xref: /openbmc/linux/drivers/tty/serial/21285.c (revision f59a3ee6) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Driver for the serial port on the 21285 StrongArm-110 core logic chip.
4  *
5  * Based on drivers/char/serial.c
6  */
7 #include <linux/module.h>
8 #include <linux/tty.h>
9 #include <linux/ioport.h>
10 #include <linux/init.h>
11 #include <linux/console.h>
12 #include <linux/device.h>
13 #include <linux/tty_flip.h>
14 #include <linux/serial_core.h>
15 #include <linux/serial.h>
16 #include <linux/io.h>
17 
18 #include <asm/irq.h>
19 #include <asm/mach-types.h>
20 #include <asm/system_info.h>
21 #include <asm/hardware/dec21285.h>
22 #include <mach/hardware.h>
23 
24 #define BAUD_BASE		(mem_fclk_21285/64)
25 
26 #define SERIAL_21285_NAME	"ttyFB"
27 #define SERIAL_21285_MAJOR	204
28 #define SERIAL_21285_MINOR	4
29 
30 #define RXSTAT_DUMMY_READ	0x80000000
31 #define RXSTAT_FRAME		(1 << 0)
32 #define RXSTAT_PARITY		(1 << 1)
33 #define RXSTAT_OVERRUN		(1 << 2)
34 #define RXSTAT_ANYERR		(RXSTAT_FRAME|RXSTAT_PARITY|RXSTAT_OVERRUN)
35 
36 #define H_UBRLCR_BREAK		(1 << 0)
37 #define H_UBRLCR_PARENB		(1 << 1)
38 #define H_UBRLCR_PAREVN		(1 << 2)
39 #define H_UBRLCR_STOPB		(1 << 3)
40 #define H_UBRLCR_FIFO		(1 << 4)
41 
42 static const char serial21285_name[] = "Footbridge UART";
43 
44 /*
45  * We only need 2 bits of data, so instead of creating a whole structure for
46  * this, use bits of the private_data pointer of the uart port structure.
47  */
48 #define tx_enabled_bit	0
49 #define rx_enabled_bit	1
50 
51 static bool is_enabled(struct uart_port *port, int bit)
52 {
53 	unsigned long *private_data = (unsigned long *)&port->private_data;
54 
55 	if (test_bit(bit, private_data))
56 		return true;
57 	return false;
58 }
59 
60 static void enable(struct uart_port *port, int bit)
61 {
62 	unsigned long *private_data = (unsigned long *)&port->private_data;
63 
64 	set_bit(bit, private_data);
65 }
66 
67 static void disable(struct uart_port *port, int bit)
68 {
69 	unsigned long *private_data = (unsigned long *)&port->private_data;
70 
71 	clear_bit(bit, private_data);
72 }
73 
74 #define is_tx_enabled(port)	is_enabled(port, tx_enabled_bit)
75 #define tx_enable(port)		enable(port, tx_enabled_bit)
76 #define tx_disable(port)	disable(port, tx_enabled_bit)
77 
78 #define is_rx_enabled(port)	is_enabled(port, rx_enabled_bit)
79 #define rx_enable(port)		enable(port, rx_enabled_bit)
80 #define rx_disable(port)	disable(port, rx_enabled_bit)
81 
82 /*
83  * The documented expression for selecting the divisor is:
84  *  BAUD_BASE / baud - 1
85  * However, typically BAUD_BASE is not divisible by baud, so
86  * we want to select the divisor that gives us the minimum
87  * error.  Therefore, we want:
88  *  int(BAUD_BASE / baud - 0.5) ->
89  *  int(BAUD_BASE / baud - (baud >> 1) / baud) ->
90  *  int((BAUD_BASE - (baud >> 1)) / baud)
91  */
92 
93 static void serial21285_stop_tx(struct uart_port *port)
94 {
95 	if (is_tx_enabled(port)) {
96 		disable_irq_nosync(IRQ_CONTX);
97 		tx_disable(port);
98 	}
99 }
100 
101 static void serial21285_start_tx(struct uart_port *port)
102 {
103 	if (!is_tx_enabled(port)) {
104 		enable_irq(IRQ_CONTX);
105 		tx_enable(port);
106 	}
107 }
108 
109 static void serial21285_stop_rx(struct uart_port *port)
110 {
111 	if (is_rx_enabled(port)) {
112 		disable_irq_nosync(IRQ_CONRX);
113 		rx_disable(port);
114 	}
115 }
116 
117 static irqreturn_t serial21285_rx_chars(int irq, void *dev_id)
118 {
119 	struct uart_port *port = dev_id;
120 	unsigned int status, ch, flag, rxs, max_count = 256;
121 
122 	status = *CSR_UARTFLG;
