1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * altera_jtaguart.c -- Altera JTAG UART driver
4  *
5  * Based on mcf.c -- Freescale ColdFire UART driver
6  *
7  * (C) Copyright 2003-2007, Greg Ungerer <gerg@snapgear.com>
8  * (C) Copyright 2008, Thomas Chou <thomas@wytron.com.tw>
9  * (C) Copyright 2010, Tobias Klauser <tklauser@distanz.ch>
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/init.h>
14 #include <linux/interrupt.h>
15 #include <linux/module.h>
16 #include <linux/console.h>
17 #include <linux/of.h>
18 #include <linux/tty.h>
19 #include <linux/tty_flip.h>
20 #include <linux/serial.h>
21 #include <linux/serial_core.h>
22 #include <linux/platform_device.h>
23 #include <linux/io.h>
24 #include <linux/altera_jtaguart.h>
25 
26 #define DRV_NAME "altera_jtaguart"
27 
28 /*
29  * Altera JTAG UART register definitions according to the Altera JTAG UART
30  * datasheet: https://www.altera.com/literature/hb/nios2/n2cpu_nii51009.pdf
31  */
32 
33 #define ALTERA_JTAGUART_SIZE			8
34 
35 #define ALTERA_JTAGUART_DATA_REG		0
36 
37 #define ALTERA_JTAGUART_DATA_DATA_MSK		0x000000FF
38 #define ALTERA_JTAGUART_DATA_RVALID_MSK		0x00008000
39 #define ALTERA_JTAGUART_DATA_RAVAIL_MSK		0xFFFF0000
40 #define ALTERA_JTAGUART_DATA_RAVAIL_OFF		16
41 
42 #define ALTERA_JTAGUART_CONTROL_REG		4
43 
44 #define ALTERA_JTAGUART_CONTROL_RE_MSK		0x00000001
45 #define ALTERA_JTAGUART_CONTROL_WE_MSK		0x00000002
46 #define ALTERA_JTAGUART_CONTROL_RI_MSK		0x00000100
47 #define ALTERA_JTAGUART_CONTROL_RI_OFF		8
48 #define ALTERA_JTAGUART_CONTROL_WI_MSK		0x00000200
49 #define ALTERA_JTAGUART_CONTROL_AC_MSK		0x00000400
50 #define ALTERA_JTAGUART_CONTROL_WSPACE_MSK	0xFFFF0000
51 #define ALTERA_JTAGUART_CONTROL_WSPACE_OFF	16
52 
53 /*
54  * Local per-uart structure.
55  */
56 struct altera_jtaguart {
57 	struct uart_port port;
58 	unsigned int sigs;	/* Local copy of line sigs */
59 	unsigned long imr;	/* Local IMR mirror */
60 };
61 
62 static unsigned int altera_jtaguart_tx_empty(struct uart_port *port)
63 {
64 	return (readl(port->membase + ALTERA_JTAGUART_CONTROL_REG) &
65 		ALTERA_JTAGUART_CONTROL_WSPACE_MSK) ? TIOCSER_TEMT : 0;
66 }
67 
68 static unsigned int altera_jtaguart_get_mctrl(struct uart_port *port)
69 {
70 	return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
71 }
72 
73 static void altera_jtaguart_set_mctrl(struct uart_port *port, unsigned int sigs)
74 {
75 }
76 
77 static void altera_jtaguart_start_tx(struct uart_port *port)
78 {
79 	struct altera_jtaguart *pp =
80 	    container_of(port, struct altera_jtaguart, port);
81 
82 	pp->imr |= ALTERA_JTAGUART_CONTROL_WE_MSK;
83 	writel(pp->imr, port->membase + ALTERA_JTAGUART_CONTROL_REG);
84 }
85 
86 static void altera_jtaguart_stop_tx(struct uart_port *port)
87 {
88 	struct altera_jtaguart *pp =
89 	    container_of(port, struct altera_jtaguart, port);
90 
91 	pp->imr &= ~ALTERA_JTAGUART_CONTROL_WE_MSK;
92 	writel(pp->imr, port->membase + ALTERA_JTAGUART_CONTROL_REG);
93 }
94 
95 static void altera_jtaguart_stop_rx(struct uart_port *port)
96 {
97 	struct altera_jtaguart *pp =
98 	    container_of(port, struct altera_jtaguart, port);
99 
