1 // SPDX-License-Identifier: GPL-2.0-only
2 /****************************************************************************
3  * Driver for Solarflare network controllers and boards
4  * Copyright 2018 Solarflare Communications Inc.
5  * Copyright 2019-2020 Xilinx Inc.
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License version 2 as published
9  * by the Free Software Foundation, incorporated herein by reference.
10  */
11 
12 #include <net/ip6_checksum.h>
13 
14 #include "net_driver.h"
15 #include "tx_common.h"
16 #include "nic_common.h"
17 #include "mcdi_functions.h"
18 #include "ef100_regs.h"
19 #include "io.h"
20 #include "ef100_tx.h"
21 #include "ef100_nic.h"
22 
ef100_tx_probe(struct efx_tx_queue * tx_queue)23 int ef100_tx_probe(struct efx_tx_queue *tx_queue)
24 {
25 	/* Allocate an extra descriptor for the QMDA status completion entry */
26 	return efx_nic_alloc_buffer(tx_queue->efx, &tx_queue->txd,
27 				    (tx_queue->ptr_mask + 2) *
28 				    sizeof(efx_oword_t),
29 				    GFP_KERNEL);
30 }
31 
ef100_tx_init(struct efx_tx_queue * tx_queue)32 void ef100_tx_init(struct efx_tx_queue *tx_queue)
33 {
34 	/* must be the inverse of lookup in efx_get_tx_channel */
35 	tx_queue->core_txq =
36 		netdev_get_tx_queue(tx_queue->efx->net_dev,
37 				    tx_queue->channel->channel -
38 				    tx_queue->efx->tx_channel_offset);
39 
40 	/* This value is purely documentational; as EF100 never passes through
41 	 * the switch statement in tx.c:__efx_enqueue_skb(), that switch does
42 	 * not handle case 3.  EF100's TSOv3 descriptors are generated by
43 	 * ef100_make_tso_desc().
44 	 * Meanwhile, all efx_mcdi_tx_init() cares about is that it's not 2.
45 	 */
46 	tx_queue->tso_version = 3;
47 	if (efx_mcdi_tx_init(tx_queue))
48 		netdev_WARN(tx_queue->efx->net_dev,
49 			    "failed to initialise TXQ %d\n", tx_queue->queue);
50 }
51 
ef100_tx_can_tso(struct efx_tx_queue * tx_queue,struct sk_buff * skb)52 static bool ef100_tx_can_tso(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
53 {
54 	struct efx_nic *efx = tx_queue->efx;
55 	struct ef100_nic_data *nic_data;
56 	struct efx_tx_buffer *buffer;
57 	size_t header_len;
58 	u32 mss;
59 
60 	nic_data = efx->nic_data;
61 
62 	if (!skb_is_gso_tcp(skb))
63 		return false;
64 	if (!(efx->net_dev->features & NETIF_F_TSO))
65 		return false;
66 
67 	mss = skb_shinfo(skb)->gso_size;
68 	if (unlikely(mss < 4)) {
69 		WARN_ONCE(1, "MSS of %u is too small for TSO\n", mss);
70 		return false;
71 	}
72 
73 	header_len = efx_tx_tso_header_length(skb);
74 	if (header_len > nic_data->tso_max_hdr_len)
75 		return false;
76 
77 	if (skb_shinfo(skb)->gso_segs > nic_data->tso_max_payload_num_segs) {
78 		/* net_dev->gso_max_segs should've caught this */
79 		WARN_ON_ONCE(1);
80 		return false;
81 	}
82 
83 	if (skb->data_len / mss > nic_data->tso_max_frames)
84 		return false;
85 
86 	/* net_dev->gso_max_size should've caught this */
87 	if (WARN_ON_ONCE(skb->data_len > nic_data->tso_max_payload_len))
88 		return false;
89 
90 	/* Reserve an empty buffer for the TSO V3 descriptor.
91 	 * Convey the length of the header since we already know it.
