summaryrefslogtreecommitdiff
path: root/drivers/i2c/i2c-gpio.c
blob: cfdeadc752cd32be66888400996d1113b0a9b10f (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
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
/*
 * (C) Copyright 2015, Samsung Electronics
 * Przemyslaw Marczak <p.marczak@samsung.com>
 *
 * This file is based on: drivers/i2c/soft-i2c.c,
 * with added driver-model support and code cleanup.
 */
#include <common.h>
#include <errno.h>
#include <dm.h>
#include <i2c.h>
#include <log.h>
#include <asm/gpio.h>
#include <linux/delay.h>

#define DEFAULT_UDELAY	5
#define RETRIES		0
#define I2C_ACK		0
#define I2C_NOACK	1

DECLARE_GLOBAL_DATA_PTR;

enum {
	PIN_SDA = 0,
	PIN_SCL,
	PIN_COUNT,
};

struct i2c_gpio_bus {
	/**
	  * udelay - delay [us] between GPIO toggle operations,
	  * which is 1/4 of I2C speed clock period.
	 */
	int udelay;
	 /* sda, scl */
	struct gpio_desc gpios[PIN_COUNT];

	int (*get_sda)(struct i2c_gpio_bus *bus);
	void (*set_sda)(struct i2c_gpio_bus *bus, int bit);
	void (*set_scl)(struct i2c_gpio_bus *bus, int bit);
};

static int i2c_gpio_sda_get(struct i2c_gpio_bus *bus)
{
	struct gpio_desc *sda = &bus->gpios[PIN_SDA];

	return dm_gpio_get_value(sda);
}

static void i2c_gpio_sda_set(struct i2c_gpio_bus *bus, int bit)
{
	struct gpio_desc *sda = &bus->gpios[PIN_SDA];

	if (bit)
		dm_gpio_set_dir_flags(sda, GPIOD_IS_IN);
	else
		dm_gpio_set_dir_flags(sda, GPIOD_IS_OUT);
}

static void i2c_gpio_scl_set(struct i2c_gpio_bus *bus, int bit)
{
	struct gpio_desc *scl = &bus->gpios[PIN_SCL];
	int count = 0;

	if (bit) {
		dm_gpio_set_dir_flags(scl, GPIOD_IS_IN);
		while (!dm_gpio_get_value(scl) && count++ < 100000)
			udelay(1);

		if (!dm_gpio_get_value(scl))
			pr_err("timeout waiting on slave to release scl\n");
	} else {
		dm_gpio_set_dir_flags(scl, GPIOD_IS_OUT);
	}
}

/* variant for output only gpios which cannot support clock stretching */
static void i2c_gpio_scl_set_output_only(struct i2c_gpio_bus *bus, int bit)
{
	struct gpio_desc *scl = &bus->gpios[PIN_SCL];
	ulong flags = GPIOD_IS_OUT;

	if (bit)
		flags |= GPIOD_IS_OUT_ACTIVE;
	dm_gpio_set_dir_flags(scl, flags);
}

static void i2c_gpio_write_bit(struct i2c_gpio_bus *bus, int delay, uchar bit)
{
	bus->set_scl(bus, 0);
	udelay(delay);
	bus->set_sda(bus, bit);
	udelay(delay);
	bus->set_scl(bus, 1);
	udelay(2 * delay);
}

static int i2c_gpio_read_bit(struct i2c_gpio_bus *bus, int delay)
{
	int value;

	bus->set_scl(bus, 1);
	udelay(delay);
	value = bus->get_sda(bus);
	udelay(delay);
	bus->set_scl(bus, 0);
	udelay(2 * delay);

	return value;
}

/* START: High -> Low on SDA while SCL is High */
static void i2c_gpio_send_start(struct i2c_gpio_bus *bus, int delay)
{
	udelay(delay);
	bus->set_sda(bus, 1);
	udelay(delay);
	bus->set_scl(bus, 1);
	udelay(delay);
	bus->set_sda(bus, 0);
	udelay(delay);
}

