summaryrefslogtreecommitdiffstats
path: root/drivers/i2c/busses/i2c-cros-ec-tunnel.c
blob: 8ca5cbbcec915072cfa8a8de4d9d8df7c708dd82 (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
/*
 *  Copyright (C) 2013 Google, Inc
 *
 *  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.
 *
 * Expose an I2C passthrough to the ChromeOS EC.
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/mfd/cros_ec.h>
#include <linux/mfd/cros_ec_commands.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#define I2C_MAX_RETRIES 3

/**
 * struct ec_i2c_device - Driver data for I2C tunnel
 *
 * @dev: Device node
 * @adap: I2C adapter
 * @ec: Pointer to EC device
 * @remote_bus: The EC bus number we tunnel to on the other side.
 * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
 * @response_buf: Buffer for receiving data; we expect most transfers to fit.
 */

struct ec_i2c_device {
	struct device *dev;
	struct i2c_adapter adap;
	struct cros_ec_device *ec;

	u16 remote_bus;

	u8 request_buf[256];
	u8 response_buf[256];
};

/**
 * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
 *
 * @i2c_msgs: The i2c messages to read
 * @num: The number of i2c messages.
 *
 * Returns the number of bytes the messages will take up.
 */
static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
{
	int i;
	int size;

	size = sizeof(struct ec_params_i2c_passthru);
	size += num * sizeof(struct ec_params_i2c_passthru_msg);
	for (i = 0; i < num; i++)
		if (!(i2c_msgs[i].flags & I2C_M_RD))
			size += i2c_msgs[i].len;

	return size;
}

/**
 * ec_i2c_construct_message - construct a message to go to the EC
 *
 * This function effectively stuffs the standard i2c_msg format of Linux into
 * a format that the EC understands.
 *
 * @buf: The buffer to fill.  We assume that the buffer is big enough.
 * @i2c_msgs: The i2c messages to read.
 * @num: The number of i2c messages.
 * @bus_num: The remote bus number we want to talk to.
 *
 * Returns 0 or a negative error number.
 */
static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
				    int num, u16 bus_num)
{
	struct ec_params_i2c_passthru *params;
	u8 *out_data;
	int i;

	out_data = buf + sizeof(struct ec_params_i2c_passthru) +
		   num * sizeof(struct ec_params_i2c_passthru_msg);

	params = (struct ec_params_i2c_passthru *)buf;
	params->port = bus_num;
	params->num_msgs = num;
	for (i = 0; i < num; i++) {
		const struct i2c_msg *i2c_msg = &i2c_msgs[i];
		struct ec_params_i2c_passthru_msg *msg = &params->msg[i];

		msg->len = i2c_msg->len;
		msg->addr_flags = i2c_msg->addr;

		if (i2c_msg->flags & I2C_M_TEN)
			msg->addr_flags |= EC_I2C_FLAG_10BIT;

		if (i2c_msg->flags & I2C_M_RD) {
			msg->addr_flags |= EC_I2C_FLAG_READ;
		} else {
			memcpy(out_data, i2c_msg->buf, msg->len);
			out_data += msg->len;
		}
	}

	return 0;
}

/**
 * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
 *
 * @i2c_msgs: The i2c messages to to fill up.
 * @num: The number of i2c messages expected.
 *
 * Returns the number of response bytes expeced.
 */
static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
{
	int size;
	int i;

	size = sizeof(struct ec_response_i2c_passthru);
	for (i = 0; i < num; i++)
		if (i2c_msgs[i].flags & I2C_M_RD)
			size += i2c_msgs[i].len;

	return size;
}

/**
 * ec_i2c_parse_response - Parse a response from the EC
 *
 * We'll take the EC's response and copy it back into msgs.
 *
 * @buf: The buffer to parse.
 * @i2c_msgs: The i2c messages to to fill up.
 * @num: The number of i2c messages; will be modified to include the actual
 *	 number received.
 *
 * Returns 0 or a negative error number.
 */
static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
				 int *num)
{
	const struct ec_response_i2c_passthru *resp;
	const u8 *in_data;
	int i;

	in_data = buf + sizeof(struct ec_response_i2c_passthru);

	resp = (const struct ec_response_i2c_passthru *)buf;
	if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
		return -ETIMEDOUT;
	else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
		return -EREMOTEIO;

