xref: /illumos-gate/usr/src/uts/common/io/bge/bge_send.c (revision a2876d03ca2556102e024ae4a50bb4db8fe562b0)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright (c) 2010-2013, by Broadcom, Inc.
24  * All Rights Reserved.
25  */
26 
27 /*
28  * Copyright (c) 2002, 2010, Oracle and/or its affiliates.
29  * All rights reserved.
30  */
31 
32 #include "bge_impl.h"
33 
34 
35 /*
36  * The transmit-side code uses an allocation process which is similar
37  * to some theme park roller-coaster rides, where riders sit in cars
38  * that can go individually, but work better in a train.
39  *
40  * 1)	RESERVE a place - this doesn't refer to any specific car or
41  *	seat, just that you will get a ride.  The attempt to RESERVE a
42  *	place can fail if all spaces in all cars are already committed.
43  *
44  * 2)	Prepare yourself; this may take an arbitrary (but not unbounded)
45  *	time, and you can back out at this stage, in which case you must
46  *	give up (RENOUNCE) your place.
47  *
48  * 3)	CLAIM your space - a specific car (the next sequentially
49  *	numbered one) is allocated at this stage, and is guaranteed
50  *	to be part of the next train to depart.  Once you've done
51  *	this, you can't back out, nor wait for any external event
52  *	or resource.
53  *
54  * 4)	Occupy your car - when all CLAIMED cars are OCCUPIED, they
55  *	all depart together as a single train!
56  *
57  * 5)	At the end of the ride, you climb out of the car and RENOUNCE
58  *	your right to it, so that it can be recycled for another rider.
59  *
60  * For each rider, these have to occur in this order, but the riders
61  * don't have to stay in the same order at each stage.  In particular,
62  * they may overtake each other between RESERVING a place and CLAIMING
63  * it, or between CLAIMING and OCCUPYING a space.
64  *
65  * Once a car is CLAIMED, the train currently being assembled can't go
66  * without that car (this guarantees that the cars in a single train
67  * make up a consecutively-numbered set).  Therefore, when any train
68  * leaves, we know there can't be any riders in transit between CLAIMING
69  * and OCCUPYING their cars.  There can be some who have RESERVED but
70  * not yet CLAIMED their places.  That's OK, though, because they'll go
71  * into the next train.
72  */
73 
74 #define	BGE_DBG		BGE_DBG_SEND	/* debug flag for this code	*/
75 
76 /*
77  * ========== Send-side recycle routines ==========
78  */
79 
80 /*
81  * Recycle all the completed buffers in the specified send ring up to
82  * (but not including) the consumer index in the status block.
83  *
84  * This function must advance (srp->tc_next) AND adjust (srp->tx_free)
85  * to account for the packets it has recycled.
86  *
87  * This is a trivial version that just does that and nothing more, but
88  * it suffices while there's only one method for sending messages (by
89  * copying) and that method doesn't need any special per-buffer action
90  * for recycling.
91  */
92 static boolean_t bge_recycle_ring(bge_t *bgep, send_ring_t *srp);
93 #pragma	inline(bge_recycle_ring)
94 
95 static boolean_t
96 bge_recycle_ring(bge_t *bgep, send_ring_t *srp)
97 {
98 	sw_sbd_t *ssbdp;
99 	bge_queue_item_t *buf_item;
100 	bge_queue_item_t *buf_item_head;
101 	bge_queue_item_t *buf_item_tail;
102 	bge_queue_t *txbuf_queue;
103 	uint64_t slot;
104 	uint64_t n;
105 
106 	ASSERT(mutex_owned(srp->tc_lock));
107 
108 	/*
109 	 * We're about to release one or more places :-)
110 	 * These ASSERTions check that our invariants still hold:
111 	 *	there must always be at least one free place
112 	 *	at this point, there must be at least one place NOT free
113 	 *	we're not about to free more places than were claimed!
