xref: /openbmc/linux/drivers/char/ipmi/ssif_bmc.c (revision e64c82b8)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * The driver for BMC side of SSIF interface
4  *
5  * Copyright (c) 2022, Ampere Computing LLC
6  *
7  */
8 
9 #include <linux/i2c.h>
10 #include <linux/miscdevice.h>
11 #include <linux/module.h>
12 #include <linux/of.h>
13 #include <linux/platform_device.h>
14 #include <linux/poll.h>
15 #include <linux/sched.h>
16 #include <linux/mutex.h>
17 #include <linux/spinlock.h>
18 #include <linux/timer.h>
19 #include <linux/jiffies.h>
20 #include <linux/ipmi_ssif_bmc.h>
21 
22 #define DEVICE_NAME                             "ipmi-ssif-host"
23 
24 #define GET_8BIT_ADDR(addr_7bit)                (((addr_7bit) << 1) & 0xff)
25 
26 /* A standard SMBus Transaction is limited to 32 data bytes */
27 #define MAX_PAYLOAD_PER_TRANSACTION             32
28 /* Transaction includes the address, the command, the length and the PEC byte */
29 #define MAX_TRANSACTION                         (MAX_PAYLOAD_PER_TRANSACTION + 4)
30 
31 #define MAX_IPMI_DATA_PER_START_TRANSACTION     30
32 #define MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION    31
33 
34 #define SSIF_IPMI_SINGLEPART_WRITE              0x2
35 #define SSIF_IPMI_SINGLEPART_READ               0x3
36 #define SSIF_IPMI_MULTIPART_WRITE_START         0x6
37 #define SSIF_IPMI_MULTIPART_WRITE_MIDDLE        0x7
38 #define SSIF_IPMI_MULTIPART_WRITE_END           0x8
39 #define SSIF_IPMI_MULTIPART_READ_START          0x3
40 #define SSIF_IPMI_MULTIPART_READ_MIDDLE         0x9
41 
42 /*
43  * IPMI 2.0 Spec, section 12.7 SSIF Timing,
44  * Request-to-Response Time is T6max(250ms) - T1max(20ms) - 3ms = 227ms
45  * Recover ssif_bmc from busy state if it takes up to 500ms
46  */
47 #define RESPONSE_TIMEOUT                        500 /* ms */
48 
49 struct ssif_part_buffer {
50 	u8 address;
51 	u8 smbus_cmd;
52 	u8 length;
53 	u8 payload[MAX_PAYLOAD_PER_TRANSACTION];
54 	u8 pec;
55 	u8 index;
56 };
57 
58 /*
59  * SSIF internal states:
60  *   SSIF_READY         0x00 : Ready state
61  *   SSIF_START         0x01 : Start smbus transaction
62  *   SSIF_SMBUS_CMD     0x02 : Received SMBus command
63  *   SSIF_REQ_RECVING   0x03 : Receiving request
64  *   SSIF_RES_SENDING   0x04 : Sending response
65  *   SSIF_ABORTING      0x05 : Aborting state
66  */
67 enum ssif_state {
68 	SSIF_READY,
69 	SSIF_START,
70 	SSIF_SMBUS_CMD,
71 	SSIF_REQ_RECVING,
72 	SSIF_RES_SENDING,
73 	SSIF_ABORTING,
74 	SSIF_STATE_MAX
75 };
76 
77 struct ssif_bmc_ctx {
78 	struct i2c_client       *client;
79 	struct miscdevice       miscdev;
80 	int                     msg_idx;
81 	bool                    pec_support;
82 	/* ssif bmc spinlock */
83 	spinlock_t              lock;
84 	wait_queue_head_t       wait_queue;
85 	u8                      running;
86 	enum ssif_state         state;
87 	/* Timeout waiting for response */
88 	struct timer_list       response_timer;
89 	bool                    response_timer_inited;
90 	/* Flag to identify a Multi-part Read Transaction */
91 	bool                    is_singlepart_read;
92 	u8                      nbytes_processed;
93 	u8                      remain_len;
94 	u8                      recv_len;
95 	/* Block Number of a Multi-part Read Transaction */
96 	u8                      block_num;
97 	bool                    request_available;
98 	bool                    response_in_progress;
99 	bool                    busy;
