| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Microchip / Atmel ECC (I2C) driver. |
| * |
| * Copyright (c) 2017, Microchip Technology Inc. |
| * Author: Tudor Ambarus |
| */ |
| |
| #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); |
| } |
| |
| static struct workqueue_struct *atmel_wq; |
| |
| 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); |
| queue_work(atmel_wq, &work_data->work); |
| } |
| EXPORT_SYMBOL(atmel_i2c_enqueue); |
| |
| void atmel_i2c_flush_queue(void) |
| { |
| flush_workqueue(atmel_wq); |
| } |
| EXPORT_SYMBOL(atmel_i2c_flush_queue); |
| |
| 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, "%u 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); |
| |
| return device_sanity_check(client); |
| } |
| EXPORT_SYMBOL(atmel_i2c_probe); |
| |
| static int __init atmel_i2c_init(void) |
| { |
| atmel_wq = alloc_workqueue("atmel_wq", 0, 0); |
| return atmel_wq ? 0 : -ENOMEM; |
| } |
| |
| static void __exit atmel_i2c_exit(void) |
| { |
| destroy_workqueue(atmel_wq); |
| } |
| |
| module_init(atmel_i2c_init); |
| module_exit(atmel_i2c_exit); |
| |
| MODULE_AUTHOR("Tudor Ambarus"); |
| MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver"); |
| MODULE_LICENSE("GPL v2"); |