xref: /openbmc/linux/drivers/tty/serial/liteuart.c (revision a774aa4580d4339a37e4810f303b6a39ddc745ea) 
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 	u8 ch;
77 
78 	while (!litex_read8(membase + OFF_RXEMPTY)) {
79 		ch = litex_read8(membase + OFF_RXTX);
80 		port->icount.rx++;
81 
82 		/* necessary for RXEMPTY to refresh its value */
83 		litex_write8(membase + OFF_EV_PENDING, EV_RX);
84 
85 		/* no overflow bits in status */
86 		if (!(uart_handle_sysrq_char(port, ch)))
87 			uart_insert_char(port, 1, 0, ch, TTY_NORMAL);
88 	}
89 
90 	tty_flip_buffer_push(&port->state->port);
91 
92 	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
93 }
94 
95 static void liteuart_putchar(struct uart_port *port, unsigned char ch)
96 {
97 	while (litex_read8(port->membase + OFF_TXFULL))
98 		cpu_relax();
99 
100 	litex_write8(port->membase + OFF_RXTX, ch);
101 }
102 
103 static unsigned int liteuart_tx_empty(struct uart_port *port)
104 {
105 	/* not really tx empty, just checking if tx is not full */
106 	if (!litex_read8(port->membase + OFF_TXFULL))
107 		return TIOCSER_TEMT;
108 
109 	return 0;
110 }
111 
112 static void liteuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
113 {
114 	/* modem control register is not present in LiteUART */
115 }
116 
117 static unsigned int liteuart_get_mctrl(struct uart_port *port)
118 {
119 	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
120 }
121 
122 static void liteuart_stop_tx(struct uart_port *port)
123 {
124 }
125 
126 static void liteuart_start_tx(struct uart_port *port)
127 {
128 	struct circ_buf *xmit = &port->state->xmit;
129 	unsigned char ch;
130 
131 	if (unlikely(port->x_char)) {
132 		litex_write8(port->membase + OFF_RXTX, port->x_char);
133 		port->icount.tx++;
134 		port->x_char = 0;
135 	} else if (!uart_circ_empty(xmit)) {
136 		while (xmit->head != xmit->tail) {
137 			ch = xmit->buf[xmit->tail];
138 			uart_xmit_advance(port, 1);
139 			liteuart_putchar(port, ch);
140 		}
141 	}
142 
143 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
144 		uart_write_wakeup(port);
145 }
146 
147 static void liteuart_stop_rx(struct uart_port *port)
148 {
149 	struct liteuart_port *uart = to_liteuart_port(port);
150 
151 	/* just delete timer */
152 	del_timer(&uart->timer);
153 }
154 
155 static int liteuart_startup(struct uart_port *port)
156 {
157 	struct liteuart_port *uart = to_liteuart_port(port);
158 
159 	/* disable events */
160 	litex_write8(port->membase + OFF_EV_ENABLE, 0);
161 
162 	/* prepare timer for polling */
163 	timer_setup(&uart->timer, liteuart_timer, 0);
164 	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
165 
166 	return 0;
167 }
168 
169 static void liteuart_shutdown(struct uart_port *port)
170 {
171 }
172 
173 static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
174 				 const struct ktermios *old)
175 {
176 	unsigned int baud;
177 	unsigned long flags;
178 
179 	spin_lock_irqsave(&port->lock, flags);
180 
181 	/* update baudrate */
182 	baud = uart_get_baud_rate(port, new, old, 0, 460800);
183 	uart_update_timeout(port, new->c_cflag, baud);
184 
185 	spin_unlock_irqrestore(&port->lock, flags);
186 }
187 
188 static const char *liteuart_type(struct uart_port *port)
189 {
190 	return "liteuart";
191 }
192 
193 static void liteuart_config_port(struct uart_port *port, int flags)
194 {
195 	/*
196 	 * Driver core for serial ports forces a non-zero value for port type.
197 	 * Write an arbitrary value here to accommodate the serial core driver,
198 	 * as ID part of UAPI is redundant.
