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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/interrupt.h>
11#include <linux/litex.h>
12#include <linux/module.h>
13#include <linux/of.h>
14#include <linux/platform_device.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
45struct liteuart_port {
46 struct uart_port port;
47 struct timer_list timer;
48 u8 irq_reg;
49};
50
51#define to_liteuart_port(port) container_of(port, struct liteuart_port, port)
52
53static DEFINE_XARRAY_FLAGS(liteuart_array, XA_FLAGS_ALLOC);
54
55#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
56static struct console liteuart_console;
57#endif
58
59static 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
71static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)
72{
73 struct liteuart_port *uart = to_liteuart_port(port);
74
75 if (set)
76 uart->irq_reg |= mask;
77 else
78 uart->irq_reg &= ~mask;
79
80 if (port->irq)
81 litex_write8(port->membase + OFF_EV_ENABLE, uart->irq_reg);
82}
83
84static void liteuart_stop_tx(struct uart_port *port)
85{
86 liteuart_update_irq_reg(port, false, EV_TX);
87}
88
89static void liteuart_start_tx(struct uart_port *port)
90{
91 liteuart_update_irq_reg(port, true, EV_TX);
92}
93
94static void liteuart_stop_rx(struct uart_port *port)
95{
96 struct liteuart_port *uart = to_liteuart_port(port);
97
98 /* just delete timer */
99 timer_delete(&uart->timer);
100}
101
102static void liteuart_rx_chars(struct uart_port *port)
103{
104 unsigned char __iomem *membase = port->membase;
105 u8 ch;
106
107 while (!litex_read8(membase + OFF_RXEMPTY)) {
108 ch = litex_read8(membase + OFF_RXTX);
109 port->icount.rx++;
110
111 /* necessary for RXEMPTY to refresh its value */
112 litex_write8(membase + OFF_EV_PENDING, EV_RX);
113
114 /* no overflow bits in status */
115 if (!(uart_handle_sysrq_char(port, ch)))
116 uart_insert_char(port, 1, 0, ch, TTY_NORMAL);
117 }
118
119 tty_flip_buffer_push(&port->state->port);
120}
121
122static void liteuart_tx_chars(struct uart_port *port)
123{
124 u8 ch;
125
126 uart_port_tx(port, ch,
127 !litex_read8(port->membase + OFF_TXFULL),
128 litex_write8(port->membase + OFF_RXTX, ch));
129}
130
131static irqreturn_t liteuart_interrupt(int irq, void *data)
132{
133 struct liteuart_port *uart = data;
134 struct uart_port *port = &uart->port;
135 unsigned long flags;
136 u8 isr;
137
138 /*
139 * if polling, the context would be "in_serving_softirq", so use
140 * irq[save|restore] spin_lock variants to cover all possibilities
141 */
142 uart_port_lock_irqsave(port, &flags);
143 isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
144 if (isr & EV_RX)
145 liteuart_rx_chars(port);
146 if (isr & EV_TX)
147 liteuart_tx_chars(port);
148 uart_port_unlock_irqrestore(port, flags);
149
150 return IRQ_RETVAL(isr);
151}
152
153static void liteuart_timer(struct timer_list *t)
154{
155 struct liteuart_port *uart = timer_container_of(uart, t, timer);
156 struct uart_port *port = &uart->port;
157
158 liteuart_interrupt(0, port);
159 mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
160}
161
162static unsigned int liteuart_tx_empty(struct uart_port *port)
163{
164 /* not really tx empty, just checking if tx is not full */
165 if (!litex_read8(port->membase + OFF_TXFULL))
166 return TIOCSER_TEMT;
167
168 return 0;
169}
170
171static void liteuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
172{
173 /* modem control register is not present in LiteUART */
174}
175
176static unsigned int liteuart_get_mctrl(struct uart_port *port)
177{
178 return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
179}
180
181static int liteuart_startup(struct uart_port *port)
182{
183 struct liteuart_port *uart = to_liteuart_port(port);
184 unsigned long flags;
185 int ret;
186
187 if (port->irq) {