114 	 */
115 	ASSERT(srp->tx_free <= srp->desc.nslots);
116 
117 	buf_item_head = buf_item_tail = NULL;
118 	for (n = 0, slot = srp->tc_next; slot != *srp->cons_index_p;
119 	    slot = NEXT(slot, srp->desc.nslots)) {
120 		ssbdp = &srp->sw_sbds[slot];
121 		ASSERT(ssbdp->pbuf != NULL);
122 		buf_item = ssbdp->pbuf;
123 		if (buf_item_head == NULL)
124 			buf_item_head = buf_item_tail = buf_item;
125 		else {
126 			buf_item_tail->next = buf_item;
127 			buf_item_tail = buf_item;
128 		}
129 		ssbdp->pbuf = NULL;
130 		n++;
131 	}
132 	if (n == 0)
133 		return (B_FALSE);
134 
135 	/*
136 	 * Reset the watchdog count: to 0 if all buffers are
137 	 * now free, or to 1 if some are still outstanding.
138 	 * Note: non-synchonised access here means we may get
139 	 * the "wrong" answer, but only in a harmless fashion
140 	 * (i.e. we deactivate the watchdog because all buffers
141 	 * are apparently free, even though another thread may
142 	 * have claimed one before we leave here; in this case
143 	 * the watchdog will restart on the next send() call).
144 	 */
145 	bgep->watchdog = (slot == srp->tx_next) ? 0 : 1;
146 
147 	/*
148 	 * Update recycle index and free tx BD number
149 	 */
150 	srp->tc_next = slot;
151 	ASSERT(srp->tx_free + n <= srp->desc.nslots);
152 	bge_atomic_renounce(&srp->tx_free, n);
153 
154 	/*
155 	 * Return tx buffers to buffer push queue
156 	 */
157 	txbuf_queue = srp->txbuf_push_queue;
158 	mutex_enter(txbuf_queue->lock);
159 	buf_item_tail->next = txbuf_queue->head;
160 	txbuf_queue->head = buf_item_head;
161 	txbuf_queue->count += n;
162 	mutex_exit(txbuf_queue->lock);
163 
164 	/*
165 	 * Check if we need exchange the tx buffer push and pop queue
166 	 */
167 	if ((srp->txbuf_pop_queue->count < srp->tx_buffers_low) &&
168 	    (srp->txbuf_pop_queue->count < txbuf_queue->count)) {
169 		srp->txbuf_push_queue = srp->txbuf_pop_queue;
170 		srp->txbuf_pop_queue = txbuf_queue;
171 	}
172 
173 	if (srp->tx_flow != 0 || bgep->tx_resched_needed)
174 		ddi_trigger_softintr(bgep->drain_id);
175 
176 	return (B_TRUE);
177 }
178 
179 /*
180  * Recycle all returned slots in all rings.
181  *
182  * To give priority to low-numbered rings, whenever we have recycled any
183  * slots in any ring except 0, we restart scanning again from ring 0.
184  * Thus, for example, if rings 0, 3, and 10 are carrying traffic, the
185  * pattern of recycles might go 0, 3, 10, 3, 0, 10, 0:
186  *
187  *	0	found some - recycle them
188  *	1..2					none found
189  *	3	found some - recycle them	and restart scan
190  *	0..9					none found
191  *	10	found some - recycle them	and restart scan
192  *	0..2					none found
193  *	3	found some more - recycle them	and restart scan
194  *	0	found some more - recycle them
195  *	0..9					none found
196  *	10	found some more - recycle them	and restart scan
197  *	0	found some more - recycle them
198  *	1..15					none found
199  *
200  * The routine returns only when a complete scan has been performed
201  * without finding any slots to recycle.
202  *
203  * Note: the expression (BGE_SEND_RINGS_USED > 1) yields a compile-time
204  * constant and allows the compiler to optimise away the outer do-loop
205  * if only one send ring is being used.
206  */
207 boolean_t bge_recycle(bge_t *bgep, bge_status_t *bsp);
208 #pragma	no_inline(bge_recycle)
209 
210 boolean_t
211 bge_recycle(bge_t *bgep, bge_status_t *bsp)
212 {
213 	send_ring_t *srp;
214 	uint64_t ring;
215 	uint64_t tx_rings = bgep->chipid.tx_rings;
216 	boolean_t tx_done = B_FALSE;
217 
218 restart:
219 	ring = 0;
220 	srp = &bgep->send[ring];
221 	do {
222 		/*
223 		 * For each ring, (srp->cons_index_p) points to the
224 		 * proper index within the status block (which has
225 		 * already been sync'd by the caller).
