diff options
Diffstat (limited to 'drivers/crypto/atmel-i2c.c')
| -rw-r--r-- | drivers/crypto/atmel-i2c.c | 377 |
1 files changed, 377 insertions, 0 deletions
diff --git a/drivers/crypto/atmel-i2c.c b/drivers/crypto/atmel-i2c.c new file mode 100644 index 000000000..e8e8281e0 --- /dev/null +++ b/drivers/crypto/atmel-i2c.c @@ -0,0 +1,377 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Microchip / Atmel ECC (I2C) driver. + * + * Copyright (c) 2017, Microchip Technology Inc. + * Author: Tudor Ambarus <tudor.ambarus@microchip.com> + */ + +#include <linux/bitrev.h> +#include <linux/crc16.h> +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/err.h> +#include <linux/errno.h> +#include <linux/i2c.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/scatterlist.h> +#include <linux/slab.h> +#include <linux/workqueue.h> +#include "atmel-i2c.h" + +static const struct { + u8 value; + const char *error_text; +} error_list[] = { + { 0x01, "CheckMac or Verify miscompare" }, + { 0x03, "Parse Error" }, + { 0x05, "ECC Fault" }, + { 0x0F, "Execution Error" }, + { 0xEE, "Watchdog about to expire" }, + { 0xFF, "CRC or other communication error" }, +}; + +/** + * atmel_i2c_checksum() - Generate 16-bit CRC as required by ATMEL ECC. + * CRC16 verification of the count, opcode, param1, param2 and data bytes. + * The checksum is saved in little-endian format in the least significant + * two bytes of the command. CRC polynomial is 0x8005 and the initial register + * value should be zero. + * + * @cmd : structure used for communicating with the device. + */ +static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd) +{ + u8 *data = &cmd->count; + size_t len = cmd->count - CRC_SIZE; + __le16 *__crc16 = (__le16 *)(data + len); + + *__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len))); +} + +void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd) +{ + cmd->word_addr = COMMAND; + cmd->opcode = OPCODE_READ; + /* + * Read the word from Configuration zone that contains the lock bytes + * (UserExtra, Selector, LockValue, LockConfig). + */ + cmd->param1 = CONFIG_ZONE; + cmd->param2 = cpu_to_le16(DEVICE_LOCK_ADDR); + cmd->count = READ_COUNT; + + atmel_i2c_checksum(cmd); + + cmd->msecs = MAX_EXEC_TIME_READ; + cmd->rxsize = READ_RSP_SIZE; +} +EXPORT_SYMBOL(atmel_i2c_init_read_cmd); + +void atmel_i2c_init_random_cmd(struct atmel_i2c_cmd *cmd) +{ + cmd->word_addr = COMMAND; + cmd->opcode = OPCODE_RANDOM; + cmd->param1 = 0; + cmd->param2 = 0; + cmd->count = RANDOM_COUNT; + + atmel_i2c_checksum(cmd); + + cmd->msecs = MAX_EXEC_TIME_RANDOM; + cmd->rxsize = RANDOM_RSP_SIZE; +} +EXPORT_SYMBOL(atmel_i2c_init_random_cmd); + +void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid) +{ + cmd->word_addr = COMMAND; + cmd->count = GENKEY_COUNT; + cmd->opcode = OPCODE_GENKEY; + cmd->param1 = GENKEY_MODE_PRIVATE; + /* a random private key will be generated and stored in slot keyID */ + cmd->param2 = cpu_to_le16(keyid); + + atmel_i2c_checksum(cmd); + + cmd->msecs = MAX_EXEC_TIME_GENKEY; + cmd->rxsize = GENKEY_RSP_SIZE; +} +EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd); + +int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd, + struct scatterlist *pubkey) +{ + size_t copied; + + cmd->word_addr = COMMAND; + cmd->count = ECDH_COUNT; + cmd->opcode = OPCODE_ECDH; + cmd->param1 = ECDH_PREFIX_MODE; + /* private key slot */ + cmd->param2 = cpu_to_le16(DATA_SLOT_2); + + /* + * The device only supports NIST P256 ECC keys. The public key size will + * always be the same. Use a macro for the key size to avoid unnecessary + * computations. + */ + copied = sg_copy_to_buffer(pubkey, + sg_nents_for_len(pubkey, + ATMEL_ECC_PUBKEY_SIZE), + cmd->data, ATMEL_ECC_PUBKEY_SIZE); + if (copied != ATMEL_ECC_PUBKEY_SIZE) + return -EINVAL; + + atmel_i2c_checksum(cmd); + + cmd->msecs = MAX_EXEC_TIME_ECDH; + cmd->rxsize = ECDH_RSP_SIZE; + + return 0; +} +EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd); + +/* + * After wake and after execution of a command, there will be error, status, or + * result bytes in the device's output register that can be retrieved by the + * system. When the length of that group is four bytes, the codes returned are + * detailed in error_list. + */ +static int atmel_i2c_status(struct device *dev, u8 *status) +{ + size_t err_list_len = ARRAY_SIZE(error_list); + int i; + u8 err_id = status[1]; + + if (*status != STATUS_SIZE) + return 0; + + if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR) + return 0; + + for (i = 0; i < err_list_len; i++) + if (error_list[i].value == err_id) + break; + + /* if err_id is not in the error_list then ignore it */ + if (i != err_list_len) { + dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text); + return err_id; + } + + return 0; +} + +static int atmel_i2c_wakeup(struct i2c_client *client) +{ + struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); + u8 status[STATUS_RSP_SIZE]; + int ret; + + /* + * The device ignores any levels or transitions on the SCL pin when the + * device is idle, asleep or during waking up. Don't check for error + * when waking up the device. + */ + i2c_transfer_buffer_flags(client, i2c_priv->wake_token, + i2c_priv->wake_token_sz, I2C_M_IGNORE_NAK); + + /* + * Wait to wake the device. Typical execution times for ecdh and