1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  *  Driver for Conexant Digicolor serial ports (USART)
4  *
5  * Author: Baruch Siach <baruch@tkos.co.il>
6  *
7  * Copyright (C) 2014 Paradox Innovation Ltd.
8  */
9 
10 #include <linux/module.h>
11 #include <linux/console.h>
12 #include <linux/serial_core.h>
13 #include <linux/serial.h>
14 #include <linux/clk.h>
15 #include <linux/io.h>
16 #include <linux/tty.h>
17 #include <linux/tty_flip.h>
18 #include <linux/of.h>
19 #include <linux/platform_device.h>
20 #include <linux/workqueue.h>
21 
22 #define UA_ENABLE			0x00
23 #define UA_ENABLE_ENABLE		BIT(0)
24 
25 #define UA_CONTROL			0x01
26 #define UA_CONTROL_RX_ENABLE		BIT(0)
27 #define UA_CONTROL_TX_ENABLE		BIT(1)
28 #define UA_CONTROL_SOFT_RESET		BIT(2)
29 
30 #define UA_STATUS			0x02
31 #define UA_STATUS_PARITY_ERR		BIT(0)
32 #define UA_STATUS_FRAME_ERR		BIT(1)
33 #define UA_STATUS_OVERRUN_ERR		BIT(2)
34 #define UA_STATUS_TX_READY		BIT(6)
35 
36 #define UA_CONFIG			0x03
37 #define UA_CONFIG_CHAR_LEN		BIT(0)
38 #define UA_CONFIG_STOP_BITS		BIT(1)
39 #define UA_CONFIG_PARITY		BIT(2)
40 #define UA_CONFIG_ODD_PARITY		BIT(4)
41 
42 #define UA_EMI_REC			0x04
43 
44 #define UA_HBAUD_LO			0x08
45 #define UA_HBAUD_HI			0x09
46 
47 #define UA_STATUS_FIFO			0x0a
48 #define UA_STATUS_FIFO_RX_EMPTY		BIT(2)
49 #define UA_STATUS_FIFO_RX_INT_ALMOST	BIT(3)
50 #define UA_STATUS_FIFO_TX_FULL		BIT(4)
51 #define UA_STATUS_FIFO_TX_INT_ALMOST	BIT(7)
52 
53 #define UA_CONFIG_FIFO			0x0b
54 #define UA_CONFIG_FIFO_RX_THRESH	7
55 #define UA_CONFIG_FIFO_RX_FIFO_MODE	BIT(3)
56 #define UA_CONFIG_FIFO_TX_FIFO_MODE	BIT(7)
57 
58 #define UA_INTFLAG_CLEAR		0x1c
59 #define UA_INTFLAG_SET			0x1d
60 #define UA_INT_ENABLE			0x1e
61 #define UA_INT_STATUS			0x1f
62 
63 #define UA_INT_TX			BIT(0)
64 #define UA_INT_RX			BIT(1)
65 
66 #define DIGICOLOR_USART_NR		3
67 
68 /*
69  * We use the 16 bytes hardware FIFO to buffer Rx traffic. Rx interrupt is
70  * only produced when the FIFO is filled more than a certain configurable
71  * threshold. Unfortunately, there is no way to set this threshold below half
72  * FIFO. This means that we must periodically poll the FIFO status register to
73  * see whether there are waiting Rx bytes.
