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1/*
2 * dashtty.c - tty driver for Dash channels interface.
3 *
4 * Copyright (C) 2007,2008,2012 Imagination Technologies
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file COPYING in the main directory of this archive
8 * for more details.
9 *
10 */
11
12#include <linux/atomic.h>
13#include <linux/completion.h>
14#include <linux/console.h>
15#include <linux/delay.h>
16#include <linux/export.h>
17#include <linux/init.h>
18#include <linux/kernel.h>
19#include <linux/kthread.h>
20#include <linux/moduleparam.h>
21#include <linux/mutex.h>
22#include <linux/sched.h>
23#include <linux/serial.h>
24#include <linux/slab.h>
25#include <linux/spinlock.h>
26#include <linux/string.h>
27#include <linux/timer.h>
28#include <linux/tty.h>
29#include <linux/tty_driver.h>
30#include <linux/tty_flip.h>
31#include <linux/uaccess.h>
32
33#include <asm/da.h>
34
35/* Channel error codes */
36#define CONAOK 0
37#define CONERR 1
38#define CONBAD 2
39#define CONPRM 3
40#define CONADR 4
41#define CONCNT 5
42#define CONCBF 6
43#define CONCBE 7
44#define CONBSY 8
45
46/* Default channel for the console */
47#define CONSOLE_CHANNEL 1
48
49#define NUM_TTY_CHANNELS 6
50
51/* Auto allocate */
52#define DA_TTY_MAJOR 0
53
54/* A speedy poll rate helps the userland debug process connection response.
55 * But, if you set it too high then no other userland processes get much
56 * of a look in.
57 */
58#define DA_TTY_POLL (HZ / 50)
59
60/*
61 * A short put delay improves latency but has a high throughput overhead
62 */
63#define DA_TTY_PUT_DELAY (HZ / 100)
64
65static atomic_t num_channels_need_poll = ATOMIC_INIT(0);
66
67static struct timer_list poll_timer;
68
69static struct tty_driver *channel_driver;
70
71static struct timer_list put_timer;
72static struct task_struct *dashtty_thread;
73
74/*
75 * The console_poll parameter determines whether the console channel should be
76 * polled for input.
77 * By default the console channel isn't polled at all, in order to avoid the
78 * overhead, but that means it isn't possible to have a login on /dev/console.
79 */
80static bool console_poll;
81module_param(console_poll, bool, S_IRUGO);
82
83#define RX_BUF_SIZE 1024
84
85enum {
86 INCHR = 1,
87 OUTCHR,
88 RDBUF,
89 WRBUF,
90 RDSTAT
91};
92
93/**
94 * struct dashtty_port - Wrapper struct for dashtty tty_port.
95 * @port: TTY port data
96 * @rx_lock: Lock for rx_buf.
97 * This protects between the poll timer and user context.
98 * It's also held during read SWITCH operations.
99 * @rx_buf: Read buffer
100 * @xmit_lock: Lock for xmit_*, and port.xmit_buf.
101 * This protects between user context and kernel thread.
102 * It's also held during write SWITCH operations.
103 * @xmit_cnt: Size of xmit buffer contents
104 * @xmit_head: Head of xmit buffer where data is written
105 * @xmit_tail: Tail of xmit buffer where data is read
106 * @xmit_empty: Completion for xmit buffer being empty
107 */
108struct dashtty_port {
109 struct tty_port port;
110 spinlock_t rx_lock;
111 void *rx_buf;
112 struct mutex xmit_lock;
113 unsigned int xmit_cnt;
114 unsigned int xmit_head;
115 unsigned int xmit_tail;
116 struct completion xmit_empty;
117};
118
119static struct dashtty_port dashtty_ports[NUM_TTY_CHANNELS];
120
121static atomic_t dashtty_xmit_cnt = ATOMIC_INIT(0);
122static wait_queue_head_t dashtty_waitqueue;
123
124/*
125 * Low-level DA channel access routines
126 */
127static int chancall(int in_bios_function, int in_channel,
128 int in_arg2, void *in_arg3,
129 void *in_arg4)
130{
131 register int bios_function asm("D1Ar1") = in_bios_function;
132 register int channel asm("D0Ar2") = in_channel;
133 register int arg2 asm("D1Ar3") = in_arg2;
134 register void *arg3 asm("D0Ar4") = in_arg3;
135 register void *arg4 asm("D1Ar5") = in_arg4;
136 register int bios_call asm("D0Ar6") = 3;
137 register int result asm("D0Re0");
138
139 asm volatile (
140 "MSETL [A0StP++], %6,%4,%2\n\t"
141 "ADD A0StP, A0StP, #8\n\t"
142 "SWITCH #0x0C30208\n\t"
143 "GETD %0, [A0StP+#-8]\n\t"
144 "SUB A0StP, A0StP, #(4*6)+8\n\t"
145 : "=d" (result) /* outs */
146 : "d" (bios_function),
147 "d" (channel),
148 "d" (arg2),
149 "d" (arg3),
150 "d" (arg4),
151 "d" (bios_call) /* ins */
152 : "memory");
153
154 return result;
155}
156
157/*
158 * Attempts to fetch count bytes from channel and returns actual count.
