summaryrefslogtreecommitdiffstats
path: root/drivers/net/ethernet/intel/i40e/i40e_txrx.h
blob: 768290dc6f48b983d3e5d7e630016a10211e9a52 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright(c) 2013 - 2018 Intel Corporation. */

#ifndef _I40E_TXRX_H_
#define _I40E_TXRX_H_

#include <net/xdp.h>

/* Interrupt Throttling and Rate Limiting Goodies */
#define I40E_DEFAULT_IRQ_WORK      256

/* The datasheet for the X710 and XL710 indicate that the maximum value for
 * the ITR is 8160usec which is then called out as 0xFF0 with a 2usec
 * resolution. 8160 is 0x1FE0 when written out in hex. So instead of storing
 * the register value which is divided by 2 lets use the actual values and
 * avoid an excessive amount of translation.
 */
#define I40E_ITR_DYNAMIC	0x8000	/* use top bit as a flag */
#define I40E_ITR_MASK		0x1FFE	/* mask for ITR register value */
#define I40E_MIN_ITR		     2	/* reg uses 2 usec resolution */
#define I40E_ITR_20K		    50
#define I40E_ITR_8K		   122
#define I40E_MAX_ITR		  8160	/* maximum value as per datasheet */
#define ITR_TO_REG(setting) ((setting) & ~I40E_ITR_DYNAMIC)
#define ITR_REG_ALIGN(setting) __ALIGN_MASK(setting, ~I40E_ITR_MASK)
#define ITR_IS_DYNAMIC(setting) (!!((setting) & I40E_ITR_DYNAMIC))

#define I40E_ITR_RX_DEF		(I40E_ITR_20K | I40E_ITR_DYNAMIC)
#define I40E_ITR_TX_DEF		(I40E_ITR_20K | I40E_ITR_DYNAMIC)

/* 0x40 is the enable bit for interrupt rate limiting, and must be set if
 * the value of the rate limit is non-zero
 */
#define INTRL_ENA                  BIT(6)
#define I40E_MAX_INTRL             0x3B    /* reg uses 4 usec resolution */
#define INTRL_REG_TO_USEC(intrl) ((intrl & ~INTRL_ENA) << 2)

/**
 * i40e_intrl_usec_to_reg - convert interrupt rate limit to register
 * @intrl: interrupt rate limit to convert
 *
 * This function converts a decimal interrupt rate limit to the appropriate
 * register format expected by the firmware when setting interrupt rate limit.
 */
static inline u16 i40e_intrl_usec_to_reg(int intrl)
{
	if (intrl >> 2)
		return ((intrl >> 2) | INTRL_ENA);
	else
		return 0;
}

#define I40E_QUEUE_END_OF_LIST 0x7FF

/* this enum matches hardware bits and is meant to be used by DYN_CTLN
 * registers and QINT registers or more generally anywhere in the manual
 * mentioning ITR_INDX, ITR_NONE cannot be used as an index 'n' into any
 * register but instead is a special value meaning "don't update" ITR0/1/2.
 */
enum i40e_dyn_idx_t {
	I40E_IDX_ITR0 = 0,
	I40E_IDX_ITR1 = 1,
	I40E_IDX_ITR2 = 2,
	I40E_ITR_NONE = 3	/* ITR_NONE must not be used as an index */
};

/* these are indexes into ITRN registers */
#define I40E_RX_ITR    I40E_IDX_ITR0
#define I40E_TX_ITR    I40E_IDX_ITR1

/* Supported RSS offloads */
#define I40E_DEFAULT_RSS_HENA ( \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV4_UDP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV4_SCTP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV4_TCP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV4_OTHER) | \
	BIT_ULL(I40E_FILTER_PCTYPE_FRAG_IPV4) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV6_UDP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV6_TCP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV6_SCTP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV6_OTHER) | \
	BIT_ULL(I40E_FILTER_PCTYPE_FRAG_IPV6) | \
	BIT_ULL(I40E_FILTER_PCTYPE_L2_PAYLOAD))

#define I40E_DEFAULT_RSS_HENA_EXPANDED (I40E_DEFAULT_RSS_HENA | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV4_TCP_SYN_NO_ACK) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_UNICAST_IPV4_UDP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_MULTICAST_IPV4_UDP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_IPV6_TCP_SYN_NO_ACK) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_UNICAST_IPV6_UDP) | \
	BIT_ULL(I40E_FILTER_PCTYPE_NONF_MULTICAST_IPV6_UDP))