199 	 */
200 	port->type = 1;
201 }
202 
203 static int liteuart_verify_port(struct uart_port *port,
204 				struct serial_struct *ser)
205 {
206 	if (port->type != PORT_UNKNOWN && ser->type != 1)
207 		return -EINVAL;
208 
209 	return 0;
210 }
211 
212 static const struct uart_ops liteuart_ops = {
213 	.tx_empty	= liteuart_tx_empty,
214 	.set_mctrl	= liteuart_set_mctrl,
215 	.get_mctrl	= liteuart_get_mctrl,
216 	.stop_tx	= liteuart_stop_tx,
217 	.start_tx	= liteuart_start_tx,
218 	.stop_rx	= liteuart_stop_rx,
219 	.startup	= liteuart_startup,
220 	.shutdown	= liteuart_shutdown,
221 	.set_termios	= liteuart_set_termios,
222 	.type		= liteuart_type,
223 	.config_port	= liteuart_config_port,
224 	.verify_port	= liteuart_verify_port,
225 };
226 
227 static int liteuart_probe(struct platform_device *pdev)
228 {
229 	struct liteuart_port *uart;
230 	struct uart_port *port;
231 	struct xa_limit limit;
232 	int dev_id, ret;
233 
234 	/* look for aliases; auto-enumerate for free index if not found */
235 	dev_id = of_alias_get_id(pdev->dev.of_node, "serial");
236 	if (dev_id < 0)
237 		limit = XA_LIMIT(0, CONFIG_SERIAL_LITEUART_MAX_PORTS);
238 	else
239 		limit = XA_LIMIT(dev_id, dev_id);
240 
241 	uart = devm_kzalloc(&pdev->dev, sizeof(struct liteuart_port), GFP_KERNEL);
242 	if (!uart)
243 		return -ENOMEM;
244 
245 	ret = xa_alloc(&liteuart_array, &dev_id, uart, limit, GFP_KERNEL);
246 	if (ret)
247 		return ret;
248 
249 	uart->id = dev_id;
250 	port = &uart->port;
251 
252 	/* get membase */
253 	port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
254 	if (IS_ERR(port->membase)) {
255 		ret = PTR_ERR(port->membase);
256 		goto err_erase_id;
257 	}
258 
259 	/* values not from device tree */
260 	port->dev = &pdev->dev;
261 	port->iotype = UPIO_MEM;
262 	port->flags = UPF_BOOT_AUTOCONF;
263 	port->ops = &liteuart_ops;
264 	port->fifosize = 16;
265 	port->type = PORT_UNKNOWN;
266 	port->line = dev_id;
267 	spin_lock_init(&port->lock);
268 
269 	platform_set_drvdata(pdev, port);
270 
271 	ret = uart_add_one_port(&liteuart_driver, &uart->port);
272 	if (ret)
273 		goto err_erase_id;
274 
275 	return 0;
276 
277 err_erase_id:
278 	xa_erase(&liteuart_array, uart->id);
279 
280 	return ret;
281 }
282 
283 static int liteuart_remove(struct platform_device *pdev)
284 {
285 	struct uart_port *port = platform_get_drvdata(pdev);
286 	struct liteuart_port *uart = to_liteuart_port(port);
287 
288 	uart_remove_one_port(&liteuart_driver, port);
289 	xa_erase(&liteuart_array, uart->id);
290 
291 	return 0;
292 }
293 
294 static const struct of_device_id liteuart_of_match[] = {
295 	{ .compatible = "litex,liteuart" },
296 	{}
297 };
298 MODULE_DEVICE_TABLE(of, liteuart_of_match);
299 
300 static struct platform_driver liteuart_platform_driver = {
301 	.probe = liteuart_probe,
302 	.remove = liteuart_remove,
303 	.driver = {
304 		.name = KBUILD_MODNAME,
305 		.of_match_table = liteuart_of_match,
306 	},
307 };
308 
309 #ifdef CONFIG_SERIAL_LITEUART_CONSOLE
310 
311 static void liteuart_console_write(struct console *co, const char *s,
312 	unsigned int count)
313 {
314 	struct liteuart_port *uart;
315 	struct uart_port *port;
316 	unsigned long flags;
317 
318 	uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
319 	port = &uart->port;
320 
321 	spin_lock_irqsave(&port->lock, flags);
322 	uart_console_write(port, s, count, liteuart_putchar);
323 	spin_unlock_irqrestore(&port->lock, flags);
324 }
325 
326 static int liteuart_console_setup(struct console *co, char *options)
327 {
328 	struct liteuart_port *uart;
329 	struct uart_port *port;
330 	int baud = 115200;
331 	int bits = 8;
332 	int parity = 'n';
333 	int flow = 'n';
334 
335 	uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
336 	if (!uart)
337 		return -ENODEV;
338 
339 	port = &uart->port;
340 	if (!port->membase)
341 		return -ENODEV;
342 
343 	if (options)
344 		uart_parse_options(options, &baud, &parity, &bits, &flow);
345 
346 	return uart_set_options(port, co, baud, parity, bits, flow);
347 }
348 
349 static struct console liteuart_console = {
350 	.name = KBUILD_MODNAME,
351 	.write = liteuart_console_write,
352 	.device = uart_console_device,
353 	.setup = liteuart_console_setup,
354 	.flags = CON_PRINTBUFFER,
355 	.index = -1,
356 	.data = &liteuart_driver,
357 };
358 
359 static int __init liteuart_console_init(void)
360 {
361 	register_console(&liteuart_console);
362 
363 	return 0;
364 }
365 console_initcall(liteuart_console_init);
366 
367 static void early_liteuart_write(struct console *console, const char *s,
368 				    unsigned int count)
369 {
370 	struct earlycon_device *device = console->data;
371 	struct uart_port *port = &device->port;
372 
373 	uart_console_write(port, s, count, liteuart_putchar);
374 }
375 
376 static int __init early_liteuart_setup(struct earlycon_device *device,
377 				       const char *options)
378 {
379 	if (!device->port.membase)
380 		return -ENODEV;
381 
382 	device->con->write = early_liteuart_write;
383 	return 0;
384 }
385 
386 OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup);
387 #endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
388 
389 static int __init liteuart_init(void)
390 {
391 	int res;
392 
393 	res = uart_register_driver(&liteuart_driver);
394 	if (res)
395 		return res;
396 
397 	res = platform_driver_register(&liteuart_platform_driver);
398 	if (res)
399 		uart_unregister_driver(&liteuart_driver);
400 
401 	return res;
402 }
403 
404 static void __exit liteuart_exit(void)
405 {
406 	platform_driver_unregister(&liteuart_platform_driver);
407 	uart_unregister_driver(&liteuart_driver);
408 }
409 
410 module_init(liteuart_init);
411 module_exit(liteuart_exit);
412 
413 MODULE_AUTHOR("Antmicro <www.antmicro.com>");
414 MODULE_DESCRIPTION("LiteUART serial driver");
415 MODULE_LICENSE("GPL v2");
416 MODULE_ALIAS("platform:liteuart");
417