xref: /linux/drivers/pci/doe.c (revision 2697b79a469b68e3ad3640f55284359c1396278d)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Data Object Exchange
4  *	PCIe r6.0, sec 6.30 DOE
5  *
6  * Copyright (C) 2021 Huawei
7  *	Jonathan Cameron <Jonathan.Cameron@huawei.com>
8  *
9  * Copyright (C) 2022 Intel Corporation
10  *	Ira Weiny <ira.weiny@intel.com>
11  */
12 
13 #define dev_fmt(fmt) "DOE: " fmt
14 
15 #include <linux/bitfield.h>
16 #include <linux/delay.h>
17 #include <linux/jiffies.h>
18 #include <linux/mutex.h>
19 #include <linux/pci.h>
20 #include <linux/pci-doe.h>
21 #include <linux/workqueue.h>
22 
23 #include "pci.h"
24 
25 #define PCI_DOE_PROTOCOL_DISCOVERY 0
26 
27 /* Timeout of 1 second from 6.30.2 Operation, PCI Spec r6.0 */
28 #define PCI_DOE_TIMEOUT HZ
29 #define PCI_DOE_POLL_INTERVAL	(PCI_DOE_TIMEOUT / 128)
30 
31 #define PCI_DOE_FLAG_CANCEL	0
32 #define PCI_DOE_FLAG_DEAD	1
33 
34 /* Max data object length is 2^18 dwords */
35 #define PCI_DOE_MAX_LENGTH	(1 << 18)
36 
37 /**
38  * struct pci_doe_mb - State for a single DOE mailbox
39  *
40  * This state is used to manage a single DOE mailbox capability.  All fields
41  * should be considered opaque to the consumers and the structure passed into
42  * the helpers below after being created by pci_doe_create_mb().
43  *
44  * @pdev: PCI device this mailbox belongs to
45  * @cap_offset: Capability offset
46  * @prots: Array of protocols supported (encoded as long values)
47  * @wq: Wait queue for work item
48  * @work_queue: Queue of pci_doe_work items
49  * @flags: Bit array of PCI_DOE_FLAG_* flags
50  */
51 struct pci_doe_mb {
52 	struct pci_dev *pdev;
53 	u16 cap_offset;
54 	struct xarray prots;
55 
56 	wait_queue_head_t wq;
57 	struct workqueue_struct *work_queue;
58 	unsigned long flags;
59 };
60 
61 struct pci_doe_protocol {
62 	u16 vid;
63 	u8 type;
64 };
65 
66 /**
67  * struct pci_doe_task - represents a single query/response
68  *
69  * @prot: DOE Protocol
70  * @request_pl: The request payload
71  * @request_pl_sz: Size of the request payload (bytes)
72  * @response_pl: The response payload
73  * @response_pl_sz: Size of the response payload (bytes)
74  * @rv: Return value.  Length of received response or error (bytes)
75  * @complete: Called when task is complete
76  * @private: Private data for the consumer
77  * @work: Used internally by the mailbox
78  * @doe_mb: Used internally by the mailbox
79  */
80 struct pci_doe_task {
81 	struct pci_doe_protocol prot;
82 	const __le32 *request_pl;
83 	size_t request_pl_sz;
84 	__le32 *response_pl;
85 	size_t response_pl_sz;
86 	int rv;
87 	void (*complete)(struct pci_doe_task *task);
88 	void *private;
89 
90 	/* initialized by pci_doe_submit_task() */
91 	struct work_struct work;
92 	struct pci_doe_mb *doe_mb;
93 };
94 
95 static int pci_doe_wait(struct pci_doe_mb *doe_mb, unsigned long timeout)
96 {
97 	if (wait_event_timeout(doe_mb->wq,
98 			       test_bit(PCI_DOE_FLAG_CANCEL, &doe_mb->flags),
99 			       timeout))
100 		return -EIO;
101 	return 0;
102 }
103 
104 static void pci_doe_write_ctrl(struct pci_doe_mb *doe_mb, u32 val)
105 {
106 	struct pci_dev *pdev = doe_mb->pdev;
107 	int offset = doe_mb->cap_offset;
108 
109 	pci_write_config_dword(pdev, offset + PCI_DOE_CTRL, val);
110 }
111 
112 static int pci_doe_abort(struct pci_doe_mb *doe_mb)
113 {
114 	struct pci_dev *pdev = doe_mb->pdev;
115 	int offset = doe_mb->cap_offset;
116 	unsigned long timeout_jiffies;
117 
118 	pci_dbg(pdev, "[%x] Issuing Abort\n", offset);
119 
120 	timeout_jiffies = jiffies + PCI_DOE_TIMEOUT;
121 	pci_doe_write_ctrl(doe_mb, PCI_DOE_CTRL_ABORT);
122 
123 	do {
124 		int rc;
125 		u32 val;