188 ret = request_irq(port->irq, liteuart_interrupt, 0,
189 KBUILD_MODNAME, uart);
190 if (ret) {
191 dev_warn(port->dev,
192 "line %d irq %d failed: switch to polling\n",
193 port->line, port->irq);
194 port->irq = 0;
195 }
196 }
197
198 uart_port_lock_irqsave(port, &flags);
199 /* only enabling rx irqs during startup */
200 liteuart_update_irq_reg(port, true, EV_RX);
201 uart_port_unlock_irqrestore(port, flags);
202
203 if (!port->irq) {
204 timer_setup(&uart->timer, liteuart_timer, 0);
205 mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
206 }
207
208 return 0;
209}
210
211static void liteuart_shutdown(struct uart_port *port)
212{
213 struct liteuart_port *uart = to_liteuart_port(port);
214 unsigned long flags;
215
216 uart_port_lock_irqsave(port, &flags);
217 liteuart_update_irq_reg(port, false, EV_RX | EV_TX);
218 uart_port_unlock_irqrestore(port, flags);
219
220 if (port->irq)
221 free_irq(port->irq, port);
222 else
223 timer_delete_sync(&uart->timer);
224}
225
226static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
227 const struct ktermios *old)
228{
229 unsigned int baud;
230 unsigned long flags;
231
232 uart_port_lock_irqsave(port, &flags);
233
234 /* update baudrate */
235 baud = uart_get_baud_rate(port, new, old, 0, 460800);
236 uart_update_timeout(port, new->c_cflag, baud);
237
238 uart_port_unlock_irqrestore(port, flags);
239}
240
241static const char *liteuart_type(struct uart_port *port)
242{
243 return "liteuart";
244}
245
246static void liteuart_config_port(struct uart_port *port, int flags)
247{
248 /*
249 * Driver core for serial ports forces a non-zero value for port type.
250 * Write an arbitrary value here to accommodate the serial core driver,
251 * as ID part of UAPI is redundant.
252 */
253 port->type = 1;
254}
255
256static int liteuart_verify_port(struct uart_port *port,
257 struct serial_struct *ser)
258{
259 if (port->type != PORT_UNKNOWN && ser->type != 1)
260 return -EINVAL;
261
262 return 0;
263}
264
265static const struct uart_ops liteuart_ops = {
266 .tx_empty = liteuart_tx_empty,
267 .set_mctrl = liteuart_set_mctrl,
268 .get_mctrl = liteuart_get_mctrl,
269 .stop_tx = liteuart_stop_tx,
270 .start_tx = liteuart_start_tx,
271 .stop_rx = liteuart_stop_rx,
272 .startup = liteuart_startup,
273 .shutdown = liteuart_shutdown,
274 .set_termios = liteuart_set_termios,
275 .type = liteuart_type,
276 .config_port = liteuart_config_port,
277 .verify_port = liteuart_verify_port,
278};
279
280static int liteuart_probe(struct platform_device *pdev)
281{
282 struct liteuart_port *uart;
283 struct uart_port *port;
284 struct xa_limit limit;
285 int dev_id, ret;
286
287 uart = devm_kzalloc(&pdev->dev, sizeof(struct liteuart_port), GFP_KERNEL);
288 if (!uart)
289 return -ENOMEM;
290
291 port = &uart->port;
292
293 /* get membase */
294 port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
295 if (IS_ERR(port->membase))
296 return PTR_ERR(port->membase);
297
298 ret = platform_get_irq_optional(pdev, 0);
299 if (ret < 0 && ret != -ENXIO)
300 return ret;
301 if (ret > 0)
302 port->irq = ret;
303
304 /* look for aliases; auto-enumerate for free index if not found */
305 dev_id = of_alias_get_id(pdev->dev.of_node, "serial");
306 if (dev_id < 0)
307 limit = XA_LIMIT(0, CONFIG_SERIAL_LITEUART_MAX_PORTS);
308 else
309 limit = XA_LIMIT(dev_id, dev_id);
310
311 ret = xa_alloc(&liteuart_array, &dev_id, uart, limit, GFP_KERNEL);
312 if (ret)
313 return ret;
314
315 /* values not from device tree */
316 port->dev = &pdev->dev;
317 port->iotype = UPIO_MEM;
318 port->flags = UPF_BOOT_AUTOCONF;
319 port->ops = &liteuart_ops;
320 port->fifosize = 16;
321 port->type = PORT_UNKNOWN;
322 port->line = dev_id;
323 spin_lock_init(&port->lock);
324
325 platform_set_drvdata(pdev, port);
326
327 ret = uart_add_one_port(&liteuart_driver, &uart->port);
