xref: /linux/drivers/tty/serial/21285.c (revision 40d269c000bda9fcd276a0412a9cebd3f6e344c5) 
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, rxs, max_count = 256;
121 	u8 ch, flag;
122 
123 	status = *CSR_UARTFLG;
124 	while (!(status & 0x10) && max_count--) {
125 		ch = *CSR_UARTDR;
126 		flag = TTY_NORMAL;
127 		port->icount.rx++;
128 
129 		rxs = *CSR_RXSTAT | RXSTAT_DUMMY_READ;
130 		if (unlikely(rxs & RXSTAT_ANYERR)) {
131 			if (rxs & RXSTAT_PARITY)
132 				port->icount.parity++;
133 			else if (rxs & RXSTAT_FRAME)
134 				port->icount.frame++;
135 			if (rxs & RXSTAT_OVERRUN)
136 				port->icount.overrun++;
137 
138 			rxs &= port->read_status_mask;
139 
140 			if (rxs & RXSTAT_PARITY)
141 				flag = TTY_PARITY;
142 			else if (rxs & RXSTAT_FRAME)
143 				flag = TTY_FRAME;
144 		}
145 
146 		uart_insert_char(port, rxs, RXSTAT_OVERRUN, ch, flag);
147 
148 		status = *CSR_UARTFLG;
149 	}
150 	tty_flip_buffer_push(&port->state->port);
151 
152 	return IRQ_HANDLED;
153 }
154 
155 static irqreturn_t serial21285_tx_chars(int irq, void *dev_id)
156 {
157 	struct uart_port *port = dev_id;
158 	u8 ch;
159 
160 	uart_port_tx_limited(port, ch, 256,
161 		!(*CSR_UARTFLG & 0x20),
162 		*CSR_UARTDR = ch,
163 		({}));
164 
165 	return IRQ_HANDLED;
166 }
167 
168 static unsigned int serial21285_tx_empty(struct uart_port *port)
169 {
170 	return (*CSR_UARTFLG & 8) ? 0 : TIOCSER_TEMT;
171 }
172 
173 /* no modem control lines */
174 static unsigned int serial21285_get_mctrl(struct uart_port *port)
175 {
176 	return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
177 }
178 
179 static void serial21285_set_mctrl(struct uart_port *port, unsigned int mctrl)
180 {
181 }
182 
183 static void serial21285_break_ctl(struct uart_port *port, int break_state)
184 {
185 	unsigned long flags;
186 	unsigned int h_lcr;
187 
188 	uart_port_lock_irqsave(port, &flags);
189 	h_lcr = *CSR_H_UBRLCR;
190 	if (break_state)
191 		h_lcr |= H_UBRLCR_BREAK;
192 	else
193 		h_lcr &= ~H_UBRLCR_BREAK;
194 	*CSR_H_UBRLCR = h_lcr;
195 	uart_port_unlock_irqrestore(port, flags);
196 }
197 
198 static int serial21285_startup(struct uart_port *port)
199 {
200 	int ret;
201 
202 	tx_enable(port);
203 	rx_enable(port);
204 
205 	ret = request_irq(IRQ_CONRX, serial21285_rx_chars, 0,
206 			  serial21285_name, port);
207 	if (ret == 0) {
208 		ret = request_irq(IRQ_CONTX, serial21285_tx_chars, 0,
209 				  serial21285_name, port);
210 		if (ret)
211 			free_irq(IRQ_CONRX, port);
212 	}
213 
214 	return ret;
215 }
216 
217 static void serial21285_shutdown(struct uart_port *port)
218 {
219 	free_irq(IRQ_CONTX, port);
220 	free_irq(IRQ_CONRX, port);
221 }
222 
223 static void
224 serial21285_set_termios(struct uart_port *port, struct ktermios *termios,
225 			const struct ktermios *old)
226 {
227 	unsigned long flags;
228 	unsigned int baud, quot, h_lcr, b;
229 
230 	/*
231 	 * We don't support modem control lines.
232 	 */
233 	termios->c_cflag &= ~(HUPCL | CRTSCTS | CMSPAR);
234 	termios->c_cflag |= CLOCAL;
235 
236 	/*
237 	 * We don't support BREAK character recognition.
238 	 */
239 	termios->c_iflag &= ~(IGNBRK | BRKINT);
240 
241 	/*
242 	 * Ask the core to calculate the divisor for us.
