spi_bitbang: short transfer status fix
[linux-2.6.git] / drivers / spi / spi_bitbang.c
1 /*
2  * spi_bitbang.c - polling/bitbanging SPI master controller driver utilities
3  *
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.
8  *
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.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
17  */
18
19 #include <linux/init.h>
20 #include <linux/spinlock.h>
21 #include <linux/workqueue.h>
22 #include <linux/interrupt.h>
23 #include <linux/delay.h>
24 #include <linux/errno.h>
25 #include <linux/platform_device.h>
26
27 #include <linux/spi/spi.h>
28 #include <linux/spi/spi_bitbang.h>
29
30
31 /*----------------------------------------------------------------------*/
32
33 /*
34  * FIRST PART (OPTIONAL):  word-at-a-time spi_transfer support.
35  * Use this for GPIO or shift-register level hardware APIs.
36  *
37  * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
38  * to glue code.  These bitbang setup() and cleanup() routines are always
39  * used, though maybe they're called from controller-aware code.
40  *
41  * chipselect() and friends may use use spi_device->controller_data and
42  * controller registers as appropriate.
43  *
44  *
45  * NOTE:  SPI controller pins can often be used as GPIO pins instead,
46  * which means you could use a bitbang driver either to get hardware
47  * working quickly, or testing for differences that aren't speed related.
48  */
49
50 struct spi_bitbang_cs {
51         unsigned        nsecs;  /* (clock cycle time)/2 */
52         u32             (*txrx_word)(struct spi_device *spi, unsigned nsecs,
53                                         u32 word, u8 bits);
54         unsigned        (*txrx_bufs)(struct spi_device *,
55                                         u32 (*txrx_word)(
56                                                 struct spi_device *spi,
57                                                 unsigned nsecs,
58                                                 u32 word, u8 bits),
59                                         unsigned, struct spi_transfer *);
60 };
61
62 static unsigned bitbang_txrx_8(
63         struct spi_device       *spi,
64         u32                     (*txrx_word)(struct spi_device *spi,
65                                         unsigned nsecs,
66                                         u32 word, u8 bits),
67         unsigned                ns,
68         struct spi_transfer     *t
69 ) {
70         unsigned                bits = spi->bits_per_word;
71         unsigned                count = t->len;
72         const u8                *tx = t->tx_buf;
73         u8                      *rx = t->rx_buf;
74
75         while (likely(count > 0)) {
76                 u8              word = 0;
77
78                 if (tx)
79                         word = *tx++;
80                 word = txrx_word(spi, ns, word, bits);
81                 if (rx)
82                         *rx++ = word;
83                 count -= 1;
84         }
85         return t->len - count;
86 }
87
88 static unsigned bitbang_txrx_16(
89         struct spi_device       *spi,
90         u32                     (*txrx_word)(struct spi_device *spi,
91                                         unsigned nsecs,
92                                         u32 word, u8 bits),
93         unsigned                ns,
94         struct spi_transfer     *t
95 ) {
96         unsigned                bits = spi->bits_per_word;
97         unsigned                count = t->len;
98         const u16               *tx = t->tx_buf;
99         u16                     *rx = t->rx_buf;
100
101         while (likely(count > 1)) {
102                 u16             word = 0;
103
104                 if (tx)
105                         word = *tx++;
106                 word = txrx_word(spi, ns, word, bits);
107                 if (rx)
108                         *rx++ = word;
109                 count -= 2;
110         }
111         return t->len - count;
112 }
113
114 static unsigned bitbang_txrx_32(
115         struct spi_device       *spi,
116         u32                     (*txrx_word)(struct spi_device *spi,
117                                         unsigned nsecs,
118                                         u32 word, u8 bits),
119         unsigned                ns,
120         struct spi_transfer     *t
121 ) {
122         unsigned                bits = spi->bits_per_word;
123         unsigned                count = t->len;
124         const u32               *tx = t->tx_buf;
125         u32                     *rx = t->rx_buf;
126
127         while (likely(count > 3)) {
128                 u32             word = 0;
129
130                 if (tx)
131                         word = *tx++;
132                 word = txrx_word(spi, ns, word, bits);
