ssif_bmc.c

  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
 49struct 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 */
 67enum 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
 77struct 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
107static 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
112static 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 */
133static 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 */
172static 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(msg.len) ||
181	    count > sizeof(struct ipmi_ssif_msg))
182		return -EINVAL;
183
184	if (copy_from_user(&msg, buf, count))
185		return -EFAULT;
186
187	if (!msg.len || msg.len > IPMI_SSIF_PAYLOAD_MAX ||
188	    count < sizeof_field(struct ipmi_ssif_msg, len) + msg.len)
189		return -EINVAL;
190
191	spin_lock_irqsave(&ssif_bmc->lock, flags);
192	while (ssif_bmc->response_in_progress) {
193		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
194		if (file->f_flags & O_NONBLOCK)
195			return -EAGAIN;
196		ret = wait_event_interruptible(ssif_bmc->wait_queue,
197					       !ssif_bmc->response_in_progress);
198		if (ret)
199			return ret;
200		spin_lock_irqsave(&ssif_bmc->lock, flags);
201	}
202
203	/*
204	 * The write must complete before the response timeout fired, otherwise
205	 * the response is aborted and wait for next request
206	 * Return -EINVAL if the response is aborted
207	 */
208	ret = (ssif_bmc->response_timer_inited) ? 0 : -EINVAL;
209	if (ret)
210		goto exit;
211
212	timer_delete(&ssif_bmc->response_timer);
213	ssif_bmc->response_timer_inited = false;
214
215	memcpy(&ssif_bmc->response, &msg, count);
216	ssif_bmc->is_singlepart_read = (msg.len <= MAX_PAYLOAD_PER_TRANSACTION);
217
218	ssif_bmc->response_in_progress = true;
219
220	/* ssif_bmc not busy */
221	ssif_bmc->busy = false;
222
223	/* Clean old request buffer */
224	memset(&ssif_bmc->request, 0, sizeof(struct ipmi_ssif_msg));
225exit:
226	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
227
228	return (ret < 0) ? ret : count;
229}
230
231static int ssif_bmc_open(struct inode *inode, struct file *file)
232{
233	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
234	int ret = 0;
235
236	spin_lock_irq(&ssif_bmc->lock);
237	if (!ssif_bmc->running)
238		ssif_bmc->running = 1;
239	else
240		ret = -EBUSY;
241	spin_unlock_irq(&ssif_bmc->lock);
242
243	return ret;
244}
245
246static __poll_t ssif_bmc_poll(struct file *file, poll_table *wait)
247{
248	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
249	__poll_t mask = 0;
250
251	poll_wait(file, &ssif_bmc->wait_queue, wait);
252
253	spin_lock_irq(&ssif_bmc->lock);
254	/* The request is available, userspace application can get the request */
255	if (ssif_bmc->request_available)
256		mask |= EPOLLIN;
257
258	spin_unlock_irq(&ssif_bmc->lock);
259
260	return mask;
261}
262
263static int ssif_bmc_release(struct inode *inode, struct file *file)
264{
265	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
266
267	spin_lock_irq(&ssif_bmc->lock);
268	ssif_bmc->running = 0;
269	spin_unlock_irq(&ssif_bmc->lock);
270
271	return 0;
272}
273
274/*
275 * System calls to device interface for user apps
276 */
277static const struct file_operations ssif_bmc_fops = {
278	.owner		= THIS_MODULE,
279	.open		= ssif_bmc_open,
280	.read		= ssif_bmc_read,
281	.write		= ssif_bmc_write,
282	.release	= ssif_bmc_release,
283	.poll		= ssif_bmc_poll,
284};
285
286/* Called with ssif_bmc->lock held. */
287static void complete_response(struct ssif_bmc_ctx *ssif_bmc)
288{
289	/* Invalidate response in buffer to denote it having been sent. */
290	ssif_bmc->response.len = 0;