100 	bool                    aborting;
101 	/* Buffer for SSIF Transaction part*/
102 	struct ssif_part_buffer part_buf;
103 	struct ipmi_ssif_msg    response;
104 	struct ipmi_ssif_msg    request;
105 };
106 
107 static inline struct ssif_bmc_ctx *to_ssif_bmc(struct file *file)
108 {
109 	return container_of(file->private_data, struct ssif_bmc_ctx, miscdev);
110 }
111 
112 static const char *state_to_string(enum ssif_state state)
113 {
114 	switch (state) {
115 	case SSIF_READY:
116 		return "SSIF_READY";
117 	case SSIF_START:
118 		return "SSIF_START";
119 	case SSIF_SMBUS_CMD:
120 		return "SSIF_SMBUS_CMD";
121 	case SSIF_REQ_RECVING:
122 		return "SSIF_REQ_RECVING";
123 	case SSIF_RES_SENDING:
124 		return "SSIF_RES_SENDING";
125 	case SSIF_ABORTING:
126 		return "SSIF_ABORTING";
127 	default:
128 		return "SSIF_STATE_UNKNOWN";
129 	}
130 }
131 
132 /* Handle SSIF message that will be sent to user */
133 static ssize_t ssif_bmc_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
134 {
135 	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
136 	struct ipmi_ssif_msg msg;
137 	unsigned long flags;
138 	ssize_t ret;
139 
140 	spin_lock_irqsave(&ssif_bmc->lock, flags);
141 	while (!ssif_bmc->request_available) {
142 		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
143 		if (file->f_flags & O_NONBLOCK)
144 			return -EAGAIN;
145 		ret = wait_event_interruptible(ssif_bmc->wait_queue,
146 					       ssif_bmc->request_available);
147 		if (ret)
148 			return ret;
149 		spin_lock_irqsave(&ssif_bmc->lock, flags);
150 	}
151 
152 	if (count < min_t(ssize_t,
153 			  sizeof_field(struct ipmi_ssif_msg, len) + ssif_bmc->request.len,
154 			  sizeof(struct ipmi_ssif_msg))) {
155 		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
156 		ret = -EINVAL;
157 	} else {
158 		count = min_t(ssize_t,
159 			      sizeof_field(struct ipmi_ssif_msg, len) + ssif_bmc->request.len,
160 			      sizeof(struct ipmi_ssif_msg));
161 		memcpy(&msg, &ssif_bmc->request, count);
162 		ssif_bmc->request_available = false;
163 		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
164 
165 		ret = copy_to_user(buf, &msg, count);
166 	}
167 
168 	return (ret < 0) ? ret : count;
169 }
170 
171 /* Handle SSIF message that is written by user */
172 static ssize_t ssif_bmc_write(struct file *file, const char __user *buf, size_t count,
173 			      loff_t *ppos)
174 {
175 	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
176 	struct ipmi_ssif_msg msg;
177 	unsigned long flags;
178 	ssize_t ret;
179 
180 	if (count > sizeof(struct ipmi_ssif_msg))
181 		return -EINVAL;
182 
183 	if (copy_from_user(&msg, buf, count))
184 		return -EFAULT;
185 
186 	if (!msg.len || count < sizeof_field(struct ipmi_ssif_msg, len) + msg.len)
187 		return -EINVAL;
188 
189 	spin_lock_irqsave(&ssif_bmc->lock, flags);
190 	while (ssif_bmc->response_in_progress) {
191 		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
192 		if (file->f_flags & O_NONBLOCK)
193 			return -EAGAIN;
194 		ret = wait_event_interruptible(ssif_bmc->wait_queue,
195 					       !ssif_bmc->response_in_progress);
196 		if (ret)
197 			return ret;
198 		spin_lock_irqsave(&ssif_bmc->lock, flags);
199 	}
200 
201 	/*
202 	 * The write must complete before the response timeout fired, otherwise
203 	 * the response is aborted and wait for next request
204 	 * Return -EINVAL if the response is aborted
205 	 */
206 	ret = (ssif_bmc->response_timer_inited) ? 0 : -EINVAL;