126 
127 		rc = pci_doe_wait(doe_mb, PCI_DOE_POLL_INTERVAL);
128 		if (rc)
129 			return rc;
130 		pci_read_config_dword(pdev, offset + PCI_DOE_STATUS, &val);
131 
132 		/* Abort success! */
133 		if (!FIELD_GET(PCI_DOE_STATUS_ERROR, val) &&
134 		    !FIELD_GET(PCI_DOE_STATUS_BUSY, val))
135 			return 0;
136 
137 	} while (!time_after(jiffies, timeout_jiffies));
138 
139 	/* Abort has timed out and the MB is dead */
140 	pci_err(pdev, "[%x] ABORT timed out\n", offset);
141 	return -EIO;
142 }
143 
144 static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
145 			    struct pci_doe_task *task)
146 {
147 	struct pci_dev *pdev = doe_mb->pdev;
148 	int offset = doe_mb->cap_offset;
149 	size_t length, remainder;
150 	u32 val;
151 	int i;
152 
153 	/*
154 	 * Check the DOE busy bit is not set. If it is set, this could indicate
155 	 * someone other than Linux (e.g. firmware) is using the mailbox. Note
156 	 * it is expected that firmware and OS will negotiate access rights via
157 	 * an, as yet to be defined, method.
158 	 */
159 	pci_read_config_dword(pdev, offset + PCI_DOE_STATUS, &val);
160 	if (FIELD_GET(PCI_DOE_STATUS_BUSY, val))
161 		return -EBUSY;
162 
163 	if (FIELD_GET(PCI_DOE_STATUS_ERROR, val))
164 		return -EIO;
165 
166 	/* Length is 2 DW of header + length of payload in DW */
167 	length = 2 + DIV_ROUND_UP(task->request_pl_sz, sizeof(__le32));
168 	if (length > PCI_DOE_MAX_LENGTH)
169 		return -EIO;
170 	if (length == PCI_DOE_MAX_LENGTH)
171 		length = 0;
172 
173 	/* Write DOE Header */
174 	val = FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_1_VID, task->prot.vid) |
175 		FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, task->prot.type);
176 	pci_write_config_dword(pdev, offset + PCI_DOE_WRITE, val);
177 	pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
178 			       FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH,
179 					  length));
180 
181 	/* Write payload */
182 	for (i = 0; i < task->request_pl_sz / sizeof(__le32); i++)
183 		pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
184 				       le32_to_cpu(task->request_pl[i]));
185 
186 	/* Write last payload dword */
187 	remainder = task->request_pl_sz % sizeof(__le32);
188 	if (remainder) {
189 		val = 0;
190 		memcpy(&val, &task->request_pl[i], remainder);
191 		le32_to_cpus(&val);
192 		pci_write_config_dword(pdev, offset + PCI_DOE_WRITE, val);
193 	}
194 
195 	pci_doe_write_ctrl(doe_mb, PCI_DOE_CTRL_GO);
196 
197 	return 0;
198 }
199 
200 static bool pci_doe_data_obj_ready(struct pci_doe_mb *doe_mb)
201 {
202 	struct pci_dev *pdev = doe_mb->pdev;
203 	int offset = doe_mb->cap_offset;
204 	u32 val;
205 
206 	pci_read_config_dword(pdev, offset + PCI_DOE_STATUS, &val);
207 	if (FIELD_GET(PCI_DOE_STATUS_DATA_OBJECT_READY, val))
208 		return true;
209 	return false;
210 }
211 
212 static int pci_doe_recv_resp(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
213 {
214 	size_t length, payload_length, remainder, received;
215 	struct pci_dev *pdev = doe_mb->pdev;
216 	int offset = doe_mb->cap_offset;
217 	int i = 0;
218 	u32 val;
219 
220 	/* Read the first dword to get the protocol */
221 	pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
222 	if ((FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_VID, val) != task->prot.vid) ||
223 	    (FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, val) != task->prot.type)) {
224 		dev_err_ratelimited(&pdev->dev, "[%x] expected [VID, Protocol] = [%04x, %02x], got [%04x, %02x]\n",
225 				    doe_mb->cap_offset, task->prot.vid, task->prot.type,
226 				    FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_VID, val),
