summaryrefslogtreecommitdiffstats
path: root/drivers/spi/spi-bcm2835aux.c
blob: 40dfb7f58efec56618c621cfe90adeea95033126 (plain) (blame)
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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for Broadcom BCM2835 auxiliary SPI Controllers
 *
 * the driver does not rely on the native chipselects at all
 * but only uses the gpio type chipselects
 *
 * Based on: spi-bcm2835.c
 *
 * Copyright (C) 2015 Martin Sperl
 */

#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/regmap.h>
#include <linux/spi/spi.h>
#include <linux/spinlock.h>

/* define polling limits */
static unsigned int polling_limit_us = 30;
module_param(polling_limit_us, uint, 0664);
MODULE_PARM_DESC(polling_limit_us,
		 "time in us to run a transfer in polling mode - if zero no polling is used\n");

/*
 * spi register defines
 *
 * note there is garbage in the "official" documentation,
 * so some data is taken from the file:
 *   brcm_usrlib/dag/vmcsx/vcinclude/bcm2708_chip/aux_io.h
 * inside of:
 *   http://www.broadcom.com/docs/support/videocore/Brcm_Android_ICS_Graphics_Stack.tar.gz
 */

/* SPI register offsets */
#define BCM2835_AUX_SPI_CNTL0	0x00
#define BCM2835_AUX_SPI_CNTL1	0x04
#define BCM2835_AUX_SPI_STAT	0x08
#define BCM2835_AUX_SPI_PEEK	0x0C
#define BCM2835_AUX_SPI_IO	0x20
#define BCM2835_AUX_SPI_TXHOLD	0x30

/* Bitfields in CNTL0 */
#define BCM2835_AUX_SPI_CNTL0_SPEED	0xFFF00000
#define BCM2835_AUX_SPI_CNTL0_SPEED_MAX	0xFFF
#define BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT	20
#define BCM2835_AUX_SPI_CNTL0_CS	0x000E0000
#define BCM2835_AUX_SPI_CNTL0_POSTINPUT	0x00010000
#define BCM2835_AUX_SPI_CNTL0_VAR_CS	0x00008000
#define BCM2835_AUX_SPI_CNTL0_VAR_WIDTH	0x00004000
#define BCM2835_AUX_SPI_CNTL0_DOUTHOLD	0x00003000
#define BCM2835_AUX_SPI_CNTL0_ENABLE	0x00000800
#define BCM2835_AUX_SPI_CNTL0_IN_RISING	0x00000400
#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO	0x00000200
#define BCM2835_AUX_SPI_CNTL0_OUT_RISING	0x00000100
#define BCM2835_AUX_SPI_CNTL0_CPOL	0x00000080
#define BCM2835_AUX_SPI_CNTL0_MSBF_OUT	0x00000040
#define BCM2835_AUX_SPI_CNTL0_SHIFTLEN	0x0000003F

/* Bitfields in CNTL1 */
#define BCM2835_AUX_SPI_CNTL1_CSHIGH	0x00000700
#define BCM2835_AUX_SPI_CNTL1_TXEMPTY	0x00000080
#define BCM2835_AUX_SPI_CNTL1_IDLE	0x00000040
#define BCM2835_AUX_SPI_CNTL1_MSBF_IN	0x00000002
#define BCM2835_AUX_SPI_CNTL1_KEEP_IN	0x00000001

