xref: /openbmc/linux/drivers/tty/serial/liteuart.c (revision ca538cc7271dea86773712b84ed02b22aaed1a12) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * LiteUART serial controller (LiteX) Driver
4  *
5  * Copyright (C) 2019-2020 Antmicro <www.antmicro.com>
6  */
7 
8 #include <linux/bits.h>
9 #include <linux/console.h>
10 #include <linux/litex.h>
11 #include <linux/module.h>
12 #include <linux/of.h>
13 #include <linux/of_address.h>
14 #include <linux/of_platform.h>
15 #include <linux/serial.h>
16 #include <linux/serial_core.h>
17 #include <linux/slab.h>
18 #include <linux/timer.h>
19 #include <linux/tty_flip.h>
20 #include <linux/xarray.h>
21 
22 /*
23  * CSRs definitions (base address offsets + width)
24  *
25  * The definitions below are true for LiteX SoC configured for 8-bit CSR Bus,
26  * 32-bit aligned.
27  *
28  * Supporting other configurations might require new definitions or a more
29  * generic way of indexing the LiteX CSRs.
30  *
31  * For more details on how CSRs are defined and handled in LiteX, see comments
32  * in the LiteX SoC Driver: drivers/soc/litex/litex_soc_ctrl.c
33  */
34 #define OFF_RXTX	0x00
35 #define OFF_TXFULL	0x04
36 #define OFF_RXEMPTY	0x08
37 #define OFF_EV_STATUS	0x0c
38 #define OFF_EV_PENDING	0x10
39 #define OFF_EV_ENABLE	0x14
40 
41 /* events */
42 #define EV_TX		BIT(0)
43 #define EV_RX		BIT(1)
44 
45 struct liteuart_port {
46 	struct uart_port port;
47 	struct timer_list timer;
48 	u32 id;
49 };
50 
51 #define to_liteuart_port(port)	container_of(port, struct liteuart_port, port)
52 
53 static DEFINE_XARRAY_FLAGS(liteuart_array, XA_FLAGS_ALLOC);
54 
55 #ifdef CONFIG_SERIAL_LITEUART_CONSOLE
56 static struct console liteuart_console;
57 #endif
58 
59 static struct uart_driver liteuart_driver = {
60 	.owner = THIS_MODULE,
61 	.driver_name = KBUILD_MODNAME,
62 	.dev_name = "ttyLXU",
63 	.major = 0,
64 	.minor = 0,
65 	.nr = CONFIG_SERIAL_LITEUART_MAX_PORTS,
66 #ifdef CONFIG_SERIAL_LITEUART_CONSOLE
67 	.cons = &liteuart_console,
68 #endif
69 };
70 
71 static void liteuart_timer(struct timer_list *t)
72 {
73 	struct liteuart_port *uart = from_timer(uart, t, timer);
74 	struct uart_port *port = &uart->port;
75 	unsigned char __iomem *membase = port->membase;
76 	int ch;
77 	unsigned long status;
78 
79 	while ((status = !litex_read8(membase + OFF_RXEMPTY)) == 1) {
80 		ch = litex_read8(membase + OFF_RXTX);
81 		port->icount.rx++;
82 
83 		/* necessary for RXEMPTY to refresh its value */
84 		litex_write8(membase + OFF_EV_PENDING, EV_RX);
85 
86 		/* no overflow bits in status */
87 		if (!(uart_handle_sysrq_char(port, ch)))
88 			uart_insert_char(port, status, 0, ch, TTY_NORMAL);
89 	}
90 
91 	tty_flip_buffer_push(&port->state->port);
92 
93 	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
94 }
95 
96 static void liteuart_putchar(struct uart_port *port, unsigned char ch)
97 {
98 	while (litex_read8(port->membase + OFF_TXFULL))
99 		cpu_relax();
100 
101 	litex_write8(port->membase + OFF_RXTX, ch);
102 }
103 
104 static unsigned int liteuart_tx_empty(struct uart_port *port)
105 {
106 	/* not really tx empty, just checking if tx is not full */
107 	if (!litex_read8(port->membase + OFF_TXFULL))
108 		return TIOCSER_TEMT;
109 
110 	return 0;
111 }
112 
113 static void liteuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
114 {
115 	/* modem control register is not present in LiteUART */
116 }
117 
118 static unsigned int liteuart_get_mctrl(struct uart_port *port)
119 {
120 	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
121 }
122 
123 static void liteuart_stop_tx(struct uart_port *port)
124 {
125 }
126 
127 static void liteuart_start_tx(struct uart_port *port)
128 {
129 	struct circ_buf *xmit = &port->state->xmit;
130 	unsigned char ch;
131 
132 	if (unlikely(port->x_char)) {
133 		litex_write8(port->membase + OFF_RXTX, port->x_char);
