1 /*
2 * Copyright (c) 2018 Intel Corporation.
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 /**
8 * @file
9 * @brief Public functions for the Precision Time Protocol time specification.
10 *
11 * References are to version 2019 of IEEE 1588, ("PTP")
12 * and version 2020 of IEEE 802.1AS ("gPTP").
13 */
14
15 #ifndef ZEPHYR_INCLUDE_NET_PTP_TIME_H_
16 #define ZEPHYR_INCLUDE_NET_PTP_TIME_H_
17
18 /**
19 * @brief Precision Time Protocol time specification
20 * @defgroup ptp_time PTP time
21 * @since 1.13
22 * @version 0.8.0
23 * @ingroup networking
24 * @{
25 */
26
27 #include <zephyr/net/net_core.h>
28 #include <zephyr/net/net_time.h>
29 #include <zephyr/toolchain.h>
30
31 #ifdef __cplusplus
32 extern "C" {
33 #endif
34
35 /**
36 * @brief (Generalized) Precision Time Protocol Timestamp format.
37 *
38 * @details This structure represents a timestamp according to the Precision
39 * Time Protocol standard ("PTP", IEEE 1588, section 5.3.3), the Generalized
40 * Precision Time Protocol standard ("gPTP", IEEE 802.1AS, section 6.4.3.4), or
41 * any other well-defined context in which precision structured timestamps are
42 * required on network messages in Zephyr.
43 *
44 * Seconds are encoded as a 48 bits unsigned integer. Nanoseconds are encoded
45 * as a 32 bits unsigned integer.
46 *
47 * In the context of (g)PTP, @em timestamps designate the time, relative to a
48 * local clock ("LocalClock") at which the message timestamp point passes a
49 * reference plane marking the boundary between the PTP Instance and the network
50 * medium (IEEE 1855, section 7.3.4.2; IEEE 802.1AS, section 8.4.3).
51 *
52 * The exact definitions of the <em>message timestamp point</em> and
53 * <em>reference plane</em> depends on the network medium and use case.
54 *
55 * For (g)PTP the media-specific message timestamp points and reference planes
56 * are defined in the standard. In non-PTP contexts specific to Zephyr,
57 * timestamps are measured relative to the same local clock but with a
58 * context-specific message timestamp point and reference plane, defined below
59 * per use case.
60 *
61 * A @em "LocalClock" is a freerunning clock, embedded into a well-defined
62 * entity (e.g. a PTP Instance) and provides a common time to that entity
63 * relative to an arbitrary epoch (IEEE 1855, section 3.1.26, IEEE 802.1AS,
64 * section 3.16).
65 *
66 * In Zephyr, the local clock is usually any instance of a kernel system clock
67 * driver, counter driver, RTC API driver or low-level counter/timer peripheral
68 * (e.g. an ethernet peripheral with hardware timestamp support or a radio
69 * timer) with sufficient precision for the context in which it is used.
70 *
71 * See IEEE 802.1AS, Annex B for specific performance requirements regarding
72 * conformance of local clocks in the gPTP context. See IEEE 1588, Annex A,
73 * section A5.4 for general performance requirements regarding PTP local clocks.
74 * See IEEE 802.15.4-2020, section 15.7 for requirements in the context of
75 * ranging applications and ibid., section 6.7.6 for the relation between guard
76 * times and clock accuracy which again influence the precision required for
77 * subprotocols like CSL, TSCH, RIT, etc.
78 *
79 * Applications that use timestamps across different subsystems or media must
80 * ensure that they understand the definition of the respective reference planes
81 * and interpret timestamps accordingly. Applications must further ensure that
82 * timestamps are either all referenced to the same local clock or convert
83 * between clocks based on sufficiently precise conversion algorithms.
84 *
85 * Timestamps may be measured on ingress (RX timestamps) or egress (TX
86 * timestamps) of network messages. Timestamps can also be used to schedule a
87 * network message to a well-defined point in time in the future at which it is
88 * to be sent over the medium (timed TX). A future timestamp and a duration,
89 * both referenced to the local clock, may be given to specify a time window at
90 * which a network device should expect incoming messages (RX window).
91 *
92 * In Zephyr this timestamp structure is currently used in the following
93 * contexts:
94 * * gPTP for Full Duplex Point-to-Point IEEE 802.3 links (IEEE 802.1AS,
95 * section 11): the reference plane and message timestamp points are as
96 * defined in the standard.