207 	if (ret)
208 		goto exit;
209 
210 	del_timer(&ssif_bmc->response_timer);
211 	ssif_bmc->response_timer_inited = false;
212 
213 	memcpy(&ssif_bmc->response, &msg, count);
214 	ssif_bmc->is_singlepart_read = (msg.len <= MAX_PAYLOAD_PER_TRANSACTION);
215 
216 	ssif_bmc->response_in_progress = true;
217 
218 	/* ssif_bmc not busy */
219 	ssif_bmc->busy = false;
220 
221 	/* Clean old request buffer */
222 	memset(&ssif_bmc->request, 0, sizeof(struct ipmi_ssif_msg));
223 exit:
224 	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
225 
226 	return (ret < 0) ? ret : count;
227 }
228 
229 static int ssif_bmc_open(struct inode *inode, struct file *file)
230 {
231 	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
232 	int ret = 0;
233 
234 	spin_lock_irq(&ssif_bmc->lock);
235 	if (!ssif_bmc->running)
236 		ssif_bmc->running = 1;
237 	else
238 		ret = -EBUSY;
239 	spin_unlock_irq(&ssif_bmc->lock);
240 
241 	return ret;
242 }
243 
244 static __poll_t ssif_bmc_poll(struct file *file, poll_table *wait)
245 {
246 	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
247 	__poll_t mask = 0;
248 
249 	poll_wait(file, &ssif_bmc->wait_queue, wait);
250 
251 	spin_lock_irq(&ssif_bmc->lock);
252 	/* The request is available, userspace application can get the request */
253 	if (ssif_bmc->request_available)
254 		mask |= EPOLLIN;
255 
256 	spin_unlock_irq(&ssif_bmc->lock);
257 
258 	return mask;
259 }
260 
261 static int ssif_bmc_release(struct inode *inode, struct file *file)
262 {
263 	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
264 
265 	spin_lock_irq(&ssif_bmc->lock);
266 	ssif_bmc->running = 0;
267 	spin_unlock_irq(&ssif_bmc->lock);
268 
269 	return 0;
270 }
271 
272 /*
273  * System calls to device interface for user apps
274  */
275 static const struct file_operations ssif_bmc_fops = {
276 	.owner		= THIS_MODULE,
277 	.open		= ssif_bmc_open,
278 	.read		= ssif_bmc_read,
279 	.write		= ssif_bmc_write,
280 	.release	= ssif_bmc_release,
281 	.poll		= ssif_bmc_poll,
282 };
283 
284 /* Called with ssif_bmc->lock held. */
285 static void complete_response(struct ssif_bmc_ctx *ssif_bmc)
286 {
287 	/* Invalidate response in buffer to denote it having been sent. */
288 	ssif_bmc->response.len = 0;
289 	ssif_bmc->response_in_progress = false;
290 	ssif_bmc->nbytes_processed = 0;
291 	ssif_bmc->remain_len = 0;
292 	ssif_bmc->busy = false;
293 	memset(&ssif_bmc->part_buf, 0, sizeof(struct ssif_part_buffer));
294 	wake_up_all(&ssif_bmc->wait_queue);
295 }
296 
297 static void response_timeout(struct timer_list *t)
298 {
299 	struct ssif_bmc_ctx *ssif_bmc = from_timer(ssif_bmc, t, response_timer);
300 	unsigned long flags;
301 
302 	spin_lock_irqsave(&ssif_bmc->lock, flags);
303 
304 	/* Do nothing if the response is in progress */
305 	if (!ssif_bmc->response_in_progress) {
306 		/* Recover ssif_bmc from busy */
307 		ssif_bmc->busy = false;
308 		ssif_bmc->response_timer_inited = false;
309 		/* Set aborting flag */
310 		ssif_bmc->aborting = true;
311 	}
312 
313 	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
314 }
315 
316 /* Called with ssif_bmc->lock held. */
317 static void handle_request(struct ssif_bmc_ctx *ssif_bmc)
318 {
319 	/* set ssif_bmc to busy waiting for response */
320 	ssif_bmc->busy = true;
321 	/* Request message is available to process */
322 	ssif_bmc->request_available = true;
323 	/* Clean old response buffer */