159 */
160static int fetch_data(unsigned int channel)
161{
162 struct dashtty_port *dport = &dashtty_ports[channel];
163 int received = 0;
164
165 spin_lock_bh(&dport->rx_lock);
166 /* check the port isn't being shut down */
167 if (!dport->rx_buf)
168 goto unlock;
169 if (chancall(RDBUF, channel, RX_BUF_SIZE,
170 (void *)dport->rx_buf, &received) == CONAOK) {
171 if (received) {
172 int space;
173 unsigned char *cbuf;
174
175 space = tty_prepare_flip_string(&dport->port, &cbuf,
176 received);
177
178 if (space <= 0)
179 goto unlock;
180
181 memcpy(cbuf, dport->rx_buf, space);
182 tty_flip_buffer_push(&dport->port);
183 }
184 }
185unlock:
186 spin_unlock_bh(&dport->rx_lock);
187
188 return received;
189}
190
191/**
192 * find_channel_to_poll() - Returns number of the next channel to poll.
193 * Returns: The number of the next channel to poll, or -1 if none need
194 * polling.
195 */
196static int find_channel_to_poll(void)
197{
198 static int last_polled_channel;
199 int last = last_polled_channel;
200 int chan;
201 struct dashtty_port *dport;
202
203 for (chan = last + 1; ; ++chan) {
204 if (chan >= NUM_TTY_CHANNELS)
205 chan = 0;
206
207 dport = &dashtty_ports[chan];
208 if (dport->rx_buf) {
209 last_polled_channel = chan;
210 return chan;
211 }
212
213 if (chan == last)
214 break;
215 }
216 return -1;
217}
218
219/**
220 * put_channel_data() - Write out a block of channel data.
221 * @chan: DA channel number.
222 *
223 * Write a single block of data out to the debug adapter. If the circular buffer
224 * is wrapped then only the first block is written.
225 *
226 * Returns: 1 if the remote buffer was too full to accept data.
227 * 0 otherwise.
228 */
229static int put_channel_data(unsigned int chan)
230{
231 struct dashtty_port *dport;
232 struct tty_struct *tty;
233 int number_written;
234 unsigned int count = 0;
235
236 dport = &dashtty_ports[chan];
237 mutex_lock(&dport->xmit_lock);
238 if (dport->xmit_cnt) {
239 count = min((unsigned int)(SERIAL_XMIT_SIZE - dport->xmit_tail),
240 dport->xmit_cnt);
241 chancall(WRBUF, chan, count,
242 dport->port.xmit_buf + dport->xmit_tail,
243 &number_written);
244 dport->xmit_cnt -= number_written;
245 if (!dport->xmit_cnt) {
246 /* reset pointers to avoid wraps */
247 dport->xmit_head = 0;
248 dport->xmit_tail = 0;
249 complete(&dport->xmit_empty);
250 } else {
251 dport->xmit_tail += number_written;
252 if (dport->xmit_tail >= SERIAL_XMIT_SIZE)
253 dport->xmit_tail -= SERIAL_XMIT_SIZE;
254 }
255 atomic_sub(number_written, &dashtty_xmit_cnt);
256 }
257 mutex_unlock(&dport->xmit_lock);
258
259 /* if we've made more data available, wake up tty */
260 if (count && number_written) {
261 tty = tty_port_tty_get(&dport->port);
262 if (tty) {
263 tty_wakeup(tty);
264 tty_kref_put(tty);
265 }
266 }
267
268 /* did the write fail? */
269 return count && !number_written;
270}
271
272/**
273 * put_data() - Kernel thread to write out blocks of channel data to DA.
274 * @arg: Unused.
