL;
398}
399
400static void arc_serial_release_port(struct uart_port *port)
401{
402}
403
404static int arc_serial_request_port(struct uart_port *port)
405{
406 return 0;
407}
408
409/*
410 * Verify the new serial_struct (for TIOCSSERIAL).
411 */
412static int
413arc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
414{
415 if (port->type != PORT_UNKNOWN && ser->type != PORT_ARC)
416 return -EINVAL;
417
418 return 0;
419}
420
421/*
422 * Configure/autoconfigure the port.
423 */
424static void arc_serial_config_port(struct uart_port *port, int flags)
425{
426 if (flags & UART_CONFIG_TYPE)
427 port->type = PORT_ARC;
428}
429
430#ifdef CONFIG_CONSOLE_POLL
431
432static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
433{
434 while (!(UART_GET_STATUS(port) & TXEMPTY))
435 cpu_relax();
436
437 UART_SET_DATA(port, chr);
438}
439
440static int arc_serial_poll_getchar(struct uart_port *port)
441{
442 unsigned char chr;
443
444 while (!(UART_GET_STATUS(port) & RXEMPTY))
445 cpu_relax();
446
447 chr = UART_GET_DATA(port);
448 return chr;
449}
450#endif
451
452static const struct uart_ops arc_serial_pops = {
453 .tx_empty = arc_serial_tx_empty,
454 .set_mctrl = arc_serial_set_mctrl,
455 .get_mctrl = arc_serial_get_mctrl,
456 .stop_tx = arc_serial_stop_tx,
457 .start_tx = arc_serial_start_tx,
458 .stop_rx = arc_serial_stop_rx,
459 .break_ctl = arc_serial_break_ctl,
460 .startup = arc_serial_startup,
461 .shutdown = arc_serial_shutdown,
462 .set_termios = arc_serial_set_termios,
463 .type = arc_serial_type,
464 .release_port = arc_serial_release_port,
465 .request_port = arc_serial_request_port,
466 .config_port = arc_serial_config_port,
467 .verify_port = arc_serial_verify_port,
468#ifdef CONFIG_CONSOLE_POLL
469 .poll_put_char = arc_serial_poll_putchar,
470 .poll_get_char = arc_serial_poll_getchar,
471#endif
472};
473
474#ifdef CONFIG_SERIAL_ARC_CONSOLE
475
476static int arc_serial_console_setup(struct console *co, char *options)
477{
478 struct uart_port *port;
479 int baud = 115200;
480 int bits = 8;
481 int parity = 'n';
482 int flow = 'n';
483
484 if (co->index < 0 || co->index >= CONFIG_SERIAL_ARC_NR_PORTS)
485 return -ENODEV;
486
487 /*
488 * The uart port backing the console (e.g. ttyARC1) might not have been
489 * init yet. If so, defer the console setup to after the port.
490 */
491 port = &arc_uart_ports[co->index].port;
492 if (!port->membase)
493 return -ENODEV;
494
495 if (options)
496 uart_parse_options(options, &baud, &parity, &bits, &flow);
497
498 /*
499 * Serial core will call port->ops->set_termios( )
500 * which will set the baud reg
501 */
502 return uart_set_options(port, co, baud, parity, bits, flow);
503}
504
505static void arc_serial_console_putchar(struct uart_port *port, unsigned char ch)
506{
507 while (!(UART_GET_STATUS(port) & TXEMPTY))
508 cpu_relax();
509
510 UART_SET_DATA(port, (unsigned char)ch);
511}
512
513/*
514 * Interrupts are disabled on entering
515 */
516static void arc_serial_console_write(struct console *co, const char *s,
517 unsigned int count)
518{
519 struct uart_port *port = &arc_uart_ports[co->index].port;
520 unsigned long flags;
521
522 uart_port_lock_irqsave(port, &flags);
523 uart_console_write(port, s, count, arc_serial_console_putchar);
524 uart_port_unlock_irqrestore(port, flags);
525}
526
527static struct console arc_console = {
528 .name = ARC_SERIAL_DEV_NAME,
529 .write = arc_serial_console_write,
530 .device = uart_console_device,
531 .setup = arc_serial_console_setup,
532 .flags = CON_PRINTBUFFER,
533 .index = -1,
534 .data = &arc_uart_driver
535};
536
