summaryrefslogtreecommitdiff
path: root/drivers/spi/spi-bcm2835.c
blob: 9025edd7dc45fde131c7c9c6004ce5434829c785 (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
/*
 * Driver for Broadcom BCM2835 SPI Controllers
 *
 * Copyright (C) 2012 Chris Boot
 * Copyright (C) 2013 Stephen Warren
 *
 * This driver is inspired by:
 * spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org>
 * spi-atmel.c, Copyright (C) 2006 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <linux/clk.h>
#include <linux/completion.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_irq.h>
#include <linux/of_device.h>
#include <linux/spi/spi.h>

/* SPI register offsets */
#define BCM2835_SPI_CS			0x00
#define BCM2835_SPI_FIFO		0x04
#define BCM2835_SPI_CLK			0x08
#define BCM2835_SPI_DLEN		0x0c
#define BCM2835_SPI_LTOH		0x10
#define BCM2835_SPI_DC			0x14

/* Bitfields in CS */
#define BCM2835_SPI_CS_LEN_LONG		0x02000000
#define BCM2835_SPI_CS_DMA_LEN		0x01000000
#define BCM2835_SPI_CS_CSPOL2		0x00800000
#define BCM2835_SPI_CS_CSPOL1		0x00400000
#define BCM2835_SPI_CS_CSPOL0		0x00200000
#define BCM2835_SPI_CS_RXF		0x00100000
#define BCM2835_SPI_CS_RXR		0x00080000
#define BCM2835_SPI_CS_TXD		0x00040000
#define BCM2835_SPI_CS_RXD		0x00020000
#define BCM2835_SPI_CS_DONE		0x00010000
#define BCM2835_SPI_CS_LEN		0x00002000
#define BCM2835_SPI_CS_REN		0x00001000
#define BCM2835_SPI_CS_ADCS		0x00000800
#define BCM2835_SPI_CS_INTR		0x00000400
#define BCM2835_SPI_CS_INTD		0x00000200
#define BCM2835_SPI_CS_DMAEN		0x00000100
#define BCM2835_SPI_CS_TA		0x00000080
#define BCM2835_SPI_CS_CSPOL		0x00000040
#define BCM2835_SPI_CS_CLEAR_RX		0x00000020
#define BCM2835_SPI_CS_CLEAR_TX		0x00000010
#define BCM2835_SPI_CS_CPOL		0x00000008
#define BCM2835_SPI_CS_CPHA		0x00000004
#define BCM2835_SPI_CS_CS_10		0x00000002
#define BCM2835_SPI_CS_CS_01		0x00000001

#define BCM2835_SPI_TIMEOUT_MS	30000
#define BCM2835_SPI_MODE_BITS	(SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_NO_CS)

#define DRV_NAME	"spi-bcm2835"

struct bcm2835_spi {
	void __iomem *regs;
	struct clk *clk;
	int irq;
	struct completion done;
	const u8 *tx_buf;
	u8 *rx_buf;
	int len;
};

static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg)
{
	return readl(bs->regs + reg);
}

static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned reg, u32 val)
{
	writel(val, bs->regs + reg);
}

static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs, int len)
{
	u8 byte;

	while (len--) {
		byte = bcm2835_rd(bs, BCM2835_SPI_FIFO);
		if (bs->rx_buf)
			*bs->rx_buf++ = byte;
	}
}

static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs, int len)
{
	u8 byte;

	if (len > bs->len)
		len = bs->len;

	while (len--) {
		byte = bs->tx_buf ? *bs->tx_buf++ : 0;
		bcm2835_wr(bs, BCM2835_SPI_FIFO, byte);
		bs->len--;
	}
}

static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id)
{
	struct spi_master *master = dev_id;
	struct bcm2835_spi *bs = spi_master_get_devdata(master);
	u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);

