1 // SPDX-License-Identifier: GPL-2.0+
2 // Expose an I2C passthrough to the ChromeOS EC.
3 //
4 // Copyright (C) 2013 Google, Inc.
5 
6 #include <linux/acpi.h>
7 #include <linux/module.h>
8 #include <linux/i2c.h>
9 #include <linux/platform_data/cros_ec_commands.h>
10 #include <linux/platform_data/cros_ec_proto.h>
11 #include <linux/platform_device.h>
12 #include <linux/slab.h>
13 
14 #define I2C_MAX_RETRIES 3
15 
16 /**
17  * struct ec_i2c_device - Driver data for I2C tunnel
18  *
19  * @dev: Device node
20  * @adap: I2C adapter
21  * @ec: Pointer to EC device
22  * @remote_bus: The EC bus number we tunnel to on the other side.
23  * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
24  * @response_buf: Buffer for receiving data; we expect most transfers to fit.
25  */
26 
27 struct ec_i2c_device {
28 	struct device *dev;
29 	struct i2c_adapter adap;
30 	struct cros_ec_device *ec;
31 
32 	u16 remote_bus;
33 
34 	u8 request_buf[256];
35 	u8 response_buf[256];
36 };
37 
38 /**
39  * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
40  *
41  * @i2c_msgs: The i2c messages to read
42  * @num: The number of i2c messages.
43  *
44  * Returns the number of bytes the messages will take up.
45  */
46 static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
47 {
48 	int i;
49 	int size;
50 
51 	size = sizeof(struct ec_params_i2c_passthru);
52 	size += num * sizeof(struct ec_params_i2c_passthru_msg);
53 	for (i = 0; i < num; i++)
54 		if (!(i2c_msgs[i].flags & I2C_M_RD))
55 			size += i2c_msgs[i].len;
56 
57 	return size;
58 }
59 
60 /**
61  * ec_i2c_construct_message - construct a message to go to the EC
62  *
63  * This function effectively stuffs the standard i2c_msg format of Linux into
64  * a format that the EC understands.
65  *
66  * @buf: The buffer to fill.  We assume that the buffer is big enough.
67  * @i2c_msgs: The i2c messages to read.
68  * @num: The number of i2c messages.
69  * @bus_num: The remote bus number we want to talk to.
70  *
71  * Returns 0 or a negative error number.
72  */
73 static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
74 				    int num, u16 bus_num)
75 {
76 	struct ec_params_i2c_passthru *params;
77 	u8 *out_data;
78 	int i;
79 
80 	out_data = buf + sizeof(struct ec_params_i2c_passthru) +
81 		   num * sizeof(struct ec_params_i2c_passthru_msg);
82 
83 	params = (struct ec_params_i2c_passthru *)buf;
84 	params->port = bus_num;
85 	params->num_msgs = num;
86 	for (i = 0; i < num; i++) {
87 		const struct i2c_msg *i2c_msg = &i2c_msgs[i];
88 		struct ec_params_i2c_passthru_msg *msg = &params->msg[i];
89 
90 		msg->len = i2c_msg->len;
91 		msg->addr_flags = i2c_msg->addr;
92 
93 		if (i2c_msg->flags & I2C_M_TEN)
94 			return -EINVAL;
95 
96 		if (i2c_msg->flags & I2C_M_RD) {
97 			msg->addr_flags |= EC_I2C_FLAG_READ;
98 		} else {
99 			memcpy(out_data, i2c_msg->buf, msg->len);
100 			out_data += msg->len;
101 		}
102 	}
103 
104 	return 0;
105 }
106 
107 /**
108  * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
109  *
110  * @i2c_msgs: The i2c messages to fill up.
111  * @num: The number of i2c messages expected.
112  *
113  * Returns the number of response bytes expeced.
114  */
115 static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
116 {
117 	int size;
118 	int i;
119 
120 	size = sizeof(struct ec_response_i2c_passthru);
121 	for (i = 0; i < num; i++)
122 		if (i2c_msgs[i].flags & I2C_M_RD)
123 			size += i2c_msgs[i].len;
124 
125 	return size;
126 }
127 
128 /**
129  * ec_i2c_parse_response - Parse a response from the EC
130  *
131  * We'll take the EC's response and copy it back into msgs.
132  *
133  * @buf: The buffer to parse.
134  * @i2c_msgs: The i2c messages to fill up.
135  * @num: The number of i2c messages; will be modified to include the actual
136  *	 number received.
137  *
138  * Returns 0 or a negative error number.