/* Bitfields in STAT */
#define BCM2835_AUX_SPI_STAT_TX_LVL	0xFF000000
#define BCM2835_AUX_SPI_STAT_RX_LVL	0x00FF0000
#define BCM2835_AUX_SPI_STAT_TX_FULL	0x00000400
#define BCM2835_AUX_SPI_STAT_TX_EMPTY	0x00000200
#define BCM2835_AUX_SPI_STAT_RX_FULL	0x00000100
#define BCM2835_AUX_SPI_STAT_RX_EMPTY	0x00000080
#define BCM2835_AUX_SPI_STAT_BUSY	0x00000040
#define BCM2835_AUX_SPI_STAT_BITCOUNT	0x0000003F

struct bcm2835aux_spi {
	void __iomem *regs;
	struct clk *clk;
	int irq;
	u32 cntl[2];
	const u8 *tx_buf;
	u8 *rx_buf;
	int tx_len;
	int rx_len;
	int pending;

	u64 count_transfer_polling;
	u64 count_transfer_irq;
	u64 count_transfer_irq_after_poll;

	struct dentry *debugfs_dir;
};

#if defined(CONFIG_DEBUG_FS)
static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs,
				      const char *dname)
{
	char name[64];
	struct dentry *dir;

	/* get full name */
	snprintf(name, sizeof(name), "spi-bcm2835aux-%s", dname);

	/* the base directory */
	dir = debugfs_create_dir(name, NULL);
	bs->debugfs_dir = dir;

	/* the counters */
	debugfs_create_u64("count_transfer_polling", 0444, dir,
			   &bs->count_transfer_polling);
	debugfs_create_u64("count_transfer_irq", 0444, dir,
			   &bs->count_transfer_irq);
	debugfs_create_u64("count_transfer_irq_after_poll", 0444, dir,
			   &bs->count_transfer_irq_after_poll);
}

static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs)
{
	debugfs_remove_recursive(bs->debugfs_dir);
	bs->debugfs_dir = NULL;
}
#else
static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs,
				      const char *dname)
{
}

static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs)
{
}
#endif /* CONFIG_DEBUG_FS */

static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned reg)
{
	return readl(bs->regs + reg);
}

static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned reg,
				 u32 val)
{
	writel(val, bs->regs + reg);
}

static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs)
{
	u32 data;
	int count = min(bs->rx_len, 3);

	data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO);
	if (bs->rx_buf) {
		switch (count) {
		case 3:
			*bs->rx_buf++ = (data >> 16) & 0xff;
			/* fallthrough */
		case 2:
			*bs->rx_buf++ = (data >> 8) & 0xff;
			/* fallthrough */
		case 1:
			*bs->rx_buf++ = (data >> 0) & 0xff;
			/* fallthrough - no default */
		}
	}
	bs->rx_len -= count;
	bs->pending -= count;
}

static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs)
{
	u32 data;
	u8 byte;
	int count;
	int i;

	/* gather up to 3 bytes to write to the FIFO */
	count = min(bs->tx_len, 3);
	data = 0;
	for (i = 0; i < count; i++) {
		byte = bs->tx_buf ? *bs->tx_buf++ : 0;
		data |= byte << (8 * (2 - i));
	}

	/* and set the variable bit-length */
	data |= (count * 8) << 24;

	/* and decrement length */
	bs->tx_len -= count;
	bs->pending += count;

	/* write to the correct TX-register */
	if (bs->tx_len)
		bcm2835aux_wr(bs, BCM2835_AUX_SPI_TXHOLD, data);
	else
		bcm2835aux_wr(bs, BCM2835_AUX_SPI_IO, data);
}

static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs)
{
	/* disable spi clearing fifo and interrupts */
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, 0);
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0,
		      BCM2835_AUX_SPI_CNTL0_CLEARFIFO);
}

static void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs)
{
	u32 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT);

	/* check if we have data to read */
	for (; bs->rx_len && (stat & BCM2835_AUX_SPI_STAT_RX_LVL);
	     stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT))
		bcm2835aux_rd_fifo(bs);

	/* check if we have data to write */
	while (bs->tx_len &&
	       (bs->pending < 12) &&
	       (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
		  BCM2835_AUX_SPI_STAT_TX_FULL))) {
		bcm2835aux_wr_fifo(bs);
	}
}

static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
{
	struct spi_master *master = dev_id;
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	/* IRQ may be shared, so return if our interrupts are disabled */
	if (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_CNTL1) &
	      (BCM2835_AUX_SPI_CNTL1_TXEMPTY | BCM2835_AUX_SPI_CNTL1_IDLE)))
		return IRQ_NONE;

