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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Driver for Broadcom BCM2835 auxiliary SPI Controllers
4 *
5 * the driver does not rely on the native chipselects at all
6 * but only uses the gpio type chipselects
7 *
8 * Based on: spi-bcm2835.c
9 *
10 * Copyright (C) 2015 Martin Sperl
11 */
12
13#include <linux/clk.h>
14#include <linux/completion.h>
15#include <linux/debugfs.h>
16#include <linux/delay.h>
17#include <linux/err.h>
18#include <linux/interrupt.h>
19#include <linux/io.h>
20#include <linux/kernel.h>
21#include <linux/module.h>
22#include <linux/of.h>
23#include <linux/of_address.h>
24#include <linux/of_device.h>
25#include <linux/of_irq.h>
26#include <linux/regmap.h>
27#include <linux/spi/spi.h>
28#include <linux/spinlock.h>
29
30/* define polling limits */
31static unsigned int polling_limit_us = 30;
32module_param(polling_limit_us, uint, 0664);
33MODULE_PARM_DESC(polling_limit_us,
34 "time in us to run a transfer in polling mode - if zero no polling is used\n");
35
36/*
37 * spi register defines
38 *
39 * note there is garbage in the "official" documentation,
40 * so some data is taken from the file:
41 * brcm_usrlib/dag/vmcsx/vcinclude/bcm2708_chip/aux_io.h
42 * inside of:
43 * http://www.broadcom.com/docs/support/videocore/Brcm_Android_ICS_Graphics_Stack.tar.gz
44 */
45
46/* SPI register offsets */
47#define BCM2835_AUX_SPI_CNTL0 0x00
48#define BCM2835_AUX_SPI_CNTL1 0x04
49#define BCM2835_AUX_SPI_STAT 0x08
50#define BCM2835_AUX_SPI_PEEK 0x0C
51#define BCM2835_AUX_SPI_IO 0x20
52#define BCM2835_AUX_SPI_TXHOLD 0x30
53
54/* Bitfields in CNTL0 */
55#define BCM2835_AUX_SPI_CNTL0_SPEED 0xFFF00000
56#define BCM2835_AUX_SPI_CNTL0_SPEED_MAX 0xFFF
57#define BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT 20
58#define BCM2835_AUX_SPI_CNTL0_CS 0x000E0000
59#define BCM2835_AUX_SPI_CNTL0_POSTINPUT 0x00010000
60#define BCM2835_AUX_SPI_CNTL0_VAR_CS 0x00008000
61#define BCM2835_AUX_SPI_CNTL0_VAR_WIDTH 0x00004000
62#define BCM2835_AUX_SPI_CNTL0_DOUTHOLD 0x00003000
63#define BCM2835_AUX_SPI_CNTL0_ENABLE 0x00000800
64#define BCM2835_AUX_SPI_CNTL0_IN_RISING 0x00000400
65#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO 0x00000200
66#define BCM2835_AUX_SPI_CNTL0_OUT_RISING 0x00000100
67#define BCM2835_AUX_SPI_CNTL0_CPOL 0x00000080
68#define BCM2835_AUX_SPI_CNTL0_MSBF_OUT 0x00000040
69#define BCM2835_AUX_SPI_CNTL0_SHIFTLEN 0x0000003F
70
71/* Bitfields in CNTL1 */
72#define BCM2835_AUX_SPI_CNTL1_CSHIGH 0x00000700
73#define BCM2835_AUX_SPI_CNTL1_TXEMPTY 0x00000080
74#define BCM2835_AUX_SPI_CNTL1_IDLE 0x00000040
75#define BCM2835_AUX_SPI_CNTL1_MSBF_IN 0x00000002
76#define BCM2835_AUX_SPI_CNTL1_KEEP_IN 0x00000001
77
78/* Bitfields in STAT */
79#define BCM2835_AUX_SPI_STAT_TX_LVL 0xFF000000
80#define BCM2835_AUX_SPI_STAT_RX_LVL 0x00FF0000
81#define BCM2835_AUX_SPI_STAT_TX_FULL 0x00000400
82#define BCM2835_AUX_SPI_STAT_TX_EMPTY 0x00000200
83#define BCM2835_AUX_SPI_STAT_RX_FULL 0x00000100
84#define BCM2835_AUX_SPI_STAT_RX_EMPTY 0x00000080
85#define BCM2835_AUX_SPI_STAT_BUSY 0x00000040
86#define BCM2835_AUX_SPI_STAT_BITCOUNT 0x0000003F
87
88struct bcm2835aux_spi {
89 void __iomem *regs;
90 struct clk *clk;
91 int irq;
92 u32 cntl[2];
93 const u8 *tx_buf;
94 u8 *rx_buf;
95 int tx_len;
96 int rx_len;
97 int pending;
98
99 u64 count_transfer_polling;
100 u64 count_transfer_irq;
101 u64 count_transfer_irq_after_poll;
102
103 struct dentry *debugfs_dir;
104};
105
106#if defined(CONFIG_DEBUG_FS)
107static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs,
108 const char *dname)
109{
110 char name[64];
111 struct dentry *dir;
112
113 /* get full name */
114 snprintf(name, sizeof(name), "spi-bcm2835aux-%s", dname);
115
116 /* the base directory */
117 dir = debugfs_create_dir(name, NULL);
118 bs->debugfs_dir = dir;
119
120 /* the counters */
121 debugfs_create_u64("count_transfer_polling", 0444, dir,
122 &bs->count_transfer_polling);
123 debugfs_create_u64("count_transfer_irq", 0444, dir,