92 	 */
93 	buffer = efx_tx_queue_get_insert_buffer(tx_queue);
94 	buffer->flags = EFX_TX_BUF_TSO_V3 | EFX_TX_BUF_CONT;
95 	buffer->len = header_len;
96 	buffer->unmap_len = 0;
97 	buffer->skb = skb;
98 	++tx_queue->insert_count;
99 	return true;
100 }
101 
ef100_tx_desc(struct efx_tx_queue * tx_queue,unsigned int index)102 static efx_oword_t *ef100_tx_desc(struct efx_tx_queue *tx_queue, unsigned int index)
103 {
104 	if (likely(tx_queue->txd.addr))
105 		return ((efx_oword_t *)tx_queue->txd.addr) + index;
106 	else
107 		return NULL;
108 }
109 
ef100_notify_tx_desc(struct efx_tx_queue * tx_queue)110 static void ef100_notify_tx_desc(struct efx_tx_queue *tx_queue)
111 {
112 	unsigned int write_ptr;
113 	efx_dword_t reg;
114 
115 	tx_queue->xmit_pending = false;
116 
117 	if (unlikely(tx_queue->notify_count == tx_queue->write_count))
118 		return;
119 
120 	write_ptr = tx_queue->write_count & tx_queue->ptr_mask;
121 	/* The write pointer goes into the high word */
122 	EFX_POPULATE_DWORD_1(reg, ERF_GZ_TX_RING_PIDX, write_ptr);
123 	efx_writed_page(tx_queue->efx, &reg,
124 			ER_GZ_TX_RING_DOORBELL, tx_queue->queue);
125 	tx_queue->notify_count = tx_queue->write_count;
126 }
127 
ef100_tx_push_buffers(struct efx_tx_queue * tx_queue)128 static void ef100_tx_push_buffers(struct efx_tx_queue *tx_queue)
129 {
130 	ef100_notify_tx_desc(tx_queue);
131 	++tx_queue->pushes;
132 }
133 
ef100_set_tx_csum_partial(const struct sk_buff * skb,struct efx_tx_buffer * buffer,efx_oword_t * txd)134 static void ef100_set_tx_csum_partial(const struct sk_buff *skb,
135 				      struct efx_tx_buffer *buffer, efx_oword_t *txd)
136 {
137 	efx_oword_t csum;
138 	int csum_start;
139 
140 	if (!skb || skb->ip_summed != CHECKSUM_PARTIAL)
141 		return;
142 
143 	/* skb->csum_start has the offset from head, but we need the offset
144 	 * from data.
145 	 */
146 	csum_start = skb_checksum_start_offset(skb);
147 	EFX_POPULATE_OWORD_3(csum,
148 			     ESF_GZ_TX_SEND_CSO_PARTIAL_EN, 1,
149 			     ESF_GZ_TX_SEND_CSO_PARTIAL_START_W,
150 			     csum_start >> 1,
151 			     ESF_GZ_TX_SEND_CSO_PARTIAL_CSUM_W,
152 			     skb->csum_offset >> 1);
153 	EFX_OR_OWORD(*txd, *txd, csum);
154 }
155 
ef100_set_tx_hw_vlan(const struct sk_buff * skb,efx_oword_t * txd)156 static void ef100_set_tx_hw_vlan(const struct sk_buff *skb, efx_oword_t *txd)
157 {
158 	u16 vlan_tci = skb_vlan_tag_get(skb);
159 	efx_oword_t vlan;
160 
161 	EFX_POPULATE_OWORD_2(vlan,
162 			     ESF_GZ_TX_SEND_VLAN_INSERT_EN, 1,
163 			     ESF_GZ_TX_SEND_VLAN_INSERT_TCI, vlan_tci);
164 	EFX_OR_OWORD(*txd, *txd, vlan);
165 }
166 
ef100_make_send_desc(struct efx_nic * efx,const struct sk_buff * skb,struct efx_tx_buffer * buffer,efx_oword_t * txd,unsigned int segment_count)167 static void ef100_make_send_desc(struct efx_nic *efx,
168 				 const struct sk_buff *skb,
169 				 struct efx_tx_buffer *buffer, efx_oword_t *txd,
170 				 unsigned int segment_count)
171 {
172 	/* TX send descriptor */
173 	EFX_POPULATE_OWORD_3(*txd,
174 			     ESF_GZ_TX_SEND_NUM_SEGS, segment_count,
175 			     ESF_GZ_TX_SEND_LEN, buffer->len,
176 			     ESF_GZ_TX_SEND_ADDR, buffer->dma_addr);
177 
178 	if (likely(efx->net_dev->features & NETIF_F_HW_CSUM))