97 * * IEEE 802.15.4 timed TX and RX: Timestamps designate the point in time at
98 * which the end of the last symbol of the start-of-frame delimiter (SFD) (or
99 * equivalently, the start of the first symbol of the PHY header) is at the
100 * local antenna. The standard also refers to this as the "RMARKER" (IEEE
101 * 802.15.4-2020, section 6.9.1) or "symbol boundary" (ibid., section 6.5.2),
102 * depending on the context. In the context of beacon timestamps, the
103 * difference between the timestamp measurement plane and the reference plane
104 * is defined by the MAC PIB attribute "macSyncSymbolOffset", ibid., section
105 * 8.4.3.1, table 8-94.
106 *
107 * If further use cases are added to Zephyr using this timestamp structure,
108 * their clock performance requirements, message timestamp points and reference
109 * plane definition SHALL be added to the above list.
110 */
111 struct net_ptp_time {
112 /** Seconds encoded on 48 bits. */
113 union {
114
115 /** @cond INTERNAL_HIDDEN */
116 struct {
117 #ifdef CONFIG_LITTLE_ENDIAN
118 uint32_t low;
119 uint16_t high;
120 uint16_t unused;
121 #else
122 uint16_t unused;
123 uint16_t high;
124 uint32_t low;
125 #endif
126 } _sec;
127 /** @endcond */
128
129 /** Second value. */
130 uint64_t second;
131 };
132
133 /** Nanoseconds. */
134 uint32_t nanosecond;
135 };
136
137 #ifdef __cplusplus
138 }
139 #endif
140
141 /**
142 * @brief Generalized Precision Time Protocol Extended Timestamp format.
143 *
144 * @details This structure represents an extended timestamp according to the
145 * Generalized Precision Time Protocol standard (IEEE 802.1AS), see section
146 * 6.4.3.5.
147 *
148 * Seconds are encoded as 48 bits unsigned integer. Fractional nanoseconds are
149 * encoded as 48 bits, their unit is 2*(-16) ns.
150 *
151 * A precise definition of PTP timestamps and their uses in Zephyr is given in
152 * the description of @ref net_ptp_time.
153 */
154 struct net_ptp_extended_time {
155 /** Seconds encoded on 48 bits. */
156 union {
157
158 /** @cond INTERNAL_HIDDEN */
159 struct {
160 #ifdef CONFIG_LITTLE_ENDIAN
161 uint32_t low;
162 uint16_t high;
163 uint16_t unused;
164 #else
165 uint16_t unused;
166 uint16_t high;
167 uint32_t low;
168 #endif
169 } _sec;
170 /** @endcond */
171
172 /** Second value. */
173 uint64_t second;
174 };
175
176 /** Fractional nanoseconds on 48 bits. */
177 union {
178
179 /** @cond INTERNAL_HIDDEN */
180 struct {
181 #ifdef CONFIG_LITTLE_ENDIAN
182 uint32_t low;
183 uint16_t high;
184 uint16_t unused;
185 #else
186 uint16_t unused;
187 uint16_t high;
188 uint32_t low;
189 #endif
190 } _fns;
191 /** @endcond */
192
193 /** Fractional nanoseconds value. */
194 uint64_t fract_nsecond;
195 };
196 } __packed;
197
198 /**
199 * @brief Convert a PTP timestamp to a nanosecond precision timestamp, both
200 * related to the local network reference clock.
201 *
202 * @note Only timestamps representing up to ~290 years can be converted to
203 * nanosecond timestamps. Larger timestamps will return the maximum
204 * representable nanosecond precision timestamp.
205 *
206 * @param ts the PTP timestamp
207 *
208 * @return the corresponding nanosecond precision timestamp
209 */
net_ptp_time_to_ns(struct net_ptp_time * ts)210 static inline net_time_t net_ptp_time_to_ns(struct net_ptp_time *ts)
211 {
212 if (!ts) {
213 return 0;
214 }
215
216 if (ts->second >= NET_TIME_SEC_MAX) {
217 return NET_TIME_MAX;
218 }
219
220 return ((int64_t)ts->second * NSEC_PER_SEC) + ts->nanosecond;
221 }
222
223 /**
224 * @brief Convert a nanosecond precision timestamp to a PTP timestamp, both
225 * related to the local network reference clock.
226 *
227 * @param nsec a nanosecond precision timestamp
228 *
229 * @return the corresponding PTP timestamp
230 */
ns_to_net_ptp_time(net_time_t nsec)231 static inline struct net_ptp_time ns_to_net_ptp_time(net_time_t nsec)
232 {
233 struct net_ptp_time ts;
234
235 __ASSERT_NO_MSG(nsec >= 0);
236
237 ts.second = nsec / NSEC_PER_SEC;
238 ts.nanosecond = nsec % NSEC_PER_SEC;
239 return ts;
240 }
241
242 /**
243 * @}
244 */
245
246 #endif /* ZEPHYR_INCLUDE_NET_PTP_TIME_H_ */
247