134 		port->icount.tx++;
135 		port->x_char = 0;
136 	} else if (!uart_circ_empty(xmit)) {
137 		while (xmit->head != xmit->tail) {
138 			ch = xmit->buf[xmit->tail];
139 			uart_xmit_advance(port, 1);
140 			liteuart_putchar(port, ch);
141 		}
142 	}
143 
144 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
145 		uart_write_wakeup(port);
146 }
147 
148 static void liteuart_stop_rx(struct uart_port *port)
149 {
150 	struct liteuart_port *uart = to_liteuart_port(port);
151 
152 	/* just delete timer */
153 	del_timer(&uart->timer);
154 }
155 
156 static int liteuart_startup(struct uart_port *port)
157 {
158 	struct liteuart_port *uart = to_liteuart_port(port);
159 
160 	/* disable events */
161 	litex_write8(port->membase + OFF_EV_ENABLE, 0);
162 
163 	/* prepare timer for polling */
164 	timer_setup(&uart->timer, liteuart_timer, 0);
165 	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
166 
167 	return 0;
168 }
169 
170 static void liteuart_shutdown(struct uart_port *port)
171 {
172 }
173 
174 static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
175 				 const struct ktermios *old)
176 {
177 	unsigned int baud;
178 	unsigned long flags;
179 
180 	spin_lock_irqsave(&port->lock, flags);
181 
182 	/* update baudrate */
183 	baud = uart_get_baud_rate(port, new, old, 0, 460800);
184 	uart_update_timeout(port, new->c_cflag, baud);
185 
186 	spin_unlock_irqrestore(&port->lock, flags);
187 }
188 
189 static const char *liteuart_type(struct uart_port *port)
190 {
191 	return "liteuart";
192 }
193 
194 static void liteuart_config_port(struct uart_port *port, int flags)
195 {
196 	/*
197 	 * Driver core for serial ports forces a non-zero value for port type.
198 	 * Write an arbitrary value here to accommodate the serial core driver,
199 	 * as ID part of UAPI is redundant.
200 	 */
201 	port->type = 1;
202 }
203 
204 static int liteuart_verify_port(struct uart_port *port,
205 				struct serial_struct *ser)
206 {
207 	if (port->type != PORT_UNKNOWN && ser->type != 1)
208 		return -EINVAL;
209 
210 	return 0;
211 }
212 
213 static const struct uart_ops liteuart_ops = {
214 	.tx_empty	= liteuart_tx_empty,
215 	.set_mctrl	= liteuart_set_mctrl,
216 	.get_mctrl	= liteuart_get_mctrl,
217 	.stop_tx	= liteuart_stop_tx,
218 	.start_tx	= liteuart_start_tx,
219 	.stop_rx	= liteuart_stop_rx,
220 	.startup	= liteuart_startup,
221 	.shutdown	= liteuart_shutdown,
222 	.set_termios	= liteuart_set_termios,
223 	.type		= liteuart_type,
224 	.config_port	= liteuart_config_port,
225 	.verify_port	= liteuart_verify_port,
226 };
227 
228 static int liteuart_probe(struct platform_device *pdev)
229 {
230 	struct liteuart_port *uart;
231 	struct uart_port *port;
232 	struct xa_limit limit;
233 	int dev_id, ret;
234 
235 	/* look for aliases; auto-enumerate for free index if not found */
236 	dev_id = of_alias_get_id(pdev->dev.of_node, "serial");
237 	if (dev_id < 0)
238 		limit = XA_LIMIT(0, CONFIG_SERIAL_LITEUART_MAX_PORTS);
239 	else
240 		limit = XA_LIMIT(dev_id, dev_id);
241 
242 	uart = devm_kzalloc(&pdev->dev, sizeof(struct liteuart_port), GFP_KERNEL);
243 	if (!uart)
244 		return -ENOMEM;
245 
246 	ret = xa_alloc(&liteuart_array, &dev_id, uart, limit, GFP_KERNEL);
247 	if (ret)
248 		return ret;
249 
250 	uart->id = dev_id;
251 	port = &uart->port;
252 
253 	/* get membase */
254 	port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
255 	if (IS_ERR(port->membase)) {
256 		ret = PTR_ERR(port->membase);
257 		goto err_erase_id;
258 	}
259 
260 	/* values not from device tree */
261 	port->dev = &pdev->dev;
262 	port->iotype = UPIO_MEM;
263 	port->flags = UPF_BOOT_AUTOCONF;
264 	port->ops = &liteuart_ops;
265 	port->fifosize = 16;
266 	port->type = PORT_UNKNOWN;
267 	port->line = dev_id;
268 	spin_lock_init(&port->lock);
269 
270 	platform_set_drvdata(pdev, port);
271 
