1/*
2 * Driver for LM70EVAL-LLP board for the LM70 sensor
3 *
4 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 */
16
17#include <linux/init.h>
18#include <linux/module.h>
19#include <linux/kernel.h>
20#include <linux/delay.h>
21#include <linux/device.h>
22#include <linux/parport.h>
23#include <linux/sysfs.h>
24#include <linux/workqueue.h>
25
26
27#include <linux/spi/spi.h>
28#include <linux/spi/spi_bitbang.h>
29
30
31/*
32 * The LM70 communicates with a host processor using a 3-wire variant of
33 * the SPI/Microwire bus interface. This driver specifically supports an
34 * NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel
35 * port to bitbang an SPI-parport bridge.  Accordingly, this is an SPI
36 * master controller driver.  The hwmon/lm70 driver is a "SPI protocol
37 * driver", layered on top of this one and usable without the lm70llp.
38 *
39 * Datasheet and Schematic:
40 * The LM70 is a temperature sensor chip from National Semiconductor; its
41 * datasheet is available at http://www.national.com/pf/LM/LM70.html
42 * The schematic for this particular board (the LM70EVAL-LLP) is
43 * available (on page 4) here:
44 *  http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
45 *
46 * Also see Documentation/spi/spi-lm70llp.  The SPI<->parport code here is
47 * (heavily) based on spi-butterfly by David Brownell.
48 *
49 * The LM70 LLP connects to the PC parallel port in the following manner:
50 *
51 *   Parallel                 LM70 LLP
52 *     Port      Direction   JP2 Header
53 *  -----------  ---------  ------------
54 *      D0    2      -         -
55 *      D1    3     -->      V+   5
56 *      D2    4     -->      V+   5
57 *      D3    5     -->      V+   5
58 *      D4    6     -->      V+   5
59 *      D5    7     -->      nCS  8
60 *      D6    8     -->      SCLK 3
61 *      D7    9     -->      SI/O 5
62 *     GND   25      -       GND  7
63 *    Select 13     <--      SI/O 1
64 *
65 * Note that parport pin 13 actually gets inverted by the transistor
66 * arrangement which lets either the parport or the LM70 drive the
67 * SI/SO signal (see the schematic for details).
68 */
69
70#define DRVNAME		"spi-lm70llp"
71
72#define lm70_INIT	0xBE
73#define SIO		0x10
74#define nCS		0x20
75#define SCLK		0x40
76
77/*-------------------------------------------------------------------------*/
78
79struct spi_lm70llp {
80	struct spi_bitbang	bitbang;
81	struct parport		*port;
82	struct pardevice	*pd;
83	struct spi_device	*spidev_lm70;
84	struct spi_board_info	info;
85	//struct device		*dev;
86};
87
88/* REVISIT : ugly global ; provides "exclusive open" facility */
89static struct spi_lm70llp *lm70llp;
90
91
92/*-------------------------------------------------------------------*/
93
94static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
95{
96	return spi->controller_data;
97}
98
99/*---------------------- LM70 LLP eval board-specific inlines follow */
100
101/* NOTE:  we don't actually need to reread the output values, since they'll
102 * still be what we wrote before.  Plus, going through parport builds in
103 * a ~1ms/operation delay; these SPI transfers could easily be faster.
104 */
105
106static inline void deassertCS(struct spi_lm70llp *pp)
107{
108	u8 data = parport_read_data(pp->port);
109
110	data &= ~0x80;		/* pull D7/SI-out low while de-asserted */
111	parport_write_data(pp->port, data | nCS);
112}
113
114static inline void assertCS(struct spi_lm70llp *pp)
115{
116	u8 data = parport_read_data(pp->port);
117
118	data |= 0x80;		/* pull D7/SI-out high so lm70 drives SO-in */
119	parport_write_data(pp->port, data & ~nCS);
120}
121
122static inline void clkHigh(struct spi_lm70llp *pp)
123{
124	u8 data = parport_read_data(pp->port);
125	parport_write_data(pp->port, data | SCLK);
126}
127
128static inline void clkLow(struct spi_lm70llp *pp)
129{
130	u8 data = parport_read_data(pp->port);
131	parport_write_data(pp->port, data & ~SCLK);
132}
133
134/*------------------------- SPI-LM70-specific inlines ----------------------*/
135
136static inline void spidelay(unsigned d)
137{
138	udelay(d);
139}
140
141static inline void setsck(struct spi_device *s, int is_on)
142{
143	struct spi_lm70llp *pp = spidev_to_pp(s);
144
145	if (is_on)
146		clkHigh(pp);
147	else
148		clkLow(pp);
149}
150
151static inline void setmosi(struct spi_device *s, int is_on)
152{
153	/* FIXME update D7 ... this way we can put the chip
154	 * into shutdown mode and read the manufacturer ID,
155	 * but we can't put it back into operational mode.
156	 */
157}
158
159/*
160 * getmiso:
161 * Why do we return 0 when the SIO line is high and vice-versa?
162 * The fact is, the lm70 eval board from NS (which this driver drives),
163 * is wired in just such a way : when the lm70's SIO goes high, a transistor
164 * switches it to low reflecting this on the parport (pin 13), and vice-versa.