243 	 */
244 	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
245 	quot = uart_get_divisor(port, baud);
246 	b = port->uartclk / (16 * quot);
247 	tty_termios_encode_baud_rate(termios, b, b);
248 
249 	switch (termios->c_cflag & CSIZE) {
250 	case CS5:
251 		h_lcr = 0x00;
252 		break;
253 	case CS6:
254 		h_lcr = 0x20;
255 		break;
256 	case CS7:
257 		h_lcr = 0x40;
258 		break;
259 	default: /* CS8 */
260 		h_lcr = 0x60;
261 		break;
262 	}
263 
264 	if (termios->c_cflag & CSTOPB)
265 		h_lcr |= H_UBRLCR_STOPB;
266 	if (termios->c_cflag & PARENB) {
267 		h_lcr |= H_UBRLCR_PARENB;
268 		if (!(termios->c_cflag & PARODD))
269 			h_lcr |= H_UBRLCR_PAREVN;
270 	}
271 
272 	if (port->fifosize)
273 		h_lcr |= H_UBRLCR_FIFO;
274 
275 	uart_port_lock_irqsave(port, &flags);
276 
277 	/*
278 	 * Update the per-port timeout.
279 	 */
280 	uart_update_timeout(port, termios->c_cflag, baud);
281 
282 	/*
283 	 * Which character status flags are we interested in?
284 	 */
285 	port->read_status_mask = RXSTAT_OVERRUN;
286 	if (termios->c_iflag & INPCK)
287 		port->read_status_mask |= RXSTAT_FRAME | RXSTAT_PARITY;
288 
289 	/*
290 	 * Which character status flags should we ignore?
291 	 */
292 	port->ignore_status_mask = 0;
293 	if (termios->c_iflag & IGNPAR)
294 		port->ignore_status_mask |= RXSTAT_FRAME | RXSTAT_PARITY;
295 	if (termios->c_iflag & IGNBRK && termios->c_iflag & IGNPAR)
296 		port->ignore_status_mask |= RXSTAT_OVERRUN;
297 
298 	/*
299 	 * Ignore all characters if CREAD is not set.
300 	 */
301 	if ((termios->c_cflag & CREAD) == 0)
302 		port->ignore_status_mask |= RXSTAT_DUMMY_READ;
303 
304 	quot -= 1;
305 
306 	*CSR_UARTCON = 0;
307 	*CSR_L_UBRLCR = quot & 0xff;
308 	*CSR_M_UBRLCR = (quot >> 8) & 0x0f;
309 	*CSR_H_UBRLCR = h_lcr;
310 	*CSR_UARTCON = 1;
311 
312 	uart_port_unlock_irqrestore(port, flags);
313 }
314 
315 static const char *serial21285_type(struct uart_port *port)
316 {
317 	return port->type == PORT_21285 ? "DC21285" : NULL;
318 }
319 
320 static void serial21285_release_port(struct uart_port *port)
321 {
322 	release_mem_region(port->mapbase, 32);
323 }
324 
325 static int serial21285_request_port(struct uart_port *port)
326 {
327 	return request_mem_region(port->mapbase, 32, serial21285_name)
328 			 != NULL ? 0 : -EBUSY;
329 }
330 
331 static void serial21285_config_port(struct uart_port *port, int flags)
332 {
333 	if (flags & UART_CONFIG_TYPE && serial21285_request_port(port) == 0)
334 		port->type = PORT_21285;
335 }
336 
337 /*
338  * verify the new serial_struct (for TIOCSSERIAL).
339  */
340 static int serial21285_verify_port(struct uart_port *port, struct serial_struct *ser)
341 {
342 	int ret = 0;
343 	if (ser->type != PORT_UNKNOWN && ser->type != PORT_21285)
344 		ret = -EINVAL;
345 	if (ser->irq <= 0)
346 		ret = -EINVAL;
347 	if (ser->baud_base != port->uartclk / 16)
348 		ret = -EINVAL;
349 	return ret;
350 }
351 
352 static const struct uart_ops serial21285_ops = {
353 	.tx_empty	= serial21285_tx_empty,
354 	.get_mctrl	= serial21285_get_mctrl,
355 	.set_mctrl	= serial21285_set_mctrl,
356 	.stop_tx	= serial21285_stop_tx,
357 	.start_tx	= serial21285_start_tx,
358 	.stop_rx	= serial21285_stop_rx,
359 	.break_ctl	= serial21285_break_ctl,
360 	.startup	= serial21285_startup,
361 	.shutdown	= serial21285_shutdown,
362 	.set_termios	= serial21285_set_termios,
363 	.type		= serial21285_type,
364 	.release_port	= serial21285_release_port,
365 	.request_port	= serial21285_request_port,
366 	.config_port	= serial21285_config_port,
367 	.verify_port	= serial21285_verify_port,
368 };
369 
370 static struct uart_port serial21285_port = {
371 	.mapbase	= 0x42000160,
372 	.iotype		= UPIO_MEM,
