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 /* 35 * This is the amount we read on the first try. 25 was chosen to fit a 36 * fair number of read responses in the buffer so a 2nd retry can be 37 * avoided in small message cases. 38 */ 39 u8 buffer[sizeof(struct tpm_header) + 25]; 40 }; 41 42 static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz, 43 size_t len) 44 { 45 struct priv_data *priv = dev_get_drvdata(&chip->dev); 46 struct i2c_client *client = to_i2c_client(chip->dev.parent); 47 s32 status; 48 49 priv->len = 0; 50 51 if (len <= 2) 52 return -EIO; 53 54 status = i2c_master_send(client, buf, len); 55 56 dev_dbg(&chip->dev, 57 "%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__, 58 (int)min_t(size_t, 64, len), buf, len, status); 59 60 if (status < 0) 61 return status; 62 63 /* 64 * The upper layer does not support incomplete sends. 65 */ 66 if (status != len) 67 return -E2BIG; 68 69 return 0; 70 } 71 72 static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count) 73 { 74 struct priv_data *priv = dev_get_drvdata(&chip->dev); 75 struct i2c_client *client = to_i2c_client(chip->dev.parent); 76 struct tpm_header *hdr = (struct tpm_header *)priv->buffer; 77 u32 expected_len; 78 int rc; 79 80 if (priv->len == 0) 81 return -EIO; 82 83 /* 84 * Get the message size from the message header, if we didn't get the 85 * whole message in read_status then we need to re-read the 86 * message. 87 */ 88 expected_len = be32_to_cpu(hdr->length); 89 if (expected_len > count) 90 return -ENOMEM; 91 92 if (priv->len >= expected_len) { 93 dev_dbg(&chip->dev, 94 "%s early(buf=%*ph count=%0zx) -> ret=%d\n", __func__, 95 (int)min_t(size_t, 64, expected_len), buf, count, 96 expected_len); 97 memcpy(buf, priv->buffer, expected_len); 98 return expected_len; 99 } 100 101 rc = i2c_master_recv(client, buf, expected_len); 102 dev_dbg(&chip->dev, 103 "%s reread(buf=%*ph count=%0zx) -> ret=%d\n", __func__, 104 (int)min_t(size_t, 64, expected_len), buf, count, 105 expected_len); 106 return rc; 107 } 108 109 static void i2c_atmel_cancel(struct tpm_chip *chip) 110 { 111 dev_err(&chip->dev, "TPM operation cancellation was requested, but is not supported"); 112 } 113 114 static u8 i2c_atmel_read_status(struct tpm_chip *chip) 115 { 116 struct priv_data *priv = dev_get_drvdata(&chip->dev); 117 struct i2c_client *client = to_i2c_client(chip->dev.parent); 118 int rc; 119 120 /* 121 * The TPM fails the I2C read until it is ready, so we do the entire 122 * transfer here and buffer it locally. This way the common code can 123 * properly handle the timeouts. 124 */ 125 priv->len = 0; 126 memset(priv->buffer, 0, sizeof(priv->buffer)); 127 128 129 /* 130 * Once the TPM has completed the command the command remains readable 131 * until another command is issued. 132 */ 133 rc = i2c_master_recv(client, priv->buffer, sizeof(priv->buffer)); 134 dev_dbg(&chip->dev, 135 "%s: sts=%d", __func__, rc); 136 if (rc <= 0) 137 return 0; 138 139 priv->len = rc; 140 141 return ATMEL_STS_OK; 142 } 143 144 static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status) 145 { 146 return false; 147 } 148 149 static const struct tpm_class_ops i2c_atmel = { 150 .flags = TPM_OPS_AUTO_STARTUP, 151 .status = i2c_atmel_read_status, 152 .recv = i2c_atmel_recv, 153 .send = i2c_atmel_send, 154 .cancel = i2c_atmel_cancel, 155 .req_complete_mask = ATMEL_STS_OK, 156 .req_complete_val = ATMEL_STS_OK, 157 .req_canceled = i2c_atmel_req_canceled, 158 }; 159 160 static int i2c_atmel_probe(struct i2c_client *client) 161 { 162 struct tpm_chip *chip; 163 struct device *dev = &client->dev; 164 struct priv_data *priv; 165 166 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 167 return -ENODEV; 168 169 chip = tpmm_chip_alloc(dev, &i2c_atmel); 170 if (IS_ERR(chip)) 171 return PTR_ERR(chip); 172 173 priv = devm_kzalloc(dev, sizeof(struct priv_data), GFP_KERNEL); 174 if (!priv) 175 return -ENOMEM; 176 177 /* Default timeouts */ 178 chip->timeout_a = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT); 179 chip->timeout_b = msecs_to_jiffies(TPM_I2C_LONG_TIMEOUT); 180 chip->timeout_c = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT); 181 chip->timeout_d = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT); 182 183 dev_set_drvdata(&chip->dev, priv); 184 185 /* 186 * There is no known way to probe for this device, and all version 187 * information seems to be read via TPM commands. Thus we rely on the 188 * TPM startup process in the common code to detect the device. 189 */ 190 191 return tpm_chip_register(chip); 192 } 193 194 static void 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 } 200 201 static const struct i2c_device_id i2c_atmel_id[] = { 202 { I2C_DRIVER_NAME }, 203 {} 204 }; 205 MODULE_DEVICE_TABLE(i2c, i2c_atmel_id); 206 207 #ifdef CONFIG_OF 208 static const struct of_device_id i2c_atmel_of_match[] = { 209 {.compatible = "atmel,at97sc3204t"}, 210 {}, 211 }; 212 MODULE_DEVICE_TABLE(of, i2c_atmel_of_match); 213 #endif 214 215 static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume); 216 217 static struct i2c_driver i2c_atmel_driver = { 218 .id_table = i2c_atmel_id, 219 .probe = i2c_atmel_probe, 220 .remove = i2c_atmel_remove, 221 .driver = { 222 .name = I2C_DRIVER_NAME, 223 .pm = &i2c_atmel_pm_ops, 224 .of_match_table = of_match_ptr(i2c_atmel_of_match), 225 }, 226 }; 227 228 module_i2c_driver(i2c_atmel_driver); 229 230 MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>"); 231 MODULE_DESCRIPTION("Atmel TPM I2C Driver"); 232 MODULE_LICENSE("GPL"); 233