xref: /linux/drivers/tty/serial/digicolor-usart.c (revision 2ba9268dd603d23e17643437b2246acb6844953b) 
1 /*
2  *  Driver for Conexant Digicolor serial ports (USART)
3  *
4  * Author: Baruch Siach <baruch@tkos.co.il>
5  *
6  * Copyright (C) 2014 Paradox Innovation Ltd.
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2 of the License, or
11  * (at your option) any later version.
12  */
13 
14 #include <linux/module.h>
15 #include <linux/console.h>
16 #include <linux/serial_core.h>
17 #include <linux/serial.h>
18 #include <linux/clk.h>
19 #include <linux/io.h>
20 #include <linux/tty.h>
21 #include <linux/tty_flip.h>
22 #include <linux/of.h>
23 #include <linux/platform_device.h>
24 #include <linux/workqueue.h>
25 
26 #define UA_ENABLE			0x00
27 #define UA_ENABLE_ENABLE		BIT(0)
28 
29 #define UA_CONTROL			0x01
30 #define UA_CONTROL_RX_ENABLE		BIT(0)
31 #define UA_CONTROL_TX_ENABLE		BIT(1)
32 #define UA_CONTROL_SOFT_RESET		BIT(2)
33 
34 #define UA_STATUS			0x02
35 #define UA_STATUS_PARITY_ERR		BIT(0)
36 #define UA_STATUS_FRAME_ERR		BIT(1)
37 #define UA_STATUS_OVERRUN_ERR		BIT(2)
38 #define UA_STATUS_TX_READY		BIT(6)
39 
40 #define UA_CONFIG			0x03
41 #define UA_CONFIG_CHAR_LEN		BIT(0)
42 #define UA_CONFIG_STOP_BITS		BIT(1)
43 #define UA_CONFIG_PARITY		BIT(2)
44 #define UA_CONFIG_ODD_PARITY		BIT(4)
45 
46 #define UA_EMI_REC			0x04
47 
48 #define UA_HBAUD_LO			0x08
49 #define UA_HBAUD_HI			0x09
50 
51 #define UA_STATUS_FIFO			0x0a
52 #define UA_STATUS_FIFO_RX_EMPTY		BIT(2)
53 #define UA_STATUS_FIFO_RX_INT_ALMOST	BIT(3)
54 #define UA_STATUS_FIFO_TX_FULL		BIT(4)
55 #define UA_STATUS_FIFO_TX_INT_ALMOST	BIT(7)
56 
57 #define UA_CONFIG_FIFO			0x0b
58 #define UA_CONFIG_FIFO_RX_THRESH	7
59 #define UA_CONFIG_FIFO_RX_FIFO_MODE	BIT(3)
60 #define UA_CONFIG_FIFO_TX_FIFO_MODE	BIT(7)
61 
62 #define UA_INTFLAG_CLEAR		0x1c
63 #define UA_INTFLAG_SET			0x1d
64 #define UA_INT_ENABLE			0x1e
65 #define UA_INT_STATUS			0x1f
66 
67 #define UA_INT_TX			BIT(0)
68 #define UA_INT_RX			BIT(1)
69 
70 #define DIGICOLOR_USART_NR		3
71 
72 /*
73  * We use the 16 bytes hardware FIFO to buffer Rx traffic. Rx interrupt is
74  * only produced when the FIFO is filled more than a certain configurable
75  * threshold. Unfortunately, there is no way to set this threshold below half
76  * FIFO. This means that we must periodically poll the FIFO status register to
77  * see whether there are waiting Rx bytes.
