1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Microchip / Atmel ECC (I2C) driver. |
4 | * |
5 | * Copyright (c) 2017, Microchip Technology Inc. |
6 | * Author: Tudor Ambarus |
7 | */ |
8 | |
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" |
23 | |
24 | static const struct { |
25 | u8 value; |
26 | const char *error_text; |
27 | } error_list[] = { |
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" }, |
34 | }; |
35 | |
36 | /** |
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. |
42 | * |
43 | * @cmd : structure used for communicating with the device. |
44 | */ |
45 | static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd) |
46 | { |
47 | u8 *data = &cmd->count; |
48 | size_t len = cmd->count - CRC_SIZE; |
49 | __le16 *__crc16 = (__le16 *)(data + len); |
50 | |
51 | *__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len))); |
52 | } |
53 | |
54 | void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd) |
55 | { |
56 | cmd->word_addr = COMMAND; |
57 | cmd->opcode = OPCODE_READ; |
58 | /* |
59 | * Read the word from Configuration zone that contains the lock bytes |
60 | * (UserExtra, Selector, LockValue, LockConfig). |
61 | */ |
62 | cmd->param1 = CONFIGURATION_ZONE; |
63 | cmd->param2 = cpu_to_le16(DEVICE_LOCK_ADDR); |
64 | cmd->count = READ_COUNT; |
65 | |
66 | atmel_i2c_checksum(cmd); |
67 | |
68 | cmd->msecs = MAX_EXEC_TIME_READ; |
69 | cmd->rxsize = READ_RSP_SIZE; |
70 | } |
71 | EXPORT_SYMBOL(atmel_i2c_init_read_cmd); |
72 | |
73 | void atmel_i2c_init_random_cmd(struct atmel_i2c_cmd *cmd) |
74 | { |
75 | cmd->word_addr = COMMAND; |
76 | cmd->opcode = OPCODE_RANDOM; |
77 | cmd->param1 = 0; |
78 | cmd->param2 = 0; |
79 | cmd->count = RANDOM_COUNT; |
80 | |
81 | atmel_i2c_checksum(cmd); |
82 | |
83 | cmd->msecs = MAX_EXEC_TIME_RANDOM; |
84 | cmd->rxsize = RANDOM_RSP_SIZE; |
85 | } |
86 | EXPORT_SYMBOL(atmel_i2c_init_random_cmd); |
87 | |
88 | void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid) |
89 | { |
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); |
96 | |
97 | atmel_i2c_checksum(cmd); |
98 | |
99 | cmd->msecs = MAX_EXEC_TIME_GENKEY; |
100 | cmd->rxsize = GENKEY_RSP_SIZE; |
101 | } |
102 | EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd); |
103 | |
104 | int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd, |
105 | struct scatterlist *pubkey) |
106 | { |
107 | size_t copied; |
108 | |
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); |
115 | |
116 | /* |
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 |
119 | * computations. |
120 | */ |
121 | copied = sg_copy_to_buffer(sgl: pubkey, |
122 | nents: sg_nents_for_len(sg: pubkey, |
123 | ATMEL_ECC_PUBKEY_SIZE), |
124 | buf: cmd->data, ATMEL_ECC_PUBKEY_SIZE); |
125 | if (copied != ATMEL_ECC_PUBKEY_SIZE) |
126 | return -EINVAL; |
127 | |
128 | atmel_i2c_checksum(cmd); |
129 | |
130 | cmd->msecs = MAX_EXEC_TIME_ECDH; |
131 | cmd->rxsize = ECDH_RSP_SIZE; |
132 | |
133 | return 0; |
134 | } |
135 | EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd); |
136 | |
137 | /* |
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. |
142 | */ |
143 | static int atmel_i2c_status(struct device *dev, u8 *status) |
144 | { |
145 | size_t err_list_len = ARRAY_SIZE(error_list); |
146 | int i; |
147 | u8 err_id = status[1]; |
148 | |
149 | if (*status != STATUS_SIZE) |
150 | return 0; |
151 | |
152 | if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR) |
153 | return 0; |
154 | |
155 | for (i = 0; i < err_list_len; i++) |
156 | if (error_list[i].value == err_id) |
157 | break; |
158 | |
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); |
162 | return err_id; |
163 | } |
164 | |
165 | return 0; |
166 | } |
167 | |
168 | static int atmel_i2c_wakeup(struct i2c_client *client) |
169 | { |