373 	.irq		= 0,
374 	.fifosize	= 16,
375 	.ops		= &serial21285_ops,
376 	.flags		= UPF_BOOT_AUTOCONF,
377 };
378 
379 static void serial21285_setup_ports(void)
380 {
381 	serial21285_port.uartclk = mem_fclk_21285 / 4;
382 }
383 
384 #ifdef CONFIG_SERIAL_21285_CONSOLE
385 static void serial21285_console_putchar(struct uart_port *port, unsigned char ch)
386 {
387 	while (*CSR_UARTFLG & 0x20)
388 		barrier();
389 	*CSR_UARTDR = ch;
390 }
391 
392 static void
393 serial21285_console_write(struct console *co, const char *s,
394 			  unsigned int count)
395 {
396 	uart_console_write(&serial21285_port, s, count, serial21285_console_putchar);
397 }
398 
399 static void __init
400 serial21285_get_options(struct uart_port *port, int *baud,
401 			int *parity, int *bits)
402 {
403 	if (*CSR_UARTCON == 1) {
404 		unsigned int tmp;
405 
406 		tmp = *CSR_H_UBRLCR;
407 		switch (tmp & 0x60) {
408 		case 0x00:
409 			*bits = 5;
410 			break;
411 		case 0x20:
412 			*bits = 6;
413 			break;
414 		case 0x40:
415 			*bits = 7;
416 			break;
417 		default:
418 		case 0x60:
419 			*bits = 8;
420 			break;
421 		}
422 
423 		if (tmp & H_UBRLCR_PARENB) {
424 			*parity = 'o';
425 			if (tmp & H_UBRLCR_PAREVN)
426 				*parity = 'e';
427 		}
428 
429 		tmp = *CSR_L_UBRLCR | (*CSR_M_UBRLCR << 8);
430 
431 		*baud = port->uartclk / (16 * (tmp + 1));
432 	}
433 }
434 
435 static int __init serial21285_console_setup(struct console *co, char *options)
436 {
437 	struct uart_port *port = &serial21285_port;
438 	int baud = 9600;
439 	int bits = 8;
440 	int parity = 'n';
441 	int flow = 'n';
442 
443 	/*
444 	 * Check whether an invalid uart number has been specified, and
445 	 * if so, search for the first available port that does have
446 	 * console support.
447 	 */
448 	if (options)
449 		uart_parse_options(options, &baud, &parity, &bits, &flow);
450 	else
451 		serial21285_get_options(port, &baud, &parity, &bits);
452 
453 	return uart_set_options(port, co, baud, parity, bits, flow);
454 }
455 
456 static struct uart_driver serial21285_reg;
457 
458 static struct console serial21285_console =
459 {
460 	.name		= SERIAL_21285_NAME,
461 	.write		= serial21285_console_write,
462 	.device		= uart_console_device,
463 	.setup		= serial21285_console_setup,
464 	.flags		= CON_PRINTBUFFER,
465 	.index		= -1,
466 	.data		= &serial21285_reg,
467 };
468 
469 static int __init rs285_console_init(void)
470 {
471 	serial21285_setup_ports();
472 	register_console(&serial21285_console);
473 	return 0;
474 }
475 console_initcall(rs285_console_init);
476 
477 #define SERIAL_21285_CONSOLE	&serial21285_console
478 #else
479 #define SERIAL_21285_CONSOLE	NULL
480 #endif
481 
482 static struct uart_driver serial21285_reg = {
483 	.owner			= THIS_MODULE,
484 	.driver_name		= "ttyFB",
485 	.dev_name		= "ttyFB",
486 	.major			= SERIAL_21285_MAJOR,
487 	.minor			= SERIAL_21285_MINOR,
488 	.nr			= 1,
489 	.cons			= SERIAL_21285_CONSOLE,
490 };
491 
492 static int __init serial21285_init(void)
493 {
494 	int ret;
495 
496 	printk(KERN_INFO "Serial: 21285 driver\n");
497 
498 	serial21285_setup_ports();
499 
500 	ret = uart_register_driver(&serial21285_reg);
501 	if (ret == 0)
502 		uart_add_one_port(&serial21285_reg, &serial21285_port);
503 
504 	return ret;
505 }
506 
507 static void __exit serial21285_exit(void)
508 {
509 	uart_remove_one_port(&serial21285_reg, &serial21285_port);
510 	uart_unregister_driver(&serial21285_reg);
511 }
512 
513 module_init(serial21285_init);
514 module_exit(serial21285_exit);
515 
516 MODULE_LICENSE("GPL");
517 MODULE_DESCRIPTION("Intel Footbridge (21285) serial driver");
518 MODULE_ALIAS_CHARDEV(SERIAL_21285_MAJOR, SERIAL_21285_MINOR);
519