124 &bs->count_transfer_irq);
125 debugfs_create_u64("count_transfer_irq_after_poll", 0444, dir,
126 &bs->count_transfer_irq_after_poll);
127}
128
129static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs)
130{
131 debugfs_remove_recursive(bs->debugfs_dir);
132 bs->debugfs_dir = NULL;
133}
134#else
135static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs,
136 const char *dname)
137{
138}
139
140static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs)
141{
142}
143#endif /* CONFIG_DEBUG_FS */
144
145static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned int reg)
146{
147 return readl(bs->regs + reg);
148}
149
150static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned int reg,
151 u32 val)
152{
153 writel(val, bs->regs + reg);
154}
155
156static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs)
157{
158 u32 data;
159 int count = min(bs->rx_len, 3);
160
161 data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO);
162 if (bs->rx_buf) {
163 switch (count) {
164 case 3:
165 *bs->rx_buf++ = (data >> 16) & 0xff;
166 fallthrough;
167 case 2:
168 *bs->rx_buf++ = (data >> 8) & 0xff;
169 fallthrough;
170 case 1:
171 *bs->rx_buf++ = (data >> 0) & 0xff;
172 /* fallthrough - no default */
173 }
174 }
175 bs->rx_len -= count;
176 bs->pending -= count;
177}
178
179static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs)
180{
181 u32 data;
182 u8 byte;
183 int count;
184 int i;
185
186 /* gather up to 3 bytes to write to the FIFO */
187 count = min(bs->tx_len, 3);
188 data = 0;
189 for (i = 0; i < count; i++) {
190 byte = bs->tx_buf ? *bs->tx_buf++ : 0;
191 data |= byte << (8 * (2 - i));
192 }
193
194 /* and set the variable bit-length */
195 data |= (count * 8) << 24;
196
197 /* and decrement length */
198 bs->tx_len -= count;
199 bs->pending += count;
200
201 /* write to the correct TX-register */
202 if (bs->tx_len)
203 bcm2835aux_wr(bs, BCM2835_AUX_SPI_TXHOLD, data);
204 else
205 bcm2835aux_wr(bs, BCM2835_AUX_SPI_IO, data);
206}
207
208static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs)
209{
210 /* disable spi clearing fifo and interrupts */
211 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, 0);
212 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0,
213 BCM2835_AUX_SPI_CNTL0_CLEARFIFO);
214}
215
216static void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs)
217{
218 u32 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT);
219
220 /* check if we have data to read */
221 for (; bs->rx_len && (stat & BCM2835_AUX_SPI_STAT_RX_LVL);
222 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT))
223 bcm2835aux_rd_fifo(bs);
224
225 /* check if we have data to write */
226 while (bs->tx_len &&
227 (bs->pending < 12) &&
228 (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
229 BCM2835_AUX_SPI_STAT_TX_FULL))) {
230 bcm2835aux_wr_fifo(bs);
231 }
232}
233
234static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
235{
236 struct spi_master *master = dev_id;
237 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
238
239 /* IRQ may be shared, so return if our interrupts are disabled */
240 if (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_CNTL1) &
241 (BCM2835_AUX_SPI_CNTL1_TXEMPTY | BCM2835_AUX_SPI_CNTL1_IDLE)))
242 return IRQ_NONE;
243
244 /* do common fifo handling */
245 bcm2835aux_spi_transfer_helper(bs);
246
247 if (!bs->tx_len) {
248 /* disable tx fifo empty interrupt */
249 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
250 BCM2835_AUX_SPI_CNTL1_IDLE);
251 }
252
253 /* and if rx_len is 0 then disable interrupts and wake up completion */
254 if (!bs->rx_len) {
255 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
256 spi_finalize_current_transfer(master);
257 }
258
259 return IRQ_HANDLED;
260}
261
262static int __bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
263 struct spi_device *spi,
264 struct spi_transfer *tfr)
265{
266 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
267
268 /* enable interrupts */