	/*
	 * RXR - RX needs Reading. This means 12 (or more) bytes have been
	 * transmitted and hence 12 (or more) bytes have been received.
	 *
	 * The FIFO is 16-bytes deep. We check for this interrupt to keep the
	 * FIFO full; we have a 4-byte-time buffer for IRQ latency. We check
	 * this before DONE (TX empty) just in case we delayed processing this
	 * interrupt for some reason.
	 *
	 * We only check for this case if we have more bytes to TX; at the end
	 * of the transfer, we ignore this pipelining optimization, and let
	 * bcm2835_spi_finish_transfer() drain the RX FIFO.
	 */
	if (bs->len && (cs & BCM2835_SPI_CS_RXR)) {
		/* Read 12 bytes of data */
		bcm2835_rd_fifo(bs, 12);

		/* Write up to 12 bytes */
		bcm2835_wr_fifo(bs, 12);

		/*
		 * We must have written something to the TX FIFO due to the
		 * bs->len check above, so cannot be DONE. Hence, return
		 * early. Note that DONE could also be set if we serviced an
		 * RXR interrupt really late.
		 */
		return IRQ_HANDLED;
	}

	/*
	 * DONE - TX empty. This occurs when we first enable the transfer
	 * since we do not pre-fill the TX FIFO. At any other time, given that
	 * we refill the TX FIFO above based on RXR, and hence ignore DONE if
	 * RXR is set, DONE really does mean end-of-transfer.
	 */
	if (cs & BCM2835_SPI_CS_DONE) {
		if (bs->len) { /* First interrupt in a transfer */
			bcm2835_wr_fifo(bs, 16);
		} else { /* Transfer complete */
			/* Disable SPI interrupts */
			cs &= ~(BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD);
			bcm2835_wr(bs, BCM2835_SPI_CS, cs);

			/*
			 * Wake up bcm2835_spi_transfer_one(), which will call
			 * bcm2835_spi_finish_transfer(), to drain the RX FIFO.
			 */
			complete(&bs->done);
		}

		return IRQ_HANDLED;
	}

	return IRQ_NONE;
}

static int bcm2835_spi_start_transfer(struct spi_device *spi,
		struct spi_transfer *tfr)
{
	struct bcm2835_spi *bs = spi_master_get_devdata(spi->master);
	unsigned long spi_hz, clk_hz, cdiv;
	u32 cs = BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA;

	spi_hz = tfr->speed_hz;
	clk_hz = clk_get_rate(bs->clk);

	if (spi_hz >= clk_hz / 2) {
		cdiv = 2; /* clk_hz/2 is the fastest we can go */
	} else if (spi_hz) {
		/* CDIV must be a power of two */
		cdiv = roundup_pow_of_two(DIV_ROUND_UP(clk_hz, spi_hz));

		if (cdiv >= 65536)
			cdiv = 0; /* 0 is the slowest we can go */
	} else
		cdiv = 0; /* 0 is the slowest we can go */

	if (spi->mode & SPI_CPOL)
		cs |= BCM2835_SPI_CS_CPOL;
	if (spi->mode & SPI_CPHA)
		cs |= BCM2835_SPI_CS_CPHA;

	if (!(spi->mode & SPI_NO_CS)) {
		if (spi->mode & SPI_CS_HIGH) {
			cs |= BCM2835_SPI_CS_CSPOL;
			cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select;
		}

		cs |= spi->chip_select;
	}

	reinit_completion(&bs->done);
	bs->tx_buf = tfr->tx_buf;
	bs->rx_buf = tfr->rx_buf;
	bs->len = tfr->len;

	bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);
	/*
	 * Enable the HW block. This will immediately trigger a DONE (TX
	 * empty) interrupt, upon which we will fill the TX FIFO with the
	 * first TX bytes. Pre-filling the TX FIFO here to avoid the
	 * interrupt doesn't work:-(
	 */
	bcm2835_wr(bs, BCM2835_SPI_CS, cs);

	return 0;
}

static int bcm2835_spi_finish_transfer(struct spi_device *spi,
		struct spi_transfer *tfr, bool cs_change)
{
	struct bcm2835_spi *bs = spi_master_get_devdata(spi->master);
	u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);