275 *
276 * This kernel thread runs while @dashtty_xmit_cnt != 0, and loops over the
277 * channels to write out any buffered data. If any of the channels stall due to
278 * the remote buffer being full, a hold off happens to allow the debugger to
279 * drain the buffer.
280 */
281static int put_data(void *arg)
282{
283 unsigned int chan, stall;
284
285 __set_current_state(TASK_RUNNING);
286 while (!kthread_should_stop()) {
287 /*
288 * For each channel see if there's anything to transmit in the
289 * port's xmit_buf.
290 */
291 stall = 0;
292 for (chan = 0; chan < NUM_TTY_CHANNELS; ++chan)
293 stall += put_channel_data(chan);
294
295 /*
296 * If some of the buffers are full, hold off for a short while
297 * to allow them to empty.
298 */
299 if (stall)
300 msleep(25);
301
302 wait_event_interruptible(dashtty_waitqueue,
303 atomic_read(&dashtty_xmit_cnt));
304 }
305
306 return 0;
307}
308
309/*
310 * This gets called every DA_TTY_POLL and polls the channels for data
311 */
312static void dashtty_timer(unsigned long ignored)
313{
314 int channel;
315
316 /* If there are no ports open do nothing and don't poll again. */
317 if (!atomic_read(&num_channels_need_poll))
318 return;
319
320 channel = find_channel_to_poll();
321
322 /* Did we find a channel to poll? */
323 if (channel >= 0)
324 fetch_data(channel);
325
326 mod_timer(&poll_timer, jiffies + DA_TTY_POLL);
327}
328
329static void add_poll_timer(struct timer_list *poll_timer)
330{
331 setup_pinned_timer(poll_timer, dashtty_timer, 0);
332 poll_timer->expires = jiffies + DA_TTY_POLL;
333
334 /*
335 * Always attach the timer to the boot CPU. The DA channels are per-CPU
336 * so all polling should be from a single CPU.
337 */
338 add_timer_on(poll_timer, 0);
339}
340
341static int dashtty_port_activate(struct tty_port *port, struct tty_struct *tty)
342{
343 struct dashtty_port *dport = container_of(port, struct dashtty_port,
344 port);
345 void *rx_buf;
346
347 /* Allocate the buffer we use for writing data */
348 if (tty_port_alloc_xmit_buf(port) < 0)
349 goto err;
350
351 /* Allocate the buffer we use for reading data */
352 rx_buf = kzalloc(RX_BUF_SIZE, GFP_KERNEL);
353 if (!rx_buf)
354 goto err_free_xmit;
355
356 spin_lock_bh(&dport->rx_lock);
357 dport->rx_buf = rx_buf;
358 spin_unlock_bh(&dport->rx_lock);
359
360 /*
361 * Don't add the poll timer if we're opening a console. This
362 * avoids the overhead of polling the Dash but means it is not
363 * possible to have a login on /dev/console.
364 *
365 */
366 if (console_poll || dport != &dashtty_ports[CONSOLE_CHANNEL])
367 if (atomic_inc_return(&num_channels_need_poll) == 1)
368 add_poll_timer(&poll_timer);
369
370 return 0;
371err_free_xmit:
372 tty_port_free_xmit_buf(port);
373err:
374 return -ENOMEM;
375}
376
377static void dashtty_port_shutdown(struct tty_port *port)
378{
379 struct dashtty_port *dport = container_of(port, struct dashtty_port,
380 port);
381 void *rx_buf;
382 unsigned int count;
383
384 /* stop reading */
385 if (console_poll || dport != &dashtty_ports[CONSOLE_CHANNEL])
386 if (atomic_dec_and_test(&num_channels_need_poll))
387 del_timer_sync(&poll_timer);
388
389 mutex_lock(&dport->xmit_lock);
390 count = dport->xmit_cnt;
391 mutex_unlock(&dport->xmit_lock);
392 if (count) {
393 /*
394 * There's still data to write out, so wake and wait for the
395 * writer thread to drain the buffer.