269 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
270 BCM2835_AUX_SPI_CNTL1_TXEMPTY |
271 BCM2835_AUX_SPI_CNTL1_IDLE);
272
273 /* and wait for finish... */
274 return 1;
275}
276
277static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
278 struct spi_device *spi,
279 struct spi_transfer *tfr)
280{
281 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
282
283 /* update statistics */
284 bs->count_transfer_irq++;
285
286 /* fill in registers and fifos before enabling interrupts */
287 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
288 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
289
290 /* fill in tx fifo with data before enabling interrupts */
291 while ((bs->tx_len) &&
292 (bs->pending < 12) &&
293 (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
294 BCM2835_AUX_SPI_STAT_TX_FULL))) {
295 bcm2835aux_wr_fifo(bs);
296 }
297
298 /* now run the interrupt mode */
299 return __bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
300}
301
302static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master,
303 struct spi_device *spi,
304 struct spi_transfer *tfr)
305{
306 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
307 unsigned long timeout;
308
309 /* update statistics */
310 bs->count_transfer_polling++;
311
312 /* configure spi */
313 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
314 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
315
316 /* set the timeout to at least 2 jiffies */
317 timeout = jiffies + 2 + HZ * polling_limit_us / 1000000;
318
319 /* loop until finished the transfer */
320 while (bs->rx_len) {
321
322 /* do common fifo handling */
323 bcm2835aux_spi_transfer_helper(bs);
324
325 /* there is still data pending to read check the timeout */
326 if (bs->rx_len && time_after(jiffies, timeout)) {
327 dev_dbg_ratelimited(&spi->dev,
328 "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
329 jiffies - timeout,
330 bs->tx_len, bs->rx_len);
331 /* forward to interrupt handler */
332 bs->count_transfer_irq_after_poll++;
333 return __bcm2835aux_spi_transfer_one_irq(master,
334 spi, tfr);
335 }
336 }
337
338 /* and return without waiting for completion */
339 return 0;
340}
341
342static int bcm2835aux_spi_transfer_one(struct spi_master *master,
343 struct spi_device *spi,
344 struct spi_transfer *tfr)
345{
346 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
347 unsigned long spi_hz, clk_hz, speed;
348 unsigned long hz_per_byte, byte_limit;
349
350 /* calculate the registers to handle
351 *
352 * note that we use the variable data mode, which
353 * is not optimal for longer transfers as we waste registers
354 * resulting (potentially) in more interrupts when transferring
355 * more than 12 bytes
356 */
357
358 /* set clock */
359 spi_hz = tfr->speed_hz;
360 clk_hz = clk_get_rate(bs->clk);
361
362 if (spi_hz >= clk_hz / 2) {
363 speed = 0;
364 } else if (spi_hz) {
365 speed = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1;
366 if (speed > BCM2835_AUX_SPI_CNTL0_SPEED_MAX)
367 speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
368 } else { /* the slowest we can go */
369 speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
370 }
371 /* mask out old speed from previous spi_transfer */
372 bs->cntl[0] &= ~(BCM2835_AUX_SPI_CNTL0_SPEED);
373 /* set the new speed */
374 bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT;
375
376 tfr->effective_speed_hz = clk_hz / (2 * (speed + 1));
377
378 /* set transmit buffers and length */
379 bs->tx_buf = tfr->tx_buf;
380 bs->rx_buf = tfr->rx_buf;
381 bs->tx_len = tfr->len;
382 bs->rx_len = tfr->len;
383 bs->pending = 0;
384
385 /* Calculate the estimated time in us the transfer runs. Note that
386 * there are 2 idle clocks cycles after each chunk getting
387 * transferred - in our case the chunk size is 3 bytes, so we
388 * approximate this by 9 cycles/byte. This is used to find the number
389 * of Hz per byte per polling limit. E.g., we can transfer 1 byte in
390 * 30 µs per 300,000 Hz of bus clock.