291	ssif_bmc->response_in_progress = false;
292	ssif_bmc->nbytes_processed = 0;
293	ssif_bmc->remain_len = 0;
294	ssif_bmc->busy = false;
295	wake_up_all(&ssif_bmc->wait_queue);
296}
297
298static void response_timeout(struct timer_list *t)
299{
300	struct ssif_bmc_ctx *ssif_bmc = timer_container_of(ssif_bmc, t,
301							   response_timer);
302	unsigned long flags;
303
304	spin_lock_irqsave(&ssif_bmc->lock, flags);
305
306	/* Do nothing if the response is in progress */
307	if (!ssif_bmc->response_in_progress) {
308		/* Recover ssif_bmc from busy */
309		ssif_bmc->busy = false;
310		ssif_bmc->response_timer_inited = false;
311		/* Set aborting flag */
312		ssif_bmc->aborting = true;
313	}
314
315	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
316}
317
318/* Called with ssif_bmc->lock held. */
319static void handle_request(struct ssif_bmc_ctx *ssif_bmc)
320{
321	/* set ssif_bmc to busy waiting for response */
322	ssif_bmc->busy = true;
323	/* Request message is available to process */
324	ssif_bmc->request_available = true;
325	/* Clean old response buffer */
326	memset(&ssif_bmc->response, 0, sizeof(struct ipmi_ssif_msg));
327	/* This is the new READ request.*/
328	wake_up_all(&ssif_bmc->wait_queue);
329
330	/* Armed timer to recover slave from busy state in case of no response */
331	if (!ssif_bmc->response_timer_inited) {
332		timer_setup(&ssif_bmc->response_timer, response_timeout, 0);
333		ssif_bmc->response_timer_inited = true;
334	}
335	mod_timer(&ssif_bmc->response_timer, jiffies + msecs_to_jiffies(RESPONSE_TIMEOUT));
336}
337
338static void calculate_response_part_pec(struct ssif_part_buffer *part)
339{
340	u8 addr = part->address;
341
342	/* PEC - Start Read Address */
343	part->pec = i2c_smbus_pec(0, &addr, 1);
344	/* PEC - SSIF Command */
345	part->pec = i2c_smbus_pec(part->pec, &part->smbus_cmd, 1);
346	/* PEC - Restart Write Address */
347	addr = addr | 0x01;
348	part->pec = i2c_smbus_pec(part->pec, &addr, 1);
349	part->pec = i2c_smbus_pec(part->pec, &part->length, 1);
350	if (part->length)
351		part->pec = i2c_smbus_pec(part->pec, part->payload, part->length);
352}
353
354static void set_singlepart_response_buffer(struct ssif_bmc_ctx *ssif_bmc)
355{
356	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
357
358	part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
359	part->length = (u8)ssif_bmc->response.len;
360
361	/* Clear the rest to 0 */
362	memset(part->payload + part->length, 0, MAX_PAYLOAD_PER_TRANSACTION - part->length);
363	memcpy(&part->payload[0], &ssif_bmc->response.payload[0], part->length);
364}
365
366static void set_multipart_response_buffer(struct ssif_bmc_ctx *ssif_bmc)
367{
368	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
369	u8 part_len = 0;
370
371	part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
372	switch (part->smbus_cmd) {
373	case SSIF_IPMI_MULTIPART_READ_START:
374		/*
375		 * Read Start length is 32 bytes.
376		 * Read Start transfer first 30 bytes of IPMI response
377		 * and 2 special code 0x00, 0x01.
378		 */
379		ssif_bmc->nbytes_processed = 0;
380		ssif_bmc->block_num = 0;
381		part->length = MAX_PAYLOAD_PER_TRANSACTION;
382		part_len = MAX_IPMI_DATA_PER_START_TRANSACTION;
383		ssif_bmc->remain_len = ssif_bmc->response.len - part_len;
384
385		part->payload[0] = 0x00; /* Start Flag */
386		part->payload[1] = 0x01; /* Start Flag */
387
388		memcpy(&part->payload[2], &ssif_bmc->response.payload[0], part_len);
389		break;
390
391	case SSIF_IPMI_MULTIPART_READ_MIDDLE:
392		/*
393		 * IPMI READ Middle or READ End messages can carry up to 31 bytes
394		 * IPMI data plus block number byte.
