xref: /openbmc/linux/drivers/char/tpm/tpm_i2c_atmel.c (revision a2cce7a9)
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 
52 static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len)
53 {
54 	struct priv_data *priv = chip->vendor.priv;
55 	struct i2c_client *client = to_i2c_client(chip->pdev);
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->pdev,
66 		"%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__,
67 		(int)min_t(size_t, 64, len), buf, len, status);
68 	return status;
69 }
70 
71 static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count)
72 {
73 	struct priv_data *priv = chip->vendor.priv;
74 	struct i2c_client *client = to_i2c_client(chip->pdev);
75 	struct tpm_output_header *hdr =
76 		(struct tpm_output_header *)priv->buffer;
77 	u32 expected_len;
78 	int rc;
79 
80 	if (priv->len == 0)
81 		return -EIO;
82 
83 	/* Get the message size from the message header, if we didn't get the
84 	 * whole message in read_status then we need to re-read the
85 	 * message. */
86 	expected_len = be32_to_cpu(hdr->length);
87 	if (expected_len > count)
88 		return -ENOMEM;
89 
90 	if (priv->len >= expected_len) {
91 		dev_dbg(chip->pdev,
92 			"%s early(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
93 			(int)min_t(size_t, 64, expected_len), buf, count,
94 			expected_len);
95 		memcpy(buf, priv->buffer, expected_len);
96 		return expected_len;
97 	}
98 
99 	rc = i2c_master_recv(client, buf, expected_len);
100 	dev_dbg(chip->pdev,
101 		"%s reread(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
102 		(int)min_t(size_t, 64, expected_len), buf, count,
103 		expected_len);
104 	return rc;
105 }
106 
107 static void i2c_atmel_cancel(struct tpm_chip *chip)
108 {
109 	dev_err(chip->pdev, "TPM operation cancellation was requested, but is not supported");
110 }
111 
112 static u8 i2c_atmel_read_status(struct tpm_chip *chip)
113 {
114 	struct priv_data *priv = chip->vendor.priv;
115 	struct i2c_client *client = to_i2c_client(chip->pdev);
116 	int rc;
117 
118 	/* The TPM fails the I2C read until it is ready, so we do the entire
119 	 * transfer here and buffer it locally. This way the common code can
120 	 * properly handle the timeouts. */
121 	priv->len = 0;
122 	memset(priv->buffer, 0, sizeof(priv->buffer));
123 
124 
125 	/* Once the TPM has completed the command the command remains readable
126 	 * until another command is issued. */
127 	rc = i2c_master_recv(client, priv->buffer, sizeof(priv->buffer));
128 	dev_dbg(chip->pdev,
129 		"%s: sts=%d", __func__, rc);
130 	if (rc <= 0)
131 		return 0;
132 
133 	priv->len = rc;
134 
135 	return ATMEL_STS_OK;
136 }
137 
138 static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
139 {
140 	return false;
141 }
142 
143 static const struct tpm_class_ops i2c_atmel = {
144 	.status = i2c_atmel_read_status,
145 	.recv = i2c_atmel_recv,
146 	.send = i2c_atmel_send,
147 	.cancel = i2c_atmel_cancel,
148 	.req_complete_mask = ATMEL_STS_OK,
149 	.req_complete_val = ATMEL_STS_OK,
150 	.req_canceled = i2c_atmel_req_canceled,
151 };
152 
153 static int i2c_atmel_probe(struct i2c_client *client,
154 			   const struct i2c_device_id *id)
155 {
156 	struct tpm_chip *chip;
157 	struct device *dev = &client->dev;
158 
159 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
160 		return -ENODEV;
161 
162 	chip = tpmm_chip_alloc(dev, &i2c_atmel);
163 	if (IS_ERR(chip))
164 		return PTR_ERR(chip);
165 
166 	chip->vendor.priv = devm_kzalloc(dev, sizeof(struct priv_data),
167 					 GFP_KERNEL);
168 	if (!chip->vendor.priv)
169 		return -ENOMEM;
170 
171 	/* Default timeouts */
172 	chip->vendor.timeout_a = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
173 	chip->vendor.timeout_b = msecs_to_jiffies(TPM_I2C_LONG_TIMEOUT);
174 	chip->vendor.timeout_c = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
175 	chip->vendor.timeout_d = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
176 	chip->vendor.irq = 0;
177 
178 	/* There is no known way to probe for this device, and all version
179 	 * information seems to be read via TPM commands. Thus we rely on the
180 	 * TPM startup process in the common code to detect the device. */
181 	if (tpm_get_timeouts(chip))
182 		return -ENODEV;
183 
184 	if (tpm_do_selftest(chip))
185 		return -ENODEV;
186 
187 	return tpm_chip_register(chip);
188 }
189 
190 static int i2c_atmel_remove(struct i2c_client *client)
191 {
192 	struct device *dev = &(client->dev);
193 	struct tpm_chip *chip = dev_get_drvdata(dev);
194 	tpm_chip_unregister(chip);
195 	return 0;
196 }
197 
198 static const struct i2c_device_id i2c_atmel_id[] = {
199 	{I2C_DRIVER_NAME, 0},
200 	{}
201 };
202 MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
203 
204 #ifdef CONFIG_OF
205 static const struct of_device_id i2c_atmel_of_match[] = {
206 	{.compatible = "atmel,at97sc3204t"},
207 	{},
208 };
209 MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
210 #endif
211 
212 static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
213 
214 static struct i2c_driver i2c_atmel_driver = {
215 	.id_table = i2c_atmel_id,
216 	.probe = i2c_atmel_probe,
217 	.remove = i2c_atmel_remove,
218 	.driver = {
219 		.name = I2C_DRIVER_NAME,
220 		.owner = THIS_MODULE,
221 		.pm = &i2c_atmel_pm_ops,
222 		.of_match_table = of_match_ptr(i2c_atmel_of_match),
223 	},
224 };
225 
226 module_i2c_driver(i2c_atmel_driver);
227 
228 MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
229 MODULE_DESCRIPTION("Atmel TPM I2C Driver");
230 MODULE_LICENSE("GPL");
231