226 		 */
227 		ASSERT(srp->cons_index_p == SEND_INDEX_P(bsp, ring));
228 
229 		if (*srp->cons_index_p == srp->tc_next)
230 			continue;		/* no slots to recycle	*/
231 		if (mutex_tryenter(srp->tc_lock) == 0)
232 			continue;		/* already in process	*/
233 		tx_done |= bge_recycle_ring(bgep, srp);
234 		mutex_exit(srp->tc_lock);
235 
236 		/*
237 		 * Restart from ring 0, if we're not on ring 0 already.
238 		 * As H/W selects send BDs totally based on priority and
239 		 * available BDs on the higher priority ring are always
240 		 * selected first, driver should keep consistence with H/W
241 		 * and gives lower-numbered ring with higher priority.
242 		 */
243 		if (tx_rings > 1 && ring > 0)
244 			goto restart;
245 
246 		/*
247 		 * Loop over all rings (if there *are* multiple rings)
248 		 */
249 	} while (++srp, ++ring < tx_rings);
250 
251 	return (tx_done);
252 }
253 
254 
255 /*
256  * ========== Send-side transmit routines ==========
257  */
258 #define	TCP_CKSUM_OFFSET	16
259 #define	UDP_CKSUM_OFFSET	6
260 
261 static void
262 bge_pseudo_cksum(uint8_t *buf)
263 {
264 	uint32_t cksum;
265 	uint16_t iphl;
266 	uint16_t proto;
267 
268 	/*
269 	 * Point it to the ip header.
270 	 */
271 	buf += sizeof (struct ether_header);
272 
273 	/*
274 	 * Calculate the pseudo-header checksum.
275 	 */
276 	iphl = 4 * (buf[0] & 0xF);
277 	cksum = (((uint16_t)buf[2])<<8) + buf[3] - iphl;
278 	cksum += proto = buf[9];
279 	cksum += (((uint16_t)buf[12])<<8) + buf[13];
280 	cksum += (((uint16_t)buf[14])<<8) + buf[15];
281 	cksum += (((uint16_t)buf[16])<<8) + buf[17];
282 	cksum += (((uint16_t)buf[18])<<8) + buf[19];
283 	cksum = (cksum>>16) + (cksum & 0xFFFF);
284 	cksum = (cksum>>16) + (cksum & 0xFFFF);
285 
286 	/*
287 	 * Point it to the TCP/UDP header, and
288 	 * update the checksum field.
289 	 */
290 	buf += iphl + ((proto == IPPROTO_TCP) ?
291 	    TCP_CKSUM_OFFSET : UDP_CKSUM_OFFSET);
292 
293 	/*
294 	 * A real possibility that pointer cast is a problem.
295 	 * Should be fixed when we know the code better.
296 	 * E_BAD_PTR_CAST_ALIGN is added to make it temporarily clean.
297 	 */
298 	*(uint16_t *)buf = htons((uint16_t)cksum);
299 }
300 
301 static bge_queue_item_t *
302 bge_get_txbuf(bge_t *bgep, send_ring_t *srp)
303 {
304 	bge_queue_item_t *txbuf_item;
305 	bge_queue_t *txbuf_queue;
306 
307 	txbuf_queue = srp->txbuf_pop_queue;
308 	mutex_enter(txbuf_queue->lock);
309 	if (txbuf_queue->count == 0) {
310 		mutex_exit(txbuf_queue->lock);
311 		txbuf_queue = srp->txbuf_push_queue;
312 		mutex_enter(txbuf_queue->lock);
313 		if (txbuf_queue->count == 0) {
314 			mutex_exit(txbuf_queue->lock);
315 			/* Try to allocate more tx buffers */
316 			if (srp->tx_array < srp->tx_array_max) {