324 	memset(&ssif_bmc->response, 0, sizeof(struct ipmi_ssif_msg));
325 	/* This is the new READ request.*/
326 	wake_up_all(&ssif_bmc->wait_queue);
327 
328 	/* Armed timer to recover slave from busy state in case of no response */
329 	if (!ssif_bmc->response_timer_inited) {
330 		timer_setup(&ssif_bmc->response_timer, response_timeout, 0);
331 		ssif_bmc->response_timer_inited = true;
332 	}
333 	mod_timer(&ssif_bmc->response_timer, jiffies + msecs_to_jiffies(RESPONSE_TIMEOUT));
334 }
335 
336 static void calculate_response_part_pec(struct ssif_part_buffer *part)
337 {
338 	u8 addr = part->address;
339 
340 	/* PEC - Start Read Address */
341 	part->pec = i2c_smbus_pec(0, &addr, 1);
342 	/* PEC - SSIF Command */
343 	part->pec = i2c_smbus_pec(part->pec, &part->smbus_cmd, 1);
344 	/* PEC - Restart Write Address */
345 	addr = addr | 0x01;
346 	part->pec = i2c_smbus_pec(part->pec, &addr, 1);
347 	part->pec = i2c_smbus_pec(part->pec, &part->length, 1);
348 	if (part->length)
349 		part->pec = i2c_smbus_pec(part->pec, part->payload, part->length);
350 }
351 
352 static void set_singlepart_response_buffer(struct ssif_bmc_ctx *ssif_bmc)
353 {
354 	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
355 
356 	part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
357 	part->length = (u8)ssif_bmc->response.len;
358 
359 	/* Clear the rest to 0 */
360 	memset(part->payload + part->length, 0, MAX_PAYLOAD_PER_TRANSACTION - part->length);
361 	memcpy(&part->payload[0], &ssif_bmc->response.payload[0], part->length);
362 }
363 
364 static void set_multipart_response_buffer(struct ssif_bmc_ctx *ssif_bmc)
365 {
366 	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
367 	u8 part_len = 0;
368 
369 	part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
370 	switch (part->smbus_cmd) {
371 	case SSIF_IPMI_MULTIPART_READ_START:
372 		/*
373 		 * Read Start length is 32 bytes.
374 		 * Read Start transfer first 30 bytes of IPMI response
375 		 * and 2 special code 0x00, 0x01.
376 		 */
377 		ssif_bmc->nbytes_processed = 0;
378 		ssif_bmc->block_num = 0;
379 		part->length = MAX_PAYLOAD_PER_TRANSACTION;
380 		part_len = MAX_IPMI_DATA_PER_START_TRANSACTION;
381 		ssif_bmc->remain_len = ssif_bmc->response.len - part_len;
382 
383 		part->payload[0] = 0x00; /* Start Flag */
384 		part->payload[1] = 0x01; /* Start Flag */
385 
386 		memcpy(&part->payload[2], &ssif_bmc->response.payload[0], part_len);
387 		break;
388 
389 	case SSIF_IPMI_MULTIPART_READ_MIDDLE:
390 		/*
391 		 * IPMI READ Middle or READ End messages can carry up to 31 bytes
392 		 * IPMI data plus block number byte.
393 		 */
394 		if (ssif_bmc->remain_len <= MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION) {
395 			/*
396 			 * This is READ End message
397 			 *  Return length is the remaining response data length
398 			 *  plus block number
399 			 *  Block number 0xFF is to indicate this is last message
400 			 *
401 			 */
402 			/* Clean the buffer */
403 			memset(&part->payload[0], 0, MAX_PAYLOAD_PER_TRANSACTION);
404 			part->length = ssif_bmc->remain_len + 1;
405 			part_len = ssif_bmc->remain_len;
406 			ssif_bmc->block_num = 0xFF;
407 			part->payload[0] = ssif_bmc->block_num;
408 		} else {
409 			/*
410 			 * This is READ Middle message
411 			 *  Response length is the maximum SMBUS transfer length
412 			 *  Block number byte is incremented
413 			 * Return length is maximum SMBUS transfer length
414 			 */
415 			part->length = MAX_PAYLOAD_PER_TRANSACTION;