genkey + * are around tens of milliseconds. Delta is chosen to 50 microseconds. + */ + usleep_range(TWHI_MIN, TWHI_MAX); + + ret = i2c_master_recv(client, status, STATUS_SIZE); + if (ret < 0) + return ret; + + return atmel_i2c_status(&client->dev, status); +} + +static int atmel_i2c_sleep(struct i2c_client *client) +{ + u8 sleep = SLEEP_TOKEN; + + return i2c_master_send(client, &sleep, 1); +} + +/* + * atmel_i2c_send_receive() - send a command to the device and receive its + * response. + * @client: i2c client device + * @cmd : structure used to communicate with the device + * + * After the device receives a Wake token, a watchdog counter starts within the + * device. After the watchdog timer expires, the device enters sleep mode + * regardless of whether some I/O transmission or command execution is in + * progress. If a command is attempted when insufficient time remains prior to + * watchdog timer execution, the device will return the watchdog timeout error + * code without attempting to execute the command. There is no way to reset the + * counter other than to put the device into sleep or idle mode and then + * wake it up again. + */ +int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd) +{ + struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); + int ret; + + mutex_lock(&i2c_priv->lock); + + ret = atmel_i2c_wakeup(client); + if (ret) + goto err; + + /* send the command */ + ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE); + if (ret < 0) + goto err; + + /* delay the appropriate amount of time for command to execute */ + msleep(cmd->msecs); + + /* receive the response */ + ret = i2c_master_recv(client, cmd->data, cmd->rxsize); + if (ret < 0) + goto err; + + /* put the device into low-power mode */ + ret = atmel_i2c_sleep(client); + if (ret < 0) + goto err; + + mutex_unlock(&i2c_priv->lock); + return atmel_i2c_status(&client->dev, cmd->data); +err: + mutex_unlock(&i2c_priv->lock); + return ret; +} +EXPORT_SYMBOL(atmel_i2c_send_receive); + +static void atmel_i2c_work_handler(struct work_struct *work) +{ + struct atmel_i2c_work_data *work_data = + container_of(work, struct atmel_i2c_work_data, work); + struct atmel_i2c_cmd *cmd = &work_data->cmd; + struct i2c_client *client = work_data->client; + int status; + + status = atmel_i2c_send_receive(client, cmd); + work_data->cbk(work_data, work_data->areq, status); +} + +void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data, + void (*cbk)(struct atmel_i2c_work_data *work_data, + void *areq, int status), + void *areq) +{ + work_data->cbk = (void *)cbk; + work_data->areq = areq; + + INIT_WORK(&work_data->work, atmel_i2c_work_handler); + schedule_work(&work_data->work); +} +EXPORT_SYMBOL(atmel_i2c_enqueue); + +static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate) +{ + u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC); + + /* return the size of the wake_token in bytes */ + return DIV_ROUND_UP(no_of_bits, 8); +} + +static int device_sanity_check(struct i2c_client *client) +{ + struct atmel_i2c_cmd *cmd; + int ret; + + cmd = kmalloc(sizeof(*cmd), GFP_KERNEL); + if (!cmd) + return -ENOMEM; + + atmel_i2c_init_read_cmd(cmd); + + ret = atmel_i2c_send_receive(client, cmd); + if (ret) + goto free_cmd; + + /* + * It is vital that the Configuration, Data and OTP zones be locked + * prior to release into the field of the system containing the device. + * Failure to lock these zones may permit modification of any secret + * keys and may lead to other security problems. + */ + if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) { + dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n"); + ret = -ENOTSUPP; + } + + /* fall through */ +free_cmd: + kfree(cmd); + return ret; +} + +int atmel_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id) +{ + struct atmel_i2c_client_priv *i2c_priv; + struct device *dev = &client->dev; + int ret; + u32 bus_clk_rate; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { + dev_err(dev, "I2C_FUNC_I2C not supported\n"); + return -ENODEV; + } + + bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev); + if (!bus_clk_rate) { + ret = device_property_read_u32(&client->adapter->dev, + "clock-frequency", &bus_clk_rate); + if (ret) { + dev_err(dev, "failed to read clock-frequency property\n"); + return ret; + } + } + + if (bus_clk_rate > 1000000L) { + dev_err(dev, "%d exceeds maximum supported clock frequency (1MHz)\n", + bus_clk_rate); + return -EINVAL; + } + + i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL); + if (!i2c_priv) + return -ENOMEM; + + i2c_priv->client = client; + mutex_init(&i2c_priv->lock); + + /* + * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate - + * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz + * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE. + */ + i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate); + + memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token)); + + atomic_set(&i2c_priv->tfm_count, 0); + + i2c_set_clientdata(client, i2c_priv); + + ret = device_sanity_check(client); + if (ret) + return ret; + + return 0; +} +EXPORT_SYMBOL(atmel_i2c_probe); + +MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>"); +MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver"); +MODULE_LICENSE("GPL v2"); |