227 				    FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, val));
228 		return -EIO;
229 	}
230 
231 	pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
232 	/* Read the second dword to get the length */
233 	pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
234 	pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
235 
236 	length = FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH, val);
237 	/* A value of 0x0 indicates max data object length */
238 	if (!length)
239 		length = PCI_DOE_MAX_LENGTH;
240 	if (length < 2)
241 		return -EIO;
242 
243 	/* First 2 dwords have already been read */
244 	length -= 2;
245 	received = task->response_pl_sz;
246 	payload_length = DIV_ROUND_UP(task->response_pl_sz, sizeof(__le32));
247 	remainder = task->response_pl_sz % sizeof(__le32);
248 
249 	/* remainder signifies number of data bytes in last payload dword */
250 	if (!remainder)
251 		remainder = sizeof(__le32);
252 
253 	if (length < payload_length) {
254 		received = length * sizeof(__le32);
255 		payload_length = length;
256 		remainder = sizeof(__le32);
257 	}
258 
259 	if (payload_length) {
260 		/* Read all payload dwords except the last */
261 		for (; i < payload_length - 1; i++) {
262 			pci_read_config_dword(pdev, offset + PCI_DOE_READ,
263 					      &val);
264 			task->response_pl[i] = cpu_to_le32(val);
265 			pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
266 		}
267 
268 		/* Read last payload dword */
269 		pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
270 		cpu_to_le32s(&val);
271 		memcpy(&task->response_pl[i], &val, remainder);
272 		/* Prior to the last ack, ensure Data Object Ready */
273 		if (!pci_doe_data_obj_ready(doe_mb))
274 			return -EIO;
275 		pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
276 		i++;
277 	}
278 
279 	/* Flush excess length */
280 	for (; i < length; i++) {
281 		pci_read_config_dword(pdev, offset + PCI_DOE_READ, &val);
282 		pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
283 	}
284 
285 	/* Final error check to pick up on any since Data Object Ready */
286 	pci_read_config_dword(pdev, offset + PCI_DOE_STATUS, &val);
287 	if (FIELD_GET(PCI_DOE_STATUS_ERROR, val))
288 		return -EIO;
289 
290 	return received;
291 }
292 
293 static void signal_task_complete(struct pci_doe_task *task, int rv)
294 {
295 	task->rv = rv;
296 	destroy_work_on_stack(&task->work);
297 	task->complete(task);
298 }
299 
300 static void signal_task_abort(struct pci_doe_task *task, int rv)
301 {
302 	struct pci_doe_mb *doe_mb = task->doe_mb;
303 	struct pci_dev *pdev = doe_mb->pdev;
304 
305 	if (pci_doe_abort(doe_mb)) {
306 		/*
307 		 * If the device can't process an abort; set the mailbox dead
308 		 *	- no more submissions
309 		 */
310 		pci_err(pdev, "[%x] Abort failed marking mailbox dead\n",
311 			doe_mb->cap_offset);
312 		set_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags);
313 	}
314 	signal_task_complete(task, rv);
315 }
316 
317 static void doe_statemachine_work(struct work_struct *work)
318 {
319 	struct pci_doe_task *task = container_of(work, struct pci_doe_task,
320 						 work);
321 	struct pci_doe_mb *doe_mb = task->doe_mb;
322 	struct pci_dev *pdev = doe_mb->pdev;
323 	int offset = doe_mb->cap_offset;
324 	unsigned long timeout_jiffies;
325 	u32 val;
326 	int rc;
327 
328 	if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags)) {
329 		signal_task_complete(task, -EIO);
330 		return;
331 	}
332 
333 	/* Send request */
334 	rc = pci_doe_send_req(doe_mb, task);
335 	if (rc) {
336 		/*
337 		 * The specification does not provide any guidance on how to
338 		 * resolve conflicting requests from other entities.