170 | struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); |
171 | u8 status[STATUS_RSP_SIZE]; |
172 | int ret; |
173 | |
174 | /* |
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. |
178 | */ |
179 | i2c_transfer_buffer_flags(client, buf: i2c_priv->wake_token, |
180 | count: i2c_priv->wake_token_sz, I2C_M_IGNORE_NAK); |
181 | |
182 | /* |
183 | * Wait to wake the device. Typical execution times for ecdh and genkey |
184 | * are around tens of milliseconds. Delta is chosen to 50 microseconds. |
185 | */ |
186 | usleep_range(TWHI_MIN, TWHI_MAX); |
187 | |
188 | ret = i2c_master_recv(client, buf: status, STATUS_SIZE); |
189 | if (ret < 0) |
190 | return ret; |
191 | |
192 | return atmel_i2c_status(dev: &client->dev, status); |
193 | } |
194 | |
195 | static int atmel_i2c_sleep(struct i2c_client *client) |
196 | { |
197 | u8 sleep = SLEEP_TOKEN; |
198 | |
199 | return i2c_master_send(client, buf: &sleep, count: 1); |
200 | } |
201 | |
202 | /* |
203 | * atmel_i2c_send_receive() - send a command to the device and receive its |
204 | * response. |
205 | * @client: i2c client device |
206 | * @cmd : structure used to communicate with the device |
207 | * |
208 | * After the device receives a Wake token, a watchdog counter starts within the |
209 | * device. After the watchdog timer expires, the device enters sleep mode |
210 | * regardless of whether some I/O transmission or command execution is in |
211 | * progress. If a command is attempted when insufficient time remains prior to |
212 | * watchdog timer execution, the device will return the watchdog timeout error |
213 | * code without attempting to execute the command. There is no way to reset the |
214 | * counter other than to put the device into sleep or idle mode and then |
215 | * wake it up again. |
216 | */ |
217 | int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd) |
218 | { |
219 | struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); |
220 | int ret; |
221 | |
222 | mutex_lock(&i2c_priv->lock); |
223 | |
224 | ret = atmel_i2c_wakeup(client); |
225 | if (ret) |
226 | goto err; |
227 | |
228 | /* send the command */ |
229 | ret = i2c_master_send(client, buf: (u8 *)cmd, count: cmd->count + WORD_ADDR_SIZE); |
230 | if (ret < 0) |
231 | goto err; |
232 | |
233 | /* delay the appropriate amount of time for command to execute */ |
234 | msleep(msecs: cmd->msecs); |
235 | |
236 | /* receive the response */ |
237 | ret = i2c_master_recv(client, buf: cmd->data, count: cmd->rxsize); |
238 | if (ret < 0) |
239 | goto err; |
240 | |
241 | /* put the device into low-power mode */ |
242 | ret = atmel_i2c_sleep(client); |
243 | if (ret < 0) |
244 | goto err; |
245 | |
246 | mutex_unlock(lock: &i2c_priv->lock); |
247 | return atmel_i2c_status(dev: &client->dev, status: cmd->data); |
248 | err: |
249 | mutex_unlock(lock: &i2c_priv->lock); |
250 | return ret; |
251 | } |
252 | EXPORT_SYMBOL(atmel_i2c_send_receive); |
253 | |
254 | static void atmel_i2c_work_handler(struct work_struct *work) |
255 | { |
256 | struct atmel_i2c_work_data *work_data = |
257 | container_of(work, struct atmel_i2c_work_data, work); |
258 | struct atmel_i2c_cmd *cmd = &work_data->cmd; |
259 | struct i2c_client *client = work_data->client; |
260 | int status; |
261 | |
262 | status = atmel_i2c_send_receive(client, cmd); |
263 | work_data->cbk(work_data, work_data->areq, status); |
264 | } |
265 | |
266 | static struct workqueue_struct *atmel_wq; |
267 | |
268 | void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data, |
269 | void (*cbk)(struct atmel_i2c_work_data *work_data, |
270 | void *areq, int status), |
271 | void *areq) |
272 | { |
273 | work_data->cbk = (void *)cbk; |
274 | work_data->areq = areq; |
275 | |
276 | INIT_WORK(&work_data->work, atmel_i2c_work_handler); |
