1/*
2 *  Copyright (C) 2013 Google, Inc
3 *
4 *  This program is free software; you can redistribute it and/or modify
5 *  it under the terms of the GNU General Public License as published by
6 *  the Free Software Foundation; either version 2 of the License, or
7 *  (at your option) any later version.
8 *
9 * Expose an I2C passthrough to the ChromeOS EC.
10 */
11
12#include <linux/module.h>
13#include <linux/i2c.h>
14#include <linux/mfd/cros_ec.h>
15#include <linux/mfd/cros_ec_commands.h>
16#include <linux/platform_device.h>
17#include <linux/slab.h>
18
19#define I2C_MAX_RETRIES 3
20
21/**
22 * struct ec_i2c_device - Driver data for I2C tunnel
23 *
24 * @dev: Device node
25 * @adap: I2C adapter
26 * @ec: Pointer to EC device
27 * @remote_bus: The EC bus number we tunnel to on the other side.
28 * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
29 * @response_buf: Buffer for receiving data; we expect most transfers to fit.
30 */
31
32struct ec_i2c_device {
33	struct device *dev;
34	struct i2c_adapter adap;
35	struct cros_ec_device *ec;
36
37	u16 remote_bus;
38
39	u8 request_buf[256];
40	u8 response_buf[256];
41};
42
43/**
44 * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
45 *
46 * @i2c_msgs: The i2c messages to read
47 * @num: The number of i2c messages.
48 *
49 * Returns the number of bytes the messages will take up.
50 */
51static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
52{
53	int i;
54	int size;
55
56	size = sizeof(struct ec_params_i2c_passthru);
57	size += num * sizeof(struct ec_params_i2c_passthru_msg);
58	for (i = 0; i < num; i++)
59		if (!(i2c_msgs[i].flags & I2C_M_RD))
60			size += i2c_msgs[i].len;
61
62	return size;
63}
64
65/**
66 * ec_i2c_construct_message - construct a message to go to the EC
67 *
68 * This function effectively stuffs the standard i2c_msg format of Linux into
69 * a format that the EC understands.
70 *
71 * @buf: The buffer to fill.  We assume that the buffer is big enough.
72 * @i2c_msgs: The i2c messages to read.
73 * @num: The number of i2c messages.
74 * @bus_num: The remote bus number we want to talk to.
75 *
76 * Returns 0 or a negative error number.
77 */
78static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
79				    int num, u16 bus_num)
80{
81	struct ec_params_i2c_passthru *params;
82	u8 *out_data;
83	int i;
84
85	out_data = buf + sizeof(struct ec_params_i2c_passthru) +
86		   num * sizeof(struct ec_params_i2c_passthru_msg);
87
88	params = (struct ec_params_i2c_passthru *)buf;
89	params->port = bus_num;
90	params->num_msgs = num;
91	for (i = 0; i < num; i++) {
92		const struct i2c_msg *i2c_msg = &i2c_msgs[i];
93		struct ec_params_i2c_passthru_msg *msg = &params->msg[i];
94
95		msg->len = i2c_msg->len;
96		msg->addr_flags = i2c_msg->addr;
97
98		if (i2c_msg->flags & I2C_M_TEN)
99			return -EINVAL;
100
101		if (i2c_msg->flags & I2C_M_RD) {
102			msg->addr_flags |= EC_I2C_FLAG_READ;
103		} else {
104			memcpy(out_data, i2c_msg->buf, msg->len);
105			out_data += msg->len;
106		}
107	}
108
109	return 0;
110}
111
112/**
113 * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
114 *
115 * @i2c_msgs: The i2c messages to to fill up.
116 * @num: The number of i2c messages expected.
117 *
118 * Returns the number of response bytes expeced.
119 */
120static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
121{
122	int size;
123	int i;
124
125	size = sizeof(struct ec_response_i2c_passthru);
126	for (i = 0; i < num; i++)
127		if (i2c_msgs[i].flags & I2C_M_RD)
128			size += i2c_msgs[i].len;
129
130	return size;
131}
132
133/**
134 * ec_i2c_parse_response - Parse a response from the EC
135 *
136 * We'll take the EC's response and copy it back into msgs.
137 *
138 * @buf: The buffer to parse.
139 * @i2c_msgs: The i2c messages to to fill up.
140 * @num: The number of i2c messages; will be modified to include the actual
141 *	 number received.
142 *
143 * Returns 0 or a negative error number.
