summaryrefslogtreecommitdiff
path: root/drivers/bus/ts-nbus.c
blob: 38c886dc2ed6d211521523d4272121d0fceddd21 (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
362
363
364
365
366
// SPDX-License-Identifier: GPL-2.0-only
/*
 * NBUS driver for TS-4600 based boards
 *
 * Copyright (c) 2016 - Savoir-faire Linux
 * Author: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
 *
 * This driver implements a GPIOs bit-banged bus, called the NBUS by Technologic
 * Systems. It is used to communicate with the peripherals in the FPGA on the
 * TS-4600 SoM.
 */

#include <linux/bitops.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/ts-nbus.h>

#define TS_NBUS_DIRECTION_IN  0
#define TS_NBUS_DIRECTION_OUT 1
#define TS_NBUS_WRITE_ADR 0
#define TS_NBUS_WRITE_VAL 1

struct ts_nbus {
	struct pwm_device *pwm;
	struct gpio_descs *data;
	struct gpio_desc *csn;
	struct gpio_desc *txrx;
	struct gpio_desc *strobe;
	struct gpio_desc *ale;
	struct gpio_desc *rdy;
	struct mutex lock;
};

/*
 * request all gpios required by the bus.
 */
static int ts_nbus_init_pdata(struct platform_device *pdev, struct ts_nbus
		*ts_nbus)
{
	ts_nbus->data = devm_gpiod_get_array(&pdev->dev, "ts,data",
			GPIOD_OUT_HIGH);
	if (IS_ERR(ts_nbus->data)) {
		dev_err(&pdev->dev, "failed to retrieve ts,data-gpio from dts\n");
		return PTR_ERR(ts_nbus->data);
	}

	ts_nbus->csn = devm_gpiod_get(&pdev->dev, "ts,csn", GPIOD_OUT_HIGH);
	if (IS_ERR(ts_nbus->csn)) {
		dev_err(&pdev->dev, "failed to retrieve ts,csn-gpio from dts\n");
		return PTR_ERR(ts_nbus->csn);
	}

	ts_nbus->txrx = devm_gpiod_get(&pdev->dev, "ts,txrx", GPIOD_OUT_HIGH);
	if (IS_ERR(ts_nbus->txrx)) {
		dev_err(&pdev->dev, "failed to retrieve ts,txrx-gpio from dts\n");
		return PTR_ERR(ts_nbus->txrx);
	}

	ts_nbus->strobe = devm_gpiod_get(&pdev->dev, "ts,strobe", GPIOD_OUT_HIGH);
	if (IS_ERR(ts_nbus->strobe)) {
		dev_err(&pdev->dev, "failed to retrieve ts,strobe-gpio from dts\n");
		return PTR_ERR(ts_nbus->strobe);
	}

	ts_nbus->ale = devm_gpiod_get(&pdev->dev, "ts,ale", GPIOD_OUT_HIGH);
	if (IS_ERR(ts_nbus->ale)) {
		dev_err(&pdev->dev, "failed to retrieve ts,ale-gpio from dts\n");
		return PTR_ERR(ts_nbus->ale);
	}

	ts_nbus->rdy = devm_gpiod_get(&pdev->dev, "ts,rdy", GPIOD_IN);
	if (IS_ERR(ts_nbus->rdy)) {
		dev_err(&pdev->dev, "failed to retrieve ts,rdy-gpio from dts\n");
		return PTR_ERR(ts_nbus->rdy);
	}

	return 0;
}

/*
 * the data gpios are used for reading and writing values, their directions
 * should be adjusted accordingly.
 */
static void ts_nbus_set_direction(struct ts_nbus *ts_nbus, int direction)
{
	int i;

	for (i = 0; i < 8; i++) {
		if (direction == TS_NBUS_DIRECTION_IN)
			gpiod_direction_input(ts_nbus->data->desc[i]);
		else
			/* when used as output the default state of the data
			 * lines are set to high */
			gpiod_direction_output(ts_nbus->data->desc[i], 1);
	}
}