133                 if (rx)
134                         *rx++ = word;
135                 count -= 4;
136         }
137         return t->len - count;
138 }
139
140 int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
141 {
142         struct spi_bitbang_cs   *cs = spi->controller_state;
143         u8                      bits_per_word;
144         u32                     hz;
145
146         if (t) {
147                 bits_per_word = t->bits_per_word;
148                 hz = t->speed_hz;
149         } else {
150                 bits_per_word = 0;
151                 hz = 0;
152         }
153
154         /* spi_transfer level calls that work per-word */
155         if (!bits_per_word)
156                 bits_per_word = spi->bits_per_word;
157         if (bits_per_word <= 8)
158                 cs->txrx_bufs = bitbang_txrx_8;
159         else if (bits_per_word <= 16)
160                 cs->txrx_bufs = bitbang_txrx_16;
161         else if (bits_per_word <= 32)
162                 cs->txrx_bufs = bitbang_txrx_32;
163         else
164                 return -EINVAL;
165
166         /* nsecs = (clock period)/2 */
167         if (!hz)
168                 hz = spi->max_speed_hz;
169         if (hz) {
170                 cs->nsecs = (1000000000/2) / hz;
171                 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
172                         return -EINVAL;
173         }
174
175         return 0;
176 }
177 EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
178
179 /**
180  * spi_bitbang_setup - default setup for per-word I/O loops
181  */
182 int spi_bitbang_setup(struct spi_device *spi)
183 {
184         struct spi_bitbang_cs   *cs = spi->controller_state;
185         struct spi_bitbang      *bitbang;
186         int                     retval;
187         unsigned long           flags;
188
189         bitbang = spi_master_get_devdata(spi->master);
190
191         /* Bitbangers can support SPI_CS_HIGH, SPI_3WIRE, and so on;
192          * add those to master->flags, and provide the other support.
193          */
194         if ((spi->mode & ~(SPI_CPOL|SPI_CPHA|bitbang->flags)) != 0)
195                 return -EINVAL;
196
197         if (!cs) {
198                 cs = kzalloc(sizeof *cs, GFP_KERNEL);
199                 if (!cs)
200                         return -ENOMEM;
201                 spi->controller_state = cs;
202         }
203
204         if (!spi->bits_per_word)
205                 spi->bits_per_word = 8;
206
207         /* per-word shift register access, in hardware or bitbanging */
208         cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
209         if (!cs->txrx_word)
210                 return -EINVAL;
211
212         retval = bitbang->setup_transfer(spi, NULL);
213         if (retval < 0)
214                 return retval;
215
216         dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec/bit\n",
217                         __FUNCTION__, spi->mode & (SPI_CPOL | SPI_CPHA),
218                         spi->bits_per_word, 2 * cs->nsecs);
219
220         /* NOTE we _need_ to call chipselect() early, ideally with adapter
221          * setup, unless the hardware defaults cooperate to avoid confusion
222          * between normal (active low) and inverted chipselects.
223          */
224
225         /* deselect chip (low or high) */
226         spin_lock_irqsave(&bitbang->lock, flags);
227         if (!bitbang->busy) {
228                 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
229                 ndelay(cs->nsecs);
230         }
231         spin_unlock_irqrestore(&bitbang->lock, flags);
232
233         return 0;
234 }
235 EXPORT_SYMBOL_GPL(spi_bitbang_setup);
236
237 /**
238  * spi_bitbang_cleanup - default cleanup for per-word I/O loops
239  */
240 void spi_bitbang_cleanup(struct spi_device *spi)
241 {
242         kfree(spi->controller_state);
243 }
244 EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
245
246 static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
247 {
248         struct spi_bitbang_cs   *cs = spi->controller_state;
249         unsigned                nsecs = cs->nsecs;
250
251         return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
252 }
253
254 /*----------------------------------------------------------------------*/
255
256 /*
257  * SECOND PART ... simple transfer queue runner.
258  *
259  * This costs a task context per controller, running the queue by
260  * performing each transfer in sequence.  Smarter hardware can queue
261  * several DMA transfers at once, and process several controller queues
262  * in parallel; this driver doesn't match such hardware very well.
263  *
264  * Drivers can provide word-at-a-time i/o primitives, or provide
265  * transfer-at-a-time ones to leverage dma or fifo hardware.