	/* do common fifo handling */
	bcm2835aux_spi_transfer_helper(bs);

	if (!bs->tx_len) {
		/* disable tx fifo empty interrupt */
		bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
			BCM2835_AUX_SPI_CNTL1_IDLE);
	}

	/* and if rx_len is 0 then disable interrupts and wake up completion */
	if (!bs->rx_len) {
		bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
		complete(&master->xfer_completion);
	}

	return IRQ_HANDLED;
}

static int __bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
					     struct spi_device *spi,
					     struct spi_transfer *tfr)
{
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	/* enable interrupts */
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
		BCM2835_AUX_SPI_CNTL1_TXEMPTY |
		BCM2835_AUX_SPI_CNTL1_IDLE);

	/* and wait for finish... */
	return 1;
}

static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
					   struct spi_device *spi,
					   struct spi_transfer *tfr)
{
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	/* update statistics */
	bs->count_transfer_irq++;

	/* fill in registers and fifos before enabling interrupts */
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);

	/* fill in tx fifo with data before enabling interrupts */
	while ((bs->tx_len) &&
	       (bs->pending < 12) &&
	       (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
		  BCM2835_AUX_SPI_STAT_TX_FULL))) {
		bcm2835aux_wr_fifo(bs);
	}

	/* now run the interrupt mode */
	return __bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
}

static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master,
					    struct spi_device *spi,
					struct spi_transfer *tfr)
{
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	unsigned long timeout;

	/* update statistics */
	bs->count_transfer_polling++;

	/* configure spi */
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);

	/* set the timeout to at least 2 jiffies */
	timeout = jiffies + 2 + HZ * polling_limit_us / 1000000;

	/* loop until finished the transfer */
	while (bs->rx_len) {

		/* do common fifo handling */
		bcm2835aux_spi_transfer_helper(bs);

		/* there is still data pending to read check the timeout */
		if (bs->rx_len && time_after(jiffies, timeout)) {
			dev_dbg_ratelimited(&spi->dev,
					    "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
					    jiffies - timeout,
					    bs->tx_len, bs->rx_len);
			/* forward to interrupt handler */
			bs->count_transfer_irq_after_poll++;
			return __bcm2835aux_spi_transfer_one_irq(master,
							       spi, tfr);
		}
	}

	/* and return without waiting for completion */
	return 0;
}

static int bcm2835aux_spi_transfer_one(struct spi_master *master,
				       struct spi_device *spi,
				       struct spi_transfer *tfr)
{
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	unsigned long spi_hz, clk_hz, speed, spi_used_hz;
	unsigned long hz_per_byte, byte_limit;

	/* calculate the registers to handle
	 *
	 * note that we use the variable data mode, which
	 * is not optimal for longer transfers as we waste registers
	 * resulting (potentially) in more interrupts when transferring
	 * more than 12 bytes
	 */

	/* set clock */
	spi_hz = tfr->speed_hz;
	clk_hz = clk_get_rate(bs->clk);

	if (spi_hz >= clk_hz / 2) {
		speed = 0;
	} else if (spi_hz) {
		speed = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1;
		if (speed >  BCM2835_AUX_SPI_CNTL0_SPEED_MAX)
			speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
	} else { /* the slowest we can go */
		speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
	}
	/* mask out old speed from previous spi_transfer */
	bs->cntl[0] &= ~(BCM2835_AUX_SPI_CNTL0_SPEED);
	/* set the new speed */
	bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT;

	spi_used_hz = clk_hz / (2 * (speed + 1));

	/* set transmit buffers and length */
	bs->tx_buf = tfr->tx_buf;
	bs->rx_buf = tfr->rx_buf;
	bs->tx_len = tfr->len;
	bs->rx_len = tfr->len;
	bs->pending = 0;