/*
 * reset the bus in its initial state.
 * The data, csn, strobe and ale lines must be zero'ed to let the FPGA knows a
 * new transaction can be process.
 */
static void ts_nbus_reset_bus(struct ts_nbus *ts_nbus)
{
	DECLARE_BITMAP(values, 8);

	values[0] = 0;

	gpiod_set_array_value_cansleep(8, ts_nbus->data->desc,
				       ts_nbus->data->info, values);
	gpiod_set_value_cansleep(ts_nbus->csn, 0);
	gpiod_set_value_cansleep(ts_nbus->strobe, 0);
	gpiod_set_value_cansleep(ts_nbus->ale, 0);
}

/*
 * let the FPGA knows it can process.
 */
static void ts_nbus_start_transaction(struct ts_nbus *ts_nbus)
{
	gpiod_set_value_cansleep(ts_nbus->strobe, 1);
}

/*
 * read a byte value from the data gpios.
 * return 0 on success or negative errno on failure.
 */
static int ts_nbus_read_byte(struct ts_nbus *ts_nbus, u8 *val)
{
	struct gpio_descs *gpios = ts_nbus->data;
	int ret, i;

	*val = 0;
	for (i = 0; i < 8; i++) {
		ret = gpiod_get_value_cansleep(gpios->desc[i]);
		if (ret < 0)
			return ret;
		if (ret)
			*val |= BIT(i);
	}

	return 0;
}

/*
 * set the data gpios accordingly to the byte value.
 */
static void ts_nbus_write_byte(struct ts_nbus *ts_nbus, u8 byte)
{
	struct gpio_descs *gpios = ts_nbus->data;
	DECLARE_BITMAP(values, 8);

	values[0] = byte;

	gpiod_set_array_value_cansleep(8, gpios->desc, gpios->info, values);
}

/*
 * reading the bus consists of resetting the bus, then notifying the FPGA to
 * send the data in the data gpios and return the read value.
 * return 0 on success or negative errno on failure.
 */
static int ts_nbus_read_bus(struct ts_nbus *ts_nbus, u8 *val)
{
	ts_nbus_reset_bus(ts_nbus);
	ts_nbus_start_transaction(ts_nbus);

	return ts_nbus_read_byte(ts_nbus, val);
}

/*
 * writing to the bus consists of resetting the bus, then define the type of
 * command (address/value), write the data and notify the FPGA to retrieve the
 * value in the data gpios.
 */
static void ts_nbus_write_bus(struct ts_nbus *ts_nbus, int cmd, u8 val)
{
	ts_nbus_reset_bus(ts_nbus);

	if (cmd == TS_NBUS_WRITE_ADR)
		gpiod_set_value_cansleep(ts_nbus->ale, 1);

	ts_nbus_write_byte(ts_nbus, val);
	ts_nbus_start_transaction(ts_nbus);
}

/*
 * read the value in the FPGA register at the given address.
 * return 0 on success or negative errno on failure.
 */
int ts_nbus_read(struct ts_nbus *ts_nbus, u8 adr, u16 *val)
{
	int ret, i;
	u8 byte;

	/* bus access must be atomic */
	mutex_lock(&ts_nbus->lock);

	/* set the bus in read mode */
	gpiod_set_value_cansleep(ts_nbus->txrx, 0);

	/* write address */
	ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);

	/* set the data gpios direction as input before reading */
	ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_IN);

	/* reading value MSB first */
	do {
		*val = 0;
		byte = 0;
		for (i = 1; i >= 0; i--) {
			/* read a byte from the bus, leave on error */
			ret = ts_nbus_read_bus(ts_nbus, &byte);
			if (ret < 0)
				goto err;

			/* append the byte read to the final value */
			*val |= byte << (i * 8);
		}
		gpiod_set_value_cansleep(ts_nbus->csn, 1);
		ret = gpiod_get_value_cansleep(ts_nbus->rdy);
	} while (ret);

err:
	/* restore the data gpios direction as output after reading */
	ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_OUT);

	mutex_unlock(&ts_nbus->lock);

	return ret;
}
EXPORT_SYMBOL_GPL(ts_nbus_read);

