summaryrefslogtreecommitdiffstats
path: root/drivers/tty/ehv_bytechan.c
blob: 5164f9a570178244617a860d4cf5d6111082103c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
/* ePAPR hypervisor byte channel device driver
 *
 * Copyright 2009-2011 Freescale Semiconductor, Inc.
 *
 * Author: Timur Tabi <timur@freescale.com>
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2.  This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 *
 * This driver support three distinct interfaces, all of which are related to
 * ePAPR hypervisor byte channels.
 *
 * 1) An early-console (udbg) driver.  This provides early console output
 * through a byte channel.  The byte channel handle must be specified in a
 * Kconfig option.
 *
 * 2) A normal console driver.  Output is sent to the byte channel designated
 * for stdout in the device tree.  The console driver is for handling kernel
 * printk calls.
 *
 * 3) A tty driver, which is used to handle user-space input and output.  The
 * byte channel used for the console is designated as the default tty.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <asm/epapr_hcalls.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/cdev.h>
#include <linux/console.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/circ_buf.h>
#include <asm/udbg.h>

/* The size of the transmit circular buffer.  This must be a power of two. */
#define BUF_SIZE	2048

/* Per-byte channel private data */
struct ehv_bc_data {
	struct device *dev;
	struct tty_port port;
	uint32_t handle;
	unsigned int rx_irq;
	unsigned int tx_irq;

	spinlock_t lock;	/* lock for transmit buffer */
	unsigned char buf[BUF_SIZE];	/* transmit circular buffer */
	unsigned int head;	/* circular buffer head */
	unsigned int tail;	/* circular buffer tail */

	int tx_irq_enabled;	/* true == TX interrupt is enabled */
};

/* Array of byte channel objects */
static struct ehv_bc_data *bcs;

/* Byte channel handle for stdout (and stdin), taken from device tree */
static unsigned int stdout_bc;

/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
static unsigned int stdout_irq;

/**************************** SUPPORT FUNCTIONS ****************************/

/*
 * Enable the transmit interrupt
 *
 * Unlike a serial device, byte channels have no mechanism for disabling their
 * own receive or transmit interrupts.  To emulate that feature, we toggle
 * the IRQ in the kernel.
 *
 * We cannot just blindly call enable_irq() or disable_irq(), because these
 * calls are reference counted.  This means that we cannot call enable_irq()
 * if interrupts are already enabled.  This can happen in two situations:
 *
 * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
 * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
 *
 * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
 */
static void enable_tx_interrupt(struct ehv_bc_data *bc)
{
	if (!bc->tx_irq_enabled) {
		enable_irq(bc->tx_irq);
		bc->tx_irq_enabled = 1;
	}
}

static void disable_tx_interrupt(struct ehv_bc_data *bc)
{
	if (bc->tx_irq_enabled) {
		disable_irq_nosync(bc->tx_irq);
		bc->tx_irq_enabled = 0;
	}
}

/*
 * find the byte channel handle to use for the console
 *
 * The byte channel to be used for the console is specified via a "stdout"
 * property in the /chosen node.
 *
 * For compatible with legacy device trees, we also look for a "stdout" alias.
 */
static int find_console_handle(void)
{
	struct device_node *np, *np2;
	const char *sprop = NULL;
	const uint32_t *iprop;

	np = of_find_node_by_path("/chosen");
	if (np)
		sprop = of_get_property(np, "stdout-path", NULL);

	if (!np || !sprop) {
		of_node_put(np);
		np = of_find_node_by_name(NULL, "aliases");
		if (np)
			sprop = of_get_property(np, "stdout", NULL);
	}

	if (!sprop) {
		of_node_put(np);
		return 0;
	}

	/* We don't care what the aliased node is actually called.  We only
	 * care if it's compatible with "epapr,hv-byte-channel", because that
	 * indicates that it's a byte channel node.  We use a temporary
	 * variable, 'np2', because we can't release 'np' until we're done with
	 * 'sprop'.
	 */
	np2 = of_find_node_by_path(sprop);
	of_node_put(np);
	np = np2;
	if (!np) {
		pr_warning("ehv-bc: stdout node '%s' does not exist\n", sprop);
		return 0;
	}