416 			part_len = MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
417 			part->payload[0] = ssif_bmc->block_num;
418 			ssif_bmc->block_num++;
419 		}
420 
421 		ssif_bmc->remain_len -= part_len;
422 		memcpy(&part->payload[1], ssif_bmc->response.payload + ssif_bmc->nbytes_processed,
423 		       part_len);
424 		break;
425 
426 	default:
427 		/* Do not expect to go to this case */
428 		dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x\n",
429 			__func__, part->smbus_cmd);
430 		break;
431 	}
432 
433 	ssif_bmc->nbytes_processed += part_len;
434 }
435 
436 static bool supported_read_cmd(u8 cmd)
437 {
438 	if (cmd == SSIF_IPMI_SINGLEPART_READ ||
439 	    cmd == SSIF_IPMI_MULTIPART_READ_START ||
440 	    cmd == SSIF_IPMI_MULTIPART_READ_MIDDLE)
441 		return true;
442 
443 	return false;
444 }
445 
446 static bool supported_write_cmd(u8 cmd)
447 {
448 	if (cmd == SSIF_IPMI_SINGLEPART_WRITE ||
449 	    cmd == SSIF_IPMI_MULTIPART_WRITE_START ||
450 	    cmd == SSIF_IPMI_MULTIPART_WRITE_MIDDLE ||
451 	    cmd == SSIF_IPMI_MULTIPART_WRITE_END)
452 		return true;
453 
454 	return false;
455 }
456 
457 /* Process the IPMI response that will be read by master */
458 static void handle_read_processed(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
459 {
460 	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
461 
462 	/* msg_idx start from 0 */
463 	if (part->index < part->length)
464 		*val = part->payload[part->index];
465 	else if (part->index == part->length && ssif_bmc->pec_support)
466 		*val = part->pec;
467 	else
468 		*val = 0;
469 
470 	part->index++;
471 }
472 
473 static void handle_write_received(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
474 {
475 	/*
476 	 * The msg_idx must be 1 when first enter SSIF_REQ_RECVING state
477 	 * And it would never exceeded 36 bytes included the 32 bytes max payload +
478 	 * the address + the command + the len and the PEC.
479 	 */
480 	if (ssif_bmc->msg_idx < 1  || ssif_bmc->msg_idx > MAX_TRANSACTION)
481 		return;
482 
483 	if (ssif_bmc->msg_idx == 1) {
484 		ssif_bmc->part_buf.length = *val;
485 		ssif_bmc->part_buf.index = 0;
486 	} else {
487 		ssif_bmc->part_buf.payload[ssif_bmc->part_buf.index++] = *val;
488 	}
489 
490 	ssif_bmc->msg_idx++;
491 }
492 
493 static bool validate_request_part(struct ssif_bmc_ctx *ssif_bmc)
494 {
495 	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
496 	bool ret = true;
497 	u8 cpec;
498 	u8 addr;
499 
500 	if (part->index == part->length) {
501 		/* PEC is not included */
502 		ssif_bmc->pec_support = false;
503 		ret = true;
504 		goto exit;
505 	}
506 
507 	if (part->index != part->length + 1) {
508 		ret = false;
509 		goto exit;
510 	}
511 
512 	/* PEC is included */
513 	ssif_bmc->pec_support = true;
514 	part->pec = part->payload[part->length];
515 	addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
516 	cpec = i2c_smbus_pec(0, &addr, 1);
517 	cpec = i2c_smbus_pec(cpec, &part->smbus_cmd, 1);
518 	cpec = i2c_smbus_pec(cpec, &part->length, 1);
519 	/*
520 	 * As SMBus specification does not allow the length
521 	 * (byte count) in the Write-Block protocol to be zero.
522 	 * Therefore, it is illegal to have the last Middle
523 	 * transaction in the sequence carry 32-byte and have
524 	 * a length of ‘0’ in the End transaction.
525 	 * But some users may try to use this way and we should
526 	 * prevent ssif_bmc driver broken in this case.
