1 // SPDX-License-Identifier: GPL-2.0
3 * Microchip / Atmel ECC (I2C) driver.
5 * Copyright (c) 2017, Microchip Technology Inc.
6 * Author: Tudor Ambarus <tudor.ambarus@microchip.com>
9 #include <linux/bitrev.h>
10 #include <linux/crc16.h>
11 #include <linux/delay.h>
12 #include <linux/device.h>
13 #include <linux/err.h>
14 #include <linux/errno.h>
15 #include <linux/i2c.h>
16 #include <linux/init.h>
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 #include <linux/scatterlist.h>
20 #include <linux/slab.h>
21 #include <linux/workqueue.h>
22 #include "atmel-i2c.h"
26 const char *error_text;
28 { 0x01, "CheckMac or Verify miscompare" },
29 { 0x03, "Parse Error" },
30 { 0x05, "ECC Fault" },
31 { 0x0F, "Execution Error" },
32 { 0xEE, "Watchdog about to expire" },
33 { 0xFF, "CRC or other communication error" },
37 * atmel_i2c_checksum() - Generate 16-bit CRC as required by ATMEL ECC.
38 * CRC16 verification of the count, opcode, param1, param2 and data bytes.
39 * The checksum is saved in little-endian format in the least significant
40 * two bytes of the command. CRC polynomial is 0x8005 and the initial register
41 * value should be zero.
43 * @cmd : structure used for communicating with the device.
45 static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd)
47 u8 *data = &cmd->count;
48 size_t len = cmd->count - CRC_SIZE;
49 __le16 *__crc16 = (__le16 *)(data + len);
51 *__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len)));
54 void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd)
56 cmd->word_addr = COMMAND;
57 cmd->opcode = OPCODE_READ;
59 * Read the word from Configuration zone that contains the lock bytes
60 * (UserExtra, Selector, LockValue, LockConfig).
62 cmd->param1 = CONFIG_ZONE;
63 cmd->param2 = cpu_to_le16(DEVICE_LOCK_ADDR);
64 cmd->count = READ_COUNT;
66 atmel_i2c_checksum(cmd);
68 cmd->msecs = MAX_EXEC_TIME_READ;
69 cmd->rxsize = READ_RSP_SIZE;
71 EXPORT_SYMBOL(atmel_i2c_init_read_cmd);
73 void atmel_i2c_init_random_cmd(struct atmel_i2c_cmd *cmd)
75 cmd->word_addr = COMMAND;
76 cmd->opcode = OPCODE_RANDOM;
79 cmd->count = RANDOM_COUNT;
81 atmel_i2c_checksum(cmd);
83 cmd->msecs = MAX_EXEC_TIME_RANDOM;
84 cmd->rxsize = RANDOM_RSP_SIZE;
86 EXPORT_SYMBOL(atmel_i2c_init_random_cmd);
88 void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid)
90 cmd->word_addr = COMMAND;
91 cmd->count = GENKEY_COUNT;
92 cmd->opcode = OPCODE_GENKEY;
93 cmd->param1 = GENKEY_MODE_PRIVATE;
94 /* a random private key will be generated and stored in slot keyID */
95 cmd->param2 = cpu_to_le16(keyid);
97 atmel_i2c_checksum(cmd);
99 cmd->msecs = MAX_EXEC_TIME_GENKEY;
100 cmd->rxsize = GENKEY_RSP_SIZE;
102 EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd);
104 int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd,
105 struct scatterlist *pubkey)
109 cmd->word_addr = COMMAND;
110 cmd->count = ECDH_COUNT;
111 cmd->opcode = OPCODE_ECDH;
112 cmd->param1 = ECDH_PREFIX_MODE;
113 /* private key slot */
114 cmd->param2 = cpu_to_le16(DATA_SLOT_2);
117 * The device only supports NIST P256 ECC keys. The public key size will
118 * always be the same. Use a macro for the key size to avoid unnecessary
121 copied = sg_copy_to_buffer(pubkey,
122 sg_nents_for_len(pubkey,
123 ATMEL_ECC_PUBKEY_SIZE),
124 cmd->data, ATMEL_ECC_PUBKEY_SIZE);
125 if (copied != ATMEL_ECC_PUBKEY_SIZE)
128 atmel_i2c_checksum(cmd);
130 cmd->msecs = MAX_EXEC_TIME_ECDH;
131 cmd->rxsize = ECDH_RSP_SIZE;
135 EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd);
138 * After wake and after execution of a command, there will be error, status, or
139 * result bytes in the device's output register that can be retrieved by the
140 * system. When the length of that group is four bytes, the codes returned are
141 * detailed in error_list.