100 	pp->imr &= ~ALTERA_JTAGUART_CONTROL_RE_MSK;
101 	writel(pp->imr, port->membase + ALTERA_JTAGUART_CONTROL_REG);
102 }
103 
104 static void altera_jtaguart_break_ctl(struct uart_port *port, int break_state)
105 {
106 }
107 
108 static void altera_jtaguart_set_termios(struct uart_port *port,
109 					struct ktermios *termios,
110 					struct ktermios *old)
111 {
112 	/* Just copy the old termios settings back */
113 	if (old)
114 		tty_termios_copy_hw(termios, old);
115 }
116 
117 static void altera_jtaguart_rx_chars(struct altera_jtaguart *pp)
118 {
119 	struct uart_port *port = &pp->port;
120 	unsigned char ch, flag;
121 	unsigned long status;
122 
123 	while ((status = readl(port->membase + ALTERA_JTAGUART_DATA_REG)) &
124 	       ALTERA_JTAGUART_DATA_RVALID_MSK) {
125 		ch = status & ALTERA_JTAGUART_DATA_DATA_MSK;
126 		flag = TTY_NORMAL;
127 		port->icount.rx++;
128 
129 		if (uart_handle_sysrq_char(port, ch))
130 			continue;
131 		uart_insert_char(port, 0, 0, ch, flag);
132 	}
133 
134 	tty_flip_buffer_push(&port->state->port);
135 }
136 
137 static void altera_jtaguart_tx_chars(struct altera_jtaguart *pp)
138 {
139 	struct uart_port *port = &pp->port;
140 	struct circ_buf *xmit = &port->state->xmit;
141 	unsigned int pending, count;
142 
143 	if (port->x_char) {
144 		/* Send special char - probably flow control */
145 		writel(port->x_char, port->membase + ALTERA_JTAGUART_DATA_REG);
146 		port->x_char = 0;
147 		port->icount.tx++;
148 		return;
149 	}
150 
151 	pending = uart_circ_chars_pending(xmit);
152 	if (pending > 0) {
153 		count = (readl(port->membase + ALTERA_JTAGUART_CONTROL_REG) &
154 				ALTERA_JTAGUART_CONTROL_WSPACE_MSK) >>
155 			ALTERA_JTAGUART_CONTROL_WSPACE_OFF;
156 		if (count > pending)
157 			count = pending;
158 		if (count > 0) {
159 			pending -= count;
160 			while (count--) {
161 				writel(xmit->buf[xmit->tail],
162 				       port->membase + ALTERA_JTAGUART_DATA_REG);
163 				xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
164 				port->icount.tx++;
165 			}
166 			if (pending < WAKEUP_CHARS)
167 				uart_write_wakeup(port);
168 		}
169 	}
170 
171 	if (pending == 0) {
172 		pp->imr &= ~ALTERA_JTAGUART_CONTROL_WE_MSK;
173 		writel(pp->imr, port->membase + ALTERA_JTAGUART_CONTROL_REG);
174 	}
175 }
176 
177 static irqreturn_t altera_jtaguart_interrupt(int irq, void *data)
178 {
179 	struct uart_port *port = data;
180 	struct altera_jtaguart *pp =
181 	    container_of(port, struct altera_jtaguart, port);
182 	unsigned int isr;
183 
184 	isr = (readl(port->membase + ALTERA_JTAGUART_CONTROL_REG) >>
185 	       ALTERA_JTAGUART_CONTROL_RI_OFF) & pp->imr;
186 
187 	spin_lock(&port->lock);
188 
189 	if (isr & ALTERA_JTAGUART_CONTROL_RE_MSK)
190 		altera_jtaguart_rx_chars(pp);
191 	if (isr & ALTERA_JTAGUART_CONTROL_WE_MSK)
192 		altera_jtaguart_tx_chars(pp);
193 
194 	spin_unlock(&port->lock);
195 
196 	return IRQ_RETVAL(isr);
197 }
198 
199 static void altera_jtaguart_config_port(struct uart_port *port, int flags)
200 {
201 	port->type = PORT_ALTERA_JTAGUART;
202 
203 	/* Clear mask, so no surprise interrupts. */
204 	writel(0, port->membase + ALTERA_JTAGUART_CONTROL_REG);
205 }
206 