139  */
140 static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
141 				 int *num)
142 {
143 	const struct ec_response_i2c_passthru *resp;
144 	const u8 *in_data;
145 	int i;
146 
147 	in_data = buf + sizeof(struct ec_response_i2c_passthru);
148 
149 	resp = (const struct ec_response_i2c_passthru *)buf;
150 	if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
151 		return -ETIMEDOUT;
152 	else if (resp->i2c_status & EC_I2C_STATUS_NAK)
153 		return -ENXIO;
154 	else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
155 		return -EIO;
156 
157 	/* Other side could send us back fewer messages, but not more */
158 	if (resp->num_msgs > *num)
159 		return -EPROTO;
160 	*num = resp->num_msgs;
161 
162 	for (i = 0; i < *num; i++) {
163 		struct i2c_msg *i2c_msg = &i2c_msgs[i];
164 
165 		if (i2c_msgs[i].flags & I2C_M_RD) {
166 			memcpy(i2c_msg->buf, in_data, i2c_msg->len);
167 			in_data += i2c_msg->len;
168 		}
169 	}
170 
171 	return 0;
172 }
173 
174 static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
175 		       int num)
176 {
177 	struct ec_i2c_device *bus = adap->algo_data;
178 	struct device *dev = bus->dev;
179 	const u16 bus_num = bus->remote_bus;
180 	int request_len;
181 	int response_len;
182 	int alloc_size;
183 	int result;
184 	struct cros_ec_command *msg;
185 
186 	request_len = ec_i2c_count_message(i2c_msgs, num);
187 	if (request_len < 0) {
188 		dev_warn(dev, "Error constructing message %d\n", request_len);
189 		return request_len;
190 	}
191 
192 	response_len = ec_i2c_count_response(i2c_msgs, num);
193 	if (response_len < 0) {
194 		/* Unexpected; no errors should come when NULL response */
195 		dev_warn(dev, "Error preparing response %d\n", response_len);
196 		return response_len;
197 	}
198 
199 	alloc_size = max(request_len, response_len);
200 	msg = kmalloc(sizeof(*msg) + alloc_size, GFP_KERNEL);
201 	if (!msg)
202 		return -ENOMEM;
203 
204 	result = ec_i2c_construct_message(msg->data, i2c_msgs, num, bus_num);
205 	if (result) {
206 		dev_err(dev, "Error constructing EC i2c message %d\n", result);
207 		goto exit;
208 	}
209 
210 	msg->version = 0;
211 	msg->command = EC_CMD_I2C_PASSTHRU;
212 	msg->outsize = request_len;
213 	msg->insize = response_len;
214 
215 	result = cros_ec_cmd_xfer_status(bus->ec, msg);
216 	if (result < 0) {
217 		dev_err(dev, "Error transferring EC i2c message %d\n", result);
218 		goto exit;
219 	}
220 
221 	result = ec_i2c_parse_response(msg->data, i2c_msgs, &num);
222 	if (result < 0)
223 		goto exit;
224 
225 	/* Indicate success by saying how many messages were sent */
226 	result = num;
227 exit:
228 	kfree(msg);
229 	return result;
230 }
231 
232 static u32 ec_i2c_functionality(struct i2c_adapter *adap)
233 {
234 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
235 }
236 
237 static const struct i2c_algorithm ec_i2c_algorithm = {
238 	.master_xfer	= ec_i2c_xfer,
239 	.functionality	= ec_i2c_functionality,
240 };
241 
242 static int ec_i2c_probe(struct platform_device *pdev)
243 {
244 	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
245 	struct device *dev = &pdev->dev;
246 	struct ec_i2c_device *bus = NULL;
247 	u32 remote_bus;
248 	int err;
249 
250 	if (!ec->cmd_xfer) {
251 		dev_err(dev, "Missing sendrecv\n");
252 		return -EINVAL;
253 	}
254 
255 	bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
256 	if (bus == NULL)
257 		return -ENOMEM;
258 
259 	err = device_property_read_u32(dev, "google,remote-bus", &remote_bus);
260 	if (err) {
261 		dev_err(dev, "Couldn't read remote-bus property\n");
262 		return err;
263 	}
264 	bus->remote_bus = remote_bus;
265 
266 	bus->ec = ec;
267 	bus->dev = dev;
268 
269 	bus->adap.owner = THIS_MODULE;
270 	strscpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
271 	bus->adap.algo = &ec_i2c_algorithm;
272 	bus->adap.algo_data = bus;
273 	bus->adap.dev.parent = &pdev->dev;
274 	bus->adap.dev.of_node = pdev->dev.of_node;
275 	bus->adap.retries = I2C_MAX_RETRIES;
276 	ACPI_COMPANION_SET(&bus->adap.dev, ACPI_COMPANION(&pdev->dev));
277 
278 	err = i2c_add_adapter(&bus->adap);
279 	if (err)
280 		return err;
281 	platform_set_drvdata(pdev, bus);
282 
283 	return err;
284 }
285 
286 static void ec_i2c_remove(struct platform_device *dev)
287 {
288 	struct ec_i2c_device *bus = platform_get_drvdata(dev);
289 
290 	i2c_del_adapter(&bus->adap);
291 }
292 
293 static const struct of_device_id cros_ec_i2c_of_match[] __maybe_unused = {
294 	{ .compatible = "google,cros-ec-i2c-tunnel" },
295 	{},
296 };
297 MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
298 
299 static const struct acpi_device_id cros_ec_i2c_tunnel_acpi_id[] __maybe_unused = {
300 	{ "GOOG0012", 0 },
301 	{ }
302 };
303 MODULE_DEVICE_TABLE(acpi, cros_ec_i2c_tunnel_acpi_id);
304 
305 static struct platform_driver ec_i2c_tunnel_driver = {
306 	.probe = ec_i2c_probe,
307 	.remove_new = ec_i2c_remove,
308 	.driver = {
309 		.name = "cros-ec-i2c-tunnel",
310 		.acpi_match_table = ACPI_PTR(cros_ec_i2c_tunnel_acpi_id),
311 		.of_match_table = of_match_ptr(cros_ec_i2c_of_match),
312 	},
313 };
314 
315 module_platform_driver(ec_i2c_tunnel_driver);
316 
317 MODULE_LICENSE("GPL");
318 MODULE_DESCRIPTION("EC I2C tunnel driver");
319 MODULE_ALIAS("platform:cros-ec-i2c-tunnel");
320