	/* Is it a byte channel? */
	if (!of_device_is_compatible(np, "epapr,hv-byte-channel")) {
		of_node_put(np);
		return 0;
	}

	stdout_irq = irq_of_parse_and_map(np, 0);
	if (stdout_irq == NO_IRQ) {
		pr_err("ehv-bc: no 'interrupts' property in %s node\n", sprop);
		of_node_put(np);
		return 0;
	}

	/*
	 * The 'hv-handle' property contains the handle for this byte channel.
	 */
	iprop = of_get_property(np, "hv-handle", NULL);
	if (!iprop) {
		pr_err("ehv-bc: no 'hv-handle' property in %s node\n",
		       np->name);
		of_node_put(np);
		return 0;
	}
	stdout_bc = be32_to_cpu(*iprop);

	of_node_put(np);
	return 1;
}

/*************************** EARLY CONSOLE DRIVER ***************************/

#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC

/*
 * send a byte to a byte channel, wait if necessary
 *
 * This function sends a byte to a byte channel, and it waits and
 * retries if the byte channel is full.  It returns if the character
 * has been sent, or if some error has occurred.
 *
 */
static void byte_channel_spin_send(const char data)
{
	int ret, count;

	do {
		count = 1;
		ret = ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
					   &count, &data);
	} while (ret == EV_EAGAIN);
}

/*
 * The udbg subsystem calls this function to display a single character.
 * We convert CR to a CR/LF.
 */
static void ehv_bc_udbg_putc(char c)
{
	if (c == '\n')
		byte_channel_spin_send('\r');

	byte_channel_spin_send(c);
}

/*
 * early console initialization
 *
 * PowerPC kernels support an early printk console, also known as udbg.
 * This function must be called via the ppc_md.init_early function pointer.
 * At this point, the device tree has been unflattened, so we can obtain the
 * byte channel handle for stdout.
 *
 * We only support displaying of characters (putc).  We do not support
 * keyboard input.
 */
void __init udbg_init_ehv_bc(void)
{
	unsigned int rx_count, tx_count;
	unsigned int ret;

	/* Verify the byte channel handle */
	ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
				   &rx_count, &tx_count);
	if (ret)
		return;

	udbg_putc = ehv_bc_udbg_putc;
	register_early_udbg_console();

	udbg_printf("ehv-bc: early console using byte channel handle %u\n",
		    CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
}

#endif

/****************************** CONSOLE DRIVER ******************************/

static struct tty_driver *ehv_bc_driver;

/*
 * Byte channel console sending worker function.
 *
 * For consoles, if the output buffer is full, we should just spin until it
 * clears.
 */
static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
			     unsigned int count)
{
	unsigned int len;
	int ret = 0;

	while (count) {
		len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
		do {
			ret = ev_byte_channel_send(handle, &len, s);
		} while (ret == EV_EAGAIN);
		count -= len;
		s += len;
	}

	return ret;
}

/*
 * write a string to the console
 *
 * This function gets called to write a string from the kernel, typically from
 * a printk().  This function spins until all data is written.
 *
 * We copy the data to a temporary buffer because we need to insert a \r in
 * front of every \n.  It's more efficient to copy the data to the buffer than
 * it is to make multiple hcalls for each character or each newline.
 */
static void ehv_bc_console_write(struct console *co, const char *s,
				 unsigned int count)
{
	char s2[EV_BYTE_CHANNEL_MAX_BYTES];
	unsigned int i, j = 0;
	char c;

	for (i = 0; i < count; i++) {
		c = *s++;

		if (c == '\n')
			s2[j++] = '\r';

		s2[j++] = c;
		if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
			if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
				return;
			j = 0;
		}
	}

	if (j)
		ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
}

/*
 * When /dev/console is opened, the kernel iterates the console list looking
 * for one with ->device and then calls that method. On success, it expects
 * the passed-in int* to contain the minor number to use.
 */
static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
{
	*index = co->index;

	return ehv_bc_driver;
}

static struct console ehv_bc_console = {
	.name		= "ttyEHV",
	.write		= ehv_bc_console_write,
	.device		= ehv_bc_console_device,
	.flags		= CON_PRINTBUFFER | CON_ENABLED,
};