207 static int altera_jtaguart_startup(struct uart_port *port)
208 {
209 	struct altera_jtaguart *pp =
210 	    container_of(port, struct altera_jtaguart, port);
211 	unsigned long flags;
212 	int ret;
213 
214 	ret = request_irq(port->irq, altera_jtaguart_interrupt, 0,
215 			DRV_NAME, port);
216 	if (ret) {
217 		pr_err(DRV_NAME ": unable to attach Altera JTAG UART %d "
218 		       "interrupt vector=%d\n", port->line, port->irq);
219 		return ret;
220 	}
221 
222 	spin_lock_irqsave(&port->lock, flags);
223 
224 	/* Enable RX interrupts now */
225 	pp->imr = ALTERA_JTAGUART_CONTROL_RE_MSK;
226 	writel(pp->imr, port->membase + ALTERA_JTAGUART_CONTROL_REG);
227 
228 	spin_unlock_irqrestore(&port->lock, flags);
229 
230 	return 0;
231 }
232 
233 static void altera_jtaguart_shutdown(struct uart_port *port)
234 {
235 	struct altera_jtaguart *pp =
236 	    container_of(port, struct altera_jtaguart, port);
237 	unsigned long flags;
238 
239 	spin_lock_irqsave(&port->lock, flags);
240 
241 	/* Disable all interrupts now */
242 	pp->imr = 0;
243 	writel(pp->imr, port->membase + ALTERA_JTAGUART_CONTROL_REG);
244 
245 	spin_unlock_irqrestore(&port->lock, flags);
246 
247 	free_irq(port->irq, port);
248 }
249 
250 static const char *altera_jtaguart_type(struct uart_port *port)
251 {
252 	return (port->type == PORT_ALTERA_JTAGUART) ? "Altera JTAG UART" : NULL;
253 }
254 
255 static int altera_jtaguart_request_port(struct uart_port *port)
256 {
257 	/* UARTs always present */
258 	return 0;
259 }
260 
261 static void altera_jtaguart_release_port(struct uart_port *port)
262 {
263 	/* Nothing to release... */
264 }
265 
266 static int altera_jtaguart_verify_port(struct uart_port *port,
267 				       struct serial_struct *ser)
268 {
269 	if (ser->type != PORT_UNKNOWN && ser->type != PORT_ALTERA_JTAGUART)
270 		return -EINVAL;
271 	return 0;
272 }
273 
274 /*
275  *	Define the basic serial functions we support.
276  */
277 static const struct uart_ops altera_jtaguart_ops = {
278 	.tx_empty	= altera_jtaguart_tx_empty,
279 	.get_mctrl	= altera_jtaguart_get_mctrl,
280 	.set_mctrl	= altera_jtaguart_set_mctrl,
281 	.start_tx	= altera_jtaguart_start_tx,
282 	.stop_tx	= altera_jtaguart_stop_tx,
283 	.stop_rx	= altera_jtaguart_stop_rx,
284 	.break_ctl	= altera_jtaguart_break_ctl,
285 	.startup	= altera_jtaguart_startup,
286 	.shutdown	= altera_jtaguart_shutdown,
287 	.set_termios	= altera_jtaguart_set_termios,
288 	.type		= altera_jtaguart_type,
289 	.request_port	= altera_jtaguart_request_port,
290 	.release_port	= altera_jtaguart_release_port,
291 	.config_port	= altera_jtaguart_config_port,
292 	.verify_port	= altera_jtaguart_verify_port,
293 };
294 
295 #define ALTERA_JTAGUART_MAXPORTS 1
296 static struct altera_jtaguart altera_jtaguart_ports[ALTERA_JTAGUART_MAXPORTS];
297 
298 #if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE)
299 
300 #if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE_BYPASS)
301 static void altera_jtaguart_console_putc(struct uart_port *port, unsigned char c)
302 {
303 	unsigned long status;
304 	unsigned long flags;
305 
306 	spin_lock_irqsave(&port->lock, flags);