395		 */
396		if (ssif_bmc->remain_len <= MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION) {
397			/*
398			 * This is READ End message
399			 *  Return length is the remaining response data length
400			 *  plus block number
401			 *  Block number 0xFF is to indicate this is last message
402			 *
403			 */
404			/* Clean the buffer */
405			memset(&part->payload[0], 0, MAX_PAYLOAD_PER_TRANSACTION);
406			part->length = ssif_bmc->remain_len + 1;
407			part_len = ssif_bmc->remain_len;
408			ssif_bmc->block_num = 0xFF;
409			part->payload[0] = ssif_bmc->block_num;
410		} else {
411			/*
412			 * This is READ Middle message
413			 *  Response length is the maximum SMBUS transfer length
414			 *  Block number byte is incremented
415			 * Return length is maximum SMBUS transfer length
416			 */
417			part->length = MAX_PAYLOAD_PER_TRANSACTION;
418			part_len = MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
419			part->payload[0] = ssif_bmc->block_num;
420			ssif_bmc->block_num++;
421		}
422
423		ssif_bmc->remain_len -= part_len;
424		memcpy(&part->payload[1], ssif_bmc->response.payload + ssif_bmc->nbytes_processed,
425		       part_len);
426		break;
427
428	default:
429		/* Do not expect to go to this case */
430		dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x\n",
431			__func__, part->smbus_cmd);
432		break;
433	}
434
435	ssif_bmc->nbytes_processed += part_len;
436}
437
438static bool supported_read_cmd(u8 cmd)
439{
440	if (cmd == SSIF_IPMI_SINGLEPART_READ ||
441	    cmd == SSIF_IPMI_MULTIPART_READ_START ||
442	    cmd == SSIF_IPMI_MULTIPART_READ_MIDDLE)
443		return true;
444
445	return false;
446}
447
448static bool supported_write_cmd(u8 cmd)
449{
450	if (cmd == SSIF_IPMI_SINGLEPART_WRITE ||
451	    cmd == SSIF_IPMI_MULTIPART_WRITE_START ||
452	    cmd == SSIF_IPMI_MULTIPART_WRITE_MIDDLE ||
453	    cmd == SSIF_IPMI_MULTIPART_WRITE_END)
454		return true;
455
456	return false;
457}
458
459/* Process the IPMI response that will be read by master */
460static void handle_read_processed(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
461{
462	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
463
464	/* msg_idx start from 0 */
465	if (part->index < part->length)
466		*val = part->payload[part->index];
467	else if (part->index == part->length && ssif_bmc->pec_support)
468		*val = part->pec;
469	else
470		*val = 0;
471
472	part->index++;
473}
474
475static void handle_write_received(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
476{
477	/*
478	 * The msg_idx must be 1 when first enter SSIF_REQ_RECVING state
479	 * And it would never exceeded 36 bytes included the 32 bytes max payload +
480	 * the address + the command + the len and the PEC.
481	 */
482	if (ssif_bmc->msg_idx < 1  || ssif_bmc->msg_idx > MAX_TRANSACTION)
483		return;
484
485	if (ssif_bmc->msg_idx == 1) {
486		ssif_bmc->part_buf.length = *val;
487		ssif_bmc->part_buf.index = 0;
488	} else {
489		ssif_bmc->part_buf.payload[ssif_bmc->part_buf.index++] = *val;
490	}
491
492	ssif_bmc->msg_idx++;
493}
494
495static bool validate_request_part(struct ssif_bmc_ctx *ssif_bmc)
496{
497	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
498	bool ret = true;
499	u8 cpec;
500	u8 addr;
501
502	if (part->index == part->length) {
503		/* PEC is not included */
504		ssif_bmc->pec_support = false;
505		ret = true;
506		goto exit;
507	}
508
509	if (part->index != part->length + 1) {
510		ret = false;
511		goto exit;
512	}
513
514	/* PEC is included */
515	ssif_bmc->pec_support = true;
516	part->pec = part->payload[part->length];
517	addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
518	cpec = i2c_smbus_pec(0, &addr, 1);
519	cpec = i2c_smbus_pec(cpec, &part->smbus_cmd, 1);
520	cpec = i2c_smbus_pec(cpec, &part->length, 1);
521	/*
522	 * As SMBus specification does not allow the length
523	 * (byte count) in the Write-Block protocol to be zero.
524	 * Therefore, it is illegal to have the last Middle
525	 * transaction in the sequence carry 32-byte and have
526	 * a length of ‘0’ in the End transaction.
527	 * But some users may try to use this way and we should
528	 * prevent ssif_bmc driver broken in this case.