74  */
75 
76 struct digicolor_port {
77 	struct uart_port port;
78 	struct delayed_work rx_poll_work;
79 };
80 
81 static struct uart_port *digicolor_ports[DIGICOLOR_USART_NR];
82 
83 static bool digicolor_uart_tx_full(struct uart_port *port)
84 {
85 	return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
86 		  UA_STATUS_FIFO_TX_FULL);
87 }
88 
89 static bool digicolor_uart_rx_empty(struct uart_port *port)
90 {
91 	return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
92 		  UA_STATUS_FIFO_RX_EMPTY);
93 }
94 
95 static void digicolor_uart_stop_tx(struct uart_port *port)
96 {
97 	u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
98 
99 	int_enable &= ~UA_INT_TX;
100 	writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
101 }
102 
103 static void digicolor_uart_start_tx(struct uart_port *port)
104 {
105 	u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
106 
107 	int_enable |= UA_INT_TX;
108 	writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
109 }
110 
111 static void digicolor_uart_stop_rx(struct uart_port *port)
112 {
113 	u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
114 
115 	int_enable &= ~UA_INT_RX;
116 	writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
117 }
118 
119 static void digicolor_rx_poll(struct work_struct *work)
120 {
121 	struct digicolor_port *dp =
122 		container_of(to_delayed_work(work),
123 			     struct digicolor_port, rx_poll_work);
124 
125 	if (!digicolor_uart_rx_empty(&dp->port))
126 		/* force RX interrupt */
127 		writeb_relaxed(UA_INT_RX, dp->port.membase + UA_INTFLAG_SET);
128 
129 	schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));
130 }
131 
132 static void digicolor_uart_rx(struct uart_port *port)
133 {
134 	unsigned long flags;
135 
136 	spin_lock_irqsave(&port->lock, flags);
137 
138 	while (1) {
139 		u8 status, ch, ch_flag;
140 
141 		if (digicolor_uart_rx_empty(port))
142 			break;
143 
144 		ch = readb_relaxed(port->membase + UA_EMI_REC);
145 		status = readb_relaxed(port->membase + UA_STATUS);
146 
147 		port->icount.rx++;
148 		ch_flag = TTY_NORMAL;
149 
150 		if (status) {
151 			if (status & UA_STATUS_PARITY_ERR)
152 				port->icount.parity++;
153 			else if (status & UA_STATUS_FRAME_ERR)
154 				port->icount.frame++;
155 			else if (status & UA_STATUS_OVERRUN_ERR)
156 				port->icount.overrun++;
157 
158 			status &= port->read_status_mask;
159 
160 			if (status & UA_STATUS_PARITY_ERR)
161 				ch_flag = TTY_PARITY;
162 			else if (status & UA_STATUS_FRAME_ERR)
163 				ch_flag = TTY_FRAME;
164 			else if (status & UA_STATUS_OVERRUN_ERR)
165 				ch_flag = TTY_OVERRUN;
166 		}
167 
168 		if (status & port->ignore_status_mask)
169 			continue;
170 
171 		uart_insert_char(port, status, UA_STATUS_OVERRUN_ERR, ch,
172 				 ch_flag);
173 	}
174 
175 	spin_unlock_irqrestore(&port->lock, flags);
176 
177 	tty_flip_buffer_push(&port->state->port);
178 }
179 
180 static void digicolor_uart_tx(struct uart_port *port)
181 {
182 	struct circ_buf *xmit = &port->state->xmit;
183 	unsigned long flags;
184 
185 	if (digicolor_uart_tx_full(port))
186 		return;
187 
188 	spin_lock_irqsave(&port->lock, flags);
189 
190 	if (port->x_char) {
191 		writeb_relaxed(port->x_char, port->membase + UA_EMI_REC);
192 		port->icount.tx++;
193 		port->x_char = 0;
194 		goto out;
195 	}
196 
197 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
198 		digicolor_uart_stop_tx(port);
199 		goto out;
