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Chris Bootf8043872013-03-11 21:38:24 -06001/*
2 * Driver for Broadcom BCM2835 SPI Controllers
3 *
4 * Copyright (C) 2012 Chris Boot
5 * Copyright (C) 2013 Stephen Warren
6 *
7 * This driver is inspired by:
8 * spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org>
9 * spi-atmel.c, Copyright (C) 2006 Atmel Corporation
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24 */
25
26#include <linux/clk.h>
27#include <linux/completion.h>
28#include <linux/delay.h>
29#include <linux/err.h>
30#include <linux/interrupt.h>
31#include <linux/io.h>
32#include <linux/kernel.h>
33#include <linux/module.h>
34#include <linux/of.h>
35#include <linux/of_irq.h>
36#include <linux/of_device.h>
37#include <linux/spi/spi.h>
38
39/* SPI register offsets */
40#define BCM2835_SPI_CS 0x00
41#define BCM2835_SPI_FIFO 0x04
42#define BCM2835_SPI_CLK 0x08
43#define BCM2835_SPI_DLEN 0x0c
44#define BCM2835_SPI_LTOH 0x10
45#define BCM2835_SPI_DC 0x14
46
47/* Bitfields in CS */
48#define BCM2835_SPI_CS_LEN_LONG 0x02000000
49#define BCM2835_SPI_CS_DMA_LEN 0x01000000
50#define BCM2835_SPI_CS_CSPOL2 0x00800000
51#define BCM2835_SPI_CS_CSPOL1 0x00400000
52#define BCM2835_SPI_CS_CSPOL0 0x00200000
53#define BCM2835_SPI_CS_RXF 0x00100000
54#define BCM2835_SPI_CS_RXR 0x00080000
55#define BCM2835_SPI_CS_TXD 0x00040000
56#define BCM2835_SPI_CS_RXD 0x00020000
57#define BCM2835_SPI_CS_DONE 0x00010000
58#define BCM2835_SPI_CS_LEN 0x00002000
59#define BCM2835_SPI_CS_REN 0x00001000
60#define BCM2835_SPI_CS_ADCS 0x00000800
61#define BCM2835_SPI_CS_INTR 0x00000400
62#define BCM2835_SPI_CS_INTD 0x00000200
63#define BCM2835_SPI_CS_DMAEN 0x00000100
64#define BCM2835_SPI_CS_TA 0x00000080
65#define BCM2835_SPI_CS_CSPOL 0x00000040
66#define BCM2835_SPI_CS_CLEAR_RX 0x00000020
67#define BCM2835_SPI_CS_CLEAR_TX 0x00000010
68#define BCM2835_SPI_CS_CPOL 0x00000008
69#define BCM2835_SPI_CS_CPHA 0x00000004
70#define BCM2835_SPI_CS_CS_10 0x00000002
71#define BCM2835_SPI_CS_CS_01 0x00000001
72
73#define BCM2835_SPI_TIMEOUT_MS 30000
74#define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_NO_CS)
75
76#define DRV_NAME "spi-bcm2835"
77
78struct bcm2835_spi {
79 void __iomem *regs;
80 struct clk *clk;
81 int irq;
82 struct completion done;
83 const u8 *tx_buf;
84 u8 *rx_buf;
85 int len;
86};
87
88static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg)
89{
90 return readl(bs->regs + reg);
91}
92
93static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned reg, u32 val)
94{
95 writel(val, bs->regs + reg);
96}
97
98static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs, int len)
99{
100 u8 byte;
101
102 while (len--) {
103 byte = bcm2835_rd(bs, BCM2835_SPI_FIFO);
104 if (bs->rx_buf)
105 *bs->rx_buf++ = byte;
106 }
107}
108
109static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs, int len)
110{
111 u8 byte;
112
113 if (len > bs->len)
114 len = bs->len;
115
116 while (len--) {
117 byte = bs->tx_buf ? *bs->tx_buf++ : 0;
118 bcm2835_wr(bs, BCM2835_SPI_FIFO, byte);
119 bs->len--;
120 }
121}
122
123static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id)
124{
125 struct spi_master *master = dev_id;
126 struct bcm2835_spi *bs = spi_master_get_devdata(master);
127 u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
128
129 /*
130 * RXR - RX needs Reading. This means 12 (or more) bytes have been
131 * transmitted and hence 12 (or more) bytes have been received.
132 *
133 * The FIFO is 16-bytes deep. We check for this interrupt to keep the
134 * FIFO full; we have a 4-byte-time buffer for IRQ latency. We check
135 * this before DONE (TX empty) just in case we delayed processing this
136 * interrupt for some reason.
137 *
138 * We only check for this case if we have more bytes to TX; at the end
139 * of the transfer, we ignore this pipelining optimization, and let
140 * bcm2835_spi_finish_transfer() drain the RX FIFO.