527 	 */
528 	if (part->length)
529 		cpec = i2c_smbus_pec(cpec, part->payload, part->length);
530 
531 	if (cpec != part->pec)
532 		ret = false;
533 
534 exit:
535 	return ret;
536 }
537 
538 static void process_request_part(struct ssif_bmc_ctx *ssif_bmc)
539 {
540 	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
541 	unsigned int len;
542 
543 	switch (part->smbus_cmd) {
544 	case SSIF_IPMI_SINGLEPART_WRITE:
545 		/* save the whole part to request*/
546 		ssif_bmc->request.len = part->length;
547 		memcpy(ssif_bmc->request.payload, part->payload, part->length);
548 
549 		break;
550 	case SSIF_IPMI_MULTIPART_WRITE_START:
551 		ssif_bmc->request.len = 0;
552 
553 		fallthrough;
554 	case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
555 	case SSIF_IPMI_MULTIPART_WRITE_END:
556 		len = ssif_bmc->request.len + part->length;
557 		/* Do the bound check here, not allow the request len exceed 254 bytes */
558 		if (len > IPMI_SSIF_PAYLOAD_MAX) {
559 			dev_warn(&ssif_bmc->client->dev,
560 				 "Warn: Request exceeded 254 bytes, aborting");
561 			/* Request too long, aborting */
562 			ssif_bmc->aborting =  true;
563 		} else {
564 			memcpy(ssif_bmc->request.payload + ssif_bmc->request.len,
565 			       part->payload, part->length);
566 			ssif_bmc->request.len += part->length;
567 		}
568 		break;
569 	default:
570 		/* Do not expect to go to this case */
571 		dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x\n",
572 			__func__, part->smbus_cmd);
573 		break;
574 	}
575 }
576 
577 static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
578 {
579 	/* SMBUS command can vary (single or multi-part) */
580 	ssif_bmc->part_buf.smbus_cmd = *val;
581 	ssif_bmc->msg_idx = 1;
582 	memset(&ssif_bmc->part_buf.payload[0], 0, MAX_PAYLOAD_PER_TRANSACTION);
583 
584 	if (*val == SSIF_IPMI_SINGLEPART_WRITE || *val == SSIF_IPMI_MULTIPART_WRITE_START) {
585 		/*
586 		 * The response maybe not come in-time, causing host SSIF driver
587 		 * to timeout and resend a new request. In such case check for
588 		 * pending response and clear it
589 		 */
590 		if (ssif_bmc->response_in_progress)
591 			complete_response(ssif_bmc);
592 
593 		/* This is new request, flip aborting flag if set */
594 		if (ssif_bmc->aborting)
595 			ssif_bmc->aborting = false;
596 	}
597 }
598 
599 static void on_read_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
600 {
601 	if (ssif_bmc->state == SSIF_READY ||
602 	    ssif_bmc->state == SSIF_START ||
603 	    ssif_bmc->state == SSIF_REQ_RECVING ||
604 	    ssif_bmc->state == SSIF_RES_SENDING) {
605 		dev_warn(&ssif_bmc->client->dev,
606 			 "Warn: %s unexpected READ REQUESTED in state=%s\n",
607 			 __func__, state_to_string(ssif_bmc->state));
608 		ssif_bmc->state = SSIF_ABORTING;
609 		*val = 0;
610 		return;
611 
612 	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
613 		if (!supported_read_cmd(ssif_bmc->part_buf.smbus_cmd)) {
614 			dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus read command=0x%x",
615 				 ssif_bmc->part_buf.smbus_cmd);
616 			ssif_bmc->aborting = true;
617 		}
618 
619 		if (ssif_bmc->aborting)
620 			ssif_bmc->state = SSIF_ABORTING;
621 		else
622 			ssif_bmc->state = SSIF_RES_SENDING;
623 	}
624 
625 	ssif_bmc->msg_idx = 0;
626 
627 	/* Send 0 if there is nothing to send */
628 	if (!ssif_bmc->response_in_progress || ssif_bmc->state == SSIF_ABORTING) {
629 		*val = 0;
630 		return;
631 	}
632 
633 	if (ssif_bmc->is_singlepart_read)
634 		set_singlepart_response_buffer(ssif_bmc);
635 	else
636 		set_multipart_response_buffer(ssif_bmc);
637 
638 	calculate_response_part_pec(&ssif_bmc->part_buf);
639 	ssif_bmc->part_buf.index = 0;