78  */
79 
80 struct digicolor_port {
81 	struct uart_port port;
82 	struct delayed_work rx_poll_work;
83 };
84 
85 static struct uart_port *digicolor_ports[DIGICOLOR_USART_NR];
86 
87 static bool digicolor_uart_tx_full(struct uart_port *port)
88 {
89 	return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
90 		  UA_STATUS_FIFO_TX_FULL);
91 }
92 
93 static bool digicolor_uart_rx_empty(struct uart_port *port)
94 {
95 	return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
96 		  UA_STATUS_FIFO_RX_EMPTY);
97 }
98 
99 static void digicolor_uart_stop_tx(struct uart_port *port)
100 {
101 	u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
102 
103 	int_enable &= ~UA_INT_TX;
104 	writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
105 }
106 
107 static void digicolor_uart_start_tx(struct uart_port *port)
108 {
109 	u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
110 
111 	int_enable |= UA_INT_TX;
112 	writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
113 }
114 
115 static void digicolor_uart_stop_rx(struct uart_port *port)
116 {
117 	u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
118 
119 	int_enable &= ~UA_INT_RX;
120 	writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
121 }
122 
123 static void digicolor_rx_poll(struct work_struct *work)
124 {
125 	struct digicolor_port *dp =
126 		container_of(to_delayed_work(work),
127 			     struct digicolor_port, rx_poll_work);
128 
129 	if (!digicolor_uart_rx_empty(&dp->port))
130 		/* force RX interrupt */
131 		writeb_relaxed(UA_INT_RX, dp->port.membase + UA_INTFLAG_SET);
132 
133 	schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));
134 }
135 
136 static void digicolor_uart_rx(struct uart_port *port)
137 {
138 	unsigned long flags;
139 
140 	spin_lock_irqsave(&port->lock, flags);
141 
142 	while (1) {
143 		u8 status, ch;
144 		unsigned int ch_flag;
145 
146 		if (digicolor_uart_rx_empty(port))
147 			break;
148 
149 		ch = readb_relaxed(port->membase + UA_EMI_REC);
150 		status = readb_relaxed(port->membase + UA_STATUS);
151 
152 		port->icount.rx++;
153 		ch_flag = TTY_NORMAL;
154 
155 		if (status) {
156 			if (status & UA_STATUS_PARITY_ERR)
157 				port->icount.parity++;
158 			else if (status & UA_STATUS_FRAME_ERR)
159 				port->icount.frame++;
160 			else if (status & UA_STATUS_OVERRUN_ERR)
161 				port->icount.overrun++;
162 
163 			status &= port->read_status_mask;
164 
165 			if (status & UA_STATUS_PARITY_ERR)
166 				ch_flag = TTY_PARITY;
167 			else if (status & UA_STATUS_FRAME_ERR)
168 				ch_flag = TTY_FRAME;
169 			else if (status & UA_STATUS_OVERRUN_ERR)
170 				ch_flag = TTY_OVERRUN;
171 		}
172 
173 		if (status & port->ignore_status_mask)
174 			continue;
175 
176 		uart_insert_char(port, status, UA_STATUS_OVERRUN_ERR, ch,
177 				 ch_flag);
178 	}
179 
180 	spin_unlock_irqrestore(&port->lock, flags);
181 
182 	tty_flip_buffer_push(&port->state->port);
183 }
184 
185 static void digicolor_uart_tx(struct uart_port *port)
186 {
187 	struct circ_buf *xmit = &port->state->xmit;
188 	unsigned long flags;
189 
190 	if (digicolor_uart_tx_full(port))
191 		return;
192 
193 	spin_lock_irqsave(&port->lock, flags);
194 
195 	if (port->x_char) {
196 		writeb_relaxed(port->x_char, port->membase + UA_EMI_REC);
197 		port->icount.tx++;
198 		port->x_char = 0;
199 		goto out;
200 	}
201 
202 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
203 		digicolor_uart_stop_tx(port);
204 		goto out;
205 	}
206 
207 	while (!uart_circ_empty(xmit)) {