200 	}
201 
202 	while (!uart_circ_empty(xmit)) {
203 		writeb(xmit->buf[xmit->tail], port->membase + UA_EMI_REC);
204 		uart_xmit_advance(port, 1);
205 
206 		if (digicolor_uart_tx_full(port))
207 			break;
208 	}
209 
210 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
211 		uart_write_wakeup(port);
212 
213 out:
214 	spin_unlock_irqrestore(&port->lock, flags);
215 }
216 
217 static irqreturn_t digicolor_uart_int(int irq, void *dev_id)
218 {
219 	struct uart_port *port = dev_id;
220 	u8 int_status = readb_relaxed(port->membase + UA_INT_STATUS);
221 
222 	writeb_relaxed(UA_INT_RX | UA_INT_TX,
223 		       port->membase + UA_INTFLAG_CLEAR);
224 
225 	if (int_status & UA_INT_RX)
226 		digicolor_uart_rx(port);
227 	if (int_status & UA_INT_TX)
228 		digicolor_uart_tx(port);
229 
230 	return IRQ_HANDLED;
231 }
232 
233 static unsigned int digicolor_uart_tx_empty(struct uart_port *port)
234 {
235 	u8 status = readb_relaxed(port->membase + UA_STATUS);
236 
237 	return (status & UA_STATUS_TX_READY) ? TIOCSER_TEMT : 0;
238 }
239 
240 static unsigned int digicolor_uart_get_mctrl(struct uart_port *port)
241 {
242 	return TIOCM_CTS;
243 }
244 
245 static void digicolor_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
246 {
247 }
248 
249 static void digicolor_uart_break_ctl(struct uart_port *port, int state)
250 {
251 }
252 
253 static int digicolor_uart_startup(struct uart_port *port)
254 {
255 	struct digicolor_port *dp =
256 		container_of(port, struct digicolor_port, port);
257 
258 	writeb_relaxed(UA_ENABLE_ENABLE, port->membase + UA_ENABLE);
259 	writeb_relaxed(UA_CONTROL_SOFT_RESET, port->membase + UA_CONTROL);
260 	writeb_relaxed(0, port->membase + UA_CONTROL);
261 
262 	writeb_relaxed(UA_CONFIG_FIFO_RX_FIFO_MODE
263 		       | UA_CONFIG_FIFO_TX_FIFO_MODE | UA_CONFIG_FIFO_RX_THRESH,
264 		       port->membase + UA_CONFIG_FIFO);
265 	writeb_relaxed(UA_STATUS_FIFO_RX_INT_ALMOST,
266 		       port->membase + UA_STATUS_FIFO);
267 	writeb_relaxed(UA_CONTROL_RX_ENABLE | UA_CONTROL_TX_ENABLE,
268 		       port->membase + UA_CONTROL);
269 	writeb_relaxed(UA_INT_TX | UA_INT_RX,
270 		       port->membase + UA_INT_ENABLE);
271 
272 	schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));
273 
274 	return 0;
275 }
276 
277 static void digicolor_uart_shutdown(struct uart_port *port)
278 {
279 	struct digicolor_port *dp =
280 		container_of(port, struct digicolor_port, port);
281 
282 	writeb_relaxed(0, port->membase + UA_ENABLE);
283 	cancel_delayed_work_sync(&dp->rx_poll_work);
284 }
285 
286 static void digicolor_uart_set_termios(struct uart_port *port,
287 				       struct ktermios *termios,
288 				       const struct ktermios *old)
289 {
290 	unsigned int baud, divisor;
291 	u8 config = 0;
292 	unsigned long flags;
293 
294 	/* Mask termios capabilities we don't support */
295 	termios->c_cflag &= ~CMSPAR;
296 	termios->c_iflag &= ~(BRKINT | IGNBRK);
297 
298 	/* Limit baud rates so that we don't need the fractional divider */
299 	baud = uart_get_baud_rate(port, termios, old,
300 				  port->uartclk / (0x10000*16),
301 				  port->uartclk / 256);
302 	divisor = uart_get_divisor(port, baud) - 1;
303 
304 	switch (termios->c_cflag & CSIZE) {
305 	case CS7:
306 		break;
307 	case CS8:
308 	default:
309 		config |= UA_CONFIG_CHAR_LEN;
310 		termios->c_cflag &= ~CSIZE;
311 		termios->c_cflag |= CS8;
312 		break;
313 	}
314 
315 	if (termios->c_cflag & CSTOPB)