#define i40e_pf_get_default_rss_hena(pf) \
	(((pf)->hw_features & I40E_HW_MULTIPLE_TCP_UDP_RSS_PCTYPE) ? \
	  I40E_DEFAULT_RSS_HENA_EXPANDED : I40E_DEFAULT_RSS_HENA)

/* Supported Rx Buffer Sizes (a multiple of 128) */
#define I40E_RXBUFFER_256   256
#define I40E_RXBUFFER_1536  1536  /* 128B aligned standard Ethernet frame */
#define I40E_RXBUFFER_2048  2048
#define I40E_RXBUFFER_3072  3072  /* Used for large frames w/ padding */
#define I40E_MAX_RXBUFFER   9728  /* largest size for single descriptor */

/* NOTE: netdev_alloc_skb reserves up to 64 bytes, NET_IP_ALIGN means we
 * reserve 2 more, and skb_shared_info adds an additional 384 bytes more,
 * this adds up to 512 bytes of extra data meaning the smallest allocation
 * we could have is 1K.
 * i.e. RXBUFFER_256 --> 960 byte skb (size-1024 slab)
 * i.e. RXBUFFER_512 --> 1216 byte skb (size-2048 slab)
 */
#define I40E_RX_HDR_SIZE I40E_RXBUFFER_256
#define I40E_PACKET_HDR_PAD (ETH_HLEN + ETH_FCS_LEN + (VLAN_HLEN * 2))
#define i40e_rx_desc i40e_16byte_rx_desc

#define I40E_RX_DMA_ATTR \
	(DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING)

/* Attempt to maximize the headroom available for incoming frames.  We
 * use a 2K buffer for receives and need 1536/1534 to store the data for
 * the frame.  This leaves us with 512 bytes of room.  From that we need
 * to deduct the space needed for the shared info and the padding needed
 * to IP align the frame.
 *
 * Note: For cache line sizes 256 or larger this value is going to end
 *	 up negative.  In these cases we should fall back to the legacy
 *	 receive path.
 */
#if (PAGE_SIZE < 8192)
#define I40E_2K_TOO_SMALL_WITH_PADDING \
((NET_SKB_PAD + I40E_RXBUFFER_1536) > SKB_WITH_OVERHEAD(I40E_RXBUFFER_2048))

static inline int i40e_compute_pad(int rx_buf_len)
{
	int page_size, pad_size;

	page_size = ALIGN(rx_buf_len, PAGE_SIZE / 2);
	pad_size = SKB_WITH_OVERHEAD(page_size) - rx_buf_len;

	return pad_size;
}

static inline int i40e_skb_pad(void)
{
	int rx_buf_len;

	/* If a 2K buffer cannot handle a standard Ethernet frame then
	 * optimize padding for a 3K buffer instead of a 1.5K buffer.
	 *
	 * For a 3K buffer we need to add enough padding to allow for
	 * tailroom due to NET_IP_ALIGN possibly shifting us out of
	 * cache-line alignment.
	 */
	if (I40E_2K_TOO_SMALL_WITH_PADDING)
		rx_buf_len = I40E_RXBUFFER_3072 + SKB_DATA_ALIGN(NET_IP_ALIGN);
	else
		rx_buf_len = I40E_RXBUFFER_1536;

	/* if needed make room for NET_IP_ALIGN */
	rx_buf_len -= NET_IP_ALIGN;

	return i40e_compute_pad(rx_buf_len);
}

#define I40E_SKB_PAD i40e_skb_pad()
#else
#define I40E_2K_TOO_SMALL_WITH_PADDING false
#define I40E_SKB_PAD (NET_SKB_PAD + NET_IP_ALIGN)
#endif

/**
 * i40e_test_staterr - tests bits in Rx descriptor status and error fields
 * @rx_desc: pointer to receive descriptor (in le64 format)
 * @stat_err_bits: value to mask
 *
 * This function does some fast chicanery in order to return the
 * value of the mask which is really only used for boolean tests.
 * The status_error_len doesn't need to be shifted because it begins
 * at offset zero.
 */
static inline bool i40e_test_staterr(union i40e_rx_desc *rx_desc,
				     const u64 stat_err_bits)
{
	return !!(rx_desc->wb.qword1.status_error_len &
		  cpu_to_le64(stat_err_bits));
}

/* How many Rx Buffers do we bundle into one write to the hardware ? */
#define I40E_RX_BUFFER_WRITE	32	/* Must be power of 2 */

#define I40E_RX_NEXT_DESC(r, i, n)		\
	do {					\
		(i)++;				\
		if ((i) == (r)->count)		\
			i = 0;			\
		(n) = I40E_RX_DESC((r), (i));	\
	} while (0)