123 	while (!(status & 0x10) && max_count--) {
124 		ch = *CSR_UARTDR;
125 		flag = TTY_NORMAL;
126 		port->icount.rx++;
127 
128 		rxs = *CSR_RXSTAT | RXSTAT_DUMMY_READ;
129 		if (unlikely(rxs & RXSTAT_ANYERR)) {
130 			if (rxs & RXSTAT_PARITY)
131 				port->icount.parity++;
132 			else if (rxs & RXSTAT_FRAME)
133 				port->icount.frame++;
134 			if (rxs & RXSTAT_OVERRUN)
135 				port->icount.overrun++;
136 
137 			rxs &= port->read_status_mask;
138 
139 			if (rxs & RXSTAT_PARITY)
140 				flag = TTY_PARITY;
141 			else if (rxs & RXSTAT_FRAME)
142 				flag = TTY_FRAME;
143 		}
144 
145 		uart_insert_char(port, rxs, RXSTAT_OVERRUN, ch, flag);
146 
147 		status = *CSR_UARTFLG;
148 	}
149 	tty_flip_buffer_push(&port->state->port);
150 
151 	return IRQ_HANDLED;
152 }
153 
154 static irqreturn_t serial21285_tx_chars(int irq, void *dev_id)
155 {
156 	struct uart_port *port = dev_id;
157 	struct circ_buf *xmit = &port->state->xmit;
158 	int count = 256;
159 
160 	if (port->x_char) {
161 		*CSR_UARTDR = port->x_char;
162 		port->icount.tx++;
163 		port->x_char = 0;
164 		goto out;
165 	}
166 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
167 		serial21285_stop_tx(port);
168 		goto out;
169 	}
170 
171 	do {
172 		*CSR_UARTDR = xmit->buf[xmit->tail];
173 		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
174 		port->icount.tx++;
175 		if (uart_circ_empty(xmit))
176 			break;
177 	} while (--count > 0 && !(*CSR_UARTFLG & 0x20));
178 
179 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
180 		uart_write_wakeup(port);
181 
182 	if (uart_circ_empty(xmit))
183 		serial21285_stop_tx(port);
184 
185  out:
186 	return IRQ_HANDLED;
187 }
188 
189 static unsigned int serial21285_tx_empty(struct uart_port *port)
190 {
191 	return (*CSR_UARTFLG & 8) ? 0 : TIOCSER_TEMT;
192 }
193 
194 /* no modem control lines */
195 static unsigned int serial21285_get_mctrl(struct uart_port *port)
196 {
197 	return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
198 }
199 
200 static void serial21285_set_mctrl(struct uart_port *port, unsigned int mctrl)
201 {
202 }
203 
204 static void serial21285_break_ctl(struct uart_port *port, int break_state)
205 {
206 	unsigned long flags;
207 	unsigned int h_lcr;
208 
209 	spin_lock_irqsave(&port->lock, flags);
210 	h_lcr = *CSR_H_UBRLCR;
211 	if (break_state)
212 		h_lcr |= H_UBRLCR_BREAK;
213 	else
214 		h_lcr &= ~H_UBRLCR_BREAK;
215 	*CSR_H_UBRLCR = h_lcr;
216 	spin_unlock_irqrestore(&port->lock, flags);
217 }
218 
219 static int serial21285_startup(struct uart_port *port)
220 {
221 	int ret;
222 
223 	tx_enable(port);
224 	rx_enable(port);
225 
226 	ret = request_irq(IRQ_CONRX, serial21285_rx_chars, 0,
227 			  serial21285_name, port);
228 	if (ret == 0) {
229 		ret = request_irq(IRQ_CONTX, serial21285_tx_chars, 0,
230 				  serial21285_name, port);
231 		if (ret)
232 			free_irq(IRQ_CONRX, port);
233 	}
234 
235 	return ret;
236 }
237 
238 static void serial21285_shutdown(struct uart_port *port)
239 {
240 	free_irq(IRQ_CONTX, port);
241 	free_irq(IRQ_CONRX, port);
242 }
243 
244 static void
245 serial21285_set_termios(struct uart_port *port, struct ktermios *termios,
246 			const struct ktermios *old)
247 {
248 	unsigned long flags;
249 	unsigned int baud, quot, h_lcr, b;
250 
251 	/*
252 	 * We don't support modem control lines.
253 	 */
254 	termios->c_cflag &= ~(HUPCL | CRTSCTS | CMSPAR);
255 	termios->c_cflag |= CLOCAL;
256 
257 	/*
258 	 * We don't support BREAK character recognition.
259 	 */
260 	termios->c_iflag &= ~(IGNBRK | BRKINT);
261 
262 	/*
263 	 * Ask the core to calculate the divisor for us.
