summaryrefslogtreecommitdiffstats
path: root/drivers/platform/chrome/cros_ec_uart.c
blob: 788246559bbba2556d6d980c670bc5edeaf03b30 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * UART interface for ChromeOS Embedded Controller
 *
 * Copyright 2020-2022 Google LLC.
 */

#include <linux/acpi.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_data/cros_ec_proto.h>
#include <linux/serdev.h>
#include <linux/slab.h>
#include <uapi/linux/sched/types.h>

#include "cros_ec.h"

/*
 * EC sends contiguous bytes of response packet on UART AP RX.
 * TTY driver in AP accumulates incoming bytes and calls the registered callback
 * function. Byte count can range from 1 to MAX bytes supported by EC.
 * This driver should wait for long time for all callbacks to be processed.
 * Considering the worst case scenario, wait for 500 msec. This timeout should
 * account for max latency and some additional guard time.
 * Best case: Entire packet is received in ~200 ms, wait queue will be released
 * and packet will be processed.
 * Worst case: TTY driver sends bytes in multiple callbacks. In this case this
 * driver will wait for ~1 sec beyond which it will timeout.
 * This timeout value should not exceed ~500 msec because in case if
 * EC_CMD_REBOOT_EC sent, high level driver should be able to intercept EC
 * in RO.
 */
#define EC_MSG_DEADLINE_MS		500

/**
 * struct response_info - Encapsulate EC response related
 *			information for passing between function
 *			cros_ec_uart_pkt_xfer() and cros_ec_uart_rx_bytes()
 *			callback.
 * @data:		Copy the data received from EC here.
 * @max_size:		Max size allocated for the @data buffer. If the
 *			received data exceeds this value, we log an error.
 * @size:		Actual size of data received from EC. This is also
 *			used to accumulate byte count with response is received
 *			in dma chunks.
 * @exp_len:		Expected bytes of response from EC including header.
 * @status:		Re-init to 0 before sending a cmd. Updated to 1 when
 *			a response is successfully received, or an error number
 *			on failure.
 * @wait_queue:	Wait queue EC response where the cros_ec sends request
 *			to EC and waits
 */
struct response_info {
	void *data;
	size_t max_size;
	size_t size;
	size_t exp_len;
	int status;
	wait_queue_head_t wait_queue;
};

/**
 * struct cros_ec_uart - information about a uart-connected EC
 *
 * @serdev:		serdev uart device we are connected to.
 * @baudrate:		UART baudrate of attached EC device.
 * @flowcontrol:	UART flowcontrol of attached device.
 * @irq:		Linux IRQ number of associated serial device.
 * @response:		Response info passing between cros_ec_uart_pkt_xfer()
 *			and cros_ec_uart_rx_bytes()
 */
struct cros_ec_uart {
	struct serdev_device *serdev;
	u32 baudrate;
	u8 flowcontrol;
	u32 irq;
	struct response_info response;
};

static int cros_ec_uart_rx_bytes(struct serdev_device *serdev,
				 const u8 *data,
				 size_t count)
{
	struct ec_host_response *host_response;
	struct cros_ec_device *ec_dev = serdev_device_get_drvdata(serdev);
	struct cros_ec_uart *ec_uart = ec_dev->priv;
	struct response_info *resp = &ec_uart->response;

	/* Check if bytes were sent out of band */
	if (!resp->data) {
		/* Discard all bytes */
		dev_warn(ec_dev->dev, "Bytes received out of band, dropping them.\n");
		return count;
	}

	/*
	 * Check if incoming bytes + resp->size is greater than allocated
	 * buffer in din by cros_ec. This will ensure that if EC sends more
	 * bytes than max_size, waiting process will be notified with an error.
	 */
	if (resp->size + count > resp->max_size) {
		resp->status = -EMSGSIZE;
		wake_up(&resp->wait_queue);
		return count;
	}

	memcpy(resp->data + resp->size, data, count);

	resp->size += count;

	/* Read data_len if we received response header and if exp_len was not read before. */
	if (resp->size >= sizeof(*host_response) && resp->exp_len == 0) {
		host_response = (struct ec_host_response *)resp->data;
		resp->exp_len = host_response->data_len + sizeof(*host_response);
	}