/*
 * Console initialization
 *
 * This is the first function that is called after the device tree is
 * available, so here is where we determine the byte channel handle and IRQ for
 * stdout/stdin, even though that information is used by the tty and character
 * drivers.
 */
static int __init ehv_bc_console_init(void)
{
	if (!find_console_handle()) {
		pr_debug("ehv-bc: stdout is not a byte channel\n");
		return -ENODEV;
	}

#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
	/* Print a friendly warning if the user chose the wrong byte channel
	 * handle for udbg.
	 */
	if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
		pr_warning("ehv-bc: udbg handle %u is not the stdout handle\n",
			   CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
#endif

	/* add_preferred_console() must be called before register_console(),
	   otherwise it won't work.  However, we don't want to enumerate all the
	   byte channels here, either, since we only care about one. */

	add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
	register_console(&ehv_bc_console);

	pr_info("ehv-bc: registered console driver for byte channel %u\n",
		stdout_bc);

	return 0;
}
console_initcall(ehv_bc_console_init);

/******************************** TTY DRIVER ********************************/

/*
 * byte channel receive interupt handler
 *
 * This ISR is called whenever data is available on a byte channel.
 */
static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
{
	struct ehv_bc_data *bc = data;
	struct tty_struct *ttys = tty_port_tty_get(&bc->port);
	unsigned int rx_count, tx_count, len;
	int count;
	char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
	int ret;

	/* ttys could be NULL during a hangup */
	if (!ttys)
		return IRQ_HANDLED;

	/* Find out how much data needs to be read, and then ask the TTY layer
	 * if it can handle that much.  We want to ensure that every byte we
	 * read from the byte channel will be accepted by the TTY layer.
	 */
	ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
	count = tty_buffer_request_room(&bc->port, rx_count);

	/* 'count' is the maximum amount of data the TTY layer can accept at
	 * this time.  However, during testing, I was never able to get 'count'
	 * to be less than 'rx_count'.  I'm not sure whether I'm calling it
	 * correctly.
	 */

	while (count > 0) {
		len = min_t(unsigned int, count, sizeof(buffer));

		/* Read some data from the byte channel.  This function will
		 * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
		 */
		ev_byte_channel_receive(bc->handle, &len, buffer);

		/* 'len' is now the amount of data that's been received. 'len'
		 * can't be zero, and most likely it's equal to one.
		 */

		/* Pass the received data to the tty layer. */
		ret = tty_insert_flip_string(&bc->port, buffer, len);

		/* 'ret' is the number of bytes that the TTY layer accepted.
		 * If it's not equal to 'len', then it means the buffer is
		 * full, which should never happen.  If it does happen, we can
		 * exit gracefully, but we drop the last 'len - ret' characters
		 * that we read from the byte channel.
		 */
		if (ret != len)
			break;

		count -= len;
	}

	/* Tell the tty layer that we're done. */
	tty_flip_buffer_push(ttys);

	tty_kref_put(ttys);

	return IRQ_HANDLED;
}

/*
 * dequeue the transmit buffer to the hypervisor
 *
 * This function, which can be called in interrupt context, dequeues as much
 * data as possible from the transmit buffer to the byte channel.
 */
static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
{
	unsigned int count;
	unsigned int len, ret;
	unsigned long flags;

	do {
		spin_lock_irqsave(&bc->lock, flags);
		len = min_t(unsigned int,
			    CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
			    EV_BYTE_CHANNEL_MAX_BYTES);

		ret = ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);