529	 */
530	if (part->length)
531		cpec = i2c_smbus_pec(cpec, part->payload, part->length);
532
533	if (cpec != part->pec)
534		ret = false;
535
536exit:
537	return ret;
538}
539
540static void process_request_part(struct ssif_bmc_ctx *ssif_bmc)
541{
542	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
543	unsigned int len;
544
545	switch (part->smbus_cmd) {
546	case SSIF_IPMI_SINGLEPART_WRITE:
547		/* save the whole part to request*/
548		ssif_bmc->request.len = part->length;
549		memcpy(ssif_bmc->request.payload, part->payload, part->length);
550
551		break;
552	case SSIF_IPMI_MULTIPART_WRITE_START:
553		ssif_bmc->request.len = 0;
554
555		fallthrough;
556	case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
557	case SSIF_IPMI_MULTIPART_WRITE_END:
558		len = ssif_bmc->request.len + part->length;
559		/* Do the bound check here, not allow the request len exceed 254 bytes */
560		if (len > IPMI_SSIF_PAYLOAD_MAX) {
561			dev_warn(&ssif_bmc->client->dev,
562				 "Warn: Request exceeded 254 bytes, aborting");
563			/* Request too long, aborting */
564			ssif_bmc->aborting =  true;
565		} else {
566			memcpy(ssif_bmc->request.payload + ssif_bmc->request.len,
567			       part->payload, part->length);
568			ssif_bmc->request.len += part->length;
569		}
570		break;
571	default:
572		/* Do not expect to go to this case */
573		dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x\n",
574			__func__, part->smbus_cmd);
575		break;
576	}
577}
578
579static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
580{
581	/* SMBUS command can vary (single or multi-part) */
582	ssif_bmc->part_buf.smbus_cmd = *val;
583	ssif_bmc->msg_idx = 1;
584	memset(&ssif_bmc->part_buf.payload[0], 0, MAX_PAYLOAD_PER_TRANSACTION);
585
586	if (*val == SSIF_IPMI_SINGLEPART_WRITE || *val == SSIF_IPMI_MULTIPART_WRITE_START) {
587		/*
588		 * The response maybe not come in-time, causing host SSIF driver
589		 * to timeout and resend a new request. In such case check for
590		 * pending response and clear it
591		 */
592		if (ssif_bmc->response_in_progress)
593			complete_response(ssif_bmc);
594
595		/* This is new request, flip aborting flag if set */
596		if (ssif_bmc->aborting)
597			ssif_bmc->aborting = false;
598	}
599}
600
601static void on_read_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
602{
603	if (ssif_bmc->state == SSIF_READY ||
604	    ssif_bmc->state == SSIF_START ||
605	    ssif_bmc->state == SSIF_REQ_RECVING ||
606	    ssif_bmc->state == SSIF_RES_SENDING) {
607		dev_warn(&ssif_bmc->client->dev,
608			 "Warn: %s unexpected READ REQUESTED in state=%s\n",
609			 __func__, state_to_string(ssif_bmc->state));
610		ssif_bmc->state = SSIF_ABORTING;
611		*val = 0;
612		return;
613
614	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
615		if (!supported_read_cmd(ssif_bmc->part_buf.smbus_cmd)) {
616			dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus read command=0x%x",
617				 ssif_bmc->part_buf.smbus_cmd);
618			ssif_bmc->aborting = true;
619		}
620
621		if (ssif_bmc->aborting)
622			ssif_bmc->state = SSIF_ABORTING;
623		else
624			ssif_bmc->state = SSIF_RES_SENDING;
625	}
626
627	ssif_bmc->msg_idx = 0;
628
629	/* Send 0 if there is nothing to send */
630	if (!ssif_bmc->response_in_progress || ssif_bmc->state == SSIF_ABORTING) {
631		*val = 0;
632		return;
633	}
634
635	if (ssif_bmc->is_singlepart_read)
636		set_singlepart_response_buffer(ssif_bmc);
637	else
638		set_multipart_response_buffer(ssif_bmc);
639
640	calculate_response_part_pec(&ssif_bmc->part_buf);
641	ssif_bmc->part_buf.index = 0;
642	*val = ssif_bmc->part_buf.length;
