summaryrefslogtreecommitdiff
path: root/drivers/spi/spi_lm70llp.c
blob: af6526767e2acd80c870a239d33e2afb16917e1a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
/*
 * spi_lm70llp.c - driver for lm70llp eval board for the LM70 sensor
 *
 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/parport.h>
#include <linux/sysfs.h>
#include <linux/workqueue.h>


#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>


/*
 * The LM70 communicates with a host processor using a 3-wire variant of
 * the SPI/Microwire bus interface. This driver specifically supports an
 * NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel
 * port to bitbang an SPI-parport bridge.  Accordingly, this is an SPI
 * master controller driver.  The hwmon/lm70 driver is a "SPI protocol
 * driver", layered on top of this one and usable without the lm70llp.
 *
 * The LM70 is a temperature sensor chip from National Semiconductor; its
 * datasheet is available at http://www.national.com/pf/LM/LM70.html
 *
 * Also see Documentation/spi/spi-lm70llp.  The SPI<->parport code here is
 * (heavily) based on spi-butterfly by David Brownell.
 *
 * The LM70 LLP connects to the PC parallel port in the following manner:
 *
 *   Parallel                 LM70 LLP
 *     Port      Direction   JP2 Header
 *  -----------  ---------  ------------
 *      D0    2      -         -
 *      D1    3     -->      V+   5
 *      D2    4     -->      V+   5
 *      D3    5     -->      V+   5
 *      D4    6     -->      V+   5
 *      D5    7     -->      nCS  8
 *      D6    8     -->      SCLK 3
 *      D7    9     -->      SI/O 5
 *     GND   25      -       GND  7
 *    Select 13     <--      SI/O 1
 *
 * Note that parport pin 13 actually gets inverted by the transistor
 * arrangement which lets either the parport or the LM70 drive the
 * SI/SO signal.
 */

#define DRVNAME		"spi-lm70llp"

#define lm70_INIT	0xBE
#define SIO		0x10
#define nCS		0x20
#define SCLK		0x40

/*-------------------------------------------------------------------------*/

struct spi_lm70llp {
	struct spi_bitbang	bitbang;
	struct parport		*port;
	struct pardevice	*pd;
	struct spi_device	*spidev_lm70;
	struct spi_board_info	info;
	//struct device		*dev;
};

/* REVISIT : ugly global ; provides "exclusive open" facility */
static struct spi_lm70llp *lm70llp;


/*-------------------------------------------------------------------*/

static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
{
	return spi->controller_data;
}

/*---------------------- LM70 LLP eval board-specific inlines follow */

/* NOTE:  we don't actually need to reread the output values, since they'll
 * still be what we wrote before.  Plus, going through parport builds in
 * a ~1ms/operation delay; these SPI transfers could easily be faster.
 */

static inline void deassertCS(struct spi_lm70llp *pp)
{
	u8 data = parport_read_data(pp->port);
	parport_write_data(pp->port, data | nCS);
}

static inline void assertCS(struct spi_lm70llp *pp)
{
	u8 data = parport_read_data(pp->port);
	parport_write_data(pp->port, data & ~nCS);
}

static inline void clkHigh(struct spi_lm70llp *pp)
{
	u8 data = parport_read_data(pp->port);
	parport_write_data(pp->port, data | SCLK);
}

static inline void clkLow(struct spi_lm70llp *pp)
{
	u8 data = parport_read_data(pp->port);
	parport_write_data(pp->port, data & ~SCLK);
}

/*------------------------- SPI-LM70-specific inlines ----------------------*/

static inline void spidelay(unsigned d)
{
	udelay(d);
}

static inline void setsck(struct spi_device *s, int is_on)
{
	struct spi_lm70llp *pp = spidev_to_pp(s);

	if (is_on)
		clkHigh(pp);
	else
		clkLow(pp);
}

static inline void setmosi(struct spi_device *s, int is_on)
{
	/* FIXME update D7 ... this way we can put the chip
	 * into shutdown mode and read the manufacturer ID,
	 * but we can't put it back into operational mode.
	 */
}

/*
 * getmiso:
 * Why do we return 0 when the SIO line is high and vice-versa?
 * The fact is, the lm70 eval board from NS (which this driver drives),
 * is wired in just such a way : when the lm70's SIO goes high, a transistor
 * switches it to low reflecting this on the parport (pin 13), and vice-versa.
 */
static inline int getmiso(struct spi_device *s)
{
	struct spi_lm70llp *pp = spidev_to_pp(s);
	return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
}
/*--------------------------------------------------------------------*/

#define EXPAND_BITBANG_TXRX 1
#include <linux/spi/spi_bitbang.h>

static void lm70_chipselect(struct spi_device *spi, int value)
{
	struct spi_lm70llp *pp = spidev_to_pp(spi);

	if (value)
		assertCS(pp);
	else
		deassertCS(pp);
}

/*
 * Our actual bitbanger routine.
 */
static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
{
	static u32 sio=0;
	static int first_time=1;