		/* 'len' is valid only if the return code is 0 or EV_EAGAIN */
		if (!ret || (ret == EV_EAGAIN))
			bc->tail = (bc->tail + len) & (BUF_SIZE - 1);

		count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
		spin_unlock_irqrestore(&bc->lock, flags);
	} while (count && !ret);

	spin_lock_irqsave(&bc->lock, flags);
	if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
		/*
		 * If we haven't emptied the buffer, then enable the TX IRQ.
		 * We'll get an interrupt when there's more room in the
		 * hypervisor's output buffer.
		 */
		enable_tx_interrupt(bc);
	else
		disable_tx_interrupt(bc);
	spin_unlock_irqrestore(&bc->lock, flags);
}

/*
 * byte channel transmit interupt handler
 *
 * This ISR is called whenever space becomes available for transmitting
 * characters on a byte channel.
 */
static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
{
	struct ehv_bc_data *bc = data;
	struct tty_struct *ttys = tty_port_tty_get(&bc->port);

	ehv_bc_tx_dequeue(bc);
	if (ttys) {
		tty_wakeup(ttys);
		tty_kref_put(ttys);
	}

	return IRQ_HANDLED;
}

/*
 * This function is called when the tty layer has data for us send.  We store
 * the data first in a circular buffer, and then dequeue as much of that data
 * as possible.
 *
 * We don't need to worry about whether there is enough room in the buffer for
 * all the data.  The purpose of ehv_bc_tty_write_room() is to tell the tty
 * layer how much data it can safely send to us.  We guarantee that
 * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
 * too much data.
 */
static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
			    int count)
{
	struct ehv_bc_data *bc = ttys->driver_data;
	unsigned long flags;
	unsigned int len;
	unsigned int written = 0;

	while (1) {
		spin_lock_irqsave(&bc->lock, flags);
		len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
		if (count < len)
			len = count;
		if (len) {
			memcpy(bc->buf + bc->head, s, len);
			bc->head = (bc->head + len) & (BUF_SIZE - 1);
		}
		spin_unlock_irqrestore(&bc->lock, flags);
		if (!len)
			break;

		s += len;
		count -= len;
		written += len;
	}

	ehv_bc_tx_dequeue(bc);

	return written;
}

/*
 * This function can be called multiple times for a given tty_struct, which is
 * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
 *
 * The tty layer will still call this function even if the device was not
 * registered (i.e. tty_register_device() was not called).  This happens
 * because tty_register_device() is optional and some legacy drivers don't
 * use it.  So we need to check for that.
 */
static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
{
	struct ehv_bc_data *bc = &bcs[ttys->index];

	if (!bc->dev)
		return -ENODEV;

	return tty_port_open(&bc->port, ttys, filp);
}

/*
 * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
 * still call this function to close the tty device.  So we can't assume that
 * the tty port has been initialized.
 */
static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
{
	struct ehv_bc_data *bc = &bcs[ttys->index];

	if (bc->dev)
		tty_port_close(&bc->port, ttys, filp);
}

/*
 * Return the amount of space in the output buffer
 *
 * This is actually a contract between the driver and the tty layer outlining
 * how much write room the driver can guarantee will be sent OR BUFFERED.  This
 * driver MUST honor the return value.
 */
static int ehv_bc_tty_write_room(struct tty_struct *ttys)
{
	struct ehv_bc_data *bc = ttys->driver_data;
	unsigned long flags;
	int count;

	spin_lock_irqsave(&bc->lock, flags);
	count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
	spin_unlock_irqrestore(&bc->lock, flags);

	return count;
}

/*
 * Stop sending data to the tty layer
 *
 * This function is called when the tty layer's input buffers are getting full,
 * so the driver should stop sending it data.  The easiest way to do this is to
 * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
 * called.
 *
 * The hypervisor will continue to queue up any incoming data.  If there is any
 * data in the queue when the RX interrupt is enabled, we'll immediately get an
 * RX interrupt.
 */
static void ehv_bc_tty_throttle(struct tty_struct *ttys)
{
	struct ehv_bc_data *bc = ttys->driver_data;

	disable_irq(bc->rx_irq);
}

/*
 * Resume sending data to the tty layer
 *
 * This function is called after previously calling ehv_bc_tty_throttle().  The
 * tty layer's input buffers now have more room, so the driver can resume
 * sending it data.
 */
static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
{
	struct ehv_bc_data *bc = ttys->driver_data;