391 */
392 hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0;
393 byte_limit = hz_per_byte ? tfr->effective_speed_hz / hz_per_byte : 1;
394
395 /* run in polling mode for short transfers */
396 if (tfr->len < byte_limit)
397 return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
398
399 /* run in interrupt mode for all others */
400 return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
401}
402
403static int bcm2835aux_spi_prepare_message(struct spi_master *master,
404 struct spi_message *msg)
405{
406 struct spi_device *spi = msg->spi;
407 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
408
409 bs->cntl[0] = BCM2835_AUX_SPI_CNTL0_ENABLE |
410 BCM2835_AUX_SPI_CNTL0_VAR_WIDTH |
411 BCM2835_AUX_SPI_CNTL0_MSBF_OUT;
412 bs->cntl[1] = BCM2835_AUX_SPI_CNTL1_MSBF_IN;
413
414 /* handle all the modes */
415 if (spi->mode & SPI_CPOL) {
416 bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL;
417 bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_OUT_RISING;
418 } else {
419 bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_IN_RISING;
420 }
421 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
422 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
423
424 return 0;
425}
426
427static int bcm2835aux_spi_unprepare_message(struct spi_master *master,
428 struct spi_message *msg)
429{
430 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
431
432 bcm2835aux_spi_reset_hw(bs);
433
434 return 0;
435}
436
437static void bcm2835aux_spi_handle_err(struct spi_master *master,
438 struct spi_message *msg)
439{
440 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
441
442 bcm2835aux_spi_reset_hw(bs);
443}
444
445static int bcm2835aux_spi_setup(struct spi_device *spi)
446{
447 /* sanity check for native cs */
448 if (spi->mode & SPI_NO_CS)
449 return 0;
450
451 if (spi->cs_gpiod)
452 return 0;
453
454 /* for dt-backwards compatibility: only support native on CS0
455 * known things not supported with broken native CS:
456 * * multiple chip-selects: cs0-cs2 are all
457 * simultaniously asserted whenever there is a transfer
458 * this even includes SPI_NO_CS
459 * * SPI_CS_HIGH: cs are always asserted low
460 * * cs_change: cs is deasserted after each spi_transfer
461 * * cs_delay_usec: cs is always deasserted one SCK cycle
462 * after the last transfer
463 * probably more...
464 */
465 dev_warn(&spi->dev,
466 "Native CS is not supported - please configure cs-gpio in device-tree\n");
467
468 if (spi->chip_select == 0)
469 return 0;
470
471 dev_warn(&spi->dev, "Native CS is not working for cs > 0\n");
472
473 return -EINVAL;
474}
475
476static int bcm2835aux_spi_probe(struct platform_device *pdev)
477{
478 struct spi_master *master;
479 struct bcm2835aux_spi *bs;
480 unsigned long clk_hz;
481 int err;
482
483 master = devm_spi_alloc_master(&pdev->dev, sizeof(*bs));
484 if (!master)
485 return -ENOMEM;
486
487 platform_set_drvdata(pdev, master);
488 master->mode_bits = (SPI_CPOL | SPI_CS_HIGH | SPI_NO_CS);
489 master->bits_per_word_mask = SPI_BPW_MASK(8);
490 /* even though the driver never officially supported native CS
491 * allow a single native CS for legacy DT support purposes when
492 * no cs-gpio is configured.