179 		ef100_set_tx_csum_partial(skb, buffer, txd);
180 	if (efx->net_dev->features & NETIF_F_HW_VLAN_CTAG_TX &&
181 	    skb && skb_vlan_tag_present(skb))
182 		ef100_set_tx_hw_vlan(skb, txd);
183 }
184 
ef100_make_tso_desc(struct efx_nic * efx,const struct sk_buff * skb,struct efx_tx_buffer * buffer,efx_oword_t * txd,unsigned int segment_count)185 static void ef100_make_tso_desc(struct efx_nic *efx,
186 				const struct sk_buff *skb,
187 				struct efx_tx_buffer *buffer, efx_oword_t *txd,
188 				unsigned int segment_count)
189 {
190 	bool gso_partial = skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL;
191 	unsigned int len, ip_offset, tcp_offset, payload_segs;
192 	u32 mangleid = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
193 	unsigned int outer_ip_offset, outer_l4_offset;
194 	u16 vlan_tci = skb_vlan_tag_get(skb);
195 	u32 mss = skb_shinfo(skb)->gso_size;
196 	bool encap = skb->encapsulation;
197 	bool udp_encap = false;
198 	u16 vlan_enable = 0;
199 	struct tcphdr *tcp;
200 	bool outer_csum;
201 	u32 paylen;
202 
203 	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID)
204 		mangleid = ESE_GZ_TX_DESC_IP4_ID_NO_OP;
205 	if (efx->net_dev->features & NETIF_F_HW_VLAN_CTAG_TX)
206 		vlan_enable = skb_vlan_tag_present(skb);
207 
208 	len = skb->len - buffer->len;
209 	/* We use 1 for the TSO descriptor and 1 for the header */
210 	payload_segs = segment_count - 2;
211 	if (encap) {
212 		outer_ip_offset = skb_network_offset(skb);
213 		outer_l4_offset = skb_transport_offset(skb);
214 		ip_offset = skb_inner_network_offset(skb);
215 		tcp_offset = skb_inner_transport_offset(skb);
216 		if (skb_shinfo(skb)->gso_type &
217 		    (SKB_GSO_UDP_TUNNEL | SKB_GSO_UDP_TUNNEL_CSUM))
218 			udp_encap = true;
219 	} else {
220 		ip_offset =  skb_network_offset(skb);
221 		tcp_offset = skb_transport_offset(skb);
222 		outer_ip_offset = outer_l4_offset = 0;
223 	}
224 	outer_csum = skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM;
225 
226 	/* subtract TCP payload length from inner checksum */
227 	tcp = (void *)skb->data + tcp_offset;
228 	paylen = skb->len - tcp_offset;
229 	csum_replace_by_diff(&tcp->check, (__force __wsum)htonl(paylen));
230 
231 	EFX_POPULATE_OWORD_19(*txd,
232 			      ESF_GZ_TX_DESC_TYPE, ESE_GZ_TX_DESC_TYPE_TSO,
233 			      ESF_GZ_TX_TSO_MSS, mss,
234 			      ESF_GZ_TX_TSO_HDR_NUM_SEGS, 1,
235 			      ESF_GZ_TX_TSO_PAYLOAD_NUM_SEGS, payload_segs,
236 			      ESF_GZ_TX_TSO_HDR_LEN_W, buffer->len >> 1,
237 			      ESF_GZ_TX_TSO_PAYLOAD_LEN, len,
238 			      ESF_GZ_TX_TSO_CSO_OUTER_L4, outer_csum,
239 			      ESF_GZ_TX_TSO_CSO_INNER_L4, 1,
240 			      ESF_GZ_TX_TSO_INNER_L3_OFF_W, ip_offset >> 1,
241 			      ESF_GZ_TX_TSO_INNER_L4_OFF_W, tcp_offset >> 1,
242 			      ESF_GZ_TX_TSO_ED_INNER_IP4_ID, mangleid,
243 			      ESF_GZ_TX_TSO_ED_INNER_IP_LEN, 1,
244 			      ESF_GZ_TX_TSO_OUTER_L3_OFF_W, outer_ip_offset >> 1,
245 			      ESF_GZ_TX_TSO_OUTER_L4_OFF_W, outer_l4_offset >> 1,
246 			      ESF_GZ_TX_TSO_ED_OUTER_UDP_LEN, udp_encap && !gso_partial,
247 			      ESF_GZ_TX_TSO_ED_OUTER_IP_LEN, encap && !gso_partial,
248 			      ESF_GZ_TX_TSO_ED_OUTER_IP4_ID, encap ? mangleid :
249 								     ESE_GZ_TX_DESC_IP4_ID_NO_OP,