	/* If there is any data in the queue when the RX interrupt is enabled,
	 * we'll immediately get an RX interrupt.
	 */
	enable_irq(bc->rx_irq);
}

static void ehv_bc_tty_hangup(struct tty_struct *ttys)
{
	struct ehv_bc_data *bc = ttys->driver_data;

	ehv_bc_tx_dequeue(bc);
	tty_port_hangup(&bc->port);
}

/*
 * TTY driver operations
 *
 * If we could ask the hypervisor how much data is still in the TX buffer, or
 * at least how big the TX buffers are, then we could implement the
 * .wait_until_sent and .chars_in_buffer functions.
 */
static const struct tty_operations ehv_bc_ops = {
	.open		= ehv_bc_tty_open,
	.close		= ehv_bc_tty_close,
	.write		= ehv_bc_tty_write,
	.write_room	= ehv_bc_tty_write_room,
	.throttle	= ehv_bc_tty_throttle,
	.unthrottle	= ehv_bc_tty_unthrottle,
	.hangup		= ehv_bc_tty_hangup,
};

/*
 * initialize the TTY port
 *
 * This function will only be called once, no matter how many times
 * ehv_bc_tty_open() is called.  That's why we register the ISR here, and also
 * why we initialize tty_struct-related variables here.
 */
static int ehv_bc_tty_port_activate(struct tty_port *port,
				    struct tty_struct *ttys)
{
	struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
	int ret;

	ttys->driver_data = bc;

	ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
	if (ret < 0) {
		dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
		       bc->rx_irq, ret);
		return ret;
	}

	/* request_irq also enables the IRQ */
	bc->tx_irq_enabled = 1;

	ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
	if (ret < 0) {
		dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
		       bc->tx_irq, ret);
		free_irq(bc->rx_irq, bc);
		return ret;
	}

	/* The TX IRQ is enabled only when we can't write all the data to the
	 * byte channel at once, so by default it's disabled.
	 */
	disable_tx_interrupt(bc);

	return 0;
}

static void ehv_bc_tty_port_shutdown(struct tty_port *port)
{
	struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);

	free_irq(bc->tx_irq, bc);
	free_irq(bc->rx_irq, bc);
}

static const struct tty_port_operations ehv_bc_tty_port_ops = {
	.activate = ehv_bc_tty_port_activate,
	.shutdown = ehv_bc_tty_port_shutdown,
};

static int ehv_bc_tty_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct ehv_bc_data *bc;
	const uint32_t *iprop;
	unsigned int handle;
	int ret;
	static unsigned int index = 1;
	unsigned int i;

	iprop = of_get_property(np, "hv-handle", NULL);
	if (!iprop) {
		dev_err(&pdev->dev, "no 'hv-handle' property in %s node\n",
			np->name);
		return -ENODEV;
	}