#define I40E_MAX_BUFFER_TXD	8
#define I40E_MIN_TX_LEN		17

/* The size limit for a transmit buffer in a descriptor is (16K - 1).
 * In order to align with the read requests we will align the value to
 * the nearest 4K which represents our maximum read request size.
 */
#define I40E_MAX_READ_REQ_SIZE		4096
#define I40E_MAX_DATA_PER_TXD		(16 * 1024 - 1)
#define I40E_MAX_DATA_PER_TXD_ALIGNED \
	(I40E_MAX_DATA_PER_TXD & ~(I40E_MAX_READ_REQ_SIZE - 1))

/**
 * i40e_txd_use_count  - estimate the number of descriptors needed for Tx
 * @size: transmit request size in bytes
 *
 * Due to hardware alignment restrictions (4K alignment), we need to
 * assume that we can have no more than 12K of data per descriptor, even
 * though each descriptor can take up to 16K - 1 bytes of aligned memory.
 * Thus, we need to divide by 12K. But division is slow! Instead,
 * we decompose the operation into shifts and one relatively cheap
 * multiply operation.
 *
 * To divide by 12K, we first divide by 4K, then divide by 3:
 *     To divide by 4K, shift right by 12 bits
 *     To divide by 3, multiply by 85, then divide by 256
 *     (Divide by 256 is done by shifting right by 8 bits)
 * Finally, we add one to round up. Because 256 isn't an exact multiple of
 * 3, we'll underestimate near each multiple of 12K. This is actually more
 * accurate as we have 4K - 1 of wiggle room that we can fit into the last
 * segment.  For our purposes this is accurate out to 1M which is orders of
 * magnitude greater than our largest possible GSO size.
 *
 * This would then be implemented as:
 *     return (((size >> 12) * 85) >> 8) + 1;
 *
 * Since multiplication and division are commutative, we can reorder
 * operations into:
 *     return ((size * 85) >> 20) + 1;
 */
static inline unsigned int i40e_txd_use_count(unsigned int size)
{
	return ((size * 85) >> 20) + 1;
}

/* Tx Descriptors needed, worst case */
#define DESC_NEEDED (MAX_SKB_FRAGS + 6)

#define I40E_TX_FLAGS_HW_VLAN		BIT(1)
#define I40E_TX_FLAGS_SW_VLAN		BIT(2)
#define I40E_TX_FLAGS_TSO		BIT(3)
#define I40E_TX_FLAGS_IPV4		BIT(4)
#define I40E_TX_FLAGS_IPV6		BIT(5)
#define I40E_TX_FLAGS_TSYN		BIT(8)
#define I40E_TX_FLAGS_FD_SB		BIT(9)
#define I40E_TX_FLAGS_UDP_TUNNEL	BIT(10)
#define I40E_TX_FLAGS_VLAN_MASK		0xffff0000
#define I40E_TX_FLAGS_VLAN_PRIO_MASK	0xe0000000
#define I40E_TX_FLAGS_VLAN_PRIO_SHIFT	29
#define I40E_TX_FLAGS_VLAN_SHIFT	16

struct i40e_tx_buffer {
	struct i40e_tx_desc *next_to_watch;
	union {
		struct xdp_frame *xdpf;
		struct sk_buff *skb;
		void *raw_buf;
	};
	unsigned int bytecount;
	unsigned short gso_segs;

	DEFINE_DMA_UNMAP_ADDR(dma);
	DEFINE_DMA_UNMAP_LEN(len);
	u32 tx_flags;
};

struct i40e_rx_buffer {
	dma_addr_t dma;
	struct page *page;
	__u32 page_offset;
	__u16 pagecnt_bias;
};

struct i40e_queue_stats {
	u64 packets;
	u64 bytes;
};

struct i40e_tx_queue_stats {
	u64 restart_queue;
	u64 tx_busy;
	u64 tx_done_old;
	u64 tx_linearize;
	u64 tx_force_wb;
	u64 tx_stopped;
	int prev_pkt_ctr;
};

struct i40e_rx_queue_stats {
	u64 non_eop_descs;
	u64 alloc_page_failed;
	u64 alloc_buff_failed;
	u64 page_reuse_count;
	u64 page_alloc_count;
	u64 page_waive_count;
	u64 page_busy_count;
};

enum i40e_ring_state_t {
	__I40E_TX_FDIR_INIT_DONE,
	__I40E_TX_XPS_INIT_DONE,
	__I40E_RING_STATE_NBITS /* must be last */
};

