1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * ATMEL I2C TPM AT97SC3204T
4 *
5 * Copyright (C) 2012 V Lab Technologies
6 *  Teddy Reed <teddy@prosauce.org>
7 * Copyright (C) 2013, Obsidian Research Corp.
8 *  Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
9 * Device driver for ATMEL I2C TPMs.
10 *
11 * Teddy Reed determined the basic I2C command flow, unlike other I2C TPM
12 * devices the raw TCG formatted TPM command data is written via I2C and then
13 * raw TCG formatted TPM command data is returned via I2C.
14 *
15 * TGC status/locality/etc functions seen in the LPC implementation do not
16 * seem to be present.
17 */
18#include <linux/init.h>
19#include <linux/module.h>
20#include <linux/moduleparam.h>
21#include <linux/slab.h>
22#include <linux/i2c.h>
23#include "tpm.h"
24
25#define I2C_DRIVER_NAME "tpm_i2c_atmel"
26
27#define TPM_I2C_SHORT_TIMEOUT  750     /* ms */
28#define TPM_I2C_LONG_TIMEOUT   2000    /* 2 sec */
29
30#define ATMEL_STS_OK 1
31
32struct priv_data {
33	size_t len;
34	/* This is the amount we read on the first try. 25 was chosen to fit a
35	 * fair number of read responses in the buffer so a 2nd retry can be
36	 * avoided in small message cases. */
37	u8 buffer[sizeof(struct tpm_header) + 25];
38};
39
40static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len)
41{
42	struct priv_data *priv = dev_get_drvdata(&chip->dev);
43	struct i2c_client *client = to_i2c_client(chip->dev.parent);
44	s32 status;
45
46	priv->len = 0;
47
48	if (len <= 2)
49		return -EIO;
50
51	status = i2c_master_send(client, buf, len);
52
53	dev_dbg(&chip->dev,
54		"%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__,
55		(int)min_t(size_t, 64, len), buf, len, status);
56
57	if (status < 0)
58		return status;
59
60	/* The upper layer does not support incomplete sends. */
61	if (status != len)
62		return -E2BIG;
63
64	return 0;
65}
66
67static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count)
68{
69	struct priv_data *priv = dev_get_drvdata(&chip->dev);
70	struct i2c_client *client = to_i2c_client(chip->dev.parent);
71	struct tpm_header *hdr = (struct tpm_header *)priv->buffer;
72	u32 expected_len;
73	int rc;
74
75	if (priv->len == 0)
76		return -EIO;
77
78	/* Get the message size from the message header, if we didn't get the
79	 * whole message in read_status then we need to re-read the
80	 * message. */
81	expected_len = be32_to_cpu(hdr->length);
82	if (expected_len > count)
83		return -ENOMEM;
84
85	if (priv->len >= expected_len) {
86		dev_dbg(&chip->dev,
87			"%s early(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
88			(int)min_t(size_t, 64, expected_len), buf, count,
89			expected_len);
90		memcpy(buf, priv->buffer, expected_len);
91		return expected_len;
92	}
93
94	rc = i2c_master_recv(client, buf, expected_len);
95	dev_dbg(&chip->dev,
96		"%s reread(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
97		(int)min_t(size_t, 64, expected_len), buf, count,
98		expected_len);
99	return rc;
100}
101
102static void i2c_atmel_cancel(struct tpm_chip *chip)
103{
104	dev_err(&chip->dev, "TPM operation cancellation was requested, but is not supported");
105}
106
107static u8 i2c_atmel_read_status(struct tpm_chip *chip)
108{
109	struct priv_data *priv = dev_get_drvdata(&chip->dev);
110	struct i2c_client *client = to_i2c_client(chip->dev.parent);
111	int rc;
112
113	/* The TPM fails the I2C read until it is ready, so we do the entire
114	 * transfer here and buffer it locally. This way the common code can
115	 * properly handle the timeouts. */
116	priv->len = 0;
117	memset(priv->buffer, 0, sizeof(priv->buffer));
118
119
120	/* Once the TPM has completed the command the command remains readable
121	 * until another command is issued. */
122	rc = i2c_master_recv(client, priv->buffer, sizeof(priv->buffer));
123	dev_dbg(&chip->dev,
124		"%s: sts=%d", __func__, rc);
125	if (rc <= 0)
126		return 0;
127
128	priv->len = rc;
129
130	return ATMEL_STS_OK;
131}
132
133static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
134{
135	return false;
136}
137
138static const struct tpm_class_ops i2c_atmel = {
139	.flags = TPM_OPS_AUTO_STARTUP,
140	.status = i2c_atmel_read_status,
141	.recv = i2c_atmel_recv,
142	.send = i2c_atmel_send,
143	.cancel = i2c_atmel_cancel,
144	.req_complete_mask = ATMEL_STS_OK,
145	.req_complete_val = ATMEL_STS_OK,
146	.req_canceled = i2c_atmel_req_canceled,
147};
148
149static int i2c_atmel_probe(struct i2c_client *client,
150			   const struct i2c_device_id *id)
151{
152	struct tpm_chip *chip;
153	struct device *dev = &client->dev;
154	struct priv_data *priv;
155
156	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
157		return -ENODEV;
158
159	chip = tpmm_chip_alloc(dev, &i2c_atmel);
160	if (IS_ERR(chip))
161		return PTR_ERR(chip);
162
163	priv = devm_kzalloc(dev, sizeof(struct priv_data), GFP_KERNEL);
164	if (!priv)
165		return -ENOMEM;
166
167	/* Default timeouts */
168	chip->timeout_a = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
169	chip->timeout_b = msecs_to_jiffies(TPM_I2C_LONG_TIMEOUT);
170	chip->timeout_c = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
171	chip->timeout_d = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
172
173	dev_set_drvdata(&chip->dev, priv);
174
175	/* There is no known way to probe for this device, and all version
176	 * information seems to be read via TPM commands. Thus we rely on the
177	 * TPM startup process in the common code to detect the device. */
178
179	return tpm_chip_register(chip);
180}
181
182static int i2c_atmel_remove(struct i2c_client *client)
183{
184	struct device *dev = &(client->dev);
185	struct tpm_chip *chip = dev_get_drvdata(dev);
186	tpm_chip_unregister(chip);
187	return 0;
188}
189
190static const struct i2c_device_id i2c_atmel_id[] = {
191	{I2C_DRIVER_NAME, 0},
192	{}
193};
194MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
195
196#ifdef CONFIG_OF
197static const struct of_device_id i2c_atmel_of_match[] = {
198	{.compatible = "atmel,at97sc3204t"},
199	{},
200};
201MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
202#endif
203
204static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
205
206static struct i2c_driver i2c_atmel_driver = {
207	.id_table = i2c_atmel_id,
208	.probe = i2c_atmel_probe,
209	.remove = i2c_atmel_remove,
210	.driver = {
211		.name = I2C_DRIVER_NAME,
212		.pm = &i2c_atmel_pm_ops,
213		.of_match_table = of_match_ptr(i2c_atmel_of_match),
214	},
215};
216
217module_i2c_driver(i2c_atmel_driver);
218
219MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
220MODULE_DESCRIPTION("Atmel TPM I2C Driver");
221MODULE_LICENSE("GPL");
222