264 	 */
265 	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
266 	quot = uart_get_divisor(port, baud);
267 	b = port->uartclk / (16 * quot);
268 	tty_termios_encode_baud_rate(termios, b, b);
269 
270 	switch (termios->c_cflag & CSIZE) {
271 	case CS5:
272 		h_lcr = 0x00;
273 		break;
274 	case CS6:
275 		h_lcr = 0x20;
276 		break;
277 	case CS7:
278 		h_lcr = 0x40;
279 		break;
280 	default: /* CS8 */
281 		h_lcr = 0x60;
282 		break;
283 	}
284 
285 	if (termios->c_cflag & CSTOPB)
286 		h_lcr |= H_UBRLCR_STOPB;
287 	if (termios->c_cflag & PARENB) {
288 		h_lcr |= H_UBRLCR_PARENB;
289 		if (!(termios->c_cflag & PARODD))
290 			h_lcr |= H_UBRLCR_PAREVN;
291 	}
292 
293 	if (port->fifosize)
294 		h_lcr |= H_UBRLCR_FIFO;
295 
296 	spin_lock_irqsave(&port->lock, flags);
297 
298 	/*
299 	 * Update the per-port timeout.
300 	 */
301 	uart_update_timeout(port, termios->c_cflag, baud);
302 
303 	/*
304 	 * Which character status flags are we interested in?
305 	 */
306 	port->read_status_mask = RXSTAT_OVERRUN;
307 	if (termios->c_iflag & INPCK)
308 		port->read_status_mask |= RXSTAT_FRAME | RXSTAT_PARITY;
309 
310 	/*
311 	 * Which character status flags should we ignore?
312 	 */
313 	port->ignore_status_mask = 0;
314 	if (termios->c_iflag & IGNPAR)
315 		port->ignore_status_mask |= RXSTAT_FRAME | RXSTAT_PARITY;
316 	if (termios->c_iflag & IGNBRK && termios->c_iflag & IGNPAR)
317 		port->ignore_status_mask |= RXSTAT_OVERRUN;
318 
319 	/*
320 	 * Ignore all characters if CREAD is not set.
321 	 */
322 	if ((termios->c_cflag & CREAD) == 0)
323 		port->ignore_status_mask |= RXSTAT_DUMMY_READ;
324 
325 	quot -= 1;
326 
327 	*CSR_UARTCON = 0;
328 	*CSR_L_UBRLCR = quot & 0xff;
329 	*CSR_M_UBRLCR = (quot >> 8) & 0x0f;
330 	*CSR_H_UBRLCR = h_lcr;
331 	*CSR_UARTCON = 1;
332 
333 	spin_unlock_irqrestore(&port->lock, flags);
334 }
335 
336 static const char *serial21285_type(struct uart_port *port)
337 {
338 	return port->type == PORT_21285 ? "DC21285" : NULL;
339 }
340 
341 static void serial21285_release_port(struct uart_port *port)
342 {
343 	release_mem_region(port->mapbase, 32);
344 }
345 
346 static int serial21285_request_port(struct uart_port *port)
347 {
348 	return request_mem_region(port->mapbase, 32, serial21285_name)
349 			 != NULL ? 0 : -EBUSY;
350 }
351 
352 static void serial21285_config_port(struct uart_port *port, int flags)
353 {
354 	if (flags & UART_CONFIG_TYPE && serial21285_request_port(port) == 0)
355 		port->type = PORT_21285;
356 }
357 
358 /*
359  * verify the new serial_struct (for TIOCSSERIAL).
