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- // 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_master_send(client, i2c_priv->wake_token, i2c_priv->wake_token_sz);
- /*
- * 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");
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