316 		config |= UA_CONFIG_STOP_BITS;
317 
318 	if (termios->c_cflag & PARENB) {
319 		config |= UA_CONFIG_PARITY;
320 		if (termios->c_cflag & PARODD)
321 			config |= UA_CONFIG_ODD_PARITY;
322 	}
323 
324 	/* Set read status mask */
325 	port->read_status_mask = UA_STATUS_OVERRUN_ERR;
326 	if (termios->c_iflag & INPCK)
327 		port->read_status_mask |= UA_STATUS_PARITY_ERR
328 			| UA_STATUS_FRAME_ERR;
329 
330 	/* Set status ignore mask */
331 	port->ignore_status_mask = 0;
332 	if (!(termios->c_cflag & CREAD))
333 		port->ignore_status_mask |= UA_STATUS_OVERRUN_ERR
334 			| UA_STATUS_PARITY_ERR | UA_STATUS_FRAME_ERR;
335 
336 	spin_lock_irqsave(&port->lock, flags);
337 
338 	uart_update_timeout(port, termios->c_cflag, baud);
339 
340 	writeb_relaxed(config, port->membase + UA_CONFIG);
341 	writeb_relaxed(divisor & 0xff, port->membase + UA_HBAUD_LO);
342 	writeb_relaxed(divisor >> 8, port->membase + UA_HBAUD_HI);
343 
344 	spin_unlock_irqrestore(&port->lock, flags);
345 }
346 
347 static const char *digicolor_uart_type(struct uart_port *port)
348 {
349 	return (port->type == PORT_DIGICOLOR) ? "DIGICOLOR USART" : NULL;
350 }
351 
352 static void digicolor_uart_config_port(struct uart_port *port, int flags)
353 {
354 	if (flags & UART_CONFIG_TYPE)
355 		port->type = PORT_DIGICOLOR;
356 }
357 
358 static void digicolor_uart_release_port(struct uart_port *port)
359 {
360 }
361 
362 static int digicolor_uart_request_port(struct uart_port *port)
363 {
364 	return 0;
365 }
366 
367 static const struct uart_ops digicolor_uart_ops = {
368 	.tx_empty	= digicolor_uart_tx_empty,
369 	.set_mctrl	= digicolor_uart_set_mctrl,
370 	.get_mctrl	= digicolor_uart_get_mctrl,
371 	.stop_tx	= digicolor_uart_stop_tx,
372 	.start_tx	= digicolor_uart_start_tx,
373 	.stop_rx	= digicolor_uart_stop_rx,
374 	.break_ctl	= digicolor_uart_break_ctl,
375 	.startup	= digicolor_uart_startup,
376 	.shutdown	= digicolor_uart_shutdown,
377 	.set_termios	= digicolor_uart_set_termios,
378 	.type		= digicolor_uart_type,
379 	.config_port	= digicolor_uart_config_port,
380 	.release_port	= digicolor_uart_release_port,
381 	.request_port	= digicolor_uart_request_port,
382 };
383 
384 static void digicolor_uart_console_putchar(struct uart_port *port, unsigned char ch)
385 {
386 	while (digicolor_uart_tx_full(port))
387 		cpu_relax();
388 
389 	writeb_relaxed(ch, port->membase + UA_EMI_REC);
390 }
391 
392 static void digicolor_uart_console_write(struct console *co, const char *c,
393 					 unsigned n)
394 {
395 	struct uart_port *port = digicolor_ports[co->index];
396 	u8 status;
397 	unsigned long flags;
398 	int locked = 1;
399 
400 	if (oops_in_progress)
401 		locked = spin_trylock_irqsave(&port->lock, flags);
402 	else
403 		spin_lock_irqsave(&port->lock, flags);
404 
405 	uart_console_write(port, c, n, digicolor_uart_console_putchar);
406 
407 	if (locked)
408 		spin_unlock_irqrestore(&port->lock, flags);
409 
410 	/* Wait for transmitter to become empty */
411 	do {
412 		status = readb_relaxed(port->membase + UA_STATUS);
413 	} while ((status & UA_STATUS_TX_READY) == 0);
414 }
415 
416 static int digicolor_uart_console_setup(struct console *co, char *options)
417 {
418 	int baud = 115200, bits = 8, parity = 'n', flow = 'n';
419 	struct uart_port *port;
420 
421 	if (co->index < 0 || co->index >= DIGICOLOR_USART_NR)
422 		return -EINVAL;
423 
424 	port = digicolor_ports[co->index];
425 	if (!port)
426 		return -ENODEV;
427 