640 	*val = ssif_bmc->part_buf.length;
641 }
642 
643 static void on_read_processed_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
644 {
645 	if (ssif_bmc->state == SSIF_READY ||
646 	    ssif_bmc->state == SSIF_START ||
647 	    ssif_bmc->state == SSIF_REQ_RECVING ||
648 	    ssif_bmc->state == SSIF_SMBUS_CMD) {
649 		dev_warn(&ssif_bmc->client->dev,
650 			 "Warn: %s unexpected READ PROCESSED in state=%s\n",
651 			 __func__, state_to_string(ssif_bmc->state));
652 		ssif_bmc->state = SSIF_ABORTING;
653 		*val = 0;
654 		return;
655 	}
656 
657 	/* Send 0 if there is nothing to send */
658 	if (!ssif_bmc->response_in_progress || ssif_bmc->state == SSIF_ABORTING) {
659 		*val = 0;
660 		return;
661 	}
662 
663 	handle_read_processed(ssif_bmc, val);
664 }
665 
666 static void on_write_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
667 {
668 	if (ssif_bmc->state == SSIF_READY || ssif_bmc->state == SSIF_SMBUS_CMD) {
669 		ssif_bmc->state = SSIF_START;
670 
671 	} else if (ssif_bmc->state == SSIF_START ||
672 		   ssif_bmc->state == SSIF_REQ_RECVING ||
673 		   ssif_bmc->state == SSIF_RES_SENDING) {
674 		dev_warn(&ssif_bmc->client->dev,
675 			 "Warn: %s unexpected WRITE REQUEST in state=%s\n",
676 			 __func__, state_to_string(ssif_bmc->state));
677 		ssif_bmc->state = SSIF_ABORTING;
678 		return;
679 	}
680 
681 	ssif_bmc->msg_idx = 0;
682 	ssif_bmc->part_buf.address = *val;
683 }
684 
685 static void on_write_received_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
686 {
687 	if (ssif_bmc->state == SSIF_READY ||
688 	    ssif_bmc->state == SSIF_RES_SENDING) {
689 		dev_warn(&ssif_bmc->client->dev,
690 			 "Warn: %s unexpected WRITE RECEIVED in state=%s\n",
691 			 __func__, state_to_string(ssif_bmc->state));
692 		ssif_bmc->state = SSIF_ABORTING;
693 
694 	} else if (ssif_bmc->state == SSIF_START) {
695 		ssif_bmc->state = SSIF_SMBUS_CMD;
696 
697 	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
698 		if (!supported_write_cmd(ssif_bmc->part_buf.smbus_cmd)) {
699 			dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus write command=0x%x",
700 				 ssif_bmc->part_buf.smbus_cmd);
701 			ssif_bmc->aborting = true;
702 		}
703 
704 		if (ssif_bmc->aborting)
705 			ssif_bmc->state = SSIF_ABORTING;
706 		else
707 			ssif_bmc->state = SSIF_REQ_RECVING;
708 	}
709 
710 	/* This is response sending state */
711 	if (ssif_bmc->state == SSIF_REQ_RECVING)
712 		handle_write_received(ssif_bmc, val);
713 	else if (ssif_bmc->state == SSIF_SMBUS_CMD)
714 		process_smbus_cmd(ssif_bmc, val);
715 }
716 
717 static void on_stop_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
718 {
719 	if (ssif_bmc->state == SSIF_READY ||
720 	    ssif_bmc->state == SSIF_START ||
721 	    ssif_bmc->state == SSIF_SMBUS_CMD ||
722 	    ssif_bmc->state == SSIF_ABORTING) {
723 		dev_warn(&ssif_bmc->client->dev,
724 			 "Warn: %s unexpected SLAVE STOP in state=%s\n",
725 			 __func__, state_to_string(ssif_bmc->state));
726 		ssif_bmc->state = SSIF_READY;
727 
728 	} else if (ssif_bmc->state == SSIF_REQ_RECVING) {
729 		if (validate_request_part(ssif_bmc)) {
730 			process_request_part(ssif_bmc);
731 			if (ssif_bmc->part_buf.smbus_cmd == SSIF_IPMI_SINGLEPART_WRITE ||
732 			    ssif_bmc->part_buf.smbus_cmd == SSIF_IPMI_MULTIPART_WRITE_END)
733 				handle_request(ssif_bmc);
734 			ssif_bmc->state = SSIF_READY;
735 		} else {
736 			/*
737 			 * A BMC that receives an invalid request drop the data for the write
738 			 * transaction and any further transactions (read or write) until
739 			 * the next valid read or write Start transaction is received
740 			 */
741 			dev_err(&ssif_bmc->client->dev, "Error: invalid pec\n");
742 			ssif_bmc->aborting = true;