141 */
142 if (bs->len && (cs & BCM2835_SPI_CS_RXR)) {
143 /* Read 12 bytes of data */
144 bcm2835_rd_fifo(bs, 12);
145
146 /* Write up to 12 bytes */
147 bcm2835_wr_fifo(bs, 12);
148
149 /*
150 * We must have written something to the TX FIFO due to the
151 * bs->len check above, so cannot be DONE. Hence, return
152 * early. Note that DONE could also be set if we serviced an
153 * RXR interrupt really late.
154 */
155 return IRQ_HANDLED;
156 }
157
158 /*
159 * DONE - TX empty. This occurs when we first enable the transfer
160 * since we do not pre-fill the TX FIFO. At any other time, given that
161 * we refill the TX FIFO above based on RXR, and hence ignore DONE if
162 * RXR is set, DONE really does mean end-of-transfer.
163 */
164 if (cs & BCM2835_SPI_CS_DONE) {
165 if (bs->len) { /* First interrupt in a transfer */
166 bcm2835_wr_fifo(bs, 16);
167 } else { /* Transfer complete */
168 /* Disable SPI interrupts */
169 cs &= ~(BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD);
170 bcm2835_wr(bs, BCM2835_SPI_CS, cs);
171
172 /*
173 * Wake up bcm2835_spi_transfer_one(), which will call
174 * bcm2835_spi_finish_transfer(), to drain the RX FIFO.
175 */
176 complete(&bs->done);
177 }
178
179 return IRQ_HANDLED;
180 }
181
182 return IRQ_NONE;
183}
184
Chris Bootf8043872013-03-11 21:38:24 -0600185static int bcm2835_spi_start_transfer(struct spi_device *spi,
186 struct spi_transfer *tfr)
187{
188 struct bcm2835_spi *bs = spi_master_get_devdata(spi->master);
189 unsigned long spi_hz, clk_hz, cdiv;
190 u32 cs = BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA;
191
192 spi_hz = tfr->speed_hz;
193 clk_hz = clk_get_rate(bs->clk);
194
195 if (spi_hz >= clk_hz / 2) {
196 cdiv = 2; /* clk_hz/2 is the fastest we can go */
197 } else if (spi_hz) {
198 /* CDIV must be a power of two */
199 cdiv = roundup_pow_of_two(DIV_ROUND_UP(clk_hz, spi_hz));
200
201 if (cdiv >= 65536)
202 cdiv = 0; /* 0 is the slowest we can go */
203 } else
204 cdiv = 0; /* 0 is the slowest we can go */
205
206 if (spi->mode & SPI_CPOL)
207 cs |= BCM2835_SPI_CS_CPOL;
208 if (spi->mode & SPI_CPHA)
209 cs |= BCM2835_SPI_CS_CPHA;
210
211 if (!(spi->mode & SPI_NO_CS)) {
212 if (spi->mode & SPI_CS_HIGH) {
213 cs |= BCM2835_SPI_CS_CSPOL;
214 cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select;
215 }
216
217 cs |= spi->chip_select;
218 }
219
220 INIT_COMPLETION(bs->done);
221 bs->tx_buf = tfr->tx_buf;
222 bs->rx_buf = tfr->rx_buf;
223 bs->len = tfr->len;
224
225 bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);
226 /*
227 * Enable the HW block. This will immediately trigger a DONE (TX
228 * empty) interrupt, upon which we will fill the TX FIFO with the
229 * first TX bytes. Pre-filling the TX FIFO here to avoid the
230 * interrupt doesn't work:-(
231 */
232 bcm2835_wr(bs, BCM2835_SPI_CS, cs);
233
234 return 0;
235}
236
237static int bcm2835_spi_finish_transfer(struct spi_device *spi,
238 struct spi_transfer *tfr, bool cs_change)
239{
240 struct bcm2835_spi *bs = spi_master_get_devdata(spi->master);
241 u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
242
243 /* Drain RX FIFO */
244 while (cs & BCM2835_SPI_CS_RXD) {
245 bcm2835_rd_fifo(bs, 1);
246 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
247 }
248
249 if (tfr->delay_usecs)
250 udelay(tfr->delay_usecs);
251
252 if (cs_change)
253 /* Clear TA flag */
254 bcm2835_wr(bs, BCM2835_SPI_CS, cs & ~BCM2835_SPI_CS_TA);
255
256 return 0;
257}
258
Chris Bootf8043872013-03-11 21:38:24 -0600259static int bcm2835_spi_transfer_one(struct spi_master *master,
260 struct spi_message *mesg)
261{
262 struct bcm2835_spi *bs = spi_master_get_devdata(master);
263 struct spi_transfer *tfr;
264 struct spi_device *spi = mesg->spi;
265 int err = 0;
266 unsigned int timeout;
267 bool cs_change;
268
269 list_for_each_entry(tfr, &mesg->transfers, transfer_list) {
Chris Bootf8043872013-03-11 21:38:24 -0600270 err = bcm2835_spi_start_transfer(spi, tfr);
271 if (err)
272 goto out;
273
274 timeout = wait_for_completion_timeout(&bs->done,
275 msecs_to_jiffies(BCM2835_SPI_TIMEOUT_MS));