/* STOP: Low -> High on SDA while SCL is High */
static void i2c_gpio_send_stop(struct i2c_gpio_bus *bus, int delay)
{
	bus->set_scl(bus, 0);
	udelay(delay);
	bus->set_sda(bus, 0);
	udelay(delay);
	bus->set_scl(bus, 1);
	udelay(delay);
	bus->set_sda(bus, 1);
	udelay(delay);
}

/* ack should be I2C_ACK or I2C_NOACK */
static void i2c_gpio_send_ack(struct i2c_gpio_bus *bus, int delay, int ack)
{
	i2c_gpio_write_bit(bus, delay, ack);
	bus->set_scl(bus, 0);
	udelay(delay);
}

/**
 * Send a reset sequence consisting of 9 clocks with the data signal high
 * to clock any confused device back into an idle state.  Also send a
 * <stop> at the end of the sequence for belts & suspenders.
 */
static void i2c_gpio_send_reset(struct i2c_gpio_bus *bus, int delay)
{
	int j;

	for (j = 0; j < 9; j++)
		i2c_gpio_write_bit(bus, delay, 1);

	i2c_gpio_send_stop(bus, delay);
}

/* Set sda high with low clock, before reading slave data */
static void i2c_gpio_sda_high(struct i2c_gpio_bus *bus, int delay)
{
	bus->set_scl(bus, 0);
	udelay(delay);
	bus->set_sda(bus, 1);
	udelay(delay);
}

/* Send 8 bits and look for an acknowledgement */
static int i2c_gpio_write_byte(struct i2c_gpio_bus *bus, int delay, uchar data)
{
	int j;
	int nack;

	for (j = 0; j < 8; j++) {
		i2c_gpio_write_bit(bus, delay, data & 0x80);
		data <<= 1;
	}

	udelay(delay);

	/* Look for an <ACK>(negative logic) and return it */
	i2c_gpio_sda_high(bus, delay);
	nack = i2c_gpio_read_bit(bus, delay);

	return nack;	/* not a nack is an ack */
}

/**
 * if ack == I2C_ACK, ACK the byte so can continue reading, else
 * send I2C_NOACK to end the read.
 */
static uchar i2c_gpio_read_byte(struct i2c_gpio_bus *bus, int delay, int ack)
{
	int  data;
	int  j;

	i2c_gpio_sda_high(bus, delay);
	data = 0;
	for (j = 0; j < 8; j++) {
		data <<= 1;
		data |= i2c_gpio_read_bit(bus, delay);
	}
	i2c_gpio_send_ack(bus, delay, ack);

	return data;
}

/* send start and the slave chip address */
int i2c_send_slave_addr(struct i2c_gpio_bus *bus, int delay, uchar chip)
{
	i2c_gpio_send_start(bus, delay);

	if (i2c_gpio_write_byte(bus, delay, chip)) {
		i2c_gpio_send_stop(bus, delay);
		return -EIO;
	}

	return 0;
}

static int i2c_gpio_write_data(struct i2c_gpio_bus *bus, uchar chip,
			       uchar *buffer, int len,
			       bool end_with_repeated_start)
{
	unsigned int delay = bus->udelay;
	int failures = 0;

	debug("%s: chip %x buffer %p len %d\n", __func__, chip, buffer, len);

	if (i2c_send_slave_addr(bus, delay, chip << 1)) {
		debug("i2c_write, no chip responded %02X\n", chip);
		return -EIO;
	}

	while (len-- > 0) {
		if (i2c_gpio_write_byte(bus, delay, *buffer++))
			failures++;
	}

	if (!end_with_repeated_start) {
		i2c_gpio_send_stop(bus, delay);
		return failures;
	}

	if (i2c_send_slave_addr(bus, delay, (chip << 1) | 0x1)) {
		debug("i2c_write, no chip responded %02X\n", chip);
		return -EIO;
	}

	return failures;
}

static int i2c_gpio_read_data(struct i2c_gpio_bus *bus, uchar chip,
			      uchar *buffer, int len)
{
	unsigned int delay = bus->udelay;

	debug("%s: chip %x buffer: %p len %d\n", __func__, chip, buffer, len);

	while (len-- > 0)
		*buffer++ = i2c_gpio_read_byte(bus, delay, len == 0);

