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