272 	ret = uart_add_one_port(&liteuart_driver, &uart->port);
273 	if (ret)
274 		goto err_erase_id;
275 
276 	return 0;
277 
278 err_erase_id:
279 	xa_erase(&liteuart_array, uart->id);
280 
281 	return ret;
282 }
283 
284 static int liteuart_remove(struct platform_device *pdev)
285 {
286 	struct uart_port *port = platform_get_drvdata(pdev);
287 	struct liteuart_port *uart = to_liteuart_port(port);
288 
289 	uart_remove_one_port(&liteuart_driver, port);
290 	xa_erase(&liteuart_array, uart->id);
291 
292 	return 0;
293 }
294 
295 static const struct of_device_id liteuart_of_match[] = {
296 	{ .compatible = "litex,liteuart" },
297 	{}
298 };
299 MODULE_DEVICE_TABLE(of, liteuart_of_match);
300 
301 static struct platform_driver liteuart_platform_driver = {
302 	.probe = liteuart_probe,
303 	.remove = liteuart_remove,
304 	.driver = {
305 		.name = KBUILD_MODNAME,
306 		.of_match_table = liteuart_of_match,
307 	},
308 };
309 
310 #ifdef CONFIG_SERIAL_LITEUART_CONSOLE
311 
312 static void liteuart_console_write(struct console *co, const char *s,
313 	unsigned int count)
314 {
315 	struct liteuart_port *uart;
316 	struct uart_port *port;
317 	unsigned long flags;
318 
319 	uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
320 	port = &uart->port;
321 
322 	spin_lock_irqsave(&port->lock, flags);
323 	uart_console_write(port, s, count, liteuart_putchar);
324 	spin_unlock_irqrestore(&port->lock, flags);
325 }
326 
327 static int liteuart_console_setup(struct console *co, char *options)
328 {
329 	struct liteuart_port *uart;
330 	struct uart_port *port;
331 	int baud = 115200;
332 	int bits = 8;
333 	int parity = 'n';
334 	int flow = 'n';
335 
336 	uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
337 	if (!uart)
338 		return -ENODEV;
339 
340 	port = &uart->port;
341 	if (!port->membase)
342 		return -ENODEV;
343 
344 	if (options)
345 		uart_parse_options(options, &baud, &parity, &bits, &flow);
346 
347 	return uart_set_options(port, co, baud, parity, bits, flow);
348 }
349 
350 static struct console liteuart_console = {
351 	.name = KBUILD_MODNAME,
352 	.write = liteuart_console_write,
353 	.device = uart_console_device,
354 	.setup = liteuart_console_setup,
355 	.flags = CON_PRINTBUFFER,
356 	.index = -1,
357 	.data = &liteuart_driver,
358 };
359 
360 static int __init liteuart_console_init(void)
361 {
362 	register_console(&liteuart_console);
363 
364 	return 0;
365 }
366 console_initcall(liteuart_console_init);
367 
368 static void early_liteuart_write(struct console *console, const char *s,
369 				    unsigned int count)
370 {
371 	struct earlycon_device *device = console->data;
372 	struct uart_port *port = &device->port;
373 
374 	uart_console_write(port, s, count, liteuart_putchar);
375 }
376 
377 static int __init early_liteuart_setup(struct earlycon_device *device,
378 				       const char *options)
379 {
380 	if (!device->port.membase)
381 		return -ENODEV;
382 
383 	device->con->write = early_liteuart_write;
384 	return 0;
385 }
386 
387 OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup);
388 #endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
389 
390 static int __init liteuart_init(void)
391 {
392 	int res;
393 
394 	res = uart_register_driver(&liteuart_driver);
395 	if (res)
396 		return res;
397 
398 	res = platform_driver_register(&liteuart_platform_driver);
399 	if (res)
400 		uart_unregister_driver(&liteuart_driver);
401 
402 	return res;
403 }
404 
405 static void __exit liteuart_exit(void)
406 {
407 	platform_driver_unregister(&liteuart_platform_driver);
408 	uart_unregister_driver(&liteuart_driver);
409 }
410 
411 module_init(liteuart_init);
412 module_exit(liteuart_exit);
413 
414 MODULE_AUTHOR("Antmicro <www.antmicro.com>");
415 MODULE_DESCRIPTION("LiteUART serial driver");
416 MODULE_LICENSE("GPL v2");
417 MODULE_ALIAS("platform:liteuart");
418