743 		}
744 	} else if (ssif_bmc->state == SSIF_RES_SENDING) {
745 		if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num == 0xFF)
746 			/* Invalidate response buffer to denote it is sent */
747 			complete_response(ssif_bmc);
748 		ssif_bmc->state = SSIF_READY;
749 	}
750 
751 	/* Reset message index */
752 	ssif_bmc->msg_idx = 0;
753 }
754 
755 /*
756  * Callback function to handle I2C slave events
757  */
758 static int ssif_bmc_cb(struct i2c_client *client, enum i2c_slave_event event, u8 *val)
759 {
760 	unsigned long flags;
761 	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
762 	int ret = 0;
763 
764 	spin_lock_irqsave(&ssif_bmc->lock, flags);
765 
766 	switch (event) {
767 	case I2C_SLAVE_READ_REQUESTED:
768 		on_read_requested_event(ssif_bmc, val);
769 		break;
770 
771 	case I2C_SLAVE_WRITE_REQUESTED:
772 		on_write_requested_event(ssif_bmc, val);
773 		break;
774 
775 	case I2C_SLAVE_READ_PROCESSED:
776 		on_read_processed_event(ssif_bmc, val);
777 		break;
778 
779 	case I2C_SLAVE_WRITE_RECEIVED:
780 		on_write_received_event(ssif_bmc, val);
781 		break;
782 
783 	case I2C_SLAVE_STOP:
784 		on_stop_event(ssif_bmc, val);
785 		break;
786 
787 	default:
788 		dev_warn(&ssif_bmc->client->dev, "Warn: Unknown i2c slave event\n");
789 		break;
790 	}
791 
792 	if (!ssif_bmc->aborting && ssif_bmc->busy)
793 		ret = -EBUSY;
794 
795 	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
796 
797 	return ret;
798 }
799 
800 static int ssif_bmc_probe(struct i2c_client *client)
801 {
802 	struct ssif_bmc_ctx *ssif_bmc;
803 	int ret;
804 
805 	ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc), GFP_KERNEL);
806 	if (!ssif_bmc)
807 		return -ENOMEM;
808 
809 	spin_lock_init(&ssif_bmc->lock);
810 
811 	init_waitqueue_head(&ssif_bmc->wait_queue);
812 	ssif_bmc->request_available = false;
813 	ssif_bmc->response_in_progress = false;
814 	ssif_bmc->busy = false;
815 	ssif_bmc->response_timer_inited = false;
816 
817 	/* Register misc device interface */
818 	ssif_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
819 	ssif_bmc->miscdev.name = DEVICE_NAME;
820 	ssif_bmc->miscdev.fops = &ssif_bmc_fops;
821 	ssif_bmc->miscdev.parent = &client->dev;
822 	ret = misc_register(&ssif_bmc->miscdev);
823 	if (ret)
824 		return ret;
825 
826 	ssif_bmc->client = client;
827 	ssif_bmc->client->flags |= I2C_CLIENT_SLAVE;
828 
829 	/* Register I2C slave */
830 	i2c_set_clientdata(client, ssif_bmc);
831 	ret = i2c_slave_register(client, ssif_bmc_cb);
832 	if (ret)
833 		misc_deregister(&ssif_bmc->miscdev);
834 
835 	return ret;
836 }
837 
838 static void ssif_bmc_remove(struct i2c_client *client)
839 {
840 	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
841 
842 	i2c_slave_unregister(client);
843 	misc_deregister(&ssif_bmc->miscdev);
844 }
845 
846 static const struct of_device_id ssif_bmc_match[] = {
847 	{ .compatible = "ssif-bmc" },
848 	{ },
849 };
850 MODULE_DEVICE_TABLE(of, ssif_bmc_match);
851 
852 static const struct i2c_device_id ssif_bmc_id[] = {
853 	{ DEVICE_NAME, 0 },
854 	{ },
855 };
856 MODULE_DEVICE_TABLE(i2c, ssif_bmc_id);
857 
858 static struct i2c_driver ssif_bmc_driver = {
859 	.driver         = {
860 		.name           = DEVICE_NAME,
861 		.of_match_table = ssif_bmc_match,
862 	},
863 	.probe          = ssif_bmc_probe,
864 	.remove         = ssif_bmc_remove,
865 	.id_table       = ssif_bmc_id,
866 };
867 
868 module_i2c_driver(ssif_bmc_driver);
869 
870 MODULE_AUTHOR("Quan Nguyen <quan@os.amperecomputing.com>");
871 MODULE_AUTHOR("Chuong Tran <chuong@os.amperecomputing.com>");
872 MODULE_DESCRIPTION("Linux device driver of the BMC IPMI SSIF interface.");
873 MODULE_LICENSE("GPL");
874