	/* Calculate the estimated time in us the transfer runs.  Note that
	 * there are are 2 idle clocks cycles after each chunk getting
	 * transferred - in our case the chunk size is 3 bytes, so we
	 * approximate this by 9 cycles/byte.  This is used to find the number
	 * of Hz per byte per polling limit.  E.g., we can transfer 1 byte in
	 * 30 µs per 300,000 Hz of bus clock.
	 */
	hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0;
	byte_limit = hz_per_byte ? spi_used_hz / hz_per_byte : 1;

	/* run in polling mode for short transfers */
	if (tfr->len < byte_limit)
		return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);

	/* run in interrupt mode for all others */
	return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
}

static int bcm2835aux_spi_prepare_message(struct spi_master *master,
					  struct spi_message *msg)
{
	struct spi_device *spi = msg->spi;
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	bs->cntl[0] = BCM2835_AUX_SPI_CNTL0_ENABLE |
		      BCM2835_AUX_SPI_CNTL0_VAR_WIDTH |
		      BCM2835_AUX_SPI_CNTL0_MSBF_OUT;
	bs->cntl[1] = BCM2835_AUX_SPI_CNTL1_MSBF_IN;

	/* handle all the modes */
	if (spi->mode & SPI_CPOL) {
		bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL;
		bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_OUT_RISING;
	} else {
		bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_IN_RISING;
	}
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);

	return 0;
}

static int bcm2835aux_spi_unprepare_message(struct spi_master *master,
					    struct spi_message *msg)
{
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	bcm2835aux_spi_reset_hw(bs);

	return 0;
}

static void bcm2835aux_spi_handle_err(struct spi_master *master,
				      struct spi_message *msg)
{
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	bcm2835aux_spi_reset_hw(bs);
}

static int bcm2835aux_spi_setup(struct spi_device *spi)
{
	int ret;

	/* sanity check for native cs */
	if (spi->mode & SPI_NO_CS)
		return 0;
	if (gpio_is_valid(spi->cs_gpio)) {
		/* with gpio-cs set the GPIO to the correct level
		 * and as output (in case the dt has the gpio not configured
		 * as output but native cs)
		 */
		ret = gpio_direction_output(spi->cs_gpio,
					    (spi->mode & SPI_CS_HIGH) ? 0 : 1);
		if (ret)
			dev_err(&spi->dev,
				"could not set gpio %i as output: %i\n",
				spi->cs_gpio, ret);

		return ret;
	}

	/* for dt-backwards compatibility: only support native on CS0
	 * known things not supported with broken native CS:
	 * * multiple chip-selects: cs0-cs2 are all
	 *     simultaniously asserted whenever there is a transfer
	 *     this even includes SPI_NO_CS
	 * * SPI_CS_HIGH: cs are always asserted low
	 * * cs_change: cs is deasserted after each spi_transfer
	 * * cs_delay_usec: cs is always deasserted one SCK cycle
	 *     after the last transfer
	 * probably more...
	 */
	dev_warn(&spi->dev,
		 "Native CS is not supported - please configure cs-gpio in device-tree\n");

	if (spi->chip_select == 0)
		return 0;

	dev_warn(&spi->dev, "Native CS is not working for cs > 0\n");

	return -EINVAL;
}

static int bcm2835aux_spi_probe(struct platform_device *pdev)
{
	struct spi_master *master;
	struct bcm2835aux_spi *bs;
	struct resource *res;
	unsigned long clk_hz;
	int err;

	master = spi_alloc_master(&pdev->dev, sizeof(*bs));
	if (!master) {
		dev_err(&pdev->dev, "spi_alloc_master() failed\n");
		return -ENOMEM;
	}

