drivers/char/tpm/tpm_i2c_atmel.c

   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
  40 static 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
  67 static 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
 102 static 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
 107 static 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
 133 static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
 134 {
 135         return false;
 136 }
 137
 138 static 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
 149 static int i2c_atmel_probe(struct i2c_client *client,
 150                            const struct i2c_device_id *id)
 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
 182 static int 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         return 0;
 188 }
 189
 190 static const struct i2c_device_id i2c_atmel_id[] = {
 191         {I2C_DRIVER_NAME, 0},
 192         {}
 193 };
 194 MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
 195
 196 #ifdef CONFIG_OF
 197 static const struct of_device_id i2c_atmel_of_match[] = {
 198         {.compatible = "atmel,at97sc3204t"},
 199         {},
 200 };
 201 MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
 202 #endif
 203
 204 static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
 205
 206 static struct i2c_driver i2c_atmel_driver = {
 207         .id_table = i2c_atmel_id,
 208         .probe = i2c_atmel_probe,
 209         .remove = i2c_atmel_remove,
 210         .driver = {
 211                 .name = I2C_DRIVER_NAME,
 212                 .pm = &i2c_atmel_pm_ops,
 213                 .of_match_table = of_match_ptr(i2c_atmel_of_match),
 214         },
 215 };
 216
 217 module_i2c_driver(i2c_atmel_driver);
 218
 219 MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
 220 MODULE_DESCRIPTION("Atmel TPM I2C Driver");
 221 MODULE_LICENSE("GPL");