208 		writeb(xmit->buf[xmit->tail], port->membase + UA_EMI_REC);
209 		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
210 		port->icount.tx++;
211 
212 		if (digicolor_uart_tx_full(port))
213 			break;
214 	}
215 
216 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
217 		uart_write_wakeup(port);
218 
219 out:
220 	spin_unlock_irqrestore(&port->lock, flags);
221 }
222 
223 static irqreturn_t digicolor_uart_int(int irq, void *dev_id)
224 {
225 	struct uart_port *port = dev_id;
226 	u8 int_status = readb_relaxed(port->membase + UA_INT_STATUS);
227 
228 	writeb_relaxed(UA_INT_RX | UA_INT_TX,
229 		       port->membase + UA_INTFLAG_CLEAR);
230 
231 	if (int_status & UA_INT_RX)
232 		digicolor_uart_rx(port);
233 	if (int_status & UA_INT_TX)
234 		digicolor_uart_tx(port);
235 
236 	return IRQ_HANDLED;
237 }
238 
239 static unsigned int digicolor_uart_tx_empty(struct uart_port *port)
240 {
241 	u8 status = readb_relaxed(port->membase + UA_STATUS);
242 
243 	return (status & UA_STATUS_TX_READY) ? TIOCSER_TEMT : 0;
244 }
245 
246 static unsigned int digicolor_uart_get_mctrl(struct uart_port *port)
247 {
248 	return TIOCM_CTS;
249 }
250 
251 static void digicolor_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
252 {
253 }
254 
255 static void digicolor_uart_break_ctl(struct uart_port *port, int state)
256 {
257 }
258 
259 static int digicolor_uart_startup(struct uart_port *port)
260 {
261 	struct digicolor_port *dp =
262 		container_of(port, struct digicolor_port, port);
263 
264 	writeb_relaxed(UA_ENABLE_ENABLE, port->membase + UA_ENABLE);
265 	writeb_relaxed(UA_CONTROL_SOFT_RESET, port->membase + UA_CONTROL);
266 	writeb_relaxed(0, port->membase + UA_CONTROL);
267 
268 	writeb_relaxed(UA_CONFIG_FIFO_RX_FIFO_MODE
269 		       | UA_CONFIG_FIFO_TX_FIFO_MODE | UA_CONFIG_FIFO_RX_THRESH,
270 		       port->membase + UA_CONFIG_FIFO);
271 	writeb_relaxed(UA_STATUS_FIFO_RX_INT_ALMOST,
272 		       port->membase + UA_STATUS_FIFO);
273 	writeb_relaxed(UA_CONTROL_RX_ENABLE | UA_CONTROL_TX_ENABLE,
274 		       port->membase + UA_CONTROL);
275 	writeb_relaxed(UA_INT_TX | UA_INT_RX,
276 		       port->membase + UA_INT_ENABLE);
277 
278 	schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));
279 
280 	return 0;
281 }
282 
283 static void digicolor_uart_shutdown(struct uart_port *port)
284 {
285 	struct digicolor_port *dp =
286 		container_of(port, struct digicolor_port, port);
287 
288 	writeb_relaxed(0, port->membase + UA_ENABLE);
289 	cancel_delayed_work_sync(&dp->rx_poll_work);
290 }
291 
292 static void digicolor_uart_set_termios(struct uart_port *port,
293 				       struct ktermios *termios,
294 				       struct ktermios *old)
295 {
296 	unsigned int baud, divisor;
297 	u8 config = 0;
298 	unsigned long flags;
299 
300 	/* Mask termios capabilities we don't support */
301 	termios->c_cflag &= ~CMSPAR;
302 	termios->c_iflag &= ~(BRKINT | IGNBRK);
303 
304 	/* Limit baud rates so that we don't need the fractional divider */
305 	baud = uart_get_baud_rate(port, termios, old,
306 				  port->uartclk / (0x10000*16),
307 				  port->uartclk / 256);
308 	divisor = uart_get_divisor(port, baud) - 1;
309 
310 	switch (termios->c_cflag & CSIZE) {
311 	case CS7:
312 		break;
313 	case CS8:
314 	default:
315 		config |= UA_CONFIG_CHAR_LEN;
316 		break;
317 	}
318 
319 	if (termios->c_cflag & CSTOPB)
320 		config |= UA_CONFIG_STOP_BITS;
321 
322 	if (termios->c_cflag & PARENB) {
323 		config |= UA_CONFIG_PARITY;
324 		if (termios->c_cflag & PARODD)