250 			      ESF_GZ_TX_TSO_VLAN_INSERT_EN, vlan_enable,
251 			      ESF_GZ_TX_TSO_VLAN_INSERT_TCI, vlan_tci
252 		);
253 }
254 
ef100_tx_make_descriptors(struct efx_tx_queue * tx_queue,const struct sk_buff * skb,unsigned int segment_count,struct efx_rep * efv)255 static void ef100_tx_make_descriptors(struct efx_tx_queue *tx_queue,
256 				      const struct sk_buff *skb,
257 				      unsigned int segment_count,
258 				      struct efx_rep *efv)
259 {
260 	unsigned int old_write_count = tx_queue->write_count;
261 	unsigned int new_write_count = old_write_count;
262 	struct efx_tx_buffer *buffer;
263 	unsigned int next_desc_type;
264 	unsigned int write_ptr;
265 	efx_oword_t *txd;
266 	unsigned int nr_descs = tx_queue->insert_count - old_write_count;
267 
268 	if (unlikely(nr_descs == 0))
269 		return;
270 
271 	if (segment_count)
272 		next_desc_type = ESE_GZ_TX_DESC_TYPE_TSO;
273 	else
274 		next_desc_type = ESE_GZ_TX_DESC_TYPE_SEND;
275 
276 	if (unlikely(efv)) {
277 		/* Create TX override descriptor */
278 		write_ptr = new_write_count & tx_queue->ptr_mask;
279 		txd = ef100_tx_desc(tx_queue, write_ptr);
280 		++new_write_count;
281 
282 		tx_queue->packet_write_count = new_write_count;
283 		EFX_POPULATE_OWORD_3(*txd,
284 				     ESF_GZ_TX_DESC_TYPE, ESE_GZ_TX_DESC_TYPE_PREFIX,
285 				     ESF_GZ_TX_PREFIX_EGRESS_MPORT, efv->mport,
286 				     ESF_GZ_TX_PREFIX_EGRESS_MPORT_EN, 1);
287 		nr_descs--;
288 	}
289 
290 	/* if it's a raw write (such as XDP) then always SEND single frames */
291 	if (!skb)
292 		nr_descs = 1;
293 
294 	do {
295 		write_ptr = new_write_count & tx_queue->ptr_mask;
296 		buffer = &tx_queue->buffer[write_ptr];
297 		txd = ef100_tx_desc(tx_queue, write_ptr);
298 		++new_write_count;
299 
300 		/* Create TX descriptor ring entry */
301 		tx_queue->packet_write_count = new_write_count;
302 
303 		switch (next_desc_type) {
304 		case ESE_GZ_TX_DESC_TYPE_SEND:
305 			ef100_make_send_desc(tx_queue->efx, skb,
306 					     buffer, txd, nr_descs);
307 			break;
308 		case ESE_GZ_TX_DESC_TYPE_TSO:
309 			/* TX TSO descriptor */
310 			WARN_ON_ONCE(!(buffer->flags & EFX_TX_BUF_TSO_V3));
311 			ef100_make_tso_desc(tx_queue->efx, skb,
312 					    buffer, txd, nr_descs);
313 			break;
314 		default:
315 			/* TX segment descriptor */
316 			EFX_POPULATE_OWORD_3(*txd,
317 					     ESF_GZ_TX_DESC_TYPE, ESE_GZ_TX_DESC_TYPE_SEG,
318 					     ESF_GZ_TX_SEG_LEN, buffer->len,
319 					     ESF_GZ_TX_SEG_ADDR, buffer->dma_addr);
320 		}
321 		/* if it's a raw write (such as XDP) then always SEND */
322 		next_desc_type = skb ? ESE_GZ_TX_DESC_TYPE_SEG :
323 				       ESE_GZ_TX_DESC_TYPE_SEND;
324 		/* mark as an EFV buffer if applicable */
325 		if (unlikely(efv))
326 			buffer->flags |= EFX_TX_BUF_EFV;
327 
328 	} while (new_write_count != tx_queue->insert_count);
329 
330 	wmb(); /* Ensure descriptors are written before they are fetched */
331 
332 	tx_queue->write_count = new_write_count;
333 
334 	/* The write_count above must be updated before reading
335 	 * channel->holdoff_doorbell to avoid a race with the
336 	 * completion path, so ensure these operations are not
337 	 * re-ordered.  This also flushes the update of write_count
338 	 * back into the cache.