339 		 * Furthermore, it is likely that busy will not be detected
340 		 * most of the time.  Flag any detection of status busy with an
341 		 * error.
342 		 */
343 		if (rc == -EBUSY)
344 			dev_err_ratelimited(&pdev->dev, "[%x] busy detected; another entity is sending conflicting requests\n",
345 					    offset);
346 		signal_task_abort(task, rc);
347 		return;
348 	}
349 
350 	timeout_jiffies = jiffies + PCI_DOE_TIMEOUT;
351 	/* Poll for response */
352 retry_resp:
353 	pci_read_config_dword(pdev, offset + PCI_DOE_STATUS, &val);
354 	if (FIELD_GET(PCI_DOE_STATUS_ERROR, val)) {
355 		signal_task_abort(task, -EIO);
356 		return;
357 	}
358 
359 	if (!FIELD_GET(PCI_DOE_STATUS_DATA_OBJECT_READY, val)) {
360 		if (time_after(jiffies, timeout_jiffies)) {
361 			signal_task_abort(task, -EIO);
362 			return;
363 		}
364 		rc = pci_doe_wait(doe_mb, PCI_DOE_POLL_INTERVAL);
365 		if (rc) {
366 			signal_task_abort(task, rc);
367 			return;
368 		}
369 		goto retry_resp;
370 	}
371 
372 	rc  = pci_doe_recv_resp(doe_mb, task);
373 	if (rc < 0) {
374 		signal_task_abort(task, rc);
375 		return;
376 	}
377 
378 	signal_task_complete(task, rc);
379 }
380 
381 static void pci_doe_task_complete(struct pci_doe_task *task)
382 {
383 	complete(task->private);
384 }
385 
386 static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 capver, u8 *index, u16 *vid,
387 			     u8 *protocol)
388 {
389 	u32 request_pl = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX,
390 				    *index) |
391 			 FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_VER,
392 				    (capver >= 2) ? 2 : 0);
393 	__le32 request_pl_le = cpu_to_le32(request_pl);
394 	__le32 response_pl_le;
395 	u32 response_pl;
396 	int rc;
397 
398 	rc = pci_doe(doe_mb, PCI_VENDOR_ID_PCI_SIG, PCI_DOE_PROTOCOL_DISCOVERY,
399 		     &request_pl_le, sizeof(request_pl_le),
400 		     &response_pl_le, sizeof(response_pl_le));
401 	if (rc < 0)
402 		return rc;
403 
404 	if (rc != sizeof(response_pl_le))
405 		return -EIO;
406 
407 	response_pl = le32_to_cpu(response_pl_le);
408 	*vid = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_VID, response_pl);
409 	*protocol = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL,
410 			      response_pl);
411 	*index = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX,
412 			   response_pl);
413 
414 	return 0;
415 }
416 
417 static void *pci_doe_xa_prot_entry(u16 vid, u8 prot)
418 {
419 	return xa_mk_value((vid << 8) | prot);
420 }
421 
422 static int pci_doe_cache_protocols(struct pci_doe_mb *doe_mb)