317 				mutex_enter(srp->tx_lock);
318 				txbuf_item = bge_alloc_txbuf_array(bgep, srp);
319 				mutex_exit(srp->tx_lock);
320 			} else
321 				txbuf_item = NULL;
322 			return (txbuf_item);
323 		}
324 	}
325 	txbuf_item = txbuf_queue->head;
326 	txbuf_queue->head = (bge_queue_item_t *)txbuf_item->next;
327 	txbuf_queue->count--;
328 	mutex_exit(txbuf_queue->lock);
329 	txbuf_item->next = NULL;
330 
331 	return (txbuf_item);
332 }
333 
334 /*
335  * Send a message by copying it into a preallocated (and premapped) buffer
336  */
337 static void bge_send_copy(bge_t *bgep, sw_txbuf_t *txbuf, mblk_t *mp);
338 #pragma	inline(bge_send_copy)
339 
340 static void
341 bge_send_copy(bge_t *bgep, sw_txbuf_t *txbuf, mblk_t *mp)
342 {
343 	mblk_t *bp;
344 	uint32_t mblen;
345 	char *pbuf;
346 
347 	txbuf->copy_len = 0;
348 	pbuf = DMA_VPTR(txbuf->buf);
349 	for (bp = mp; bp != NULL; bp = bp->b_cont) {
350 		if ((mblen = MBLKL(bp)) == 0)
351 			continue;
352 		ASSERT(txbuf->copy_len + mblen <=
353 		    bgep->chipid.snd_buff_size);
354 		bcopy(bp->b_rptr, pbuf, mblen);
355 		pbuf += mblen;
356 		txbuf->copy_len += mblen;
357 	}
358 }
359 
360 /*
361  * Fill the Tx buffer descriptors and trigger the h/w transmission
362  */
363 static void
364 bge_send_serial(bge_t *bgep, send_ring_t *srp)
365 {
366 	send_pkt_t *pktp;
367 	uint64_t txfill_next;
368 	uint32_t count;
369 	uint32_t tx_next;
370 	sw_sbd_t *ssbdp;
371 	bge_status_t *bsp;
372 	bge_sbd_t *hw_sbd_p;
373 	bge_queue_item_t *txbuf_item;
374 	sw_txbuf_t *txbuf;
375 
376 	/*
377 	 * Try to hold the tx lock:
378 	 *	If we are in an interrupt context, use mutex_enter() to
379 	 *	ensure quick response for tx in interrupt context;
380 	 *	Otherwise, use mutex_tryenter() to serialize this h/w tx
381 	 *	BD filling and transmission triggering task.
382 	 */
383 	if (servicing_interrupt() != 0)
384 		mutex_enter(srp->tx_lock);
385 	else if (mutex_tryenter(srp->tx_lock) == 0)
386 		return;		/* already in process	*/
387 
388 	bsp = DMA_VPTR(bgep->status_block);
389 	txfill_next = srp->txfill_next;
390 	tx_next = srp->tx_next;
391 start_tx:
392 	for (count = 0; count < bgep->param_drain_max; ++count) {
393 		pktp = &srp->pktp[txfill_next];
394 		if (!pktp->tx_ready) {
395 			if (count == 0)
396 				srp->tx_block++;
397 			break;
398 		}
399 
400 		/*
401 		 * If there are no enough BDs: try to recycle more
402 		 */
403 		if (srp->tx_free <= 1)
404 			(void) bge_recycle(bgep, bsp);
405 
406 		/*
407 		 * Reserved required BDs: 1 is enough
408 		 */
409 		if (!bge_atomic_reserve(&srp->tx_free, 1)) {
410 			srp->tx_nobd++;
411 			break;
412 		}
413 
414 		/*
415 		 * Filling the tx BD
416 		 */
417 
418 		/*
419 		 * Go straight to claiming our already-reserved places
420 		 * on the train!