144 */
145static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
146				 int *num)
147{
148	const struct ec_response_i2c_passthru *resp;
149	const u8 *in_data;
150	int i;
151
152	in_data = buf + sizeof(struct ec_response_i2c_passthru);
153
154	resp = (const struct ec_response_i2c_passthru *)buf;
155	if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
156		return -ETIMEDOUT;
157	else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
158		return -EREMOTEIO;
159
160	/* Other side could send us back fewer messages, but not more */
161	if (resp->num_msgs > *num)
162		return -EPROTO;
163	*num = resp->num_msgs;
164
165	for (i = 0; i < *num; i++) {
166		struct i2c_msg *i2c_msg = &i2c_msgs[i];
167
168		if (i2c_msgs[i].flags & I2C_M_RD) {
169			memcpy(i2c_msg->buf, in_data, i2c_msg->len);
170			in_data += i2c_msg->len;
171		}
172	}
173
174	return 0;
175}
176
177static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
178		       int num)
179{
180	struct ec_i2c_device *bus = adap->algo_data;
181	struct device *dev = bus->dev;
182	const u16 bus_num = bus->remote_bus;
183	int request_len;
184	int response_len;
185	int result;
186	struct cros_ec_command msg = { };
187
188	request_len = ec_i2c_count_message(i2c_msgs, num);
189	if (request_len < 0) {
190		dev_warn(dev, "Error constructing message %d\n", request_len);
191		return request_len;
192	}
193
194	response_len = ec_i2c_count_response(i2c_msgs, num);
195	if (response_len < 0) {
196		/* Unexpected; no errors should come when NULL response */
197		dev_warn(dev, "Error preparing response %d\n", response_len);
198		return response_len;
199	}
200
201	result = ec_i2c_construct_message(msg.outdata, i2c_msgs, num, bus_num);
202	if (result)
203		return result;
204
205	msg.version = 0;
206	msg.command = EC_CMD_I2C_PASSTHRU;
207	msg.outsize = request_len;
208	msg.insize = response_len;
209
210	result = cros_ec_cmd_xfer(bus->ec, &msg);
211	if (result < 0)
212		return result;
213
214	result = ec_i2c_parse_response(msg.indata, i2c_msgs, &num);
215	if (result < 0)
216		return result;
217
218	/* Indicate success by saying how many messages were sent */
219	return num;
220}
221
222static u32 ec_i2c_functionality(struct i2c_adapter *adap)
223{
224	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
225}
226
227static const struct i2c_algorithm ec_i2c_algorithm = {
228	.master_xfer	= ec_i2c_xfer,
229	.functionality	= ec_i2c_functionality,
230};
231
232static int ec_i2c_probe(struct platform_device *pdev)
233{
234	struct device_node *np = pdev->dev.of_node;
235	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
236	struct device *dev = &pdev->dev;
237	struct ec_i2c_device *bus = NULL;
238	u32 remote_bus;
239	int err;
240
241	if (!ec->cmd_xfer) {
242		dev_err(dev, "Missing sendrecv\n");
243		return -EINVAL;
244	}
245
246	bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
247	if (bus == NULL)
248		return -ENOMEM;
249
250	err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
251	if (err) {
252		dev_err(dev, "Couldn't read remote-bus property\n");
253		return err;
254	}
255	bus->remote_bus = remote_bus;
256
257	bus->ec = ec;
258	bus->dev = dev;
259
260	bus->adap.owner = THIS_MODULE;
261	strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
262	bus->adap.algo = &ec_i2c_algorithm;
263	bus->adap.algo_data = bus;
264	bus->adap.dev.parent = &pdev->dev;
265	bus->adap.dev.of_node = np;
266	bus->adap.retries = I2C_MAX_RETRIES;
267
268	err = i2c_add_adapter(&bus->adap);
269	if (err) {
270		dev_err(dev, "cannot register i2c adapter\n");
271		return err;
272	}
273	platform_set_drvdata(pdev, bus);
274
275	return err;
276}
277
278static int ec_i2c_remove(struct platform_device *dev)
279{
280	struct ec_i2c_device *bus = platform_get_drvdata(dev);
281
282	i2c_del_adapter(&bus->adap);
283
284	return 0;
285}
286
287#ifdef CONFIG_OF
288static const struct of_device_id cros_ec_i2c_of_match[] = {
289	{ .compatible = "google,cros-ec-i2c-tunnel" },
290	{},
291};
292MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
293#endif
294
295static struct platform_driver ec_i2c_tunnel_driver = {
296	.probe = ec_i2c_probe,
297	.remove = ec_i2c_remove,
298	.driver = {
299		.name = "cros-ec-i2c-tunnel",
300		.of_match_table = of_match_ptr(cros_ec_i2c_of_match),
301	},
302};
303
304module_platform_driver(ec_i2c_tunnel_driver);
305
306MODULE_LICENSE("GPL");
307MODULE_DESCRIPTION("EC I2C tunnel driver");
308MODULE_ALIAS("platform:cros-ec-i2c-tunnel");
309