1 /*
2 * ATMEL I2C TPM AT97SC3204T
3 *
4 * Copyright (C) 2012 V Lab Technologies
5 * Teddy Reed <teddy@prosauce.org>
6 * Copyright (C) 2013, Obsidian Research Corp.
7 * Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
8 * Device driver for ATMEL I2C TPMs.
9 *
10 * Teddy Reed determined the basic I2C command flow, unlike other I2C TPM
11 * devices the raw TCG formatted TPM command data is written via I2C and then
12 * raw TCG formatted TPM command data is returned via I2C.
13 *
14 * TGC status/locality/etc functions seen in the LPC implementation do not
15 * seem to be present.
16 *
17 * This program is free software: you can redistribute it and/or modify
18 * it under the terms of the GNU General Public License as published by
19 * the Free Software Foundation, either version 2 of the License, or
20 * (at your option) any later version.
21 *
22 * This program is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU General Public License for more details.
26 *
27 * You should have received a copy of the GNU General Public License
28 * along with this program. If not, see http://www.gnu.org/licenses/>.
29 */
30 #include <linux/init.h>
31 #include <linux/module.h>
32 #include <linux/moduleparam.h>
33 #include <linux/slab.h>
34 #include <linux/i2c.h>
35 #include "tpm.h"
36
37 #define I2C_DRIVER_NAME "tpm_i2c_atmel"
38
39 #define TPM_I2C_SHORT_TIMEOUT 750 /* ms */
40 #define TPM_I2C_LONG_TIMEOUT 2000 /* 2 sec */
41
42 #define ATMEL_STS_OK 1
43
44 struct priv_data {
45 size_t len;
46 /* This is the amount we read on the first try. 25 was chosen to fit a
47 * fair number of read responses in the buffer so a 2nd retry can be
48 * avoided in small message cases. */
49 u8 buffer[sizeof(struct tpm_output_header) + 25];
50 };
51
i2c_atmel_send(struct tpm_chip * chip,u8 * buf,size_t len)52 static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len)
53 {
54 struct priv_data *priv = dev_get_drvdata(&chip->dev);
55 struct i2c_client *client = to_i2c_client(chip->dev.parent);
56 s32 status;
57
58 priv->len = 0;
59
60 if (len <= 2)
61 return -EIO;
62
63 status = i2c_master_send(client, buf, len);
64
65 dev_dbg(&chip->dev,
66 "%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__,
67 (int)min_t(size_t, 64, len), buf, len, status);
68
69 if (status < 0)
70 return status;
71
72 /* The upper layer does not support incomplete sends. */
73 if (status != len)
74 return -E2BIG;
75
76 return 0;
77 }
78
i2c_atmel_recv(struct tpm_chip * chip,u8 * buf,size_t count)79 static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count)
80 {
81 struct priv_data *priv = dev_get_drvdata(&chip->dev);
82 struct i2c_client *client = to_i2c_client(chip->dev.parent);
83 struct tpm_output_header *hdr =
84 (struct tpm_output_header *)priv->buffer;
85 u32 expected_len;
86 int rc;
87
88 if (priv->len == 0)
89 return -EIO;
90
91 /* Get the message size from the message header, if we didn't get the
92 * whole message in read_status then we need to re-read the
93 * message. */
94 expected_len = be32_to_cpu(hdr->length);
95 if (expected_len > count)
96 return -ENOMEM;
97
98 if (priv->len >= expected_len) {
99 dev_dbg(&chip->dev,
100 "%s early(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
101 (int)min_t(size_t, 64, expected_len), buf, count,
102 expected_len);
103 memcpy(buf, priv->buffer, expected_len);
104 return expected_len;
105 }
106
107 rc = i2c_master_recv(client, buf, expected_len);
108 dev_dbg(&chip->dev,
109 "%s reread(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
110 (int)min_t(size_t, 64, expected_len), buf, count,
111 expected_len);
112 return rc;
113 }
114
i2c_atmel_cancel(struct tpm_chip * chip)115 static void i2c_atmel_cancel(struct tpm_chip *chip)
116 {
