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
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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.
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16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19 #include <linux/spinlock.h>
20 #include <linux/workqueue.h>
21 #include <linux/interrupt.h>
22 #include <linux/module.h>
23 #include <linux/delay.h>
24 #include <linux/errno.h>
25 #include <linux/platform_device.h>
26 #include <linux/slab.h>
28 #include <linux/spi/spi.h>
29 #include <linux/spi/spi_bitbang.h>
32 /*----------------------------------------------------------------------*/
35 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
36 * Use this for GPIO or shift-register level hardware APIs.
38 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
39 * to glue code. These bitbang setup() and cleanup() routines are always
40 * used, though maybe they're called from controller-aware code.
42 * chipselect() and friends may use spi_device->controller_data and
43 * controller registers as appropriate.
46 * NOTE: SPI controller pins can often be used as GPIO pins instead,
47 * which means you could use a bitbang driver either to get hardware
48 * working quickly, or testing for differences that aren't speed related.
51 struct spi_bitbang_cs {
52 unsigned nsecs; /* (clock cycle time)/2 */
53 u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
55 unsigned (*txrx_bufs)(struct spi_device *,
57 struct spi_device *spi,
60 unsigned, struct spi_transfer *);
63 static unsigned bitbang_txrx_8(
64 struct spi_device *spi,
65 u32 (*txrx_word)(struct spi_device *spi,
69 struct spi_transfer *t
71 unsigned bits = t->bits_per_word;
72 unsigned count = t->len;
73 const u8 *tx = t->tx_buf;
76 while (likely(count > 0)) {
81 word = txrx_word(spi, ns, word, bits);
86 return t->len - count;
89 static unsigned bitbang_txrx_16(
90 struct spi_device *spi,
91 u32 (*txrx_word)(struct spi_device *spi,
95 struct spi_transfer *t
97 unsigned bits = t->bits_per_word;
98 unsigned count = t->len;
99 const u16 *tx = t->tx_buf;
102 while (likely(count > 1)) {
107 word = txrx_word(spi, ns, word, bits);
112 return t->len - count;
115 static unsigned bitbang_txrx_32(
116 struct spi_device *spi,
117 u32 (*txrx_word)(struct spi_device *spi,
121 struct spi_transfer *t
123 unsigned bits = t->bits_per_word;
124 unsigned count = t->len;
125 const u32 *tx = t->tx_buf;
128 while (likely(count > 3)) {
133 word = txrx_word(spi, ns, word, bits);
138 return t->len - count;
141 int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
143 struct spi_bitbang_cs *cs = spi->controller_state;
148 bits_per_word = t->bits_per_word;
155 /* spi_transfer level calls that work per-word */
157 bits_per_word = spi->bits_per_word;
158 if (bits_per_word <= 8)
159 cs->txrx_bufs = bitbang_txrx_8;
160 else if (bits_per_word <= 16)
161 cs->txrx_bufs = bitbang_txrx_16;
162 else if (bits_per_word <= 32)
163 cs->txrx_bufs = bitbang_txrx_32;
167 /* nsecs = (clock period)/2 */
169 hz = spi->max_speed_hz;
171 cs->nsecs = (1000000000/2) / hz;
172 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
178 EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
181 * spi_bitbang_setup - default setup for per-word I/O loops
183 int spi_bitbang_setup(struct spi_device *spi)
185 struct spi_bitbang_cs *cs = spi->controller_state;
186 struct spi_bitbang *bitbang;
190 bitbang = spi_master_get_devdata(spi->master);
193 cs = kzalloc(sizeof(*cs), GFP_KERNEL);
196 spi->controller_state = cs;
199 /* per-word shift register access, in hardware or bitbanging */
200 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
204 retval = bitbang->setup_transfer(spi, NULL);
208 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
210 /* NOTE we _need_ to call chipselect() early, ideally with adapter
211 * setup, unless the hardware defaults cooperate to avoid confusion
212 * between normal (active low) and inverted chipselects.
215 /* deselect chip (low or high) */
216 spin_lock_irqsave(&bitbang->lock, flags);
217 if (!bitbang->busy) {
218 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
221 spin_unlock_irqrestore(&bitbang->lock, flags);
225 EXPORT_SYMBOL_GPL(spi_bitbang_setup);
228 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
230 void spi_bitbang_cleanup(struct spi_device *spi)
232 kfree(spi->controller_state);
234 EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
236 static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
238 struct spi_bitbang_cs *cs = spi->controller_state;
239 unsigned nsecs = cs->nsecs;
241 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
244 /*----------------------------------------------------------------------*/
247 * SECOND PART ... simple transfer queue runner.
249 * This costs a task context per controller, running the queue by
250 * performing each transfer in sequence. Smarter hardware can queue
251 * several DMA transfers at once, and process several controller queues
252 * in parallel; this driver doesn't match such hardware very well.
254 * Drivers can provide word-at-a-time i/o primitives, or provide
255 * transfer-at-a-time ones to leverage dma or fifo hardware.