266  */
267 static void bitbang_work(struct work_struct *work)
268 {
269         struct spi_bitbang      *bitbang =
270                 container_of(work, struct spi_bitbang, work);
271         unsigned long           flags;
272
273         spin_lock_irqsave(&bitbang->lock, flags);
274         bitbang->busy = 1;
275         while (!list_empty(&bitbang->queue)) {
276                 struct spi_message      *m;
277                 struct spi_device       *spi;
278                 unsigned                nsecs;
279                 struct spi_transfer     *t = NULL;
280                 unsigned                tmp;
281                 unsigned                cs_change;
282                 int                     status;
283                 int                     (*setup_transfer)(struct spi_device *,
284                                                 struct spi_transfer *);
285
286                 m = container_of(bitbang->queue.next, struct spi_message,
287                                 queue);
288                 list_del_init(&m->queue);
289                 spin_unlock_irqrestore(&bitbang->lock, flags);
290
291                 /* FIXME this is made-up ... the correct value is known to
292                  * word-at-a-time bitbang code, and presumably chipselect()
293                  * should enforce these requirements too?
294                  */
295                 nsecs = 100;
296
297                 spi = m->spi;
298                 tmp = 0;
299                 cs_change = 1;
300                 status = 0;
301                 setup_transfer = NULL;
302
303                 list_for_each_entry (t, &m->transfers, transfer_list) {
304
305                         /* override or restore speed and wordsize */
306                         if (t->speed_hz || t->bits_per_word) {
307                                 setup_transfer = bitbang->setup_transfer;
308                                 if (!setup_transfer) {
309                                         status = -ENOPROTOOPT;
310                                         break;
311                                 }
312                         }
313                         if (setup_transfer) {
314                                 status = setup_transfer(spi, t);
315                                 if (status < 0)
316                                         break;
317                         }
318
319                         /* set up default clock polarity, and activate chip;
320                          * this implicitly updates clock and spi modes as
321                          * previously recorded for this device via setup().
322                          * (and also deselects any other chip that might be
323                          * selected ...)
324                          */
325                         if (cs_change) {
326                                 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
327                                 ndelay(nsecs);
328                         }
329                         cs_change = t->cs_change;
330                         if (!t->tx_buf && !t->rx_buf && t->len) {
331                                 status = -EINVAL;
332                                 break;
333                         }
334
335                         /* transfer data.  the lower level code handles any
336                          * new dma mappings it needs. our caller always gave
337                          * us dma-safe buffers.
338                          */
339                         if (t->len) {
340                                 /* REVISIT dma API still needs a designated
341                                  * DMA_ADDR_INVALID; ~0 might be better.
342                                  */
343                                 if (!m->is_dma_mapped)
344                                         t->rx_dma = t->tx_dma = 0;
345                                 status = bitbang->txrx_bufs(spi, t);
346                         }
347                         if (status > 0)
348                                 m->actual_length += status;
349                         if (status != t->len) {
350                                 /* always report some kind of error */
351                                 if (status >= 0)
352                                         status = -EREMOTEIO;
353                                 break;
354                         }
355                         status = 0;
356
357                         /* protocol tweaks before next transfer */
358                         if (t->delay_usecs)
359                                 udelay(t->delay_usecs);
360
361                         if (!cs_change)
362                                 continue;
363                         if (t->transfer_list.next == &m->transfers)
364                                 break;
365
366                         /* sometimes a short mid-message deselect of the chip
367                          * may be needed to terminate a mode or command
368                          */
369                         ndelay(nsecs);
370                         bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
371                         ndelay(nsecs);
372                 }
373
374                 m->status = status;
375                 m->complete(m->context);
376
377                 /* restore speed and wordsize */
378                 if (setup_transfer)
379                         setup_transfer(spi, NULL);
380
381                 /* normally deactivate chipselect ... unless no error and
382                  * cs_change has hinted that the next message will probably
383                  * be for this chip too.
