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
32 struct 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
i2c_atmel_send(struct tpm_chip * chip,u8 * buf,size_t bufsiz,size_t len)40 static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz,
41 size_t len)
42 {
43 struct priv_data *priv = dev_get_drvdata(&chip->dev);
44 struct i2c_client *client = to_i2c_client(chip->dev.parent);
45 s32 status;
46
47 priv->len = 0;
48
49 if (len <= 2)
50 return -EIO;
51
52 status = i2c_master_send(client, buf, len);
53
54 dev_dbg(&chip->dev,
55 "%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__,
56 (int)min_t(size_t, 64, len), buf, len, status);
57
58 if (status < 0)
59 return status;
60
61 /* The upper layer does not support incomplete sends. */
62 if (status != len)
63 return -E2BIG;
64
65 return 0;
66 }
67
i2c_atmel_recv(struct tpm_chip * chip,u8 * buf,size_t count)68 static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count)
69 {
70 struct priv_data *priv = dev_get_drvdata(&chip->dev);
71 struct i2c_client *client = to_i2c_client(chip->dev.parent);
72 struct tpm_header *hdr = (struct tpm_header *)priv->buffer;
73 u32 expected_len;
74 int rc;
75
76 if (priv->len == 0)
77 return -EIO;
78
79 /* Get the message size from the message header, if we didn't get the
80 * whole message in read_status then we need to re-read the
81 * message. */
82 expected_len = be32_to_cpu(hdr->length);
83 if (expected_len > count)
84 return -ENOMEM;
85
86 if (priv->len >= expected_len) {
87 dev_dbg(&chip->dev,
88 "%s early(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
89 (int)min_t(size_t, 64, expected_len), buf, count,
90 expected_len);
91 memcpy(buf, priv->buffer, expected_len);
92 return expected_len;
93 }
94
95 rc = i2c_master_recv(client, buf, expected_len);
96 dev_dbg(&chip->dev,
97 "%s reread(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
98 (int)min_t(size_t, 64, expected_len), buf, count,
99 expected_len);
100 return rc;
101 }
102
i2c_atmel_cancel(struct tpm_chip * chip)103 static void i2c_atmel_cancel(struct tpm_chip *chip)
104 {
105 dev_err(&chip->dev, "TPM operation cancellation was requested, but is not supported");
106 }
107
i2c_atmel_read_status(struct tpm_chip * chip)108 static u8 i2c_atmel_read_status(struct tpm_chip *chip)
109 {
110 struct priv_data *priv = dev_get_drvdata(&chip->dev);
111 struct i2c_client *client = to_i2c_client(chip->dev.parent);
112 int rc;
113
114 /* The TPM fails the I2C read until it is ready, so we do the entire
115 * transfer here and buffer it locally. This way the common code can
116 * properly handle the timeouts. */
117 priv->len = 0;
118 memset(priv->buffer, 0, sizeof(priv->buffer));
119
120
121 /* Once the TPM has completed the command the command remains readable
122 * until another command is issued. */
123 rc = i2c_master_recv(client, priv->buffer, sizeof(priv->buffer));
124 dev_dbg(&chip->dev,
125 "%s: sts=%d", __func__, rc);
126 if (rc <= 0)
127 return 0;
128
129 priv->len = rc;
130
131 return ATMEL_STS_OK;
132 }
133
i2c_atmel_req_canceled(struct tpm_chip * chip,u8 status)134 static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
135 {
136 return false;
137 }
138
139 static const struct tpm_class_ops i2c_atmel = {
140 .flags = TPM_OPS_AUTO_STARTUP,
141 .status = i2c_atmel_read_status,
142 .recv = i2c_atmel_recv,
143 .send = i2c_atmel_send,
144 .cancel = i2c_atmel_cancel,
145 .req_complete_mask = ATMEL_STS_OK,
146 .req_complete_val = ATMEL_STS_OK,
147 .req_canceled = i2c_atmel_req_canceled,
148 };
149
i2c_atmel_probe(struct i2c_client * client)150 static int i2c_atmel_probe(struct i2c_client *client)
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
i2c_atmel_remove(struct i2c_client * client)182 static void 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 }
188
189 static const struct i2c_device_id i2c_atmel_id[] = {
190 { I2C_DRIVER_NAME },
191 {}
192 };
193 MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
194
195 #ifdef CONFIG_OF
196 static const struct of_device_id i2c_atmel_of_match[] = {
197 {.compatible = "atmel,at97sc3204t"},
198 {},
199 };
200 MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
201 #endif
202
203 static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
204
205 static struct i2c_driver i2c_atmel_driver = {
206 .id_table = i2c_atmel_id,
207 .probe = i2c_atmel_probe,
208 .remove = i2c_atmel_remove,
209 .driver = {
210 .name = I2C_DRIVER_NAME,
211 .pm = &i2c_atmel_pm_ops,
212 .of_match_table = of_match_ptr(i2c_atmel_of_match),
213 },
214 };
215
216 module_i2c_driver(i2c_atmel_driver);
217
218 MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
219 MODULE_DESCRIPTION("Atmel TPM I2C Driver");
220 MODULE_LICENSE("GPL");
221