423 {
424 	u8 index = 0;
425 	u8 xa_idx = 0;
426 	u32 hdr = 0;
427 
428 	pci_read_config_dword(doe_mb->pdev, doe_mb->cap_offset, &hdr);
429 
430 	do {
431 		int rc;
432 		u16 vid;
433 		u8 prot;
434 
435 		rc = pci_doe_discovery(doe_mb, PCI_EXT_CAP_VER(hdr), &index,
436 				       &vid, &prot);
437 		if (rc)
438 			return rc;
439 
440 		pci_dbg(doe_mb->pdev,
441 			"[%x] Found protocol %d vid: %x prot: %x\n",
442 			doe_mb->cap_offset, xa_idx, vid, prot);
443 
444 		rc = xa_insert(&doe_mb->prots, xa_idx++,
445 			       pci_doe_xa_prot_entry(vid, prot), GFP_KERNEL);
446 		if (rc)
447 			return rc;
448 	} while (index);
449 
450 	return 0;
451 }
452 
453 static void pci_doe_cancel_tasks(struct pci_doe_mb *doe_mb)
454 {
455 	/* Stop all pending work items from starting */
456 	set_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags);
457 
458 	/* Cancel an in progress work item, if necessary */
459 	set_bit(PCI_DOE_FLAG_CANCEL, &doe_mb->flags);
460 	wake_up(&doe_mb->wq);
461 }
462 
463 /**
464  * pci_doe_create_mb() - Create a DOE mailbox object
465  *
466  * @pdev: PCI device to create the DOE mailbox for
467  * @cap_offset: Offset of the DOE mailbox
468  *
469  * Create a single mailbox object to manage the mailbox protocol at the
470  * cap_offset specified.
471  *
472  * RETURNS: created mailbox object on success
473  *	    ERR_PTR(-errno) on failure
474  */
475 static struct pci_doe_mb *pci_doe_create_mb(struct pci_dev *pdev,
476 					    u16 cap_offset)
477 {
478 	struct pci_doe_mb *doe_mb;
479 	int rc;
480 
481 	doe_mb = kzalloc(sizeof(*doe_mb), GFP_KERNEL);
482 	if (!doe_mb)
483 		return ERR_PTR(-ENOMEM);
484 
485 	doe_mb->pdev = pdev;
486 	doe_mb->cap_offset = cap_offset;
487 	init_waitqueue_head(&doe_mb->wq);
488 	xa_init(&doe_mb->prots);
489 
490 	doe_mb->work_queue = alloc_ordered_workqueue("%s %s DOE [%x]", 0,
491 						dev_bus_name(&pdev->dev),
492 						pci_name(pdev),
493 						doe_mb->cap_offset);
494 	if (!doe_mb->work_queue) {
495 		pci_err(pdev, "[%x] failed to allocate work queue\n",
496 			doe_mb->cap_offset);
497 		rc = -ENOMEM;
498 		goto err_free;
499 	}
500 
501 	/* Reset the mailbox by issuing an abort */
502 	rc = pci_doe_abort(doe_mb);
503 	if (rc) {
504 		pci_err(pdev, "[%x] failed to reset mailbox with abort command : %d\n",
505 			doe_mb->cap_offset, rc);
506 		goto err_destroy_wq;
507 	}
508 
509 	/*
510 	 * The state machine and the mailbox should be in sync now;
511 	 * Use the mailbox to query protocols.