	/* First time: perform SPI bitbang and return the LSB of
	 * the result of the SPI call.
	 */
	if (first_time) {
		sio = bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
		first_time=0;
		return (sio & 0x00ff);
	}
	/* Return the MSB of the result of the SPI call */
	else {
		first_time=1;
		return (sio >> 8);
	}
}

static void spi_lm70llp_attach(struct parport *p)
{
	struct pardevice	*pd;
	struct spi_lm70llp	*pp;
	struct spi_master	*master;
	int			status;

	if (lm70llp) {
		printk(KERN_WARNING
			"%s: spi_lm70llp instance already loaded. Aborting.\n",
			DRVNAME);
		return;
	}

	/* TODO:  this just _assumes_ a lm70 is there ... no probe;
	 * the lm70 driver could verify it, reading the manf ID.
	 */

	master = spi_alloc_master(p->physport->dev, sizeof *pp);
	if (!master) {
		status = -ENOMEM;
		goto out_fail;
	}
	pp = spi_master_get_devdata(master);

	master->bus_num = -1;	/* dynamic alloc of a bus number */
	master->num_chipselect = 1;

	/*
	 * SPI and bitbang hookup.
	 */
	pp->bitbang.master = spi_master_get(master);
	pp->bitbang.chipselect = lm70_chipselect;
	pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
	pp->bitbang.flags = SPI_3WIRE;

	/*
	 * Parport hookup
	 */
	pp->port = p;
	pd = parport_register_device(p, DRVNAME,
			NULL, NULL, NULL,
			PARPORT_FLAG_EXCL, pp);
	if (!pd) {
		status = -ENOMEM;
		goto out_free_master;
	}
	pp->pd = pd;

	status = parport_claim(pd);
	if (status < 0)
		goto out_parport_unreg;

	/*
	 * Start SPI ...
	 */
	status = spi_bitbang_start(&pp->bitbang);
	if (status < 0) {
		printk(KERN_WARNING
			"%s: spi_bitbang_start failed with status %d\n",
			DRVNAME, status);
		goto out_off_and_release;
	}

	/*
	 * The modalias name MUST match the device_driver name
	 * for the bus glue code to match and subsequently bind them.
	 * We are binding to the generic drivers/hwmon/lm70.c device
	 * driver.
	 */
	strcpy(pp->info.modalias, "lm70");
	pp->info.max_speed_hz = 6 * 1000 * 1000;
	pp->info.chip_select = 0;
	pp->info.mode = SPI_3WIRE | SPI_MODE_0;

	/* power up the chip, and let the LM70 control SI/SO */
	parport_write_data(pp->port, lm70_INIT);

	/* Enable access to our primary data structure via
	 * the board info's (void *)controller_data.
	 */
	pp->info.controller_data = pp;
	pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
	if (pp->spidev_lm70)
		dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
				dev_name(&pp->spidev_lm70->dev));
	else {
		printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
		status = -ENODEV;
		goto out_bitbang_stop;
	}
	pp->spidev_lm70->bits_per_word = 16;

	lm70llp = pp;

	return;

out_bitbang_stop:
	spi_bitbang_stop(&pp->bitbang);
out_off_and_release:
	/* power down */
	parport_write_data(pp->port, 0);
	mdelay(10);
	parport_release(pp->pd);
out_parport_unreg:
	parport_unregister_device(pd);
out_free_master:
	(void) spi_master_put(master);
out_fail:
	pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
}

static void spi_lm70llp_detach(struct parport *p)
{
	struct spi_lm70llp		*pp;

	if (!lm70llp || lm70llp->port != p)
		return;

	pp = lm70llp;
	spi_bitbang_stop(&pp->bitbang);

	/* power down */
	parport_write_data(pp->port, 0);
	msleep(10);

	parport_release(pp->pd);
	parport_unregister_device(pp->pd);

	(void) spi_master_put(pp->bitbang.master);

	lm70llp = NULL;
}


static struct parport_driver spi_lm70llp_drv = {
	.name =		DRVNAME,
	.attach =	spi_lm70llp_attach,
	.detach =	spi_lm70llp_detach,
};

static int __init init_spi_lm70llp(void)
{
	return parport_register_driver(&spi_lm70llp_drv);
}
module_init(init_spi_lm70llp);

static void __exit cleanup_spi_lm70llp(void)
{
	parport_unregister_driver(&spi_lm70llp_drv);
}
module_exit(cleanup_spi_lm70llp);

MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
MODULE_DESCRIPTION(
	"Parport adapter for the National Semiconductor LM70 LLP eval board");
MODULE_LICENSE("GPL");