/* some useful defines for virtchannel interface, which
 * is the only remaining user of header split
 */
#define I40E_RX_DTYPE_HEADER_SPLIT  1
#define I40E_RX_SPLIT_L2      0x1
#define I40E_RX_SPLIT_IP      0x2
#define I40E_RX_SPLIT_TCP_UDP 0x4
#define I40E_RX_SPLIT_SCTP    0x8

/* struct that defines a descriptor ring, associated with a VSI */
struct i40e_ring {
	struct i40e_ring *next;		/* pointer to next ring in q_vector */
	void *desc;			/* Descriptor ring memory */
	struct device *dev;		/* Used for DMA mapping */
	struct net_device *netdev;	/* netdev ring maps to */
	struct bpf_prog *xdp_prog;
	union {
		struct i40e_tx_buffer *tx_bi;
		struct i40e_rx_buffer *rx_bi;
		struct xdp_buff **rx_bi_zc;
	};
	DECLARE_BITMAP(state, __I40E_RING_STATE_NBITS);
	u16 queue_index;		/* Queue number of ring */
	u8 dcb_tc;			/* Traffic class of ring */
	u8 __iomem *tail;

	/* high bit set means dynamic, use accessor routines to read/write.
	 * hardware only supports 2us resolution for the ITR registers.
	 * these values always store the USER setting, and must be converted
	 * before programming to a register.
	 */
	u16 itr_setting;

	u16 count;			/* Number of descriptors */
	u16 reg_idx;			/* HW register index of the ring */
	u16 rx_buf_len;

	/* used in interrupt processing */
	u16 next_to_use;
	u16 next_to_clean;
	u16 xdp_tx_active;

	u8 atr_sample_rate;
	u8 atr_count;

	bool ring_active;		/* is ring online or not */
	bool arm_wb;		/* do something to arm write back */
	u8 packet_stride;

	u16 flags;
#define I40E_TXR_FLAGS_WB_ON_ITR		BIT(0)
#define I40E_RXR_FLAGS_BUILD_SKB_ENABLED	BIT(1)
#define I40E_TXR_FLAGS_XDP			BIT(2)

	/* stats structs */
	struct i40e_queue_stats	stats;
	struct u64_stats_sync syncp;
	union {
		struct i40e_tx_queue_stats tx_stats;
		struct i40e_rx_queue_stats rx_stats;
	};

	unsigned int size;		/* length of descriptor ring in bytes */
	dma_addr_t dma;			/* physical address of ring */

	struct i40e_vsi *vsi;		/* Backreference to associated VSI */
	struct i40e_q_vector *q_vector;	/* Backreference to associated vector */

	struct rcu_head rcu;		/* to avoid race on free */
	u16 next_to_alloc;
	struct sk_buff *skb;		/* When i40e_clean_rx_ring_irq() must
					 * return before it sees the EOP for
					 * the current packet, we save that skb
					 * here and resume receiving this
					 * packet the next time
					 * i40e_clean_rx_ring_irq() is called
					 * for this ring.
					 */

	struct i40e_channel *ch;
	u16 rx_offset;
	struct xdp_rxq_info xdp_rxq;
	struct xsk_buff_pool *xsk_pool;
} ____cacheline_internodealigned_in_smp;

static inline bool ring_uses_build_skb(struct i40e_ring *ring)
{
	return !!(ring->flags & I40E_RXR_FLAGS_BUILD_SKB_ENABLED);
}

static inline void set_ring_build_skb_enabled(struct i40e_ring *ring)
{
	ring->flags |= I40E_RXR_FLAGS_BUILD_SKB_ENABLED;
}

static inline void clear_ring_build_skb_enabled(struct i40e_ring *ring)
{
	ring->flags &= ~I40E_RXR_FLAGS_BUILD_SKB_ENABLED;
}

static inline bool ring_is_xdp(struct i40e_ring *ring)
{
	return !!(ring->flags & I40E_TXR_FLAGS_XDP);
}

static inline void set_ring_xdp(struct i40e_ring *ring)
{
	ring->flags |= I40E_TXR_FLAGS_XDP;
}

#define I40E_ITR_ADAPTIVE_MIN_INC	0x0002
#define I40E_ITR_ADAPTIVE_MIN_USECS	0x0002
#define I40E_ITR_ADAPTIVE_MAX_USECS	0x007e
#define I40E_ITR_ADAPTIVE_LATENCY	0x8000
#define I40E_ITR_ADAPTIVE_BULK		0x0000

struct i40e_ring_container {
	struct i40e_ring *ring;		/* pointer to linked list of ring(s) */
	unsigned long next_update;	/* jiffies value of next update */
	unsigned int total_bytes;	/* total bytes processed this int */
	unsigned int total_packets;	/* total packets processed this int */
	u16 count;
	u16 target_itr;			/* target ITR setting for ring(s) */
	u16 current_itr;		/* current ITR setting for ring(s) */
};