307 	while (((status = readl(port->membase + ALTERA_JTAGUART_CONTROL_REG)) &
308 		ALTERA_JTAGUART_CONTROL_WSPACE_MSK) == 0) {
309 		if ((status & ALTERA_JTAGUART_CONTROL_AC_MSK) == 0) {
310 			spin_unlock_irqrestore(&port->lock, flags);
311 			return;	/* no connection activity */
312 		}
313 		spin_unlock_irqrestore(&port->lock, flags);
314 		cpu_relax();
315 		spin_lock_irqsave(&port->lock, flags);
316 	}
317 	writel(c, port->membase + ALTERA_JTAGUART_DATA_REG);
318 	spin_unlock_irqrestore(&port->lock, flags);
319 }
320 #else
321 static void altera_jtaguart_console_putc(struct uart_port *port, unsigned char c)
322 {
323 	unsigned long flags;
324 
325 	spin_lock_irqsave(&port->lock, flags);
326 	while ((readl(port->membase + ALTERA_JTAGUART_CONTROL_REG) &
327 		ALTERA_JTAGUART_CONTROL_WSPACE_MSK) == 0) {
328 		spin_unlock_irqrestore(&port->lock, flags);
329 		cpu_relax();
330 		spin_lock_irqsave(&port->lock, flags);
331 	}
332 	writel(c, port->membase + ALTERA_JTAGUART_DATA_REG);
333 	spin_unlock_irqrestore(&port->lock, flags);
334 }
335 #endif
336 
337 static void altera_jtaguart_console_write(struct console *co, const char *s,
338 					  unsigned int count)
339 {
340 	struct uart_port *port = &(altera_jtaguart_ports + co->index)->port;
341 
342 	uart_console_write(port, s, count, altera_jtaguart_console_putc);
343 }
344 
345 static int __init altera_jtaguart_console_setup(struct console *co,
346 						char *options)
347 {
348 	struct uart_port *port;
349 
350 	if (co->index < 0 || co->index >= ALTERA_JTAGUART_MAXPORTS)
351 		return -EINVAL;
352 	port = &altera_jtaguart_ports[co->index].port;
353 	if (port->membase == NULL)
354 		return -ENODEV;
355 	return 0;
356 }
357 
358 static struct uart_driver altera_jtaguart_driver;
359 
360 static struct console altera_jtaguart_console = {
361 	.name	= "ttyJ",
362 	.write	= altera_jtaguart_console_write,
363 	.device	= uart_console_device,
364 	.setup	= altera_jtaguart_console_setup,
365 	.flags	= CON_PRINTBUFFER,
366 	.index	= -1,
367 	.data	= &altera_jtaguart_driver,
368 };
369 
370 static int __init altera_jtaguart_console_init(void)
371 {
372 	register_console(&altera_jtaguart_console);
373 	return 0;
374 }
375 
376 console_initcall(altera_jtaguart_console_init);
377 
378 #define	ALTERA_JTAGUART_CONSOLE	(&altera_jtaguart_console)
379 
380 static void altera_jtaguart_earlycon_write(struct console *co, const char *s,
381 					   unsigned int count)
382 {
383 	struct earlycon_device *dev = co->data;
384 
385 	uart_console_write(&dev->port, s, count, altera_jtaguart_console_putc);
386 }
387 
388 static int __init altera_jtaguart_earlycon_setup(struct earlycon_device *dev,
389 						 const char *options)
390 {
391 	if (!dev->port.membase)
392 		return -ENODEV;
393 
394 	dev->con->write = altera_jtaguart_earlycon_write;
395 	return 0;
396 }
397 
398 OF_EARLYCON_DECLARE(juart, "altr,juart-1.0", altera_jtaguart_earlycon_setup);
399 
400 #else
401 
402 #define	ALTERA_JTAGUART_CONSOLE	NULL
403 
404 #endif /* CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE */
405 
406 static struct uart_driver altera_jtaguart_driver = {
407 	.owner		= THIS_MODULE,
408 	.driver_name	= "altera_jtaguart",
409 	.dev_name	= "ttyJ",