537static void arc_early_serial_write(struct console *con, const char *s,
538 unsigned int n)
539{
540 struct earlycon_device *dev = con->data;
541
542 uart_console_write(&dev->port, s, n, arc_serial_console_putchar);
543}
544
545static int __init arc_early_console_setup(struct earlycon_device *dev,
546 const char *opt)
547{
548 struct uart_port *port = &dev->port;
549 unsigned int l, h, hw_val;
550
551 if (!dev->port.membase)
552 return -ENODEV;
553
554 hw_val = port->uartclk / (dev->baud * 4) - 1;
555 l = hw_val & 0xFF;
556 h = (hw_val >> 8) & 0xFF;
557
558 UART_SET_BAUDL(port, l);
559 UART_SET_BAUDH(port, h);
560
561 dev->con->write = arc_early_serial_write;
562 return 0;
563}
564OF_EARLYCON_DECLARE(arc_uart, "snps,arc-uart", arc_early_console_setup);
565
566#endif /* CONFIG_SERIAL_ARC_CONSOLE */
567
568static int arc_serial_probe(struct platform_device *pdev)
569{
570 struct device_node *np = pdev->dev.of_node;
571 struct arc_uart_port *uart;
572 struct uart_port *port;
573 int dev_id;
574 u32 val;
575
576 /* no device tree device */
577 if (!np)
578 return -ENODEV;
579
580 dev_id = of_alias_get_id(np, "serial");
581 if (dev_id < 0)
582 dev_id = 0;
583
584 if (dev_id >= ARRAY_SIZE(arc_uart_ports)) {
585 dev_err(&pdev->dev, "serial%d out of range\n", dev_id);
586 return -EINVAL;
587 }
588
589 uart = &arc_uart_ports[dev_id];
590 port = &uart->port;
591
592 if (of_property_read_u32(np, "clock-frequency", &val)) {
593 dev_err(&pdev->dev, "clock-frequency property NOTset\n");
594 return -EINVAL;
595 }
596 port->uartclk = val;
597
598 if (of_property_read_u32(np, "current-speed", &val)) {
599 dev_err(&pdev->dev, "current-speed property NOT set\n");
600 return -EINVAL;
601 }
602 uart->baud = val;
603
604 port->membase = devm_platform_ioremap_resource(pdev, 0);
605 if (IS_ERR(port->membase)) {
606 /* No point of dev_err since UART itself is hosed here */
607 return PTR_ERR(port->membase);
608 }
609
610 port->irq = irq_of_parse_and_map(np, 0);
611
612 port->dev = &pdev->dev;
613 port->iotype = UPIO_MEM;
614 port->flags = UPF_BOOT_AUTOCONF;
615 port->line = dev_id;
616 port->ops = &arc_serial_pops;
617 port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_ARC_CONSOLE);
618
619 port->fifosize = ARC_UART_TX_FIFO_SIZE;
620
621 /*
622 * uart_insert_char( ) uses it in decideding whether to ignore a
623 * char or not. Explicitly setting it here, removes the subtelty
624 */
625 port->ignore_status_mask = 0;
626
627 return uart_add_one_port(&arc_uart_driver, &arc_uart_ports[dev_id].port);
628}
629
630static const struct of_device_id arc_uart_dt_ids[] = {
631 { .compatible = "snps,arc-uart" },
632 { /* Sentinel */ }
633};
634MODULE_DEVICE_TABLE(of, arc_uart_dt_ids);
635
636static struct platform_driver arc_platform_driver = {
637 .probe = arc_serial_probe,
638 .driver = {
639 .name = DRIVER_NAME,
640 .of_match_table = arc_uart_dt_ids,
641 },
642};
643
644static int __init arc_serial_init(void)
645{
646 int ret;
647
648 ret = uart_register_driver(&arc_uart_driver);
649 if (ret)
650 return ret;
651
652 ret = platform_driver_register(&arc_platform_driver);
653 if (ret)
654 uart_unregister_driver(&arc_uart_driver);
655
656 return ret;
657}
658
659static void __exit arc_serial_exit(void)
660{
661 platform_driver_unregister(&arc_platform_driver);
662 uart_unregister_driver(&arc_uart_driver);
663}
664
665module_init(arc_serial_init);
666module_exit(arc_serial_exit);
667
668MODULE_LICENSE("GPL");
669MODULE_ALIAS("platform:" DRIVER_NAME);
670MODULE_AUTHOR("Vineet Gupta");
671MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");