339 	 */
340 	smp_mb();
341 }
342 
ef100_tx_write(struct efx_tx_queue * tx_queue)343 void ef100_tx_write(struct efx_tx_queue *tx_queue)
344 {
345 	ef100_tx_make_descriptors(tx_queue, NULL, 0, NULL);
346 	ef100_tx_push_buffers(tx_queue);
347 }
348 
ef100_ev_tx(struct efx_channel * channel,const efx_qword_t * p_event)349 int ef100_ev_tx(struct efx_channel *channel, const efx_qword_t *p_event)
350 {
351 	unsigned int tx_done =
352 		EFX_QWORD_FIELD(*p_event, ESF_GZ_EV_TXCMPL_NUM_DESC);
353 	unsigned int qlabel =
354 		EFX_QWORD_FIELD(*p_event, ESF_GZ_EV_TXCMPL_Q_LABEL);
355 	struct efx_tx_queue *tx_queue =
356 		efx_channel_get_tx_queue(channel, qlabel);
357 	unsigned int tx_index = (tx_queue->read_count + tx_done - 1) &
358 				tx_queue->ptr_mask;
359 
360 	return efx_xmit_done(tx_queue, tx_index);
361 }
362 
363 /* Add a socket buffer to a TX queue
364  *
365  * You must hold netif_tx_lock() to call this function.
366  *
367  * Returns 0 on success, error code otherwise. In case of an error this
368  * function will free the SKB.
369  */
ef100_enqueue_skb(struct efx_tx_queue * tx_queue,struct sk_buff * skb)370 netdev_tx_t ef100_enqueue_skb(struct efx_tx_queue *tx_queue,
371 			      struct sk_buff *skb)
372 {
373 	return __ef100_enqueue_skb(tx_queue, skb, NULL);
374 }
375 
__ef100_enqueue_skb(struct efx_tx_queue * tx_queue,struct sk_buff * skb,struct efx_rep * efv)376 int __ef100_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
377 			struct efx_rep *efv)
378 {
379 	unsigned int old_insert_count = tx_queue->insert_count;
380 	struct efx_nic *efx = tx_queue->efx;
381 	bool xmit_more = netdev_xmit_more();
382 	unsigned int fill_level;
383 	unsigned int segments;
384 	int rc;
385 
386 	if (!tx_queue->buffer || !tx_queue->ptr_mask) {
387 		netif_stop_queue(efx->net_dev);
388 		dev_kfree_skb_any(skb);
389 		return -ENODEV;
390 	}
391 
392 	segments = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 0;
393 	if (segments == 1)
394 		segments = 0;	/* Don't use TSO/GSO for a single segment. */
395 	if (segments && !ef100_tx_can_tso(tx_queue, skb)) {
396 		rc = efx_tx_tso_fallback(tx_queue, skb);
397 		tx_queue->tso_fallbacks++;
398 		if (rc)
399 			goto err;
400 		else
401 			return 0;
402 	}
403 
404 	if (unlikely(efv)) {
405 		struct efx_tx_buffer *buffer = __efx_tx_queue_get_insert_buffer(tx_queue);
406 
407 		/* Drop representor packets if the queue is stopped.
408 		 * We currently don't assert backoff to representors so this is
409 		 * to make sure representor traffic can't starve the main
410 		 * net device.
411 		 * And, of course, if there are no TX descriptors left.