328 if (ret)
329 goto err_erase_id;
330
331 return 0;
332
333err_erase_id:
334 xa_erase(&liteuart_array, dev_id);
335
336 return ret;
337}
338
339static void liteuart_remove(struct platform_device *pdev)
340{
341 struct uart_port *port = platform_get_drvdata(pdev);
342 unsigned int line = port->line;
343
344 uart_remove_one_port(&liteuart_driver, port);
345 xa_erase(&liteuart_array, line);
346}
347
348static const struct of_device_id liteuart_of_match[] = {
349 { .compatible = "litex,liteuart" },
350 {}
351};
352MODULE_DEVICE_TABLE(of, liteuart_of_match);
353
354static struct platform_driver liteuart_platform_driver = {
355 .probe = liteuart_probe,
356 .remove = liteuart_remove,
357 .driver = {
358 .name = KBUILD_MODNAME,
359 .of_match_table = liteuart_of_match,
360 },
361};
362
363#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
364
365static void liteuart_putchar(struct uart_port *port, unsigned char ch)
366{
367 while (litex_read8(port->membase + OFF_TXFULL))
368 cpu_relax();
369
370 litex_write8(port->membase + OFF_RXTX, ch);
371}
372
373static void liteuart_console_write(struct console *co, const char *s,
374 unsigned int count)
375{
376 struct liteuart_port *uart;
377 struct uart_port *port;
378 unsigned long flags;
379
380 uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
381 port = &uart->port;
382
383 uart_port_lock_irqsave(port, &flags);
384 uart_console_write(port, s, count, liteuart_putchar);
385 uart_port_unlock_irqrestore(port, flags);
386}
387
388static int liteuart_console_setup(struct console *co, char *options)
389{
390 struct liteuart_port *uart;
391 struct uart_port *port;
392 int baud = 115200;
393 int bits = 8;
394 int parity = 'n';
395 int flow = 'n';
396
397 uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
398 if (!uart)
399 return -ENODEV;
400
401 port = &uart->port;
402 if (!port->membase)
403 return -ENODEV;
404
405 if (options)
406 uart_parse_options(options, &baud, &parity, &bits, &flow);
407
408 return uart_set_options(port, co, baud, parity, bits, flow);
409}
410
411static struct console liteuart_console = {
412 .name = KBUILD_MODNAME,
413 .write = liteuart_console_write,
414 .device = uart_console_device,
415 .setup = liteuart_console_setup,
416 .flags = CON_PRINTBUFFER,
417 .index = -1,
418 .data = &liteuart_driver,
419};
420
421static int __init liteuart_console_init(void)
422{
423 register_console(&liteuart_console);
424
425 return 0;
426}
427console_initcall(liteuart_console_init);
428
429static void early_liteuart_write(struct console *console, const char *s,
430 unsigned int count)
431{
432 struct earlycon_device *device = console->data;
433 struct uart_port *port = &device->port;
434
435 uart_console_write(port, s, count, liteuart_putchar);
436}
437
438static int __init early_liteuart_setup(struct earlycon_device *device,
439 const char *options)
440{
441 if (!device->port.membase)
442 return -ENODEV;
443
444 device->con->write = early_liteuart_write;
445 return 0;
446}
447
448OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup);
449#endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
450
451static int __init liteuart_init(void)
452{
453 int res;
454
455 res = uart_register_driver(&liteuart_driver);
456 if (res)
457 return res;
458
459 res = platform_driver_register(&liteuart_platform_driver);
460 if (res)
461 uart_unregister_driver(&liteuart_driver);
462
463 return res;
464}
465
466static void __exit liteuart_exit(void)
467{
468 platform_driver_unregister(&liteuart_platform_driver);
469 uart_unregister_driver(&liteuart_driver);
470}
471
472module_init(liteuart_init);
473module_exit(liteuart_exit);
474
475MODULE_AUTHOR("Antmicro <www.antmicro.com>");
476MODULE_DESCRIPTION("LiteUART serial driver");
477MODULE_LICENSE("GPL v2");
478MODULE_ALIAS("platform:liteuart");