493 * Known limitations for native cs are:
494 * * multiple chip-selects: cs0-cs2 are all simultaniously asserted
495 * whenever there is a transfer - this even includes SPI_NO_CS
496 * * SPI_CS_HIGH: is ignores - cs are always asserted low
497 * * cs_change: cs is deasserted after each spi_transfer
498 * * cs_delay_usec: cs is always deasserted one SCK cycle after
499 * a spi_transfer
500 */
501 master->num_chipselect = 1;
502 master->setup = bcm2835aux_spi_setup;
503 master->transfer_one = bcm2835aux_spi_transfer_one;
504 master->handle_err = bcm2835aux_spi_handle_err;
505 master->prepare_message = bcm2835aux_spi_prepare_message;
506 master->unprepare_message = bcm2835aux_spi_unprepare_message;
507 master->dev.of_node = pdev->dev.of_node;
508 master->use_gpio_descriptors = true;
509
510 bs = spi_master_get_devdata(master);
511
512 /* the main area */
513 bs->regs = devm_platform_ioremap_resource(pdev, 0);
514 if (IS_ERR(bs->regs))
515 return PTR_ERR(bs->regs);
516
517 bs->clk = devm_clk_get(&pdev->dev, NULL);
518 if (IS_ERR(bs->clk)) {
519 err = PTR_ERR(bs->clk);
520 dev_err(&pdev->dev, "could not get clk: %d\n", err);
521 return err;
522 }
523
524 bs->irq = platform_get_irq(pdev, 0);
525 if (bs->irq <= 0)
526 return bs->irq ? bs->irq : -ENODEV;
527
528 /* this also enables the HW block */
529 err = clk_prepare_enable(bs->clk);
530 if (err) {
531 dev_err(&pdev->dev, "could not prepare clock: %d\n", err);
532 return err;
533 }
534
535 /* just checking if the clock returns a sane value */
536 clk_hz = clk_get_rate(bs->clk);
537 if (!clk_hz) {
538 dev_err(&pdev->dev, "clock returns 0 Hz\n");
539 err = -ENODEV;
540 goto out_clk_disable;
541 }
542
543 /* reset SPI-HW block */
544 bcm2835aux_spi_reset_hw(bs);
545
546 err = devm_request_irq(&pdev->dev, bs->irq,
547 bcm2835aux_spi_interrupt,
548 IRQF_SHARED,
549 dev_name(&pdev->dev), master);
550 if (err) {
551 dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
552 goto out_clk_disable;
553 }
554
555 err = spi_register_master(master);
556 if (err) {
557 dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
558 goto out_clk_disable;
559 }
560
561 bcm2835aux_debugfs_create(bs, dev_name(&pdev->dev));
562
563 return 0;
564
565out_clk_disable:
566 clk_disable_unprepare(bs->clk);
567 return err;
568}
569
570static int bcm2835aux_spi_remove(struct platform_device *pdev)
571{
572 struct spi_master *master = platform_get_drvdata(pdev);
573 struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
574
575 bcm2835aux_debugfs_remove(bs);
576
577 spi_unregister_master(master);
578
579 bcm2835aux_spi_reset_hw(bs);
580
581 /* disable the HW block by releasing the clock */
582 clk_disable_unprepare(bs->clk);
583
584 return 0;
585}
586
587static const struct of_device_id bcm2835aux_spi_match[] = {
588 { .compatible = "brcm,bcm2835-aux-spi", },
589 {}
590};
591MODULE_DEVICE_TABLE(of, bcm2835aux_spi_match);
592
593static struct platform_driver bcm2835aux_spi_driver = {
594 .driver = {
595 .name = "spi-bcm2835aux",
596 .of_match_table = bcm2835aux_spi_match,
597 },
598 .probe = bcm2835aux_spi_probe,
599 .remove = bcm2835aux_spi_remove,
600};
601module_platform_driver(bcm2835aux_spi_driver);
602
603MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux");
604MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
605MODULE_LICENSE("GPL");