crypto: atmel-ecc - factor out code that can be shared
In preparation of adding support for the random number generator in Atmel atsha204a devices, refactor the existing atmel-ecc driver (which drives hardware that is closely related) so we can share the basic I2C and command queuing routines. Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Ard Biesheuvel
committed by
Herbert Xu
Herbert Xu
parent
3c756aa346
commit
c34a320176
349
drivers/crypto/atmel-i2c.c
Normal file
349
drivers/crypto/atmel-i2c.c
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@@ -0,0 +1,349 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Microchip / Atmel ECC (I2C) driver.
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*
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* Copyright (c) 2017, Microchip Technology Inc.
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* Author: Tudor Ambarus <tudor.ambarus@microchip.com>
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*/
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#include <linux/bitrev.h>
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#include <linux/crc16.h>
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/errno.h>
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#include <linux/i2c.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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#include <linux/workqueue.h>
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#include "atmel-i2c.h"
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/**
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* atmel_i2c_checksum() - Generate 16-bit CRC as required by ATMEL ECC.
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* CRC16 verification of the count, opcode, param1, param2 and data bytes.
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* The checksum is saved in little-endian format in the least significant
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* two bytes of the command. CRC polynomial is 0x8005 and the initial register
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* value should be zero.
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*
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* @cmd : structure used for communicating with the device.
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*/
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static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd)
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{
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u8 *data = &cmd->count;
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size_t len = cmd->count - CRC_SIZE;
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u16 *__crc16 = (u16 *)(data + len);
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*__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len)));
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}
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void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd)
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{
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cmd->word_addr = COMMAND;
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cmd->opcode = OPCODE_READ;
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/*
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* Read the word from Configuration zone that contains the lock bytes
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* (UserExtra, Selector, LockValue, LockConfig).
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*/
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cmd->param1 = CONFIG_ZONE;
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cmd->param2 = DEVICE_LOCK_ADDR;
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cmd->count = READ_COUNT;
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atmel_i2c_checksum(cmd);
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cmd->msecs = MAX_EXEC_TIME_READ;
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cmd->rxsize = READ_RSP_SIZE;
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}
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EXPORT_SYMBOL(atmel_i2c_init_read_cmd);
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void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid)
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{
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cmd->word_addr = COMMAND;
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cmd->count = GENKEY_COUNT;
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cmd->opcode = OPCODE_GENKEY;
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cmd->param1 = GENKEY_MODE_PRIVATE;
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/* a random private key will be generated and stored in slot keyID */
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cmd->param2 = cpu_to_le16(keyid);
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atmel_i2c_checksum(cmd);
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cmd->msecs = MAX_EXEC_TIME_GENKEY;
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cmd->rxsize = GENKEY_RSP_SIZE;
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}
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EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd);
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int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd,
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struct scatterlist *pubkey)
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{
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size_t copied;
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cmd->word_addr = COMMAND;
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cmd->count = ECDH_COUNT;
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cmd->opcode = OPCODE_ECDH;
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cmd->param1 = ECDH_PREFIX_MODE;
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/* private key slot */
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cmd->param2 = cpu_to_le16(DATA_SLOT_2);
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/*
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* The device only supports NIST P256 ECC keys. The public key size will
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* always be the same. Use a macro for the key size to avoid unnecessary
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* computations.
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*/
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copied = sg_copy_to_buffer(pubkey,
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sg_nents_for_len(pubkey,
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ATMEL_ECC_PUBKEY_SIZE),
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cmd->data, ATMEL_ECC_PUBKEY_SIZE);
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if (copied != ATMEL_ECC_PUBKEY_SIZE)
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return -EINVAL;
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atmel_i2c_checksum(cmd);
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cmd->msecs = MAX_EXEC_TIME_ECDH;
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cmd->rxsize = ECDH_RSP_SIZE;
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return 0;
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}
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EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd);
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/*
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* After wake and after execution of a command, there will be error, status, or
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* result bytes in the device's output register that can be retrieved by the
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* system. When the length of that group is four bytes, the codes returned are
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* detailed in error_list.
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*/
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static int atmel_i2c_status(struct device *dev, u8 *status)
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{
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size_t err_list_len = ARRAY_SIZE(error_list);
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int i;
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u8 err_id = status[1];
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if (*status != STATUS_SIZE)
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return 0;
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if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR)
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return 0;
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for (i = 0; i < err_list_len; i++)
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if (error_list[i].value == err_id)
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break;
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/* if err_id is not in the error_list then ignore it */
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if (i != err_list_len) {
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dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text);
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return err_id;
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}
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return 0;
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}
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static int atmel_i2c_wakeup(struct i2c_client *client)
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{
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struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
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u8 status[STATUS_RSP_SIZE];
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int ret;
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/*
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* The device ignores any levels or transitions on the SCL pin when the
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* device is idle, asleep or during waking up. Don't check for error
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* when waking up the device.
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*/
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i2c_master_send(client, i2c_priv->wake_token, i2c_priv->wake_token_sz);
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/*
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* Wait to wake the device. Typical execution times for ecdh and genkey
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* are around tens of milliseconds. Delta is chosen to 50 microseconds.