	/* If driver received response header and payload from EC, wake up the wait queue. */
	if (resp->size >= sizeof(*host_response) && resp->size == resp->exp_len) {
		resp->status = 1;
		wake_up(&resp->wait_queue);
	}

	return count;
}

static int cros_ec_uart_pkt_xfer(struct cros_ec_device *ec_dev,
				 struct cros_ec_command *ec_msg)
{
	struct cros_ec_uart *ec_uart = ec_dev->priv;
	struct serdev_device *serdev = ec_uart->serdev;
	struct response_info *resp = &ec_uart->response;
	struct ec_host_response *host_response;
	unsigned int len;
	int ret, i;
	u8 sum;

	len = cros_ec_prepare_tx(ec_dev, ec_msg);
	dev_dbg(ec_dev->dev, "Prepared len=%d\n", len);

	/* Setup for incoming response */
	resp->data = ec_dev->din;
	resp->max_size = ec_dev->din_size;
	resp->size = 0;
	resp->exp_len = 0;
	resp->status = 0;

	ret = serdev_device_write_buf(serdev, ec_dev->dout, len);
	if (ret < 0 || ret < len) {
		dev_err(ec_dev->dev, "Unable to write data\n");
		if (ret >= 0)
			ret = -EIO;
		goto exit;
	}

	ret = wait_event_timeout(resp->wait_queue, resp->status,
				 msecs_to_jiffies(EC_MSG_DEADLINE_MS));
	if (ret == 0) {
		dev_warn(ec_dev->dev, "Timed out waiting for response.\n");
		ret = -ETIMEDOUT;
		goto exit;
	}

	if (resp->status < 0) {
		ret = resp->status;
		dev_warn(ec_dev->dev, "Error response received: %d\n", ret);
		goto exit;
	}

	host_response = (struct ec_host_response *)ec_dev->din;
	ec_msg->result = host_response->result;

	if (host_response->data_len > ec_msg->insize) {
		dev_err(ec_dev->dev, "Resp too long (%d bytes, expected %d)\n",
			host_response->data_len, ec_msg->insize);
		ret = -ENOSPC;
		goto exit;
	}

	/* Validate checksum */
	sum = 0;
	for (i = 0; i < sizeof(*host_response) + host_response->data_len; i++)
		sum += ec_dev->din[i];

	if (sum) {
		dev_err(ec_dev->dev, "Bad packet checksum calculated %x\n", sum);
		ret = -EBADMSG;
		goto exit;
	}

	memcpy(ec_msg->data, ec_dev->din + sizeof(*host_response), host_response->data_len);

	ret = host_response->data_len;

exit:
	/* Invalidate response buffer to guard against out of band rx data */
	resp->data = NULL;

	if (ec_msg->command == EC_CMD_REBOOT_EC)
		msleep(EC_REBOOT_DELAY_MS);

	return ret;
}

static int cros_ec_uart_resource(struct acpi_resource *ares, void *data)
{
	struct cros_ec_uart *ec_uart = data;
	struct acpi_resource_uart_serialbus *sb = &ares->data.uart_serial_bus;

	if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS &&
	    sb->type == ACPI_RESOURCE_SERIAL_TYPE_UART) {
		ec_uart->baudrate = sb->default_baud_rate;
		dev_dbg(&ec_uart->serdev->dev, "Baudrate %d\n", ec_uart->baudrate);

		ec_uart->flowcontrol = sb->flow_control;
		dev_dbg(&ec_uart->serdev->dev, "Flow control %d\n", ec_uart->flowcontrol);
	}

	return 0;
}

static int cros_ec_uart_acpi_probe(struct cros_ec_uart *ec_uart)
{
	int ret;
	LIST_HEAD(resources);
	struct acpi_device *adev = ACPI_COMPANION(&ec_uart->serdev->dev);

	ret = acpi_dev_get_resources(adev, &resources, cros_ec_uart_resource, ec_uart);
	if (ret < 0)
		return ret;

	acpi_dev_free_resource_list(&resources);