512 	 */
513 	rc = pci_doe_cache_protocols(doe_mb);
514 	if (rc) {
515 		pci_err(pdev, "[%x] failed to cache protocols : %d\n",
516 			doe_mb->cap_offset, rc);
517 		goto err_cancel;
518 	}
519 
520 	return doe_mb;
521 
522 err_cancel:
523 	pci_doe_cancel_tasks(doe_mb);
524 	xa_destroy(&doe_mb->prots);
525 err_destroy_wq:
526 	destroy_workqueue(doe_mb->work_queue);
527 err_free:
528 	kfree(doe_mb);
529 	return ERR_PTR(rc);
530 }
531 
532 /**
533  * pci_doe_destroy_mb() - Destroy a DOE mailbox object
534  *
535  * @doe_mb: DOE mailbox
536  *
537  * Destroy all internal data structures created for the DOE mailbox.
538  */
539 static void pci_doe_destroy_mb(struct pci_doe_mb *doe_mb)
540 {
541 	pci_doe_cancel_tasks(doe_mb);
542 	xa_destroy(&doe_mb->prots);
543 	destroy_workqueue(doe_mb->work_queue);
544 	kfree(doe_mb);
545 }
546 
547 /**
548  * pci_doe_supports_prot() - Return if the DOE instance supports the given
549  *			     protocol
550  * @doe_mb: DOE mailbox capability to query
551  * @vid: Protocol Vendor ID
552  * @type: Protocol type
553  *
554  * RETURNS: True if the DOE mailbox supports the protocol specified
555  */
556 static bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
557 {
558 	unsigned long index;
559 	void *entry;
560 
561 	/* The discovery protocol must always be supported */
562 	if (vid == PCI_VENDOR_ID_PCI_SIG && type == PCI_DOE_PROTOCOL_DISCOVERY)
563 		return true;
564 
565 	xa_for_each(&doe_mb->prots, index, entry)
566 		if (entry == pci_doe_xa_prot_entry(vid, type))
567 			return true;
568 
569 	return false;
570 }
571 
572 /**
573  * pci_doe_submit_task() - Submit a task to be processed by the state machine
574  *
575  * @doe_mb: DOE mailbox capability to submit to
576  * @task: task to be queued
577  *
578  * Submit a DOE task (request/response) to the DOE mailbox to be processed.
579  * Returns upon queueing the task object.  If the queue is full this function
580  * will sleep until there is room in the queue.
581  *
582  * task->complete will be called when the state machine is done processing this
583  * task.
584  *
585  * @task must be allocated on the stack.
586  *
587  * Excess data will be discarded.
588  *
589  * RETURNS: 0 when task has been successfully queued, -ERRNO on error
590  */
591 static int pci_doe_submit_task(struct pci_doe_mb *doe_mb,
592 			       struct pci_doe_task *task)
593 {
594 	if (!pci_doe_supports_prot(doe_mb, task->prot.vid, task->prot.type))
595 		return -EINVAL;
596 
597 	if (test_bit(PCI_DOE_FLAG_DEAD, &doe_mb->flags))
598 		return -EIO;
599 
600 	task->doe_mb = doe_mb;
601 	INIT_WORK_ONSTACK(&task->work, doe_statemachine_work);
602 	queue_work(doe_mb->work_queue, &task->work);
603 	return 0;
604 }
605 
606 /**
607  * pci_doe() - Perform Data Object Exchange
608  *
609  * @doe_mb: DOE Mailbox
610  * @vendor: Vendor ID
611  * @type: Data Object Type
612  * @request: Request payload
613  * @request_sz: Size of request payload (bytes)
614  * @response: Response payload
615  * @response_sz: Size of response payload (bytes)
616  *
617  * Submit @request to @doe_mb and store the @response.
618  * The DOE exchange is performed synchronously and may therefore sleep.
619  *
620  * Payloads are treated as opaque byte streams which are transmitted verbatim,
621  * without byte-swapping.  If payloads contain little-endian register values,
622  * the caller is responsible for conversion with cpu_to_le32() / le32_to_cpu().
623  *
624  * For convenience, arbitrary payload sizes are allowed even though PCIe r6.0
625  * sec 6.30.1 specifies the Data Object Header 2 "Length" in dwords.  The last
626  * (partial) dword is copied with byte granularity and padded with zeroes if
627  * necessary.  Callers are thus relieved of using dword-sized bounce buffers.