165 */
166static inline int getmiso(struct spi_device *s)
167{
168	struct spi_lm70llp *pp = spidev_to_pp(s);
169	return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
170}
171/*--------------------------------------------------------------------*/
172
173#include "spi-bitbang-txrx.h"
174
175static void lm70_chipselect(struct spi_device *spi, int value)
176{
177	struct spi_lm70llp *pp = spidev_to_pp(spi);
178
179	if (value)
180		assertCS(pp);
181	else
182		deassertCS(pp);
183}
184
185/*
186 * Our actual bitbanger routine.
187 */
188static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
189{
190	return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
191}
192
193static void spi_lm70llp_attach(struct parport *p)
194{
195	struct pardevice	*pd;
196	struct spi_lm70llp	*pp;
197	struct spi_master	*master;
198	int			status;
199
200	if (lm70llp) {
201		printk(KERN_WARNING
202			"%s: spi_lm70llp instance already loaded. Aborting.\n",
203			DRVNAME);
204		return;
205	}
206
207	/* TODO:  this just _assumes_ a lm70 is there ... no probe;
208	 * the lm70 driver could verify it, reading the manf ID.
209	 */
210
211	master = spi_alloc_master(p->physport->dev, sizeof *pp);
212	if (!master) {
213		status = -ENOMEM;
214		goto out_fail;
215	}
216	pp = spi_master_get_devdata(master);
217
218	/*
219	 * SPI and bitbang hookup.
220	 */
221	pp->bitbang.master = master;
222	pp->bitbang.chipselect = lm70_chipselect;
223	pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
224	pp->bitbang.flags = SPI_3WIRE;
225
226	/*
227	 * Parport hookup
228	 */
229	pp->port = p;
230	pd = parport_register_device(p, DRVNAME,
231			NULL, NULL, NULL,
232			PARPORT_FLAG_EXCL, pp);
233	if (!pd) {
234		status = -ENOMEM;
235		goto out_free_master;
236	}
237	pp->pd = pd;
238
239	status = parport_claim(pd);
240	if (status < 0)
241		goto out_parport_unreg;
242
243	/*
244	 * Start SPI ...
245	 */
246	status = spi_bitbang_start(&pp->bitbang);
247	if (status < 0) {
248		printk(KERN_WARNING
249			"%s: spi_bitbang_start failed with status %d\n",
250			DRVNAME, status);
251		goto out_off_and_release;
252	}
253
254	/*
255	 * The modalias name MUST match the device_driver name
256	 * for the bus glue code to match and subsequently bind them.
257	 * We are binding to the generic drivers/hwmon/lm70.c device
258	 * driver.
259	 */
260	strcpy(pp->info.modalias, "lm70");
261	pp->info.max_speed_hz = 6 * 1000 * 1000;
262	pp->info.chip_select = 0;
263	pp->info.mode = SPI_3WIRE | SPI_MODE_0;
264
265	/* power up the chip, and let the LM70 control SI/SO */
266	parport_write_data(pp->port, lm70_INIT);
267
268	/* Enable access to our primary data structure via
269	 * the board info's (void *)controller_data.
270	 */
271	pp->info.controller_data = pp;
272	pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
273	if (pp->spidev_lm70)
274		dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
275				dev_name(&pp->spidev_lm70->dev));
276	else {
277		printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
278		status = -ENODEV;
279		goto out_bitbang_stop;
280	}
281	pp->spidev_lm70->bits_per_word = 8;
282
283	lm70llp = pp;
284	return;
285
286out_bitbang_stop:
287	spi_bitbang_stop(&pp->bitbang);
288out_off_and_release:
289	/* power down */
290	parport_write_data(pp->port, 0);
291	mdelay(10);
292	parport_release(pp->pd);
293out_parport_unreg:
294	parport_unregister_device(pd);
295out_free_master:
296	(void) spi_master_put(master);
297out_fail:
298	pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
299}
300
301static void spi_lm70llp_detach(struct parport *p)
302{
303	struct spi_lm70llp		*pp;
304
305	if (!lm70llp || lm70llp->port != p)
306		return;
307
308	pp = lm70llp;
309	spi_bitbang_stop(&pp->bitbang);
310
311	/* power down */
312	parport_write_data(pp->port, 0);
313
314	parport_release(pp->pd);
315	parport_unregister_device(pp->pd);
316
317	(void) spi_master_put(pp->bitbang.master);
318
319	lm70llp = NULL;
320}
321
322
323static struct parport_driver spi_lm70llp_drv = {
324	.name =		DRVNAME,
325	.attach =	spi_lm70llp_attach,
326	.detach =	spi_lm70llp_detach,
327};
328
329static int __init init_spi_lm70llp(void)
330{
331	return parport_register_driver(&spi_lm70llp_drv);
332}
333module_init(init_spi_lm70llp);
334
335static void __exit cleanup_spi_lm70llp(void)
336{
337	parport_unregister_driver(&spi_lm70llp_drv);
338}
339module_exit(cleanup_spi_lm70llp);
340
341MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
342MODULE_DESCRIPTION(
343	"Parport adapter for the National Semiconductor LM70 LLP eval board");
344MODULE_LICENSE("GPL");
345