277 | queue_work(wq: atmel_wq, work: &work_data->work); |
278 | } |
279 | EXPORT_SYMBOL(atmel_i2c_enqueue); |
280 | |
281 | void atmel_i2c_flush_queue(void) |
282 | { |
283 | flush_workqueue(atmel_wq); |
284 | } |
285 | EXPORT_SYMBOL(atmel_i2c_flush_queue); |
286 | |
287 | static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate) |
288 | { |
289 | u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC); |
290 | |
291 | /* return the size of the wake_token in bytes */ |
292 | return DIV_ROUND_UP(no_of_bits, 8); |
293 | } |
294 | |
295 | static int device_sanity_check(struct i2c_client *client) |
296 | { |
297 | struct atmel_i2c_cmd *cmd; |
298 | int ret; |
299 | |
300 | cmd = kmalloc(size: sizeof(*cmd), GFP_KERNEL); |
301 | if (!cmd) |
302 | return -ENOMEM; |
303 | |
304 | atmel_i2c_init_read_cmd(cmd); |
305 | |
306 | ret = atmel_i2c_send_receive(client, cmd); |
307 | if (ret) |
308 | goto free_cmd; |
309 | |
310 | /* |
311 | * It is vital that the Configuration, Data and OTP zones be locked |
312 | * prior to release into the field of the system containing the device. |
313 | * Failure to lock these zones may permit modification of any secret |
314 | * keys and may lead to other security problems. |
315 | */ |
316 | if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) { |
317 | dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n" ); |
318 | ret = -ENOTSUPP; |
319 | } |
320 | |
321 | /* fall through */ |
322 | free_cmd: |
323 | kfree(objp: cmd); |
324 | return ret; |
325 | } |
326 | |
327 | int atmel_i2c_probe(struct i2c_client *client) |
328 | { |
329 | struct atmel_i2c_client_priv *i2c_priv; |
330 | struct device *dev = &client->dev; |
331 | int ret; |
332 | u32 bus_clk_rate; |
333 | |
334 | if (!i2c_check_functionality(adap: client->adapter, I2C_FUNC_I2C)) { |
335 | dev_err(dev, "I2C_FUNC_I2C not supported\n" ); |
336 | return -ENODEV; |
337 | } |
338 | |
339 | bus_clk_rate = i2c_acpi_find_bus_speed(dev: &client->adapter->dev); |
340 | if (!bus_clk_rate) { |
341 | ret = device_property_read_u32(dev: &client->adapter->dev, |
342 | propname: "clock-frequency" , val: &bus_clk_rate); |
343 | if (ret) { |
344 | dev_err(dev, "failed to read clock-frequency property\n" ); |
345 | return ret; |
346 | } |
347 | } |
348 | |
349 | if (bus_clk_rate > 1000000L) { |
350 | dev_err(dev, "%u exceeds maximum supported clock frequency (1MHz)\n" , |
351 | bus_clk_rate); |
352 | return -EINVAL; |
353 | } |
354 | |
355 | i2c_priv = devm_kmalloc(dev, size: sizeof(*i2c_priv), GFP_KERNEL); |
356 | if (!i2c_priv) |
357 | return -ENOMEM; |
358 | |
359 | i2c_priv->client = client; |
360 | mutex_init(&i2c_priv->lock); |
361 | |
362 | /* |
363 | * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate - |
364 | * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz |
365 | * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE. |
366 | */ |
367 | i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate); |
368 | |
369 | memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token)); |
370 | |
371 | atomic_set(v: &i2c_priv->tfm_count, i: 0); |
372 | |
373 | i2c_set_clientdata(client, data: i2c_priv); |
374 | |
375 | return device_sanity_check(client); |
376 | } |
377 | EXPORT_SYMBOL(atmel_i2c_probe); |
378 | |
379 | static int __init atmel_i2c_init(void) |
380 | { |
381 | atmel_wq = alloc_workqueue(fmt: "atmel_wq" , flags: 0, max_active: 0); |
382 | return atmel_wq ? 0 : -ENOMEM; |
383 | } |
384 | |
385 | static void __exit atmel_i2c_exit(void) |
386 | { |
387 | destroy_workqueue(wq: atmel_wq); |
388 | } |
389 | |
390 | module_init(atmel_i2c_init); |
391 | module_exit(atmel_i2c_exit); |
392 | |
393 | MODULE_AUTHOR("Tudor Ambarus" ); |
394 | MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver" ); |
395 | MODULE_LICENSE("GPL v2" ); |
396 | |