2 * polling/bitbanging SPI master controller driver utilities
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
15 #include <linux/spinlock.h>
16 #include <linux/workqueue.h>
17 #include <linux/interrupt.h>
18 #include <linux/module.h>
19 #include <linux/delay.h>
20 #include <linux/errno.h>
21 #include <linux/platform_device.h>
22 #include <linux/slab.h>
24 #include <linux/spi/spi.h>
25 #include <linux/spi/spi_bitbang.h>
28 /*----------------------------------------------------------------------*/
31 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
32 * Use this for GPIO or shift-register level hardware APIs.
34 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
35 * to glue code. These bitbang setup() and cleanup() routines are always
36 * used, though maybe they're called from controller-aware code.
38 * chipselect() and friends may use spi_device->controller_data and
39 * controller registers as appropriate.
42 * NOTE: SPI controller pins can often be used as GPIO pins instead,
43 * which means you could use a bitbang driver either to get hardware
44 * working quickly, or testing for differences that aren't speed related.
47 struct spi_bitbang_cs {
48 unsigned nsecs; /* (clock cycle time)/2 */
49 u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
51 unsigned (*txrx_bufs)(struct spi_device *,
53 struct spi_device *spi,
56 unsigned, struct spi_transfer *);
59 static unsigned bitbang_txrx_8(
60 struct spi_device *spi,
61 u32 (*txrx_word)(struct spi_device *spi,
65 struct spi_transfer *t
67 unsigned bits = t->bits_per_word;
68 unsigned count = t->len;
69 const u8 *tx = t->tx_buf;
72 while (likely(count > 0)) {
77 word = txrx_word(spi, ns, word, bits);
82 return t->len - count;
85 static unsigned bitbang_txrx_16(
86 struct spi_device *spi,
87 u32 (*txrx_word)(struct spi_device *spi,
91 struct spi_transfer *t
93 unsigned bits = t->bits_per_word;
94 unsigned count = t->len;
95 const u16 *tx = t->tx_buf;
98 while (likely(count > 1)) {
103 word = txrx_word(spi, ns, word, bits);
108 return t->len - count;
111 static unsigned bitbang_txrx_32(
112 struct spi_device *spi,
113 u32 (*txrx_word)(struct spi_device *spi,
117 struct spi_transfer *t
119 unsigned bits = t->bits_per_word;
120 unsigned count = t->len;
121 const u32 *tx = t->tx_buf;
124 while (likely(count > 3)) {
129 word = txrx_word(spi, ns, word, bits);
134 return t->len - count;
137 int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
139 struct spi_bitbang_cs *cs = spi->controller_state;
144 bits_per_word = t->bits_per_word;
151 /* spi_transfer level calls that work per-word */
153 bits_per_word = spi->bits_per_word;
154 if (bits_per_word <= 8)
155 cs->txrx_bufs = bitbang_txrx_8;
156 else if (bits_per_word <= 16)
157 cs->txrx_bufs = bitbang_txrx_16;
158 else if (bits_per_word <= 32)
159 cs->txrx_bufs = bitbang_txrx_32;
163 /* nsecs = (clock period)/2 */
165 hz = spi->max_speed_hz;
167 cs->nsecs = (1000000000/2) / hz;
168 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
174 EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
177 * spi_bitbang_setup - default setup for per-word I/O loops
179 int spi_bitbang_setup(struct spi_device *spi)
181 struct spi_bitbang_cs *cs = spi->controller_state;
182 struct spi_bitbang *bitbang;
186 bitbang = spi_master_get_devdata(spi->master);
189 cs = kzalloc(sizeof(*cs), GFP_KERNEL);
192 spi->controller_state = cs;
195 /* per-word shift register access, in hardware or bitbanging */
196 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
200 retval = bitbang->setup_transfer(spi, NULL);
204 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
206 /* NOTE we _need_ to call chipselect() early, ideally with adapter
207 * setup, unless the hardware defaults cooperate to avoid confusion
208 * between normal (active low) and inverted chipselects.
211 /* deselect chip (low or high) */
212 spin_lock_irqsave(&bitbang->lock, flags);
213 if (!bitbang->busy) {
214 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
217 spin_unlock_irqrestore(&bitbang->lock, flags);
221 EXPORT_SYMBOL_GPL(spi_bitbang_setup);
224 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
226 void spi_bitbang_cleanup(struct spi_device *spi)
228 kfree(spi->controller_state);
230 EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
232 static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
234 struct spi_bitbang_cs *cs = spi->controller_state;
235 unsigned nsecs = cs->nsecs;
237 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
240 /*----------------------------------------------------------------------*/
243 * SECOND PART ... simple transfer queue runner.
245 * This costs a task context per controller, running the queue by
246 * performing each transfer in sequence. Smarter hardware can queue
247 * several DMA transfers at once, and process several controller queues
248 * in parallel; this driver doesn't match such hardware very well.
250 * Drivers can provide word-at-a-time i/o primitives, or provide
251 * transfer-at-a-time ones to leverage dma or fifo hardware.