384                  */
385                 if (!(status == 0 && cs_change)) {
386                         ndelay(nsecs);
387                         bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
388                         ndelay(nsecs);
389                 }
390
391                 spin_lock_irqsave(&bitbang->lock, flags);
392         }
393         bitbang->busy = 0;
394         spin_unlock_irqrestore(&bitbang->lock, flags);
395 }
396
397 /**
398  * spi_bitbang_transfer - default submit to transfer queue
399  */
400 int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
401 {
402         struct spi_bitbang      *bitbang;
403         unsigned long           flags;
404         int                     status = 0;
405
406         m->actual_length = 0;
407         m->status = -EINPROGRESS;
408
409         bitbang = spi_master_get_devdata(spi->master);
410
411         spin_lock_irqsave(&bitbang->lock, flags);
412         if (!spi->max_speed_hz)
413                 status = -ENETDOWN;
414         else {
415                 list_add_tail(&m->queue, &bitbang->queue);
416                 queue_work(bitbang->workqueue, &bitbang->work);
417         }
418         spin_unlock_irqrestore(&bitbang->lock, flags);
419
420         return status;
421 }
422 EXPORT_SYMBOL_GPL(spi_bitbang_transfer);
423
424 /*----------------------------------------------------------------------*/
425
426 /**
427  * spi_bitbang_start - start up a polled/bitbanging SPI master driver
428  * @bitbang: driver handle
429  *
430  * Caller should have zero-initialized all parts of the structure, and then
431  * provided callbacks for chip selection and I/O loops.  If the master has
432  * a transfer method, its final step should call spi_bitbang_transfer; or,
433  * that's the default if the transfer routine is not initialized.  It should
434  * also set up the bus number and number of chipselects.
435  *
436  * For i/o loops, provide callbacks either per-word (for bitbanging, or for
437  * hardware that basically exposes a shift register) or per-spi_transfer
438  * (which takes better advantage of hardware like fifos or DMA engines).
439  *
440  * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
441  * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
442  * master methods.  Those methods are the defaults if the bitbang->txrx_bufs
443  * routine isn't initialized.
444  *
445  * This routine registers the spi_master, which will process requests in a
446  * dedicated task, keeping IRQs unblocked most of the time.  To stop
447  * processing those requests, call spi_bitbang_stop().
448  */
449 int spi_bitbang_start(struct spi_bitbang *bitbang)
450 {
451         int     status;
452
453         if (!bitbang->master || !bitbang->chipselect)
454                 return -EINVAL;
455
456         INIT_WORK(&bitbang->work, bitbang_work);
457         spin_lock_init(&bitbang->lock);
458         INIT_LIST_HEAD(&bitbang->queue);
459
460         if (!bitbang->master->transfer)
461                 bitbang->master->transfer = spi_bitbang_transfer;
462         if (!bitbang->txrx_bufs) {
463                 bitbang->use_dma = 0;
464                 bitbang->txrx_bufs = spi_bitbang_bufs;
465                 if (!bitbang->master->setup) {
466                         if (!bitbang->setup_transfer)
467                                 bitbang->setup_transfer =
468                                          spi_bitbang_setup_transfer;
469                         bitbang->master->setup = spi_bitbang_setup;
470                         bitbang->master->cleanup = spi_bitbang_cleanup;
471                 }
472         } else if (!bitbang->master->setup)
473                 return -EINVAL;
474
475         /* this task is the only thing to touch the SPI bits */
476         bitbang->busy = 0;
477         bitbang->workqueue = create_singlethread_workqueue(
478                         bitbang->master->dev.parent->bus_id);
479         if (bitbang->workqueue == NULL) {
480                 status = -EBUSY;
481                 goto err1;
482         }
483
484         /* driver may get busy before register() returns, especially
485          * if someone registered boardinfo for devices
486          */
487         status = spi_register_master(bitbang->master);
488         if (status < 0)
489                 goto err2;
490
491         return status;
492
493 err2:
494         destroy_workqueue(bitbang->workqueue);
495 err1:
496         return status;
497 }
498 EXPORT_SYMBOL_GPL(spi_bitbang_start);
499
500 /**
501  * spi_bitbang_stop - stops the task providing spi communication
502  */
503 int spi_bitbang_stop(struct spi_bitbang *bitbang)
504 {
505         spi_unregister_master(bitbang->master);
506
507         WARN_ON(!list_empty(&bitbang->queue));
508
509         destroy_workqueue(bitbang->workqueue);
510
511         return 0;
512 }
513 EXPORT_SYMBOL_GPL(spi_bitbang_stop);
514
515 MODULE_LICENSE("GPL");
516