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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_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, "%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);
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");