	platform_set_drvdata(pdev, master);
	master->mode_bits = (SPI_CPOL | SPI_CS_HIGH | SPI_NO_CS);
	master->bits_per_word_mask = SPI_BPW_MASK(8);
	/* even though the driver never officially supported native CS
	 * allow a single native CS for legacy DT support purposes when
	 * no cs-gpio is configured.
	 * Known limitations for native cs are:
	 * * multiple chip-selects: cs0-cs2 are all simultaniously asserted
	 *     whenever there is a transfer -  this even includes SPI_NO_CS
	 * * SPI_CS_HIGH: is ignores - cs are always asserted low
	 * * cs_change: cs is deasserted after each spi_transfer
	 * * cs_delay_usec: cs is always deasserted one SCK cycle after
	 *     a spi_transfer
	 */
	master->num_chipselect = 1;
	master->setup = bcm2835aux_spi_setup;
	master->transfer_one = bcm2835aux_spi_transfer_one;
	master->handle_err = bcm2835aux_spi_handle_err;
	master->prepare_message = bcm2835aux_spi_prepare_message;
	master->unprepare_message = bcm2835aux_spi_unprepare_message;
	master->dev.of_node = pdev->dev.of_node;

	bs = spi_master_get_devdata(master);

	/* the main area */
	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	bs->regs = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(bs->regs)) {
		err = PTR_ERR(bs->regs);
		goto out_master_put;
	}

	bs->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(bs->clk)) {
		err = PTR_ERR(bs->clk);
		dev_err(&pdev->dev, "could not get clk: %d\n", err);
		goto out_master_put;
	}

	bs->irq = platform_get_irq(pdev, 0);
	if (bs->irq <= 0) {
		dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
		err = bs->irq ? bs->irq : -ENODEV;
		goto out_master_put;
	}

	/* this also enables the HW block */
	err = clk_prepare_enable(bs->clk);
	if (err) {
		dev_err(&pdev->dev, "could not prepare clock: %d\n", err);
		goto out_master_put;
	}

	/* just checking if the clock returns a sane value */
	clk_hz = clk_get_rate(bs->clk);
	if (!clk_hz) {
		dev_err(&pdev->dev, "clock returns 0 Hz\n");
		err = -ENODEV;
		goto out_clk_disable;
	}

	/* reset SPI-HW block */
	bcm2835aux_spi_reset_hw(bs);

	err = devm_request_irq(&pdev->dev, bs->irq,
			       bcm2835aux_spi_interrupt,
			       IRQF_SHARED,
			       dev_name(&pdev->dev), master);
	if (err) {
		dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
		goto out_clk_disable;
	}

	err = devm_spi_register_master(&pdev->dev, master);
	if (err) {
		dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
		goto out_clk_disable;
	}

	bcm2835aux_debugfs_create(bs, dev_name(&pdev->dev));

	return 0;

out_clk_disable:
	clk_disable_unprepare(bs->clk);
out_master_put:
	spi_master_put(master);
	return err;
}

static int bcm2835aux_spi_remove(struct platform_device *pdev)
{
	struct spi_master *master = platform_get_drvdata(pdev);
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	bcm2835aux_debugfs_remove(bs);

	bcm2835aux_spi_reset_hw(bs);

	/* disable the HW block by releasing the clock */
	clk_disable_unprepare(bs->clk);

	return 0;
}

static const struct of_device_id bcm2835aux_spi_match[] = {
	{ .compatible = "brcm,bcm2835-aux-spi", },
	{}
};
MODULE_DEVICE_TABLE(of, bcm2835aux_spi_match);

static struct platform_driver bcm2835aux_spi_driver = {
	.driver		= {
		.name		= "spi-bcm2835aux",
		.of_match_table	= bcm2835aux_spi_match,
	},
	.probe		= bcm2835aux_spi_probe,
	.remove		= bcm2835aux_spi_remove,
};
module_platform_driver(bcm2835aux_spi_driver);

MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux");
MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
MODULE_LICENSE("GPL");