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{
151	struct tpm_chip *chip;
152	struct device *dev = &client->dev;
153	struct priv_data *priv;
154
155	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
156		return -ENODEV;
157
158	chip = tpmm_chip_alloc(dev, &i2c_atmel);
159	if (IS_ERR(chip))
160		return PTR_ERR(chip);
161
162	priv = devm_kzalloc(dev, sizeof(struct priv_data), GFP_KERNEL);
163	if (!priv)
164		return -ENOMEM;
165
166	/* Default timeouts */
167	chip->timeout_a = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
168	chip->timeout_b = msecs_to_jiffies(TPM_I2C_LONG_TIMEOUT);
169	chip->timeout_c = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
170	chip->timeout_d = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
171
172	dev_set_drvdata(&chip->dev, priv);
173
174	/* There is no known way to probe for this device, and all version
175	 * information seems to be read via TPM commands. Thus we rely on the
176	 * TPM startup process in the common code to detect the device. */
177
178	return tpm_chip_register(chip);
179}
180
181static void i2c_atmel_remove(struct i2c_client *client)
182{
183	struct device *dev = &(client->dev);
184	struct tpm_chip *chip = dev_get_drvdata(dev);
185	tpm_chip_unregister(chip);
186}
187
188static const struct i2c_device_id i2c_atmel_id[] = {
189	{I2C_DRIVER_NAME, 0},
190	{}
191};
192MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
193
194#ifdef CONFIG_OF
195static const struct of_device_id i2c_atmel_of_match[] = {
196	{.compatible = "atmel,at97sc3204t"},
197	{},
198};
199MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
200#endif
201
202static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
203
204static struct i2c_driver i2c_atmel_driver = {
205	.id_table = i2c_atmel_id,
206	.probe = i2c_atmel_probe,
207	.remove = i2c_atmel_remove,
208	.driver = {
209		.name = I2C_DRIVER_NAME,
210		.pm = &i2c_atmel_pm_ops,
211		.of_match_table = of_match_ptr(i2c_atmel_of_match),
212	},
213};
214
215module_i2c_driver(i2c_atmel_driver);
216
217MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
218MODULE_DESCRIPTION("Atmel TPM I2C Driver");
219MODULE_LICENSE("GPL");