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*/
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usleep_range(TWHI_MIN, TWHI_MAX);
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ret = i2c_master_recv(client, status, STATUS_SIZE);
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if (ret < 0)
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return ret;
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return atmel_i2c_status(&client->dev, status);
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}
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static int atmel_i2c_sleep(struct i2c_client *client)
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{
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u8 sleep = SLEEP_TOKEN;
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return i2c_master_send(client, &sleep, 1);
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}
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/*
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* atmel_i2c_send_receive() - send a command to the device and receive its
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* response.
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* @client: i2c client device
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* @cmd : structure used to communicate with the device
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*
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* After the device receives a Wake token, a watchdog counter starts within the
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* device. After the watchdog timer expires, the device enters sleep mode
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* regardless of whether some I/O transmission or command execution is in
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* progress. If a command is attempted when insufficient time remains prior to
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* watchdog timer execution, the device will return the watchdog timeout error
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* code without attempting to execute the command. There is no way to reset the
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* counter other than to put the device into sleep or idle mode and then
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* wake it up again.
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*/
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int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd)
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{
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struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
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int ret;
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mutex_lock(&i2c_priv->lock);
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ret = atmel_i2c_wakeup(client);
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if (ret)
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goto err;
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/* send the command */
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ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE);
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if (ret < 0)
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goto err;
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/* delay the appropriate amount of time for command to execute */
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msleep(cmd->msecs);
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/* receive the response */
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ret = i2c_master_recv(client, cmd->data, cmd->rxsize);
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if (ret < 0)
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goto err;
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/* put the device into low-power mode */
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ret = atmel_i2c_sleep(client);
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if (ret < 0)
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goto err;
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mutex_unlock(&i2c_priv->lock);
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return atmel_i2c_status(&client->dev, cmd->data);
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err:
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mutex_unlock(&i2c_priv->lock);
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return ret;
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}
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EXPORT_SYMBOL(atmel_i2c_send_receive);
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static void atmel_i2c_work_handler(struct work_struct *work)
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{
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struct atmel_i2c_work_data *work_data =
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container_of(work, struct atmel_i2c_work_data, work);
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struct atmel_i2c_cmd *cmd = &work_data->cmd;
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struct i2c_client *client = work_data->client;
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int status;
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status = atmel_i2c_send_receive(client, cmd);
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work_data->cbk(work_data, work_data->areq, status);
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}
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void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data,
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void (*cbk)(struct atmel_i2c_work_data *work_data,
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void *areq, int status),
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void *areq)
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{
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work_data->cbk = (void *)cbk;
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work_data->areq = areq;
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INIT_WORK(&work_data->work, atmel_i2c_work_handler);
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schedule_work(&work_data->work);
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}
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EXPORT_SYMBOL(atmel_i2c_enqueue);
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static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate)
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{
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u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC);
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/* return the size of the wake_token in bytes */
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return DIV_ROUND_UP(no_of_bits, 8);
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}
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static int device_sanity_check(struct i2c_client *client)
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{
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struct atmel_i2c_cmd *cmd;
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int ret;
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cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
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if (!cmd)
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return -ENOMEM;
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atmel_i2c_init_read_cmd(cmd);
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ret = atmel_i2c_send_receive(client, cmd);
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if (ret)
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goto free_cmd;
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/*
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* It is vital that the Configuration, Data and OTP zones be locked
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* prior to release into the field of the system containing the device.
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* Failure to lock these zones may permit modification of any secret
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* keys and may lead to other security problems.
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*/
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if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) {
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dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n");
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ret = -ENOTSUPP;
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}
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/* fall through */
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free_cmd:
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kfree(cmd);
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return ret;
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}
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int atmel_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
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{
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struct atmel_i2c_client_priv *i2c_priv;
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struct device *dev = &client->dev;
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int ret;
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u32 bus_clk_rate;
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if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
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dev_err(dev, "I2C_FUNC_I2C not supported\n");
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return -ENODEV;
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}
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bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev);
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if (!bus_clk_rate) {
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ret = device_property_read_u32(&client->adapter->dev,
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"clock-frequency", &bus_clk_rate);
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if (ret) {
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dev_err(dev, "failed to read clock-frequency property\n");
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return ret;
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}
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}
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if (bus_clk_rate > 1000000L) {
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dev_err(dev, "%d exceeds maximum supported clock frequency (1MHz)\n",
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bus_clk_rate);
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return -EINVAL;
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}
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i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL);
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if (!i2c_priv)
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return -ENOMEM;
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i2c_priv->client = client;
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mutex_init(&i2c_priv->lock);
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/*
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* WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate -
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* 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz
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* will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE.
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*/
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i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate);
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memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token));
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atomic_set(&i2c_priv->tfm_count, 0);
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i2c_set_clientdata(client, i2c_priv);
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ret = device_sanity_check(client);
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if (ret)
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return ret;
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return 0;
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}
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EXPORT_SYMBOL(atmel_i2c_probe);
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MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
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MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
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MODULE_LICENSE("GPL v2");
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