628  *
629  * RETURNS: Length of received response or negative errno.
630  * Received data in excess of @response_sz is discarded.
631  * The length may be smaller than @response_sz and the caller
632  * is responsible for checking that.
633  */
634 int pci_doe(struct pci_doe_mb *doe_mb, u16 vendor, u8 type,
635 	    const void *request, size_t request_sz,
636 	    void *response, size_t response_sz)
637 {
638 	DECLARE_COMPLETION_ONSTACK(c);
639 	struct pci_doe_task task = {
640 		.prot.vid = vendor,
641 		.prot.type = type,
642 		.request_pl = request,
643 		.request_pl_sz = request_sz,
644 		.response_pl = response,
645 		.response_pl_sz = response_sz,
646 		.complete = pci_doe_task_complete,
647 		.private = &c,
648 	};
649 	int rc;
650 
651 	rc = pci_doe_submit_task(doe_mb, &task);
652 	if (rc)
653 		return rc;
654 
655 	wait_for_completion(&c);
656 
657 	return task.rv;
658 }
659 EXPORT_SYMBOL_GPL(pci_doe);
660 
661 /**
662  * pci_find_doe_mailbox() - Find Data Object Exchange mailbox
663  *
664  * @pdev: PCI device
665  * @vendor: Vendor ID
666  * @type: Data Object Type
667  *
668  * Find first DOE mailbox of a PCI device which supports the given protocol.
669  *
670  * RETURNS: Pointer to the DOE mailbox or NULL if none was found.
671  */
672 struct pci_doe_mb *pci_find_doe_mailbox(struct pci_dev *pdev, u16 vendor,
673 					u8 type)
674 {
675 	struct pci_doe_mb *doe_mb;
676 	unsigned long index;
677 
678 	xa_for_each(&pdev->doe_mbs, index, doe_mb)
679 		if (pci_doe_supports_prot(doe_mb, vendor, type))
680 			return doe_mb;
681 
682 	return NULL;
683 }
684 EXPORT_SYMBOL_GPL(pci_find_doe_mailbox);
685 
686 void pci_doe_init(struct pci_dev *pdev)
687 {
688 	struct pci_doe_mb *doe_mb;
689 	u16 offset = 0;
690 	int rc;
691 
692 	xa_init(&pdev->doe_mbs);
693 
694 	while ((offset = pci_find_next_ext_capability(pdev, offset,
695 						      PCI_EXT_CAP_ID_DOE))) {
696 		doe_mb = pci_doe_create_mb(pdev, offset);
697 		if (IS_ERR(doe_mb)) {
698 			pci_err(pdev, "[%x] failed to create mailbox: %ld\n",
699 				offset, PTR_ERR(doe_mb));
700 			continue;
701 		}
702 
703 		rc = xa_insert(&pdev->doe_mbs, offset, doe_mb, GFP_KERNEL);
704 		if (rc) {
705 			pci_err(pdev, "[%x] failed to insert mailbox: %d\n",
706 				offset, rc);
707 			pci_doe_destroy_mb(doe_mb);
708 		}
709 	}
710 }
711 
712 void pci_doe_destroy(struct pci_dev *pdev)
713 {
714 	struct pci_doe_mb *doe_mb;
715 	unsigned long index;
716 
717 	xa_for_each(&pdev->doe_mbs, index, doe_mb)
718 		pci_doe_destroy_mb(doe_mb);
719 
720 	xa_destroy(&pdev->doe_mbs);
721 }
722 
723 void pci_doe_disconnected(struct pci_dev *pdev)
724 {
725 	struct pci_doe_mb *doe_mb;
726 	unsigned long index;
727 
728 	xa_for_each(&pdev->doe_mbs, index, doe_mb)
729 		pci_doe_cancel_tasks(doe_mb);
730 }
731