258 static int spi_bitbang_prepare_hardware(struct spi_master *spi)
260 struct spi_bitbang *bitbang;
263 bitbang = spi_master_get_devdata(spi);
265 spin_lock_irqsave(&bitbang->lock, flags);
267 spin_unlock_irqrestore(&bitbang->lock, flags);
272 static int spi_bitbang_transfer_one(struct spi_master *master,
273 struct spi_message *m)
275 struct spi_bitbang *bitbang;
277 struct spi_transfer *t = NULL;
281 struct spi_device *spi = m->spi;
283 bitbang = spi_master_get_devdata(master);
285 /* FIXME this is made-up ... the correct value is known to
286 * word-at-a-time bitbang code, and presumably chipselect()
287 * should enforce these requirements too?
294 list_for_each_entry(t, &m->transfers, transfer_list) {
296 /* override speed or wordsize? */
297 if (t->speed_hz || t->bits_per_word)
300 /* init (-1) or override (1) transfer params */
302 status = bitbang->setup_transfer(spi, t);
309 /* set up default clock polarity, and activate chip;
310 * this implicitly updates clock and spi modes as
311 * previously recorded for this device via setup().
312 * (and also deselects any other chip that might be
316 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
319 cs_change = t->cs_change;
320 if (!t->tx_buf && !t->rx_buf && t->len) {
325 /* transfer data. the lower level code handles any
326 * new dma mappings it needs. our caller always gave
327 * us dma-safe buffers.
330 /* REVISIT dma API still needs a designated
331 * DMA_ADDR_INVALID; ~0 might be better.
333 if (!m->is_dma_mapped)
334 t->rx_dma = t->tx_dma = 0;
335 status = bitbang->txrx_bufs(spi, t);
338 m->actual_length += status;
339 if (status != t->len) {
340 /* always report some kind of error */
347 /* protocol tweaks before next transfer */
349 udelay(t->delay_usecs);
352 !list_is_last(&t->transfer_list, &m->transfers)) {
353 /* sometimes a short mid-message deselect of the chip
354 * may be needed to terminate a mode or command
357 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
364 /* normally deactivate chipselect ... unless no error and
365 * cs_change has hinted that the next message will probably
366 * be for this chip too.
368 if (!(status == 0 && cs_change)) {
370 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
374 spi_finalize_current_message(master);
379 static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
381 struct spi_bitbang *bitbang;
384 bitbang = spi_master_get_devdata(spi);
386 spin_lock_irqsave(&bitbang->lock, flags);
388 spin_unlock_irqrestore(&bitbang->lock, flags);
393 /*----------------------------------------------------------------------*/
396 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
397 * @bitbang: driver handle
399 * Caller should have zero-initialized all parts of the structure, and then
400 * provided callbacks for chip selection and I/O loops. If the master has
401 * a transfer method, its final step should call spi_bitbang_transfer; or,
402 * that's the default if the transfer routine is not initialized. It should
403 * also set up the bus number and number of chipselects.
405 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
406 * hardware that basically exposes a shift register) or per-spi_transfer
407 * (which takes better advantage of hardware like fifos or DMA engines).
409 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
410 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
411 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
412 * routine isn't initialized.
414 * This routine registers the spi_master, which will process requests in a
415 * dedicated task, keeping IRQs unblocked most of the time. To stop
416 * processing those requests, call spi_bitbang_stop().
418 * On success, this routine will take a reference to master. The caller is
419 * responsible for calling spi_bitbang_stop() to decrement the reference and
420 * spi_master_put() as counterpart of spi_alloc_master() to prevent a memory
423 int spi_bitbang_start(struct spi_bitbang *bitbang)
425 struct spi_master *master = bitbang->master;
428 if (!master || !bitbang->chipselect)
431 spin_lock_init(&bitbang->lock);
433 if (!master->mode_bits)
434 master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
436 if (master->transfer || master->transfer_one_message)
439 master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
440 master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
441 master->transfer_one_message = spi_bitbang_transfer_one;
443 if (!bitbang->txrx_bufs) {
444 bitbang->use_dma = 0;
445 bitbang->txrx_bufs = spi_bitbang_bufs;
446 if (!master->setup) {
447 if (!bitbang->setup_transfer)
448 bitbang->setup_transfer =
449 spi_bitbang_setup_transfer;
450 master->setup = spi_bitbang_setup;
451 master->cleanup = spi_bitbang_cleanup;
455 /* driver may get busy before register() returns, especially
456 * if someone registered boardinfo for devices
458 ret = spi_register_master(spi_master_get(master));
460 spi_master_put(master);
464 EXPORT_SYMBOL_GPL(spi_bitbang_start);
467 * spi_bitbang_stop - stops the task providing spi communication
469 void spi_bitbang_stop(struct spi_bitbang *bitbang)
471 spi_unregister_master(bitbang->master);
473 EXPORT_SYMBOL_GPL(spi_bitbang_stop);
475 MODULE_LICENSE("GPL");