i2c-cros-ec-tunnel.c

  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
 27struct 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 */
 46static 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 */
 73static 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 */
115static 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 */
140static 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
174static 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;
227exit:
228	kfree(msg);
229	return result;
230}
231
232static u32 ec_i2c_functionality(struct i2c_adapter *adap)
233{
234	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
235}
236
237static const struct i2c_algorithm ec_i2c_algorithm = {
238	.xfer = ec_i2c_xfer,
239	.functionality = ec_i2c_functionality,
240};
241
242static 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)
251		return dev_err_probe(dev, -EPROBE_DEFER, "couldn't find parent EC device\n");
252
253	if (!ec->cmd_xfer) {
254		dev_err(dev, "Missing sendrecv\n");
255		return -EINVAL;
256	}
257
258	bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
259	if (bus == NULL)
260		return -ENOMEM;
261
262	err = device_property_read_u32(dev, "google,remote-bus", &remote_bus);
263	if (err) {
264		dev_err(dev, "Couldn't read remote-bus property\n");
265		return err;
266	}
267	bus->remote_bus = remote_bus;
268
269	bus->ec = ec;
270	bus->dev = dev;
271
272	bus->adap.owner = THIS_MODULE;
273	strscpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
274	bus->adap.algo = &ec_i2c_algorithm;
275	bus->adap.algo_data = bus;
276	bus->adap.dev.parent = &pdev->dev;
277	bus->adap.dev.of_node = pdev->dev.of_node;
278	bus->adap.retries = I2C_MAX_RETRIES;
279	ACPI_COMPANION_SET(&bus->adap.dev, ACPI_COMPANION(&pdev->dev));
280
281	err = i2c_add_adapter(&bus->adap);
282	if (err)
283		return err;
284	platform_set_drvdata(pdev, bus);
285
286	return err;
287}
288
289static void ec_i2c_remove(struct platform_device *dev)
290{
291	struct ec_i2c_device *bus = platform_get_drvdata(dev);
292
293	i2c_del_adapter(&bus->adap);
294}
295
296static const struct of_device_id cros_ec_i2c_of_match[] __maybe_unused = {
297	{ .compatible = "google,cros-ec-i2c-tunnel" },
298	{},
299};
300MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
301
302static const struct acpi_device_id cros_ec_i2c_tunnel_acpi_id[] __maybe_unused = {
303	{ "GOOG0012", 0 },
304	{ }
305};
306MODULE_DEVICE_TABLE(acpi, cros_ec_i2c_tunnel_acpi_id);
307
308static struct platform_driver ec_i2c_tunnel_driver = {
309	.probe = ec_i2c_probe,
310	.remove = ec_i2c_remove,
311	.driver = {
312		.name = "cros-ec-i2c-tunnel",
313		.acpi_match_table = ACPI_PTR(cros_ec_i2c_tunnel_acpi_id),
314		.of_match_table = of_match_ptr(cros_ec_i2c_of_match),
315	},
316};
317
318module_platform_driver(ec_i2c_tunnel_driver);
319
320MODULE_LICENSE("GPL");
321MODULE_DESCRIPTION("EC I2C tunnel driver");
322MODULE_ALIAS("platform:cros-ec-i2c-tunnel");