396 */
397 del_timer(&put_timer);
398 wake_up_interruptible(&dashtty_waitqueue);
399 wait_for_completion(&dport->xmit_empty);
400 }
401
402 /* Null the read buffer (timer could still be running!) */
403 spin_lock_bh(&dport->rx_lock);
404 rx_buf = dport->rx_buf;
405 dport->rx_buf = NULL;
406 spin_unlock_bh(&dport->rx_lock);
407 /* Free the read buffer */
408 kfree(rx_buf);
409
410 /* Free the write buffer */
411 tty_port_free_xmit_buf(port);
412}
413
414static const struct tty_port_operations dashtty_port_ops = {
415 .activate = dashtty_port_activate,
416 .shutdown = dashtty_port_shutdown,
417};
418
419static int dashtty_install(struct tty_driver *driver, struct tty_struct *tty)
420{
421 return tty_port_install(&dashtty_ports[tty->index].port, driver, tty);
422}
423
424static int dashtty_open(struct tty_struct *tty, struct file *filp)
425{
426 return tty_port_open(tty->port, tty, filp);
427}
428
429static void dashtty_close(struct tty_struct *tty, struct file *filp)
430{
431 return tty_port_close(tty->port, tty, filp);
432}
433
434static void dashtty_hangup(struct tty_struct *tty)
435{
436 int channel;
437 struct dashtty_port *dport;
438
439 channel = tty->index;
440 dport = &dashtty_ports[channel];
441
442 /* drop any data in the xmit buffer */
443 mutex_lock(&dport->xmit_lock);
444 if (dport->xmit_cnt) {
445 atomic_sub(dport->xmit_cnt, &dashtty_xmit_cnt);
446 dport->xmit_cnt = 0;
447 dport->xmit_head = 0;
448 dport->xmit_tail = 0;
449 complete(&dport->xmit_empty);
450 }
451 mutex_unlock(&dport->xmit_lock);
452
453 tty_port_hangup(tty->port);
454}
455
456/**
457 * dashtty_put_timer() - Delayed wake up of kernel thread.
458 * @ignored: unused
459 *
460 * This timer function wakes up the kernel thread if any data exists in the
461 * buffers. It is used to delay the expensive writeout until the writer has
462 * stopped writing.
463 */
464static void dashtty_put_timer(unsigned long ignored)
465{
466 if (atomic_read(&dashtty_xmit_cnt))
467 wake_up_interruptible(&dashtty_waitqueue);
468}
469
470static int dashtty_write(struct tty_struct *tty, const unsigned char *buf,
471 int total)
472{
473 int channel, count, block;
474 struct dashtty_port *dport;
475
476 /* Determine the channel */
477 channel = tty->index;
478 dport = &dashtty_ports[channel];
479
480 /*
481 * Write to output buffer.
482 *
483 * The reason that we asynchronously write the buffer is because if we
484 * were to write the buffer synchronously then because DA channels are
485 * per-CPU the buffer would be written to the channel of whatever CPU
486 * we're running on.
487 *
488 * What we actually want to happen is have all input and output done on
489 * one CPU.
490 */
491 mutex_lock(&dport->xmit_lock);
492 /* work out how many bytes we can write to the xmit buffer */
493 total = min(total, (int)(SERIAL_XMIT_SIZE - dport->xmit_cnt));
494 atomic_add(total, &dashtty_xmit_cnt);
495 dport->xmit_cnt += total;
496 /* write the actual bytes (may need splitting if it wraps) */
497 for (count = total; count; count -= block) {
498 block = min(count, (int)(SERIAL_XMIT_SIZE - dport->xmit_head));
499 memcpy(dport->port.xmit_buf + dport->xmit_head, buf, block);
500 dport->xmit_head += block;
501 if (dport->xmit_head >= SERIAL_XMIT_SIZE)
502 dport->xmit_head -= SERIAL_XMIT_SIZE;
503 buf += block;
504 }
505 count = dport->xmit_cnt;
506 /* xmit buffer no longer empty? */
507 if (count)
508 reinit_completion(&dport->xmit_empty);
509 mutex_unlock(&dport->xmit_lock);
510
511 if (total) {
512 /*
513 * If the buffer is full, wake up the kthread, otherwise allow
514 * some more time for the buffer to fill up a bit before waking
515 * it.