	/* We already told the console layer that the index for the console
	 * device is zero, so we need to make sure that we use that index when
	 * we probe the console byte channel node.
	 */
	handle = be32_to_cpu(*iprop);
	i = (handle == stdout_bc) ? 0 : index++;
	bc = &bcs[i];

	bc->handle = handle;
	bc->head = 0;
	bc->tail = 0;
	spin_lock_init(&bc->lock);

	bc->rx_irq = irq_of_parse_and_map(np, 0);
	bc->tx_irq = irq_of_parse_and_map(np, 1);
	if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
		dev_err(&pdev->dev, "no 'interrupts' property in %s node\n",
			np->name);
		ret = -ENODEV;
		goto error;
	}

	tty_port_init(&bc->port);
	bc->port.ops = &ehv_bc_tty_port_ops;

	bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i,
			&pdev->dev);
	if (IS_ERR(bc->dev)) {
		ret = PTR_ERR(bc->dev);
		dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
		goto error;
	}

	dev_set_drvdata(&pdev->dev, bc);

	dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
		ehv_bc_driver->name, i, bc->handle);

	return 0;

error:
	tty_port_destroy(&bc->port);
	irq_dispose_mapping(bc->tx_irq);
	irq_dispose_mapping(bc->rx_irq);

	memset(bc, 0, sizeof(struct ehv_bc_data));
	return ret;
}

static int ehv_bc_tty_remove(struct platform_device *pdev)
{
	struct ehv_bc_data *bc = dev_get_drvdata(&pdev->dev);

	tty_unregister_device(ehv_bc_driver, bc - bcs);

	tty_port_destroy(&bc->port);
	irq_dispose_mapping(bc->tx_irq);
	irq_dispose_mapping(bc->rx_irq);

	return 0;
}

static const struct of_device_id ehv_bc_tty_of_ids[] = {
	{ .compatible = "epapr,hv-byte-channel" },
	{}
};

static struct platform_driver ehv_bc_tty_driver = {
	.driver = {
		.owner = THIS_MODULE,
		.name = "ehv-bc",
		.of_match_table = ehv_bc_tty_of_ids,
	},
	.probe		= ehv_bc_tty_probe,
	.remove		= ehv_bc_tty_remove,
};

/**
 * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
 *
 * This function is called when this module is loaded.
 */
static int __init ehv_bc_init(void)
{
	struct device_node *np;
	unsigned int count = 0; /* Number of elements in bcs[] */
	int ret;

	pr_info("ePAPR hypervisor byte channel driver\n");

	/* Count the number of byte channels */
	for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
		count++;

	if (!count)
		return -ENODEV;

	/* The array index of an element in bcs[] is the same as the tty index
	 * for that element.  If you know the address of an element in the
	 * array, then you can use pointer math (e.g. "bc - bcs") to get its
	 * tty index.
	 */
	bcs = kzalloc(count * sizeof(struct ehv_bc_data), GFP_KERNEL);
	if (!bcs)
		return -ENOMEM;

	ehv_bc_driver = alloc_tty_driver(count);
	if (!ehv_bc_driver) {
		ret = -ENOMEM;
		goto error;
	}

	ehv_bc_driver->driver_name = "ehv-bc";
	ehv_bc_driver->name = ehv_bc_console.name;
	ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
	ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
	ehv_bc_driver->init_termios = tty_std_termios;
	ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
	tty_set_operations(ehv_bc_driver, &ehv_bc_ops);

	ret = tty_register_driver(ehv_bc_driver);
	if (ret) {
		pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
		goto error;
	}

	ret = platform_driver_register(&ehv_bc_tty_driver);
	if (ret) {
		pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
		       ret);
		goto error;
	}

	return 0;

error:
	if (ehv_bc_driver) {
		tty_unregister_driver(ehv_bc_driver);
		put_tty_driver(ehv_bc_driver);
	}

	kfree(bcs);

	return ret;
}


/**
 * ehv_bc_exit - ePAPR hypervisor byte channel driver termination
 *
 * This function is called when this driver is unloaded.
 */
static void __exit ehv_bc_exit(void)
{
	tty_unregister_driver(ehv_bc_driver);
	put_tty_driver(ehv_bc_driver);
	kfree(bcs);
}

module_init(ehv_bc_init);
module_exit(ehv_bc_exit);

MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
MODULE_DESCRIPTION("ePAPR hypervisor byte channel driver");
MODULE_LICENSE("GPL v2");
OpenPOWER on IntegriCloud