325 			config |= UA_CONFIG_ODD_PARITY;
326 	}
327 
328 	/* Set read status mask */
329 	port->read_status_mask = UA_STATUS_OVERRUN_ERR;
330 	if (termios->c_iflag & INPCK)
331 		port->read_status_mask |= UA_STATUS_PARITY_ERR
332 			| UA_STATUS_FRAME_ERR;
333 
334 	/* Set status ignore mask */
335 	port->ignore_status_mask = 0;
336 	if (!(termios->c_cflag & CREAD))
337 		port->ignore_status_mask |= UA_STATUS_OVERRUN_ERR
338 			| UA_STATUS_PARITY_ERR | UA_STATUS_FRAME_ERR;
339 
340 	spin_lock_irqsave(&port->lock, flags);
341 
342 	uart_update_timeout(port, termios->c_cflag, baud);
343 
344 	writeb_relaxed(config, port->membase + UA_CONFIG);
345 	writeb_relaxed(divisor & 0xff, port->membase + UA_HBAUD_LO);
346 	writeb_relaxed(divisor >> 8, port->membase + UA_HBAUD_HI);
347 
348 	spin_unlock_irqrestore(&port->lock, flags);
349 }
350 
351 static const char *digicolor_uart_type(struct uart_port *port)
352 {
353 	return (port->type == PORT_DIGICOLOR) ? "DIGICOLOR USART" : NULL;
354 }
355 
356 static void digicolor_uart_config_port(struct uart_port *port, int flags)
357 {
358 	if (flags & UART_CONFIG_TYPE)
359 		port->type = PORT_DIGICOLOR;
360 }
361 
362 static void digicolor_uart_release_port(struct uart_port *port)
363 {
364 }
365 
366 static int digicolor_uart_request_port(struct uart_port *port)
367 {
368 	return 0;
369 }
370 
371 static const struct uart_ops digicolor_uart_ops = {
372 	.tx_empty	= digicolor_uart_tx_empty,
373 	.set_mctrl	= digicolor_uart_set_mctrl,
374 	.get_mctrl	= digicolor_uart_get_mctrl,
375 	.stop_tx	= digicolor_uart_stop_tx,
376 	.start_tx	= digicolor_uart_start_tx,
377 	.stop_rx	= digicolor_uart_stop_rx,
378 	.break_ctl	= digicolor_uart_break_ctl,
379 	.startup	= digicolor_uart_startup,
380 	.shutdown	= digicolor_uart_shutdown,
381 	.set_termios	= digicolor_uart_set_termios,
382 	.type		= digicolor_uart_type,
383 	.config_port	= digicolor_uart_config_port,
384 	.release_port	= digicolor_uart_release_port,
385 	.request_port	= digicolor_uart_request_port,
386 };
387 
388 static void digicolor_uart_console_putchar(struct uart_port *port, int ch)
389 {
390 	while (digicolor_uart_tx_full(port))
391 		cpu_relax();
392 
393 	writeb_relaxed(ch, port->membase + UA_EMI_REC);
394 }
395 
396 static void digicolor_uart_console_write(struct console *co, const char *c,
397 					 unsigned n)
398 {
399 	struct uart_port *port = digicolor_ports[co->index];
400 	u8 status;
401 	unsigned long flags;
402 	int locked = 1;
403 
404 	if (oops_in_progress)
405 		locked = spin_trylock_irqsave(&port->lock, flags);
406 	else
407 		spin_lock_irqsave(&port->lock, flags);
408 
409 	uart_console_write(port, c, n, digicolor_uart_console_putchar);
410 
411 	if (locked)
412 		spin_unlock_irqrestore(&port->lock, flags);
413 
414 	/* Wait for transmitter to become empty */
415 	do {
416 		status = readb_relaxed(port->membase + UA_STATUS);
417 	} while ((status & UA_STATUS_TX_READY) == 0);
418 }
419 
420 static int digicolor_uart_console_setup(struct console *co, char *options)
421 {
422 	int baud = 115200, bits = 8, parity = 'n', flow = 'n';
423 	struct uart_port *port;
424 
425 	if (co->index < 0 || co->index >= DIGICOLOR_USART_NR)
426 		return -EINVAL;
427 
428 	port = digicolor_ports[co->index];
429 	if (!port)
430 		return -ENODEV;
431 
432 	if (options)
433 		uart_parse_options(options, &baud, &parity, &bits, &flow);
434 
435 	return uart_set_options(port, co, baud, parity, bits, flow);
436 }
437 
438 static struct console digicolor_console = {
439 	.name	= "ttyS",