412 		 */
413 		if (netif_tx_queue_stopped(tx_queue->core_txq) ||
414 		    unlikely(efx_tx_buffer_in_use(buffer))) {
415 			atomic64_inc(&efv->stats.tx_errors);
416 			rc = -ENOSPC;
417 			goto err;
418 		}
419 
420 		/* Also drop representor traffic if it could cause us to
421 		 * stop the queue. If we assert backoff and we haven't
422 		 * received traffic on the main net device recently then the
423 		 * TX watchdog can go off erroneously.
424 		 */
425 		fill_level = efx_channel_tx_old_fill_level(tx_queue->channel);
426 		fill_level += efx_tx_max_skb_descs(efx);
427 		if (fill_level > efx->txq_stop_thresh) {
428 			struct efx_tx_queue *txq2;
429 
430 			/* Refresh cached fill level and re-check */
431 			efx_for_each_channel_tx_queue(txq2, tx_queue->channel)
432 				txq2->old_read_count = READ_ONCE(txq2->read_count);
433 
434 			fill_level = efx_channel_tx_old_fill_level(tx_queue->channel);
435 			fill_level += efx_tx_max_skb_descs(efx);
436 			if (fill_level > efx->txq_stop_thresh) {
437 				atomic64_inc(&efv->stats.tx_errors);
438 				rc = -ENOSPC;
439 				goto err;
440 			}
441 		}
442 
443 		buffer->flags = EFX_TX_BUF_OPTION | EFX_TX_BUF_EFV;
444 		tx_queue->insert_count++;
445 	}
446 
447 	/* Map for DMA and create descriptors */
448 	rc = efx_tx_map_data(tx_queue, skb, segments);
449 	if (rc)
450 		goto err;
451 	ef100_tx_make_descriptors(tx_queue, skb, segments, efv);
452 
453 	fill_level = efx_channel_tx_old_fill_level(tx_queue->channel);
454 	if (fill_level > efx->txq_stop_thresh) {
455 		struct efx_tx_queue *txq2;
456 
457 		/* Because of checks above, representor traffic should
458 		 * not be able to stop the queue.
459 		 */
460 		WARN_ON(efv);
461 
462 		netif_tx_stop_queue(tx_queue->core_txq);
463 		/* Re-read after a memory barrier in case we've raced with
464 		 * the completion path. Otherwise there's a danger we'll never
465 		 * restart the queue if all completions have just happened.
466 		 */
467 		smp_mb();
468 		efx_for_each_channel_tx_queue(txq2, tx_queue->channel)
469 			txq2->old_read_count = READ_ONCE(txq2->read_count);
470 		fill_level = efx_channel_tx_old_fill_level(tx_queue->channel);
471 		if (fill_level < efx->txq_stop_thresh)
472 			netif_tx_start_queue(tx_queue->core_txq);
473 	}
474 
475 	tx_queue->xmit_pending = true;
476 
477 	/* If xmit_more then we don't need to push the doorbell, unless there
478 	 * are 256 descriptors already queued in which case we have to push to
479 	 * ensure we never push more than 256 at once.
480 	 *
481 	 * Always push for representor traffic, and don't account it to parent
482 	 * PF netdevice's BQL.
483 	 */
484 	if (unlikely(efv) ||
485 	    __netdev_tx_sent_queue(tx_queue->core_txq, skb->len, xmit_more) ||
486 	    tx_queue->write_count - tx_queue->notify_count > 255)
487 		ef100_tx_push_buffers(tx_queue);
488 
489 	if (segments) {
490 		tx_queue->tso_bursts++;
491 		tx_queue->tso_packets += segments;
492 		tx_queue->tx_packets  += segments;
493 	} else {
494 		tx_queue->tx_packets++;
495 	}
496 	return 0;
497 
498 err:
499 	efx_enqueue_unwind(tx_queue, old_insert_count);
500 	if (!IS_ERR_OR_NULL(skb))
501 		dev_kfree_skb_any(skb);
502 
503 	/* If we're not expecting another transmit and we had something to push
504 	 * on this queue then we need to push here to get the previous packets
505 	 * out.  We only enter this branch from before the xmit_more handling
506 	 * above, so xmit_pending still refers to the old state.
507 	 */
508 	if (tx_queue->xmit_pending && !xmit_more)
509 		ef100_tx_push_buffers(tx_queue);
510 	return rc;
511 }
512