	i2c_gpio_send_stop(bus, delay);

	return 0;
}

static int i2c_gpio_xfer(struct udevice *dev, struct i2c_msg *msg, int nmsgs)
{
	struct i2c_gpio_bus *bus = dev_get_priv(dev);
	int ret;

	for (; nmsgs > 0; nmsgs--, msg++) {
		bool next_is_read = nmsgs > 1 && (msg[1].flags & I2C_M_RD);

		if (msg->flags & I2C_M_RD) {
			ret = i2c_gpio_read_data(bus, msg->addr, msg->buf,
						 msg->len);
		} else {
			ret = i2c_gpio_write_data(bus, msg->addr, msg->buf,
						  msg->len, next_is_read);
		}

		if (ret)
			return -EREMOTEIO;
	}

	return 0;
}

static int i2c_gpio_probe(struct udevice *dev, uint chip, uint chip_flags)
{
	struct i2c_gpio_bus *bus = dev_get_priv(dev);
	unsigned int delay = bus->udelay;
	int ret;

	i2c_gpio_send_start(bus, delay);
	ret = i2c_gpio_write_byte(bus, delay, (chip << 1) | 0);
	i2c_gpio_send_stop(bus, delay);

	debug("%s: bus: %d (%s) chip: %x flags: %x ret: %d\n",
	      __func__, dev->seq, dev->name, chip, chip_flags, ret);

	return ret;
}

static int i2c_gpio_set_bus_speed(struct udevice *dev, unsigned int speed_hz)
{
	struct i2c_gpio_bus *bus = dev_get_priv(dev);

	bus->udelay = 1000000 / (speed_hz << 2);

	i2c_gpio_send_reset(bus, bus->udelay);

	return 0;
}

static int i2c_gpio_drv_probe(struct udevice *dev)
{
	if (dev_read_bool(dev, "i2c-gpio,deblock")) {
		/* @200kHz 9 clocks = 44us, 62us is ok */
		const unsigned int DELAY_ABORT_SEQ = 62;
		struct i2c_gpio_bus *bus = dev_get_priv(dev);

		return i2c_deblock_gpio_loop(&bus->gpios[PIN_SDA],
					     &bus->gpios[PIN_SCL],
					     16, 5, DELAY_ABORT_SEQ);
	}

	return 0;
}

static int i2c_gpio_ofdata_to_platdata(struct udevice *dev)
{
	struct i2c_gpio_bus *bus = dev_get_priv(dev);
	const void *blob = gd->fdt_blob;
	int node = dev_of_offset(dev);
	int ret;

	ret = gpio_request_list_by_name(dev, "gpios", bus->gpios,
					ARRAY_SIZE(bus->gpios), 0);
	if (ret < 0)
		goto error;

	bus->udelay = fdtdec_get_int(blob, node, "i2c-gpio,delay-us",
				     DEFAULT_UDELAY);

	bus->get_sda = i2c_gpio_sda_get;
	bus->set_sda = i2c_gpio_sda_set;
	if (fdtdec_get_bool(blob, node, "i2c-gpio,scl-output-only"))
		bus->set_scl = i2c_gpio_scl_set_output_only;
	else
		bus->set_scl = i2c_gpio_scl_set;

	return 0;
error:
	pr_err("Can't get %s gpios! Error: %d", dev->name, ret);
	return ret;
}

static const struct dm_i2c_ops i2c_gpio_ops = {
	.xfer		= i2c_gpio_xfer,
	.probe_chip	= i2c_gpio_probe,
	.set_bus_speed	= i2c_gpio_set_bus_speed,
};

static const struct udevice_id i2c_gpio_ids[] = {
	{ .compatible = "i2c-gpio" },
	{ }
};

U_BOOT_DRIVER(i2c_gpio) = {
	.name	= "i2c-gpio",
	.id	= UCLASS_I2C,
	.of_match = i2c_gpio_ids,
	.probe	= i2c_gpio_drv_probe,
	.ofdata_to_platdata = i2c_gpio_ofdata_to_platdata,
	.priv_auto_alloc_size = sizeof(struct i2c_gpio_bus),
	.ops	= &i2c_gpio_ops,
};