440 	.device	= uart_console_device,
441 	.write	= digicolor_uart_console_write,
442 	.setup	= digicolor_uart_console_setup,
443 	.flags	= CON_PRINTBUFFER,
444 	.index	= -1,
445 };
446 
447 static struct uart_driver digicolor_uart = {
448 	.driver_name	= "digicolor-usart",
449 	.dev_name	= "ttyS",
450 	.nr		= DIGICOLOR_USART_NR,
451 };
452 
453 static int digicolor_uart_probe(struct platform_device *pdev)
454 {
455 	struct device_node *np = pdev->dev.of_node;
456 	int ret, index;
457 	struct digicolor_port *dp;
458 	struct resource *res;
459 	struct clk *uart_clk;
460 
461 	if (!np) {
462 		dev_err(&pdev->dev, "Missing device tree node\n");
463 		return -ENXIO;
464 	}
465 
466 	index = of_alias_get_id(np, "serial");
467 	if (index < 0 || index >= DIGICOLOR_USART_NR)
468 		return -EINVAL;
469 
470 	dp = devm_kzalloc(&pdev->dev, sizeof(*dp), GFP_KERNEL);
471 	if (!dp)
472 		return -ENOMEM;
473 
474 	uart_clk = devm_clk_get(&pdev->dev, NULL);
475 	if (IS_ERR(uart_clk))
476 		return PTR_ERR(uart_clk);
477 
478 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
479 	dp->port.mapbase = res->start;
480 	dp->port.membase = devm_ioremap_resource(&pdev->dev, res);
481 	if (IS_ERR(dp->port.membase))
482 		return PTR_ERR(dp->port.membase);
483 
484 	dp->port.irq = platform_get_irq(pdev, 0);
485 	if (IS_ERR_VALUE(dp->port.irq))
486 		return dp->port.irq;
487 
488 	dp->port.iotype = UPIO_MEM;
489 	dp->port.uartclk = clk_get_rate(uart_clk);
490 	dp->port.fifosize = 16;
491 	dp->port.dev = &pdev->dev;
492 	dp->port.ops = &digicolor_uart_ops;
493 	dp->port.line = index;
494 	dp->port.type = PORT_DIGICOLOR;
495 	spin_lock_init(&dp->port.lock);
496 
497 	digicolor_ports[index] = &dp->port;
498 	platform_set_drvdata(pdev, &dp->port);
499 
500 	INIT_DELAYED_WORK(&dp->rx_poll_work, digicolor_rx_poll);
501 
502 	ret = devm_request_irq(&pdev->dev, dp->port.irq, digicolor_uart_int, 0,
503 			       dev_name(&pdev->dev), &dp->port);
504 	if (ret)
505 		return ret;
506 
507 	return uart_add_one_port(&digicolor_uart, &dp->port);
508 }
509 
510 static int digicolor_uart_remove(struct platform_device *pdev)
511 {
512 	struct uart_port *port = platform_get_drvdata(pdev);
513 
514 	uart_remove_one_port(&digicolor_uart, port);
515 
516 	return 0;
517 }
518 
519 static const struct of_device_id digicolor_uart_dt_ids[] = {
520 	{ .compatible = "cnxt,cx92755-usart", },
521 	{ }
522 };
523 MODULE_DEVICE_TABLE(of, digicolor_uart_dt_ids);
524 
525 static struct platform_driver digicolor_uart_platform = {
526 	.driver = {
527 		.name		= "digicolor-usart",
528 		.of_match_table	= of_match_ptr(digicolor_uart_dt_ids),
529 	},
530 	.probe	= digicolor_uart_probe,
531 	.remove	= digicolor_uart_remove,
532 };
533 
534 static int __init digicolor_uart_init(void)
535 {
536 	int ret;
537 
538 	if (IS_ENABLED(CONFIG_SERIAL_CONEXANT_DIGICOLOR_CONSOLE)) {
539 		digicolor_uart.cons = &digicolor_console;
540 		digicolor_console.data = &digicolor_uart;
541 	}
542 
543 	ret = uart_register_driver(&digicolor_uart);
544 	if (ret)
545 		return ret;
546 
547 	return platform_driver_register(&digicolor_uart_platform);
548 }
549 module_init(digicolor_uart_init);
550 
551 static void __exit digicolor_uart_exit(void)
552 {
553 	platform_driver_unregister(&digicolor_uart_platform);
554 	uart_unregister_driver(&digicolor_uart);
555 }
556 module_exit(digicolor_uart_exit);
557 
558 MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
559 MODULE_DESCRIPTION("Conexant Digicolor USART serial driver");
560 MODULE_LICENSE("GPL");
561