516 */
517 if (count == SERIAL_XMIT_SIZE) {
518 del_timer(&put_timer);
519 wake_up_interruptible(&dashtty_waitqueue);
520 } else {
521 mod_timer(&put_timer, jiffies + DA_TTY_PUT_DELAY);
522 }
523 }
524 return total;
525}
526
527static int dashtty_write_room(struct tty_struct *tty)
528{
529 struct dashtty_port *dport;
530 int channel;
531 int room;
532
533 channel = tty->index;
534 dport = &dashtty_ports[channel];
535
536 /* report the space in the xmit buffer */
537 mutex_lock(&dport->xmit_lock);
538 room = SERIAL_XMIT_SIZE - dport->xmit_cnt;
539 mutex_unlock(&dport->xmit_lock);
540
541 return room;
542}
543
544static int dashtty_chars_in_buffer(struct tty_struct *tty)
545{
546 struct dashtty_port *dport;
547 int channel;
548 int chars;
549
550 channel = tty->index;
551 dport = &dashtty_ports[channel];
552
553 /* report the number of bytes in the xmit buffer */
554 mutex_lock(&dport->xmit_lock);
555 chars = dport->xmit_cnt;
556 mutex_unlock(&dport->xmit_lock);
557
558 return chars;
559}
560
561static const struct tty_operations dashtty_ops = {
562 .install = dashtty_install,
563 .open = dashtty_open,
564 .close = dashtty_close,
565 .hangup = dashtty_hangup,
566 .write = dashtty_write,
567 .write_room = dashtty_write_room,
568 .chars_in_buffer = dashtty_chars_in_buffer,
569};
570
571static int __init dashtty_init(void)
572{
573 int ret;
574 int nport;
575 struct dashtty_port *dport;
576
577 if (!metag_da_enabled())
578 return -ENODEV;
579
580 channel_driver = tty_alloc_driver(NUM_TTY_CHANNELS,
581 TTY_DRIVER_REAL_RAW);
582 if (IS_ERR(channel_driver))
583 return PTR_ERR(channel_driver);
584
585 channel_driver->driver_name = "metag_da";
586 channel_driver->name = "ttyDA";
587 channel_driver->major = DA_TTY_MAJOR;
588 channel_driver->minor_start = 0;
589 channel_driver->type = TTY_DRIVER_TYPE_SERIAL;
590 channel_driver->subtype = SERIAL_TYPE_NORMAL;
591 channel_driver->init_termios = tty_std_termios;
592 channel_driver->init_termios.c_cflag |= CLOCAL;
593
594 tty_set_operations(channel_driver, &dashtty_ops);
595 for (nport = 0; nport < NUM_TTY_CHANNELS; nport++) {
596 dport = &dashtty_ports[nport];
597 tty_port_init(&dport->port);
598 dport->port.ops = &dashtty_port_ops;
599 spin_lock_init(&dport->rx_lock);
600 mutex_init(&dport->xmit_lock);
601 /* the xmit buffer starts empty, i.e. completely written */
602 init_completion(&dport->xmit_empty);
603 complete(&dport->xmit_empty);
604 }
605
606 setup_timer(&put_timer, dashtty_put_timer, 0);
607
608 init_waitqueue_head(&dashtty_waitqueue);
609 dashtty_thread = kthread_create(put_data, NULL, "ttyDA");
610 if (IS_ERR(dashtty_thread)) {
611 pr_err("Couldn't create dashtty thread\n");
612 ret = PTR_ERR(dashtty_thread);
613 goto err_destroy_ports;
614 }
615 /*
616 * Bind the writer thread to the boot CPU so it can't migrate.
617 * DA channels are per-CPU and we want all channel I/O to be on a single
618 * predictable CPU.
619 */
620 kthread_bind(dashtty_thread, 0);
621 wake_up_process(dashtty_thread);
622
623 ret = tty_register_driver(channel_driver);
624
625 if (ret < 0) {
626 pr_err("Couldn't install dashtty driver: err %d\n",
627 ret);
628 goto err_stop_kthread;
629 }
630
631 return 0;
632
633err_stop_kthread:
634 kthread_stop(dashtty_thread);
635err_destroy_ports:
636 for (nport = 0; nport < NUM_TTY_CHANNELS; nport++) {
637 dport = &dashtty_ports[nport];
638 tty_port_destroy(&dport->port);
639 }
640 put_tty_driver(channel_driver);
641 return ret;
642}
643device_initcall(dashtty_init);
644
645#ifdef CONFIG_DA_CONSOLE
646
647static void dash_console_write(struct console *co, const char *s,
648 unsigned int count)
649{
650 int actually_written;
651
652 chancall(WRBUF, CONSOLE_CHANNEL, count, (void *)s, &actually_written);
653}
654
655static struct tty_driver *dash_console_device(struct console *c, int *index)
656{
657 *index = c->index;
658 return channel_driver;
659}
660
661struct console dash_console = {
662 .name = "ttyDA",
663 .write = dash_console_write,
664 .device = dash_console_device,
665 .flags = CON_PRINTBUFFER,
666 .index = 1,
667};
668
669#endif