360  */
361 static int serial21285_verify_port(struct uart_port *port, struct serial_struct *ser)
362 {
363 	int ret = 0;
364 	if (ser->type != PORT_UNKNOWN && ser->type != PORT_21285)
365 		ret = -EINVAL;
366 	if (ser->irq <= 0)
367 		ret = -EINVAL;
368 	if (ser->baud_base != port->uartclk / 16)
369 		ret = -EINVAL;
370 	return ret;
371 }
372 
373 static const struct uart_ops serial21285_ops = {
374 	.tx_empty	= serial21285_tx_empty,
375 	.get_mctrl	= serial21285_get_mctrl,
376 	.set_mctrl	= serial21285_set_mctrl,
377 	.stop_tx	= serial21285_stop_tx,
378 	.start_tx	= serial21285_start_tx,
379 	.stop_rx	= serial21285_stop_rx,
380 	.break_ctl	= serial21285_break_ctl,
381 	.startup	= serial21285_startup,
382 	.shutdown	= serial21285_shutdown,
383 	.set_termios	= serial21285_set_termios,
384 	.type		= serial21285_type,
385 	.release_port	= serial21285_release_port,
386 	.request_port	= serial21285_request_port,
387 	.config_port	= serial21285_config_port,
388 	.verify_port	= serial21285_verify_port,
389 };
390 
391 static struct uart_port serial21285_port = {
392 	.mapbase	= 0x42000160,
393 	.iotype		= UPIO_MEM,
394 	.irq		= 0,
395 	.fifosize	= 16,
396 	.ops		= &serial21285_ops,
397 	.flags		= UPF_BOOT_AUTOCONF,
398 };
399 
400 static void serial21285_setup_ports(void)
401 {
402 	serial21285_port.uartclk = mem_fclk_21285 / 4;
403 }
404 
405 #ifdef CONFIG_SERIAL_21285_CONSOLE
406 static void serial21285_console_putchar(struct uart_port *port, unsigned char ch)
407 {
408 	while (*CSR_UARTFLG & 0x20)
409 		barrier();
410 	*CSR_UARTDR = ch;
411 }
412 
413 static void
414 serial21285_console_write(struct console *co, const char *s,
415 			  unsigned int count)
416 {
417 	uart_console_write(&serial21285_port, s, count, serial21285_console_putchar);
418 }
419 
420 static void __init
421 serial21285_get_options(struct uart_port *port, int *baud,
422 			int *parity, int *bits)
423 {
424 	if (*CSR_UARTCON == 1) {
425 		unsigned int tmp;
426 
427 		tmp = *CSR_H_UBRLCR;
428 		switch (tmp & 0x60) {
429 		case 0x00:
430 			*bits = 5;
431 			break;
432 		case 0x20:
433 			*bits = 6;
434 			break;
435 		case 0x40:
436 			*bits = 7;
437 			break;
438 		default:
439 		case 0x60:
440 			*bits = 8;
441 			break;
442 		}
443 
444 		if (tmp & H_UBRLCR_PARENB) {
445 			*parity = 'o';
446 			if (tmp & H_UBRLCR_PAREVN)
447 				*parity = 'e';
448 		}
449 
450 		tmp = *CSR_L_UBRLCR | (*CSR_M_UBRLCR << 8);
451 
452 		*baud = port->uartclk / (16 * (tmp + 1));
453 	}
454 }
455 
456 static int __init serial21285_console_setup(struct console *co, char *options)
457 {
458 	struct uart_port *port = &serial21285_port;
459 	int baud = 9600;
460 	int bits = 8;
461 	int parity = 'n';
462 	int flow = 'n';
463 
464 	/*
465 	 * Check whether an invalid uart number has been specified, and
466 	 * if so, search for the first available port that does have
467 	 * console support.
468 	 */
469 	if (options)
470 		uart_parse_options(options, &baud, &parity, &bits, &flow);
471 	else
472 		serial21285_get_options(port, &baud, &parity, &bits);
473 
474 	return uart_set_options(port, co, baud, parity, bits, flow);
475 }
476 
477 static struct uart_driver serial21285_reg;
478 
479 static struct console serial21285_console =
480 {
481 	.name		= SERIAL_21285_NAME,
482 	.write		= serial21285_console_write,
483 	.device		= uart_console_device,
484 	.setup		= serial21285_console_setup,
485 	.flags		= CON_PRINTBUFFER,
486 	.index		= -1,
487 	.data		= &serial21285_reg,
488 };
489 
490 static int __init rs285_console_init(void)
491 {
492 	serial21285_setup_ports();
493 	register_console(&serial21285_console);
494 	return 0;
495 }
496 console_initcall(rs285_console_init);
497 
498 #define SERIAL_21285_CONSOLE	&serial21285_console
499 #else
500 #define SERIAL_21285_CONSOLE	NULL
501 #endif
502 
503 static struct uart_driver serial21285_reg = {
504 	.owner			= THIS_MODULE,
505 	.driver_name		= "ttyFB",
506 	.dev_name		= "ttyFB",
507 	.major			= SERIAL_21285_MAJOR,
508 	.minor			= SERIAL_21285_MINOR,
509 	.nr			= 1,
510 	.cons			= SERIAL_21285_CONSOLE,
511 };
512 
513 static int __init serial21285_init(void)
514 {
515 	int ret;
516 
517 	printk(KERN_INFO "Serial: 21285 driver\n");
518 
519 	serial21285_setup_ports();
520 
521 	ret = uart_register_driver(&serial21285_reg);
522 	if (ret == 0)
523 		uart_add_one_port(&serial21285_reg, &serial21285_port);
524 
525 	return ret;
526 }
527 
528 static void __exit serial21285_exit(void)
529 {
530 	uart_remove_one_port(&serial21285_reg, &serial21285_port);
531 	uart_unregister_driver(&serial21285_reg);
532 }
533 
534 module_init(serial21285_init);
535 module_exit(serial21285_exit);
536 
537 MODULE_LICENSE("GPL");
538 MODULE_DESCRIPTION("Intel Footbridge (21285) serial driver");
539 MODULE_ALIAS_CHARDEV(SERIAL_21285_MAJOR, SERIAL_21285_MINOR);
540