428 	if (options)
429 		uart_parse_options(options, &baud, &parity, &bits, &flow);
430 
431 	return uart_set_options(port, co, baud, parity, bits, flow);
432 }
433 
434 static struct console digicolor_console = {
435 	.name	= "ttyS",
436 	.device	= uart_console_device,
437 	.write	= digicolor_uart_console_write,
438 	.setup	= digicolor_uart_console_setup,
439 	.flags	= CON_PRINTBUFFER,
440 	.index	= -1,
441 };
442 
443 static struct uart_driver digicolor_uart = {
444 	.driver_name	= "digicolor-usart",
445 	.dev_name	= "ttyS",
446 	.nr		= DIGICOLOR_USART_NR,
447 };
448 
449 static int digicolor_uart_probe(struct platform_device *pdev)
450 {
451 	struct device_node *np = pdev->dev.of_node;
452 	int irq, ret, index;
453 	struct digicolor_port *dp;
454 	struct resource *res;
455 	struct clk *uart_clk;
456 
457 	if (!np) {
458 		dev_err(&pdev->dev, "Missing device tree node\n");
459 		return -ENXIO;
460 	}
461 
462 	index = of_alias_get_id(np, "serial");
463 	if (index < 0 || index >= DIGICOLOR_USART_NR)
464 		return -EINVAL;
465 
466 	dp = devm_kzalloc(&pdev->dev, sizeof(*dp), GFP_KERNEL);
467 	if (!dp)
468 		return -ENOMEM;
469 
470 	uart_clk = devm_clk_get(&pdev->dev, NULL);
471 	if (IS_ERR(uart_clk))
472 		return PTR_ERR(uart_clk);
473 
474 	dp->port.membase = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
475 	if (IS_ERR(dp->port.membase))
476 		return PTR_ERR(dp->port.membase);
477 	dp->port.mapbase = res->start;
478 
479 	irq = platform_get_irq(pdev, 0);
480 	if (irq < 0)
481 		return irq;
482 	dp->port.irq = irq;
483 
484 	dp->port.iotype = UPIO_MEM;
485 	dp->port.uartclk = clk_get_rate(uart_clk);
486 	dp->port.fifosize = 16;
487 	dp->port.dev = &pdev->dev;
488 	dp->port.ops = &digicolor_uart_ops;
489 	dp->port.line = index;
490 	dp->port.type = PORT_DIGICOLOR;
491 	spin_lock_init(&dp->port.lock);
492 
493 	digicolor_ports[index] = &dp->port;
494 	platform_set_drvdata(pdev, &dp->port);
495 
496 	INIT_DELAYED_WORK(&dp->rx_poll_work, digicolor_rx_poll);
497 
498 	ret = devm_request_irq(&pdev->dev, dp->port.irq, digicolor_uart_int, 0,
499 			       dev_name(&pdev->dev), &dp->port);
500 	if (ret)
501 		return ret;
502 
503 	return uart_add_one_port(&digicolor_uart, &dp->port);
504 }
505 
506 static int digicolor_uart_remove(struct platform_device *pdev)
507 {
508 	struct uart_port *port = platform_get_drvdata(pdev);
509 
510 	uart_remove_one_port(&digicolor_uart, port);
511 
512 	return 0;
513 }
514 
515 static const struct of_device_id digicolor_uart_dt_ids[] = {
516 	{ .compatible = "cnxt,cx92755-usart", },
517 	{ }
518 };
519 MODULE_DEVICE_TABLE(of, digicolor_uart_dt_ids);
520 
521 static struct platform_driver digicolor_uart_platform = {
522 	.driver = {
523 		.name		= "digicolor-usart",
524 		.of_match_table	= of_match_ptr(digicolor_uart_dt_ids),
525 	},
526 	.probe	= digicolor_uart_probe,
527 	.remove	= digicolor_uart_remove,
528 };
529 
530 static int __init digicolor_uart_init(void)
531 {
532 	int ret;
533 
534 	if (IS_ENABLED(CONFIG_SERIAL_CONEXANT_DIGICOLOR_CONSOLE)) {
535 		digicolor_uart.cons = &digicolor_console;
536 		digicolor_console.data = &digicolor_uart;
537 	}
538 
539 	ret = uart_register_driver(&digicolor_uart);
540 	if (ret)
541 		return ret;
542 
543 	ret = platform_driver_register(&digicolor_uart_platform);
544 	if (ret)
545 		uart_unregister_driver(&digicolor_uart);
546 
547 	return ret;
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