643}
644
645static void on_read_processed_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
646{
647	if (ssif_bmc->state == SSIF_READY ||
648	    ssif_bmc->state == SSIF_START ||
649	    ssif_bmc->state == SSIF_REQ_RECVING ||
650	    ssif_bmc->state == SSIF_SMBUS_CMD) {
651		dev_warn(&ssif_bmc->client->dev,
652			 "Warn: %s unexpected READ PROCESSED in state=%s\n",
653			 __func__, state_to_string(ssif_bmc->state));
654		ssif_bmc->state = SSIF_ABORTING;
655		*val = 0;
656		return;
657	}
658
659	/* Send 0 if there is nothing to send */
660	if (!ssif_bmc->response_in_progress || ssif_bmc->state == SSIF_ABORTING) {
661		*val = 0;
662		return;
663	}
664
665	handle_read_processed(ssif_bmc, val);
666}
667
668static void on_write_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
669{
670	if (ssif_bmc->state == SSIF_READY || ssif_bmc->state == SSIF_SMBUS_CMD) {
671		ssif_bmc->state = SSIF_START;
672
673	} else if (ssif_bmc->state == SSIF_START ||
674		   ssif_bmc->state == SSIF_REQ_RECVING ||
675		   ssif_bmc->state == SSIF_RES_SENDING) {
676		dev_warn(&ssif_bmc->client->dev,
677			 "Warn: %s unexpected WRITE REQUEST in state=%s\n",
678			 __func__, state_to_string(ssif_bmc->state));
679		ssif_bmc->state = SSIF_ABORTING;
680		return;
681	}
682
683	ssif_bmc->msg_idx = 0;
684	ssif_bmc->part_buf.address = *val;
685}
686
687static void on_write_received_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
688{
689	if (ssif_bmc->state == SSIF_READY ||
690	    ssif_bmc->state == SSIF_RES_SENDING) {
691		dev_warn(&ssif_bmc->client->dev,
692			 "Warn: %s unexpected WRITE RECEIVED in state=%s\n",
693			 __func__, state_to_string(ssif_bmc->state));
694		ssif_bmc->state = SSIF_ABORTING;
695
696	} else if (ssif_bmc->state == SSIF_START) {
697		ssif_bmc->state = SSIF_SMBUS_CMD;
698
699	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
700		if (!supported_write_cmd(ssif_bmc->part_buf.smbus_cmd)) {
701			dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus write command=0x%x",
702				 ssif_bmc->part_buf.smbus_cmd);
703			ssif_bmc->aborting = true;
704		}
705
706		if (ssif_bmc->aborting)
707			ssif_bmc->state = SSIF_ABORTING;
708		else
709			ssif_bmc->state = SSIF_REQ_RECVING;
710	}
711
712	/* This is response sending state */
713	if (ssif_bmc->state == SSIF_REQ_RECVING)
714		handle_write_received(ssif_bmc, val);
715	else if (ssif_bmc->state == SSIF_SMBUS_CMD)
716		process_smbus_cmd(ssif_bmc, val);
717}
718
719static void on_stop_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
720{
721	if (ssif_bmc->state == SSIF_READY ||
722	    ssif_bmc->state == SSIF_START ||
723	    ssif_bmc->state == SSIF_SMBUS_CMD ||
724	    ssif_bmc->state == SSIF_ABORTING) {
725		dev_warn(&ssif_bmc->client->dev,
726			 "Warn: %s unexpected SLAVE STOP in state=%s\n",
727			 __func__, state_to_string(ssif_bmc->state));
728		ssif_bmc->state = SSIF_READY;
729
730	} else if (ssif_bmc->state == SSIF_REQ_RECVING) {
731		if (validate_request_part(ssif_bmc)) {
732			process_request_part(ssif_bmc);
733			if (ssif_bmc->part_buf.smbus_cmd == SSIF_IPMI_SINGLEPART_WRITE ||
734			    ssif_bmc->part_buf.smbus_cmd == SSIF_IPMI_MULTIPART_WRITE_END)
735				handle_request(ssif_bmc);
736			ssif_bmc->state = SSIF_READY;
737		} else {
738			/*
739			 * A BMC that receives an invalid request drop the data for the write
740			 * transaction and any further transactions (read or write) until
741			 * the next valid read or write Start transaction is received
742			 */
743			dev_err(&ssif_bmc->client->dev, "Error: invalid pec\n");
744			ssif_bmc->aborting = true;
745		}