410 	.major		= ALTERA_JTAGUART_MAJOR,
411 	.minor		= ALTERA_JTAGUART_MINOR,
412 	.nr		= ALTERA_JTAGUART_MAXPORTS,
413 	.cons		= ALTERA_JTAGUART_CONSOLE,
414 };
415 
416 static int altera_jtaguart_probe(struct platform_device *pdev)
417 {
418 	struct altera_jtaguart_platform_uart *platp =
419 			dev_get_platdata(&pdev->dev);
420 	struct uart_port *port;
421 	struct resource *res_mem;
422 	int i = pdev->id;
423 	int irq;
424 
425 	/* -1 emphasizes that the platform must have one port, no .N suffix */
426 	if (i == -1)
427 		i = 0;
428 
429 	if (i >= ALTERA_JTAGUART_MAXPORTS)
430 		return -EINVAL;
431 
432 	port = &altera_jtaguart_ports[i].port;
433 
434 	res_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
435 	if (res_mem)
436 		port->mapbase = res_mem->start;
437 	else if (platp)
438 		port->mapbase = platp->mapbase;
439 	else
440 		return -ENODEV;
441 
442 	irq = platform_get_irq_optional(pdev, 0);
443 	if (irq < 0 && irq != -ENXIO)
444 		return irq;
445 	if (irq > 0)
446 		port->irq = irq;
447 	else if (platp)
448 		port->irq = platp->irq;
449 	else
450 		return -ENODEV;
451 
452 	port->membase = ioremap(port->mapbase, ALTERA_JTAGUART_SIZE);
453 	if (!port->membase)
454 		return -ENOMEM;
455 
456 	port->line = i;
457 	port->type = PORT_ALTERA_JTAGUART;
458 	port->iotype = SERIAL_IO_MEM;
459 	port->ops = &altera_jtaguart_ops;
460 	port->flags = UPF_BOOT_AUTOCONF;
461 	port->dev = &pdev->dev;
462 
463 	uart_add_one_port(&altera_jtaguart_driver, port);
464 
465 	return 0;
466 }
467 
468 static int altera_jtaguart_remove(struct platform_device *pdev)
469 {
470 	struct uart_port *port;
471 	int i = pdev->id;
472 
473 	if (i == -1)
474 		i = 0;
475 
476 	port = &altera_jtaguart_ports[i].port;
477 	uart_remove_one_port(&altera_jtaguart_driver, port);
478 	iounmap(port->membase);
479 
480 	return 0;
481 }
482 
483 #ifdef CONFIG_OF
484 static const struct of_device_id altera_jtaguart_match[] = {
485 	{ .compatible = "ALTR,juart-1.0", },
486 	{ .compatible = "altr,juart-1.0", },
487 	{},
488 };
489 MODULE_DEVICE_TABLE(of, altera_jtaguart_match);
490 #endif /* CONFIG_OF */
491 
492 static struct platform_driver altera_jtaguart_platform_driver = {
493 	.probe	= altera_jtaguart_probe,
494 	.remove	= altera_jtaguart_remove,
495 	.driver	= {
496 		.name		= DRV_NAME,
497 		.of_match_table	= of_match_ptr(altera_jtaguart_match),
498 	},
499 };
500 
501 static int __init altera_jtaguart_init(void)
502 {
503 	int rc;
504 
505 	rc = uart_register_driver(&altera_jtaguart_driver);
506 	if (rc)
507 		return rc;
508 	rc = platform_driver_register(&altera_jtaguart_platform_driver);
509 	if (rc)
510 		uart_unregister_driver(&altera_jtaguart_driver);
511 	return rc;
512 }
513 
514 static void __exit altera_jtaguart_exit(void)
515 {
516 	platform_driver_unregister(&altera_jtaguart_platform_driver);
517 	uart_unregister_driver(&altera_jtaguart_driver);
518 }
519 
520 module_init(altera_jtaguart_init);
521 module_exit(altera_jtaguart_exit);
522 
523 MODULE_DESCRIPTION("Altera JTAG UART driver");
524 MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
525 MODULE_LICENSE("GPL");
526 MODULE_ALIAS("platform:" DRV_NAME);
527