276 if (!timeout) {
277 err = -ETIMEDOUT;
278 goto out;
279 }
280
281 cs_change = tfr->cs_change ||
282 list_is_last(&tfr->transfer_list, &mesg->transfers);
283
284 err = bcm2835_spi_finish_transfer(spi, tfr, cs_change);
285 if (err)
286 goto out;
287
288 mesg->actual_length += (tfr->len - bs->len);
289 }
290
291out:
292 /* Clear FIFOs, and disable the HW block */
293 bcm2835_wr(bs, BCM2835_SPI_CS,
294 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
295 mesg->status = err;
296 spi_finalize_current_message(master);
297
298 return 0;
299}
300
301static int bcm2835_spi_probe(struct platform_device *pdev)
302{
303 struct spi_master *master;
304 struct bcm2835_spi *bs;
305 struct resource *res;
306 int err;
307
308 master = spi_alloc_master(&pdev->dev, sizeof(*bs));
309 if (!master) {
310 dev_err(&pdev->dev, "spi_alloc_master() failed\n");
311 return -ENOMEM;
312 }
313
314 platform_set_drvdata(pdev, master);
315
316 master->mode_bits = BCM2835_SPI_MODE_BITS;
Stephen Warrenf4b97eb2013-03-26 20:37:58 -0600317 master->bits_per_word_mask = BIT(8 - 1);
Chris Bootf8043872013-03-11 21:38:24 -0600318 master->bus_num = -1;
319 master->num_chipselect = 3;
Chris Bootf8043872013-03-11 21:38:24 -0600320 master->transfer_one_message = bcm2835_spi_transfer_one;
321 master->dev.of_node = pdev->dev.of_node;
322
323 bs = spi_master_get_devdata(master);
324
325 init_completion(&bs->done);
326
327 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
328 if (!res) {
329 dev_err(&pdev->dev, "could not get memory resource\n");
330 err = -ENODEV;
331 goto out_master_put;
332 }
333
Laurent Navet2d6e75e2013-05-02 14:13:30 +0200334 bs->regs = devm_ioremap_resource(&pdev->dev, res);
335 if (IS_ERR(bs->regs)) {
336 err = PTR_ERR(bs->regs);
Chris Bootf8043872013-03-11 21:38:24 -0600337 goto out_master_put;
338 }
339
340 bs->clk = devm_clk_get(&pdev->dev, NULL);
341 if (IS_ERR(bs->clk)) {
342 err = PTR_ERR(bs->clk);
343 dev_err(&pdev->dev, "could not get clk: %d\n", err);
344 goto out_master_put;
345 }
346
347 bs->irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
348 if (bs->irq <= 0) {
349 dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
350 err = bs->irq ? bs->irq : -ENODEV;
351 goto out_master_put;
352 }
353
354 clk_prepare_enable(bs->clk);
355
356 err = request_irq(bs->irq, bcm2835_spi_interrupt, 0,
357 dev_name(&pdev->dev), master);
358 if (err) {
359 dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
360 goto out_clk_disable;
361 }
362
363 /* initialise the hardware */
364 bcm2835_wr(bs, BCM2835_SPI_CS,
365 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
366
367 err = spi_register_master(master);
368 if (err) {
369 dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
370 goto out_free_irq;
371 }
372
373 return 0;
374
375out_free_irq:
376 free_irq(bs->irq, master);
377out_clk_disable:
378 clk_disable_unprepare(bs->clk);
379out_master_put:
380 spi_master_put(master);
381 return err;
382}
383
384static int bcm2835_spi_remove(struct platform_device *pdev)
385{
386 struct spi_master *master = platform_get_drvdata(pdev);
387 struct bcm2835_spi *bs = spi_master_get_devdata(master);
388
389 free_irq(bs->irq, master);
390 spi_unregister_master(master);
391
392 /* Clear FIFOs, and disable the HW block */
393 bcm2835_wr(bs, BCM2835_SPI_CS,
394 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
395
396 clk_disable_unprepare(bs->clk);
397 spi_master_put(master);
398
399 return 0;
400}
401
402static const struct of_device_id bcm2835_spi_match[] = {
403 { .compatible = "brcm,bcm2835-spi", },
404 {}
405};
406MODULE_DEVICE_TABLE(of, bcm2835_spi_match);
407
408static struct platform_driver bcm2835_spi_driver = {
409 .driver = {
410 .name = DRV_NAME,
411 .owner = THIS_MODULE,
412 .of_match_table = bcm2835_spi_match,
413 },
414 .probe = bcm2835_spi_probe,
415 .remove = bcm2835_spi_remove,
416};
417module_platform_driver(bcm2835_spi_driver);
418
419MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835");
420MODULE_AUTHOR("Chris Boot <bootc@bootc.net>");
421MODULE_LICENSE("GPL v2");