drivers/char/tpm/tpm_i2c_atmel.c

   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 = 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
  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
 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
 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
 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
 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
 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");