	/* Other side could send us back fewer messages, but not more */
	if (resp->num_msgs > *num)
		return -EPROTO;
	*num = resp->num_msgs;

	for (i = 0; i < *num; i++) {
		struct i2c_msg *i2c_msg = &i2c_msgs[i];

		if (i2c_msgs[i].flags & I2C_M_RD) {
			memcpy(i2c_msg->buf, in_data, i2c_msg->len);
			in_data += i2c_msg->len;
		}
	}

	return 0;
}

static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
		       int num)
{
	struct ec_i2c_device *bus = adap->algo_data;
	struct device *dev = bus->dev;
	const u16 bus_num = bus->remote_bus;
	int request_len;
	int response_len;
	u8 *request = NULL;
	u8 *response = NULL;
	int result;
	struct cros_ec_command msg;

	request_len = ec_i2c_count_message(i2c_msgs, num);
	if (request_len < 0) {
		dev_warn(dev, "Error constructing message %d\n", request_len);
		result = request_len;
		goto exit;
	}
	response_len = ec_i2c_count_response(i2c_msgs, num);
	if (response_len < 0) {
		/* Unexpected; no errors should come when NULL response */
		dev_warn(dev, "Error preparing response %d\n", response_len);
		result = response_len;
		goto exit;
	}

	if (request_len <= ARRAY_SIZE(bus->request_buf)) {
		request = bus->request_buf;
	} else {
		request = kzalloc(request_len, GFP_KERNEL);
		if (request == NULL) {
			result = -ENOMEM;
			goto exit;
		}
	}
	if (response_len <= ARRAY_SIZE(bus->response_buf)) {
		response = bus->response_buf;
	} else {
		response = kzalloc(response_len, GFP_KERNEL);
		if (response == NULL) {
			result = -ENOMEM;
			goto exit;
		}
	}

	ec_i2c_construct_message(request, i2c_msgs, num, bus_num);

	msg.version = 0;
	msg.command = EC_CMD_I2C_PASSTHRU;
	msg.outdata = request;
	msg.outsize = request_len;
	msg.indata = response;
	msg.insize = response_len;

	result = cros_ec_cmd_xfer(bus->ec, &msg);
	if (result < 0)
		goto exit;

	result = ec_i2c_parse_response(response, i2c_msgs, &num);
	if (result < 0)
		goto exit;

	/* Indicate success by saying how many messages were sent */
	result = num;
exit:
	if (request != bus->request_buf)
		kfree(request);
	if (response != bus->response_buf)
		kfree(response);

	return result;
}

static u32 ec_i2c_functionality(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm ec_i2c_algorithm = {
	.master_xfer	= ec_i2c_xfer,
	.functionality	= ec_i2c_functionality,
};

static int ec_i2c_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
	struct device *dev = &pdev->dev;
	struct ec_i2c_device *bus = NULL;
	u32 remote_bus;
	int err;

	if (!ec->cmd_xfer) {
		dev_err(dev, "Missing sendrecv\n");
		return -EINVAL;
	}

	bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
	if (bus == NULL)
		return -ENOMEM;

	err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
	if (err) {
		dev_err(dev, "Couldn't read remote-bus property\n");
		return err;
	}
	bus->remote_bus = remote_bus;

	bus->ec = ec;
	bus->dev = dev;

	bus->adap.owner = THIS_MODULE;
	strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
	bus->adap.algo = &ec_i2c_algorithm;
	bus->adap.algo_data = bus;
	bus->adap.dev.parent = &pdev->dev;
	bus->adap.dev.of_node = np;
	bus->adap.retries = I2C_MAX_RETRIES;

	err = i2c_add_adapter(&bus->adap);
	if (err) {
		dev_err(dev, "cannot register i2c adapter\n");
		return err;
	}
	platform_set_drvdata(pdev, bus);

	return err;
}

static int ec_i2c_remove(struct platform_device *dev)
{
	struct ec_i2c_device *bus = platform_get_drvdata(dev);

	i2c_del_adapter(&bus->adap);

	return 0;
}

static struct platform_driver ec_i2c_tunnel_driver = {
	.probe = ec_i2c_probe,
	.remove = ec_i2c_remove,
	.driver = {
		.name = "cros-ec-i2c-tunnel",
	},
};

module_platform_driver(ec_i2c_tunnel_driver);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("EC I2C tunnel driver");
MODULE_ALIAS("platform:cros-ec-i2c-tunnel");