421 		 */
422 		ASSERT(pktp->txbuf_item != NULL);
423 		txbuf_item = pktp->txbuf_item;
424 		pktp->txbuf_item = NULL;
425 		pktp->tx_ready = B_FALSE;
426 
427 		txbuf = txbuf_item->item;
428 		ASSERT(txbuf->copy_len != 0);
429 		(void) ddi_dma_sync(txbuf->buf.dma_hdl,  0,
430 		    txbuf->copy_len, DDI_DMA_SYNC_FORDEV);
431 
432 		ssbdp = &srp->sw_sbds[tx_next];
433 		ASSERT(ssbdp->pbuf == NULL);
434 		ssbdp->pbuf = txbuf_item;
435 
436 		/*
437 		 * Setting hardware send buffer descriptor
438 		 */
439 		hw_sbd_p = DMA_VPTR(ssbdp->desc);
440 		hw_sbd_p->flags = 0;
441 		hw_sbd_p->host_buf_addr = txbuf->buf.cookie.dmac_laddress;
442 		hw_sbd_p->len = txbuf->copy_len;
443 		if (pktp->vlan_tci != 0) {
444 			hw_sbd_p->vlan_tci = pktp->vlan_tci;
445 			hw_sbd_p->host_buf_addr += VLAN_TAGSZ;
446 			hw_sbd_p->flags |= SBD_FLAG_VLAN_TAG;
447 		}
448 		if (pktp->pflags & HCK_IPV4_HDRCKSUM)
449 			hw_sbd_p->flags |= SBD_FLAG_IP_CKSUM;
450 		if (pktp->pflags & HCK_FULLCKSUM)
451 			hw_sbd_p->flags |= SBD_FLAG_TCP_UDP_CKSUM;
452 		if (!(bgep->chipid.flags & CHIP_FLAG_NO_JUMBO) &&
453 		    (DEVICE_5717_SERIES_CHIPSETS(bgep) ||
454 		     DEVICE_5725_SERIES_CHIPSETS(bgep) ||
455 		     DEVICE_57765_SERIES_CHIPSETS(bgep)) &&
456 		    (txbuf->copy_len > ETHERMAX))
457 			hw_sbd_p->flags |= SBD_FLAG_JMB_PKT;
458 		hw_sbd_p->flags |= SBD_FLAG_PACKET_END;
459 
460 		txfill_next = NEXT(txfill_next, BGE_SEND_BUF_MAX);
461 		tx_next = NEXT(tx_next, srp->desc.nslots);
462 	}
463 
464 	/*
465 	 * Trigger h/w to start transmission.
466 	 */
467 	if (count != 0) {
468 		bge_atomic_sub64(&srp->tx_flow, count);
469 		srp->txfill_next = txfill_next;
470 
471 		if (srp->tx_next > tx_next) {
472 			(void) ddi_dma_sync(ssbdp->desc.dma_hdl,  0,
473 			    (srp->desc.nslots - srp->tx_next) *
474 			    sizeof (bge_sbd_t),
475 			    DDI_DMA_SYNC_FORDEV);
476 			count -= srp->desc.nslots - srp->tx_next;
477 			ssbdp = &srp->sw_sbds[0];
478 		}
479 		(void) ddi_dma_sync(ssbdp->desc.dma_hdl,  0,
480 		    count*sizeof (bge_sbd_t), DDI_DMA_SYNC_FORDEV);
481 		bge_mbx_put(bgep, srp->chip_mbx_reg, tx_next);
482 		srp->tx_next = tx_next;
483 		atomic_or_32(&bgep->watchdog, 1);
484 
485 		if (srp->tx_flow != 0 && srp->tx_free > 1)
486 			goto start_tx;
487 	}
488 
489 	mutex_exit(srp->tx_lock);
490 }
491 
492 mblk_t *
493 bge_ring_tx(void *arg, mblk_t *mp)
494 {
495 	send_ring_t *srp = arg;
496 	bge_t *bgep = srp->bgep;
497 	struct ether_vlan_header *ehp;
498 	bge_queue_item_t *txbuf_item;
499 	sw_txbuf_t *txbuf;
500 	send_pkt_t *pktp;
501 	uint64_t pkt_slot;
502 	uint16_t vlan_tci;
503 	uint32_t pflags;
504 	char *pbuf;
505 
506 	ASSERT(mp->b_next == NULL);
507 
508 	/*
509 	 * Get a s/w tx buffer first
510 	 */
511 	txbuf_item = bge_get_txbuf(bgep, srp);
512 	if (txbuf_item == NULL) {
513 		/* no tx buffer available */
514 		srp->tx_nobuf++;
515 		bgep->tx_resched_needed = B_TRUE;
516 		bge_send_serial(bgep, srp);
517 		return (mp);
518 	}
519 
520 	/*
521 	 * Copy all mp fragments to the pkt buffer
522 	 */
523 	txbuf = txbuf_item->item;
524 	bge_send_copy(bgep, txbuf, mp);
525 
526 	/*
527 	 * Determine if the packet is VLAN tagged.