/*
 * write the desired value in the FPGA register at the given address.
 */
int ts_nbus_write(struct ts_nbus *ts_nbus, u8 adr, u16 val)
{
	int i;

	/* bus access must be atomic */
	mutex_lock(&ts_nbus->lock);

	/* set the bus in write mode */
	gpiod_set_value_cansleep(ts_nbus->txrx, 1);

	/* write address */
	ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);

	/* writing value MSB first */
	for (i = 1; i >= 0; i--)
		ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_VAL, (u8)(val >> (i * 8)));

	/* wait for completion */
	gpiod_set_value_cansleep(ts_nbus->csn, 1);
	while (gpiod_get_value_cansleep(ts_nbus->rdy) != 0) {
		gpiod_set_value_cansleep(ts_nbus->csn, 0);
		gpiod_set_value_cansleep(ts_nbus->csn, 1);
	}

	mutex_unlock(&ts_nbus->lock);

	return 0;
}
EXPORT_SYMBOL_GPL(ts_nbus_write);

static int ts_nbus_probe(struct platform_device *pdev)
{
	struct pwm_device *pwm;
	struct pwm_args pargs;
	struct device *dev = &pdev->dev;
	struct ts_nbus *ts_nbus;
	int ret;

	ts_nbus = devm_kzalloc(dev, sizeof(*ts_nbus), GFP_KERNEL);
	if (!ts_nbus)
		return -ENOMEM;

	mutex_init(&ts_nbus->lock);

	ret = ts_nbus_init_pdata(pdev, ts_nbus);
	if (ret < 0)
		return ret;

	pwm = devm_pwm_get(dev, NULL);
	if (IS_ERR(pwm)) {
		ret = PTR_ERR(pwm);
		if (ret != -EPROBE_DEFER)
			dev_err(dev, "unable to request PWM\n");
		return ret;
	}

	pwm_get_args(pwm, &pargs);
	if (!pargs.period) {
		dev_err(&pdev->dev, "invalid PWM period\n");
		return -EINVAL;
	}

	/*
	 * FIXME: pwm_apply_args() should be removed when switching to
	 * the atomic PWM API.
	 */
	pwm_apply_args(pwm);
	ret = pwm_config(pwm, pargs.period, pargs.period);
	if (ret < 0)
		return ret;

	/*
	 * we can now start the FPGA and populate the peripherals.
	 */
	pwm_enable(pwm);
	ts_nbus->pwm = pwm;

	/*
	 * let the child nodes retrieve this instance of the ts-nbus.
	 */
	dev_set_drvdata(dev, ts_nbus);

	ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
	if (ret < 0)
		return ret;

	dev_info(dev, "initialized\n");

	return 0;
}

static int ts_nbus_remove(struct platform_device *pdev)
{
	struct ts_nbus *ts_nbus = dev_get_drvdata(&pdev->dev);

	/* shutdown the FPGA */
	mutex_lock(&ts_nbus->lock);
	pwm_disable(ts_nbus->pwm);
	mutex_unlock(&ts_nbus->lock);

	return 0;
}

static const struct of_device_id ts_nbus_of_match[] = {
	{ .compatible = "technologic,ts-nbus", },
	{ },
};
MODULE_DEVICE_TABLE(of, ts_nbus_of_match);

static struct platform_driver ts_nbus_driver = {
	.probe		= ts_nbus_probe,
	.remove		= ts_nbus_remove,
	.driver		= {
		.name	= "ts_nbus",
		.of_match_table = ts_nbus_of_match,
	},
};

module_platform_driver(ts_nbus_driver);

MODULE_ALIAS("platform:ts_nbus");
MODULE_AUTHOR("Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>");
MODULE_DESCRIPTION("Technologic Systems NBUS");
MODULE_LICENSE("GPL v2");