117 dev_err(&chip->dev, "TPM operation cancellation was requested, but is not supported");
118 }
119
i2c_atmel_read_status(struct tpm_chip * chip)120 static u8 i2c_atmel_read_status(struct tpm_chip *chip)
121 {
122 struct priv_data *priv = dev_get_drvdata(&chip->dev);
123 struct i2c_client *client = to_i2c_client(chip->dev.parent);
124 int rc;
125
126 /* The TPM fails the I2C read until it is ready, so we do the entire
127 * transfer here and buffer it locally. This way the common code can
128 * properly handle the timeouts. */
129 priv->len = 0;
130 memset(priv->buffer, 0, sizeof(priv->buffer));
131
132
133 /* Once the TPM has completed the command the command remains readable
134 * until another command is issued. */
135 rc = i2c_master_recv(client, priv->buffer, sizeof(priv->buffer));
136 dev_dbg(&chip->dev,
137 "%s: sts=%d", __func__, rc);
138 if (rc <= 0)
139 return 0;
140
141 priv->len = rc;
142
143 return ATMEL_STS_OK;
144 }
145
i2c_atmel_req_canceled(struct tpm_chip * chip,u8 status)146 static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
147 {
148 return false;
149 }
150
151 static const struct tpm_class_ops i2c_atmel = {
152 .flags = TPM_OPS_AUTO_STARTUP,
153 .status = i2c_atmel_read_status,
154 .recv = i2c_atmel_recv,
155 .send = i2c_atmel_send,
156 .cancel = i2c_atmel_cancel,
157 .req_complete_mask = ATMEL_STS_OK,
158 .req_complete_val = ATMEL_STS_OK,
159 .req_canceled = i2c_atmel_req_canceled,
160 };
161
i2c_atmel_probe(struct i2c_client * client,const struct i2c_device_id * id)162 static int i2c_atmel_probe(struct i2c_client *client,
163 const struct i2c_device_id *id)
164 {
165 struct tpm_chip *chip;
166 struct device *dev = &client->dev;
167 struct priv_data *priv;
168
169 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
170 return -ENODEV;
171
172 chip = tpmm_chip_alloc(dev, &i2c_atmel);
173 if (IS_ERR(chip))
174 return PTR_ERR(chip);
175
176 priv = devm_kzalloc(dev, sizeof(struct priv_data), GFP_KERNEL);
177 if (!priv)
178 return -ENOMEM;
179
180 /* Default timeouts */
181 chip->timeout_a = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
182 chip->timeout_b = msecs_to_jiffies(TPM_I2C_LONG_TIMEOUT);
183 chip->timeout_c = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
184 chip->timeout_d = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
185
186 dev_set_drvdata(&chip->dev, priv);
187
188 /* There is no known way to probe for this device, and all version
189 * information seems to be read via TPM commands. Thus we rely on the
190 * TPM startup process in the common code to detect the device. */
191
192 return tpm_chip_register(chip);
193 }
194
i2c_atmel_remove(struct i2c_client * client)195 static int i2c_atmel_remove(struct i2c_client *client)
196 {
197 struct device *dev = &(client->dev);
198 struct tpm_chip *chip = dev_get_drvdata(dev);
199 tpm_chip_unregister(chip);
200 return 0;
201 }
202
203 static const struct i2c_device_id i2c_atmel_id[] = {
204 {I2C_DRIVER_NAME, 0},
205 {}
206 };
207 MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
208
209 #ifdef CONFIG_OF
210 static const struct of_device_id i2c_atmel_of_match[] = {
211 {.compatible = "atmel,at97sc3204t"},
212 {},
213 };
214 MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
215 #endif
216
217 static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
218
219 static struct i2c_driver i2c_atmel_driver = {
220 .id_table = i2c_atmel_id,
221 .probe = i2c_atmel_probe,
222 .remove = i2c_atmel_remove,
223 .driver = {
224 .name = I2C_DRIVER_NAME,
225 .pm = &i2c_atmel_pm_ops,
226 .of_match_table = of_match_ptr(i2c_atmel_of_match),
227 },
228 };
229
230 module_i2c_driver(i2c_atmel_driver);
231
232 MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
233 MODULE_DESCRIPTION("Atmel TPM I2C Driver");
234 MODULE_LICENSE("GPL");
235