	/* Drain RX FIFO */
	while (cs & BCM2835_SPI_CS_RXD) {
		bcm2835_rd_fifo(bs, 1);
		cs = bcm2835_rd(bs, BCM2835_SPI_CS);
	}

	if (tfr->delay_usecs)
		udelay(tfr->delay_usecs);

	if (cs_change)
		/* Clear TA flag */
		bcm2835_wr(bs, BCM2835_SPI_CS, cs & ~BCM2835_SPI_CS_TA);

	return 0;
}

static int bcm2835_spi_transfer_one(struct spi_master *master,
		struct spi_message *mesg)
{
	struct bcm2835_spi *bs = spi_master_get_devdata(master);
	struct spi_transfer *tfr;
	struct spi_device *spi = mesg->spi;
	int err = 0;
	unsigned int timeout;
	bool cs_change;

	list_for_each_entry(tfr, &mesg->transfers, transfer_list) {
		err = bcm2835_spi_start_transfer(spi, tfr);
		if (err)
			goto out;

		timeout = wait_for_completion_timeout(&bs->done,
				msecs_to_jiffies(BCM2835_SPI_TIMEOUT_MS));
		if (!timeout) {
			err = -ETIMEDOUT;
			goto out;
		}

		cs_change = tfr->cs_change ||
			list_is_last(&tfr->transfer_list, &mesg->transfers);

		err = bcm2835_spi_finish_transfer(spi, tfr, cs_change);
		if (err)
			goto out;

		mesg->actual_length += (tfr->len - bs->len);
	}

out:
	/* Clear FIFOs, and disable the HW block */
	bcm2835_wr(bs, BCM2835_SPI_CS,
		   BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
	mesg->status = err;
	spi_finalize_current_message(master);

	return 0;
}

static int bcm2835_spi_probe(struct platform_device *pdev)
{
	struct spi_master *master;
	struct bcm2835_spi *bs;
	struct resource *res;
	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 = BCM2835_SPI_MODE_BITS;
	master->bits_per_word_mask = SPI_BPW_MASK(8);
	master->bus_num = -1;
	master->num_chipselect = 3;
	master->transfer_one_message = bcm2835_spi_transfer_one;
	master->dev.of_node = pdev->dev.of_node;

	bs = spi_master_get_devdata(master);

	init_completion(&bs->done);

	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 = irq_of_parse_and_map(pdev->dev.of_node, 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;
	}

	clk_prepare_enable(bs->clk);

	err = request_irq(bs->irq, bcm2835_spi_interrupt, 0,
			dev_name(&pdev->dev), master);
	if (err) {
		dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
		goto out_clk_disable;
	}

	/* initialise the hardware */
	bcm2835_wr(bs, BCM2835_SPI_CS,
		   BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);

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

	return 0;

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

static int bcm2835_spi_remove(struct platform_device *pdev)
{
	struct spi_master *master = platform_get_drvdata(pdev);
	struct bcm2835_spi *bs = spi_master_get_devdata(master);

	free_irq(bs->irq, master);

	/* Clear FIFOs, and disable the HW block */
	bcm2835_wr(bs, BCM2835_SPI_CS,
		   BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);

	clk_disable_unprepare(bs->clk);

	return 0;
}

static const struct of_device_id bcm2835_spi_match[] = {
	{ .compatible = "brcm,bcm2835-spi", },
	{}
};
MODULE_DEVICE_TABLE(of, bcm2835_spi_match);

static struct platform_driver bcm2835_spi_driver = {
	.driver		= {
		.name		= DRV_NAME,
		.owner		= THIS_MODULE,
		.of_match_table	= bcm2835_spi_match,
	},
	.probe		= bcm2835_spi_probe,
	.remove		= bcm2835_spi_remove,
};
module_platform_driver(bcm2835_spi_driver);

MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835");
MODULE_AUTHOR("Chris Boot <bootc@bootc.net>");
MODULE_LICENSE("GPL v2");