/* iterator for handling rings in ring container */
#define i40e_for_each_ring(pos, head) \
	for (pos = (head).ring; pos != NULL; pos = pos->next)

static inline unsigned int i40e_rx_pg_order(struct i40e_ring *ring)
{
#if (PAGE_SIZE < 8192)
	if (ring->rx_buf_len > (PAGE_SIZE / 2))
		return 1;
#endif
	return 0;
}

#define i40e_rx_pg_size(_ring) (PAGE_SIZE << i40e_rx_pg_order(_ring))

bool i40e_alloc_rx_buffers(struct i40e_ring *rxr, u16 cleaned_count);
netdev_tx_t i40e_lan_xmit_frame(struct sk_buff *skb, struct net_device *netdev);
u16 i40e_lan_select_queue(struct net_device *netdev, struct sk_buff *skb,
			  struct net_device *sb_dev);
void i40e_clean_tx_ring(struct i40e_ring *tx_ring);
void i40e_clean_rx_ring(struct i40e_ring *rx_ring);
int i40e_setup_tx_descriptors(struct i40e_ring *tx_ring);
int i40e_setup_rx_descriptors(struct i40e_ring *rx_ring);
void i40e_free_tx_resources(struct i40e_ring *tx_ring);
void i40e_free_rx_resources(struct i40e_ring *rx_ring);
int i40e_napi_poll(struct napi_struct *napi, int budget);
void i40e_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector);
u32 i40e_get_tx_pending(struct i40e_ring *ring, bool in_sw);
void i40e_detect_recover_hung(struct i40e_vsi *vsi);
int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size);
bool __i40e_chk_linearize(struct sk_buff *skb);
int i40e_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
		  u32 flags);

/**
 * i40e_get_head - Retrieve head from head writeback
 * @tx_ring:  tx ring to fetch head of
 *
 * Returns value of Tx ring head based on value stored
 * in head write-back location
 **/
static inline u32 i40e_get_head(struct i40e_ring *tx_ring)
{
	void *head = (struct i40e_tx_desc *)tx_ring->desc + tx_ring->count;

	return le32_to_cpu(*(volatile __le32 *)head);
}

/**
 * i40e_xmit_descriptor_count - calculate number of Tx descriptors needed
 * @skb:     send buffer
 *
 * Returns number of data descriptors needed for this skb. Returns 0 to indicate
 * there is not enough descriptors available in this ring since we need at least
 * one descriptor.
 **/
static inline int i40e_xmit_descriptor_count(struct sk_buff *skb)
{
	const skb_frag_t *frag = &skb_shinfo(skb)->frags[0];
	unsigned int nr_frags = skb_shinfo(skb)->nr_frags;
	int count = 0, size = skb_headlen(skb);

	for (;;) {
		count += i40e_txd_use_count(size);

		if (!nr_frags--)
			break;

		size = skb_frag_size(frag++);
	}

	return count;
}

/**
 * i40e_maybe_stop_tx - 1st level check for Tx stop conditions
 * @tx_ring: the ring to be checked
 * @size:    the size buffer we want to assure is available
 *
 * Returns 0 if stop is not needed
 **/
static inline int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
{
	if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
		return 0;
	return __i40e_maybe_stop_tx(tx_ring, size);
}

/**
 * i40e_chk_linearize - Check if there are more than 8 fragments per packet
 * @skb:      send buffer
 * @count:    number of buffers used
 *
 * Note: Our HW can't scatter-gather more than 8 fragments to build
 * a packet on the wire and so we need to figure out the cases where we
 * need to linearize the skb.
 **/
static inline bool i40e_chk_linearize(struct sk_buff *skb, int count)
{
	/* Both TSO and single send will work if count is less than 8 */
	if (likely(count < I40E_MAX_BUFFER_TXD))
		return false;

	if (skb_is_gso(skb))
		return __i40e_chk_linearize(skb);

	/* we can support up to 8 data buffers for a single send */
	return count != I40E_MAX_BUFFER_TXD;
}

/**
 * txring_txq - Find the netdev Tx ring based on the i40e Tx ring
 * @ring: Tx ring to find the netdev equivalent of
 **/
static inline struct netdev_queue *txring_txq(const struct i40e_ring *ring)
{
	return netdev_get_tx_queue(ring->netdev, ring->queue_index);
}
#endif /* _I40E_TXRX_H_ */