746	} else if (ssif_bmc->state == SSIF_RES_SENDING) {
747		if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num == 0xFF) {
748			memset(&ssif_bmc->part_buf, 0, sizeof(struct ssif_part_buffer));
749			/* Invalidate response buffer to denote it is sent */
750			complete_response(ssif_bmc);
751		}
752		ssif_bmc->state = SSIF_READY;
753	}
754
755	/* Reset message index */
756	ssif_bmc->msg_idx = 0;
757}
758
759/*
760 * Callback function to handle I2C slave events
761 */
762static int ssif_bmc_cb(struct i2c_client *client, enum i2c_slave_event event, u8 *val)
763{
764	unsigned long flags;
765	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
766	int ret = 0;
767
768	spin_lock_irqsave(&ssif_bmc->lock, flags);
769
770	switch (event) {
771	case I2C_SLAVE_READ_REQUESTED:
772		on_read_requested_event(ssif_bmc, val);
773		break;
774
775	case I2C_SLAVE_WRITE_REQUESTED:
776		on_write_requested_event(ssif_bmc, val);
777		break;
778
779	case I2C_SLAVE_READ_PROCESSED:
780		on_read_processed_event(ssif_bmc, val);
781		break;
782
783	case I2C_SLAVE_WRITE_RECEIVED:
784		on_write_received_event(ssif_bmc, val);
785		break;
786
787	case I2C_SLAVE_STOP:
788		on_stop_event(ssif_bmc, val);
789		break;
790
791	default:
792		dev_warn(&ssif_bmc->client->dev, "Warn: Unknown i2c slave event\n");
793		break;
794	}
795
796	if (!ssif_bmc->aborting && ssif_bmc->busy)
797		ret = -EBUSY;
798
799	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
800
801	return ret;
802}
803
804static int ssif_bmc_probe(struct i2c_client *client)
805{
806	struct ssif_bmc_ctx *ssif_bmc;
807	int ret;
808
809	ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc), GFP_KERNEL);
810	if (!ssif_bmc)
811		return -ENOMEM;
812
813	spin_lock_init(&ssif_bmc->lock);
814
815	init_waitqueue_head(&ssif_bmc->wait_queue);
816	ssif_bmc->request_available = false;
817	ssif_bmc->response_in_progress = false;
818	ssif_bmc->busy = false;
819	ssif_bmc->response_timer_inited = false;
820
821	/* Register misc device interface */
822	ssif_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
823	ssif_bmc->miscdev.name = DEVICE_NAME;
824	ssif_bmc->miscdev.fops = &ssif_bmc_fops;
825	ssif_bmc->miscdev.parent = &client->dev;
826	ret = misc_register(&ssif_bmc->miscdev);
827	if (ret)
828		return ret;
829
830	ssif_bmc->client = client;
831	ssif_bmc->client->flags |= I2C_CLIENT_SLAVE;
832
833	/* Register I2C slave */
834	i2c_set_clientdata(client, ssif_bmc);
835	ret = i2c_slave_register(client, ssif_bmc_cb);
836	if (ret)
837		misc_deregister(&ssif_bmc->miscdev);
838
839	return ret;
840}
841
842static void ssif_bmc_remove(struct i2c_client *client)
843{
844	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
845
846	i2c_slave_unregister(client);
847	misc_deregister(&ssif_bmc->miscdev);
848}
849
850static const struct of_device_id ssif_bmc_match[] = {
851	{ .compatible = "ssif-bmc" },
852	{ },
853};
854MODULE_DEVICE_TABLE(of, ssif_bmc_match);
855
856static const struct i2c_device_id ssif_bmc_id[] = {
857	{ DEVICE_NAME },
858	{ }
859};
860MODULE_DEVICE_TABLE(i2c, ssif_bmc_id);
861
862static struct i2c_driver ssif_bmc_driver = {
863	.driver         = {
864		.name           = DEVICE_NAME,
865		.of_match_table = ssif_bmc_match,
866	},
867	.probe          = ssif_bmc_probe,
868	.remove         = ssif_bmc_remove,
869	.id_table       = ssif_bmc_id,
870};
871
872module_i2c_driver(ssif_bmc_driver);
873
874MODULE_AUTHOR("Quan Nguyen <quan@os.amperecomputing.com>");
875MODULE_AUTHOR("Chuong Tran <chuong@os.amperecomputing.com>");
876MODULE_DESCRIPTION("Linux device driver of the BMC IPMI SSIF interface.");
877MODULE_LICENSE("GPL");