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
44struct 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
52static 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
71static 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
107static 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
112static 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
138static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
139{
140	return false;
141}
142
143static 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
153static 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
190static 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
198static const struct i2c_device_id i2c_atmel_id[] = {
199	{I2C_DRIVER_NAME, 0},
200	{}
201};
202MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
203
204#ifdef CONFIG_OF
205static const struct of_device_id i2c_atmel_of_match[] = {
206	{.compatible = "atmel,at97sc3204t"},
207	{},
208};
209MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
210#endif
211
212static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
213
214static 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		.pm = &i2c_atmel_pm_ops,
221		.of_match_table = of_match_ptr(i2c_atmel_of_match),
222	},
223};
224
225module_i2c_driver(i2c_atmel_driver);
226
227MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
228MODULE_DESCRIPTION("Atmel TPM I2C Driver");
229MODULE_LICENSE("GPL");
230