143 static int atmel_i2c_status(struct device *dev, u8 *status)
145 size_t err_list_len = ARRAY_SIZE(error_list);
147 u8 err_id = status[1];
149 if (*status != STATUS_SIZE)
152 if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR)
155 for (i = 0; i < err_list_len; i++)
156 if (error_list[i].value == err_id)
159 /* if err_id is not in the error_list then ignore it */
160 if (i != err_list_len) {
161 dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text);
168 static int atmel_i2c_wakeup(struct i2c_client *client)
170 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
171 u8 status[STATUS_RSP_SIZE];
175 * The device ignores any levels or transitions on the SCL pin when the
176 * device is idle, asleep or during waking up. Don't check for error
177 * when waking up the device.
179 i2c_master_send(client, i2c_priv->wake_token, i2c_priv->wake_token_sz);
182 * Wait to wake the device. Typical execution times for ecdh and genkey
183 * are around tens of milliseconds. Delta is chosen to 50 microseconds.
185 usleep_range(TWHI_MIN, TWHI_MAX);
187 ret = i2c_master_recv(client, status, STATUS_SIZE);
191 return atmel_i2c_status(&client->dev, status);
194 static int atmel_i2c_sleep(struct i2c_client *client)
196 u8 sleep = SLEEP_TOKEN;
198 return i2c_master_send(client, &sleep, 1);
202 * atmel_i2c_send_receive() - send a command to the device and receive its
204 * @client: i2c client device
205 * @cmd : structure used to communicate with the device
207 * After the device receives a Wake token, a watchdog counter starts within the
208 * device. After the watchdog timer expires, the device enters sleep mode
209 * regardless of whether some I/O transmission or command execution is in
210 * progress. If a command is attempted when insufficient time remains prior to
211 * watchdog timer execution, the device will return the watchdog timeout error
212 * code without attempting to execute the command. There is no way to reset the
213 * counter other than to put the device into sleep or idle mode and then
216 int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd)
218 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
221 mutex_lock(&i2c_priv->lock);
223 ret = atmel_i2c_wakeup(client);
227 /* send the command */
228 ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE);
232 /* delay the appropriate amount of time for command to execute */
235 /* receive the response */
236 ret = i2c_master_recv(client, cmd->data, cmd->rxsize);
240 /* put the device into low-power mode */
241 ret = atmel_i2c_sleep(client);
245 mutex_unlock(&i2c_priv->lock);
246 return atmel_i2c_status(&client->dev, cmd->data);
248 mutex_unlock(&i2c_priv->lock);
251 EXPORT_SYMBOL(atmel_i2c_send_receive);
253 static void atmel_i2c_work_handler(struct work_struct *work)
255 struct atmel_i2c_work_data *work_data =
256 container_of(work, struct atmel_i2c_work_data, work);
257 struct atmel_i2c_cmd *cmd = &work_data->cmd;
258 struct i2c_client *client = work_data->client;
261 status = atmel_i2c_send_receive(client, cmd);
262 work_data->cbk(work_data, work_data->areq, status);
265 void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data,
266 void (*cbk)(struct atmel_i2c_work_data *work_data,
267 void *areq, int status),
270 work_data->cbk = (void *)cbk;
271 work_data->areq = areq;
273 INIT_WORK(&work_data->work, atmel_i2c_work_handler);
274 schedule_work(&work_data->work);
276 EXPORT_SYMBOL(atmel_i2c_enqueue);
278 static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate)
280 u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC);
282 /* return the size of the wake_token in bytes */
283 return DIV_ROUND_UP(no_of_bits, 8);
286 static int device_sanity_check(struct i2c_client *client)
288 struct atmel_i2c_cmd *cmd;
291 cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
295 atmel_i2c_init_read_cmd(cmd);
297 ret = atmel_i2c_send_receive(client, cmd);
302 * It is vital that the Configuration, Data and OTP zones be locked
303 * prior to release into the field of the system containing the device.
304 * Failure to lock these zones may permit modification of any secret
305 * keys and may lead to other security problems.
307 if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) {
308 dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n");
318 int atmel_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
320 struct atmel_i2c_client_priv *i2c_priv;
321 struct device *dev = &client->dev;
325 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
326 dev_err(dev, "I2C_FUNC_I2C not supported\n");
330 bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev);
332 ret = device_property_read_u32(&client->adapter->dev,
333 "clock-frequency", &bus_clk_rate);
335 dev_err(dev, "failed to read clock-frequency property\n");
340 if (bus_clk_rate > 1000000L) {
341 dev_err(dev, "%d exceeds maximum supported clock frequency (1MHz)\n",
346 i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL);
350 i2c_priv->client = client;
351 mutex_init(&i2c_priv->lock);
354 * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate -
355 * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz
356 * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE.
358 i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate);
360 memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token));
362 atomic_set(&i2c_priv->tfm_count, 0);
364 i2c_set_clientdata(client, i2c_priv);
366 ret = device_sanity_check(client);
372 EXPORT_SYMBOL(atmel_i2c_probe);
374 MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
375 MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
376 MODULE_LICENSE("GPL v2");