254 static int spi_bitbang_prepare_hardware(struct spi_master *spi)
256 struct spi_bitbang *bitbang;
259 bitbang = spi_master_get_devdata(spi);
261 spin_lock_irqsave(&bitbang->lock, flags);
263 spin_unlock_irqrestore(&bitbang->lock, flags);
268 static int spi_bitbang_transfer_one(struct spi_master *master,
269 struct spi_message *m)
271 struct spi_bitbang *bitbang;
273 struct spi_transfer *t = NULL;
277 struct spi_device *spi = m->spi;
279 bitbang = spi_master_get_devdata(master);
281 /* FIXME this is made-up ... the correct value is known to
282 * word-at-a-time bitbang code, and presumably chipselect()
283 * should enforce these requirements too?
290 list_for_each_entry(t, &m->transfers, transfer_list) {
292 /* override speed or wordsize? */
293 if (t->speed_hz || t->bits_per_word)
296 /* init (-1) or override (1) transfer params */
298 status = bitbang->setup_transfer(spi, t);
305 /* set up default clock polarity, and activate chip;
306 * this implicitly updates clock and spi modes as
307 * previously recorded for this device via setup().
308 * (and also deselects any other chip that might be
312 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
315 cs_change = t->cs_change;
316 if (!t->tx_buf && !t->rx_buf && t->len) {
321 /* transfer data. the lower level code handles any
322 * new dma mappings it needs. our caller always gave
323 * us dma-safe buffers.
326 /* REVISIT dma API still needs a designated
327 * DMA_ADDR_INVALID; ~0 might be better.
329 if (!m->is_dma_mapped)
330 t->rx_dma = t->tx_dma = 0;
331 status = bitbang->txrx_bufs(spi, t);
334 m->actual_length += status;
335 if (status != t->len) {
336 /* always report some kind of error */
343 /* protocol tweaks before next transfer */
345 udelay(t->delay_usecs);
348 !list_is_last(&t->transfer_list, &m->transfers)) {
349 /* sometimes a short mid-message deselect of the chip
350 * may be needed to terminate a mode or command
353 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
360 /* normally deactivate chipselect ... unless no error and
361 * cs_change has hinted that the next message will probably
362 * be for this chip too.
364 if (!(status == 0 && cs_change)) {
366 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
370 spi_finalize_current_message(master);
375 static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
377 struct spi_bitbang *bitbang;
380 bitbang = spi_master_get_devdata(spi);
382 spin_lock_irqsave(&bitbang->lock, flags);
384 spin_unlock_irqrestore(&bitbang->lock, flags);
389 /*----------------------------------------------------------------------*/
392 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
393 * @bitbang: driver handle
395 * Caller should have zero-initialized all parts of the structure, and then
396 * provided callbacks for chip selection and I/O loops. If the master has
397 * a transfer method, its final step should call spi_bitbang_transfer; or,
398 * that's the default if the transfer routine is not initialized. It should
399 * also set up the bus number and number of chipselects.
401 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
402 * hardware that basically exposes a shift register) or per-spi_transfer
403 * (which takes better advantage of hardware like fifos or DMA engines).
405 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
406 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
407 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
408 * routine isn't initialized.
410 * This routine registers the spi_master, which will process requests in a
411 * dedicated task, keeping IRQs unblocked most of the time. To stop
412 * processing those requests, call spi_bitbang_stop().
414 * On success, this routine will take a reference to master. The caller is
415 * responsible for calling spi_bitbang_stop() to decrement the reference and
416 * spi_master_put() as counterpart of spi_alloc_master() to prevent a memory
419 int spi_bitbang_start(struct spi_bitbang *bitbang)
421 struct spi_master *master = bitbang->master;
424 if (!master || !bitbang->chipselect)
427 spin_lock_init(&bitbang->lock);
429 if (!master->mode_bits)
430 master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
432 if (master->transfer || master->transfer_one_message)
435 master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
436 master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
437 master->transfer_one_message = spi_bitbang_transfer_one;
439 if (!bitbang->txrx_bufs) {
440 bitbang->use_dma = 0;
441 bitbang->txrx_bufs = spi_bitbang_bufs;
442 if (!master->setup) {
443 if (!bitbang->setup_transfer)
444 bitbang->setup_transfer =
445 spi_bitbang_setup_transfer;
446 master->setup = spi_bitbang_setup;
447 master->cleanup = spi_bitbang_cleanup;
451 /* driver may get busy before register() returns, especially
452 * if someone registered boardinfo for devices
454 ret = spi_register_master(spi_master_get(master));
456 spi_master_put(master);
460 EXPORT_SYMBOL_GPL(spi_bitbang_start);
463 * spi_bitbang_stop - stops the task providing spi communication
465 void spi_bitbang_stop(struct spi_bitbang *bitbang)
467 spi_unregister_master(bitbang->master);
469 EXPORT_SYMBOL_GPL(spi_bitbang_stop);
471 MODULE_LICENSE("GPL");