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377 lines
9.9 KiB
377 lines
9.9 KiB
// 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 <[email protected]> |
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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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static const struct { |
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u8 value; |
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const char *error_text; |
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} error_list[] = { |
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{ 0x01, "CheckMac or Verify miscompare" }, |
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{ 0x03, "Parse Error" }, |
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{ 0x05, "ECC Fault" }, |
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{ 0x0F, "Execution Error" }, |
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{ 0xEE, "Watchdog about to expire" }, |
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{ 0xFF, "CRC or other communication error" }, |
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}; |
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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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__le16 *__crc16 = (__le16 *)(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 = cpu_to_le16(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_random_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_RANDOM; |
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cmd->param1 = 0; |
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cmd->param2 = 0; |
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cmd->count = RANDOM_COUNT; |
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atmel_i2c_checksum(cmd); |
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cmd->msecs = MAX_EXEC_TIME_RANDOM; |
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cmd->rxsize = RANDOM_RSP_SIZE; |
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} |
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EXPORT_SYMBOL(atmel_i2c_init_random_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_transfer_buffer_flags(client, i2c_priv->wake_token, |
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i2c_priv->wake_token_sz, I2C_M_IGNORE_NAK); |
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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 <[email protected]>"); |
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MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver"); |
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MODULE_LICENSE("GPL v2");
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