528 	 */
529 	ASSERT(txbuf->copy_len >= sizeof (struct ether_header));
530 	pbuf = DMA_VPTR(txbuf->buf);
531 
532 	ehp = (void *)pbuf;
533 	if (ehp->ether_tpid == htons(ETHERTYPE_VLAN)) {
534 		/* Strip the vlan tag */
535 		vlan_tci = ntohs(ehp->ether_tci);
536 		pbuf = memmove(pbuf + VLAN_TAGSZ, pbuf, 2 * ETHERADDRL);
537 		txbuf->copy_len -= VLAN_TAGSZ;
538 	} else
539 		vlan_tci = 0;
540 
541 	/*
542 	 * Retrieve checksum offloading info.
543 	 */
544 	mac_hcksum_get(mp, NULL, NULL, NULL, NULL, &pflags);
545 
546 	/*
547 	 * Calculate pseudo checksum if needed.
548 	 */
549 	if ((pflags & HCK_FULLCKSUM) &&
550 	    (bgep->chipid.flags & CHIP_FLAG_PARTIAL_CSUM))
551 		bge_pseudo_cksum((uint8_t *)pbuf);
552 
553 	/*
554 	 * Packet buffer is ready to send: get and fill pkt info
555 	 */
556 	pkt_slot = bge_atomic_next(&srp->txpkt_next, BGE_SEND_BUF_MAX);
557 	pktp = &srp->pktp[pkt_slot];
558 	ASSERT(pktp->txbuf_item == NULL);
559 	pktp->txbuf_item = txbuf_item;
560 	pktp->vlan_tci = vlan_tci;
561 	pktp->pflags = pflags;
562 	atomic_inc_64(&srp->tx_flow);
563 	ASSERT(pktp->tx_ready == B_FALSE);
564 	pktp->tx_ready = B_TRUE;
565 
566 	/*
567 	 * Filling the h/w bd and trigger the h/w to start transmission
568 	 */
569 	bge_send_serial(bgep, srp);
570 
571 	srp->pushed_bytes += MBLKL(mp);
572 
573 	/*
574 	 * We've copied the contents, the message can be freed right away
575 	 */
576 	freemsg(mp);
577 	return (NULL);
578 }
579 
580 static mblk_t *
581 bge_send(bge_t *bgep, mblk_t *mp)
582 {
583 	send_ring_t *ring;
584 
585 	ring = &bgep->send[0];	/* ring 0 */
586 
587 	return (bge_ring_tx(ring, mp));
588 }
589 
590 uint_t
591 bge_send_drain(caddr_t arg)
592 {
593 	uint_t ring = 0;	/* use ring 0 */
594 	bge_t *bgep;
595 	send_ring_t *srp;
596 
597 	bgep = (void *)arg;
598 	BGE_TRACE(("bge_send_drain($%p)", (void *)bgep));
599 
600 	srp = &bgep->send[ring];
601 	bge_send_serial(bgep, srp);
602 
603 	if (bgep->tx_resched_needed &&
604 	    (srp->tx_flow < srp->tx_buffers_low) &&
605 	    (bgep->bge_mac_state == BGE_MAC_STARTED)) {
606 		mac_tx_update(bgep->mh);
607 		bgep->tx_resched_needed = B_FALSE;
608 		bgep->tx_resched++;
609 	}
610 
611 	return (DDI_INTR_CLAIMED);
612 }
613 
614 /*
615  * bge_m_tx() - send a chain of packets
616  */
617 mblk_t *
618 bge_m_tx(void *arg, mblk_t *mp)
619 {
620 	bge_t *bgep = arg;		/* private device info	*/
621 	mblk_t *next;
622 
623 	BGE_TRACE(("bge_m_tx($%p, $%p)", arg, (void *)mp));
624 
625 	ASSERT(mp != NULL);
626 	ASSERT(bgep->bge_mac_state == BGE_MAC_STARTED);
627 
628 	rw_enter(bgep->errlock, RW_READER);
629 	if ((bgep->bge_chip_state != BGE_CHIP_RUNNING) ||
630 	    !(bgep->param_link_up)) {
631 		BGE_DEBUG(("bge_m_tx: chip not running or link down"));
632 		freemsgchain(mp);
633 		mp = NULL;
634 	}
635 
636 	while (mp != NULL) {
637 		next = mp->b_next;
638 		mp->b_next = NULL;
639 
640 		if ((mp = bge_send(bgep, mp)) != NULL) {
641 			mp->b_next = next;
642 			break;
643 		}
644 
645 		mp = next;
646 	}
647 	rw_exit(bgep->errlock);
648 
649 	return (mp);
650 }
651