	/* Retrieve GpioInt and translate it to Linux IRQ number */
	ret = acpi_dev_gpio_irq_get(adev, 0);
	if (ret < 0)
		return ret;

	ec_uart->irq = ret;
	dev_dbg(&ec_uart->serdev->dev, "IRQ number %d\n", ec_uart->irq);

	return 0;
}

static const struct serdev_device_ops cros_ec_uart_client_ops = {
	.receive_buf = cros_ec_uart_rx_bytes,
};

static int cros_ec_uart_probe(struct serdev_device *serdev)
{
	struct device *dev = &serdev->dev;
	struct cros_ec_device *ec_dev;
	struct cros_ec_uart *ec_uart;
	int ret;

	ec_uart = devm_kzalloc(dev, sizeof(*ec_uart), GFP_KERNEL);
	if (!ec_uart)
		return -ENOMEM;

	ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
	if (!ec_dev)
		return -ENOMEM;

	ret = devm_serdev_device_open(dev, serdev);
	if (ret) {
		dev_err(dev, "Unable to open UART device");
		return ret;
	}

	serdev_device_set_drvdata(serdev, ec_dev);
	init_waitqueue_head(&ec_uart->response.wait_queue);

	ec_uart->serdev = serdev;

	ret = cros_ec_uart_acpi_probe(ec_uart);
	if (ret < 0) {
		dev_err(dev, "Failed to get ACPI info (%d)", ret);
		return ret;
	}

	ret = serdev_device_set_baudrate(serdev, ec_uart->baudrate);
	if (ret < 0) {
		dev_err(dev, "Failed to set up host baud rate (%d)", ret);
		return ret;
	}

	serdev_device_set_flow_control(serdev, ec_uart->flowcontrol);

	/* Initialize ec_dev for cros_ec  */
	ec_dev->phys_name = dev_name(dev);
	ec_dev->dev = dev;
	ec_dev->priv = ec_uart;
	ec_dev->irq = ec_uart->irq;
	ec_dev->cmd_xfer = NULL;
	ec_dev->pkt_xfer = cros_ec_uart_pkt_xfer;
	ec_dev->din_size = sizeof(struct ec_host_response) +
			   sizeof(struct ec_response_get_protocol_info);
	ec_dev->dout_size = sizeof(struct ec_host_request);

	serdev_device_set_client_ops(serdev, &cros_ec_uart_client_ops);

	return cros_ec_register(ec_dev);
}

static void cros_ec_uart_remove(struct serdev_device *serdev)
{
	struct cros_ec_device *ec_dev = serdev_device_get_drvdata(serdev);

	cros_ec_unregister(ec_dev);
};

static int __maybe_unused cros_ec_uart_suspend(struct device *dev)
{
	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);

	return cros_ec_suspend(ec_dev);
}

static int __maybe_unused cros_ec_uart_resume(struct device *dev)
{
	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);

	return cros_ec_resume(ec_dev);
}

static SIMPLE_DEV_PM_OPS(cros_ec_uart_pm_ops, cros_ec_uart_suspend,
			 cros_ec_uart_resume);

static const struct of_device_id cros_ec_uart_of_match[] = {
	{ .compatible = "google,cros-ec-uart" },
	{}
};
MODULE_DEVICE_TABLE(of, cros_ec_uart_of_match);

#ifdef CONFIG_ACPI
static const struct acpi_device_id cros_ec_uart_acpi_id[] = {
	{ "GOOG0019", 0 },
	{}
};

MODULE_DEVICE_TABLE(acpi, cros_ec_uart_acpi_id);
#endif

static struct serdev_device_driver cros_ec_uart_driver = {
	.driver	= {
		.name	= "cros-ec-uart",
		.acpi_match_table = ACPI_PTR(cros_ec_uart_acpi_id),
		.of_match_table = cros_ec_uart_of_match,
		.pm	= &cros_ec_uart_pm_ops,
	},
	.probe		= cros_ec_uart_probe,
	.remove		= cros_ec_uart_remove,
};

module_serdev_device_driver(cros_ec_uart_driver);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("UART interface for ChromeOS Embedded Controller");
MODULE_AUTHOR("Bhanu Prakash Maiya <bhanumaiya@chromium.org>");