1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright 2023 NXP
4 *
5 * Mock-up PTP Hardware Clock driver for virtual network devices
6 *
7 * Create a PTP clock which offers PTP time manipulation operations
8 * using a timecounter/cyclecounter on top of CLOCK_MONOTONIC_RAW.
9 */
10
11 #include <linux/ptp_clock_kernel.h>
12 #include <linux/ptp_mock.h>
13 #include <linux/timecounter.h>
14
15 /* Clamp scaled_ppm between -2,097,152,000 and 2,097,152,000,
16 * and thus "adj" between -68,719,476 and 68,719,476
17 */
18 #define MOCK_PHC_MAX_ADJ_PPB 32000000
19 /* Timestamps from ktime_get_raw() have 1 ns resolution, so the scale factor
20 * (MULT >> SHIFT) needs to be 1. Pick SHIFT as 31 bits, which translates
21 * MULT(freq 0) into 0x80000000.
22 */
23 #define MOCK_PHC_CC_SHIFT 31
24 #define MOCK_PHC_CC_MULT (1 << MOCK_PHC_CC_SHIFT)
25 #define MOCK_PHC_FADJ_SHIFT 9
26 #define MOCK_PHC_FADJ_DENOMINATOR 15625ULL
27
28 /* The largest cycle_delta that timecounter_read_delta() can handle without a
29 * 64-bit overflow during the multiplication with cc->mult, given the max "adj"
30 * we permit, is ~8.3 seconds. Make sure readouts are more frequent than that.
31 */
32 #define MOCK_PHC_REFRESH_INTERVAL (HZ * 5)
33
34 #define info_to_phc(d) container_of((d), struct mock_phc, info)
35
36 struct mock_phc {
37 struct ptp_clock_info info;
38 struct ptp_clock *clock;
39 struct timecounter tc;
40 struct cyclecounter cc;
41 spinlock_t lock;
42 };
43
mock_phc_cc_read(const struct cyclecounter * cc)44 static u64 mock_phc_cc_read(const struct cyclecounter *cc)
45 {
46 return ktime_get_raw_ns();
47 }
48
mock_phc_adjfine(struct ptp_clock_info * info,long scaled_ppm)49 static int mock_phc_adjfine(struct ptp_clock_info *info, long scaled_ppm)
50 {
51 struct mock_phc *phc = info_to_phc(info);
52 s64 adj;
53
54 adj = (s64)scaled_ppm << MOCK_PHC_FADJ_SHIFT;
55 adj = div_s64(adj, MOCK_PHC_FADJ_DENOMINATOR);
56
57 spin_lock(&phc->lock);
58 timecounter_read(&phc->tc);
59 phc->cc.mult = MOCK_PHC_CC_MULT + adj;
60 spin_unlock(&phc->lock);
61
62 return 0;
63 }
64
mock_phc_adjtime(struct ptp_clock_info * info,s64 delta)65 static int mock_phc_adjtime(struct ptp_clock_info *info, s64 delta)
66 {
67 struct mock_phc *phc = info_to_phc(info);
68
69 spin_lock(&phc->lock);
70 timecounter_adjtime(&phc->tc, delta);
71 spin_unlock(&phc->lock);
72
73 return 0;
74 }
75
mock_phc_settime64(struct ptp_clock_info * info,const struct timespec64 * ts)76 static int mock_phc_settime64(struct ptp_clock_info *info,
77 const struct timespec64 *ts)
78 {
79 struct mock_phc *phc = info_to_phc(info);
80 u64 ns = timespec64_to_ns(ts);
81
82 spin_lock(&phc->lock);
83 timecounter_init(&phc->tc, &phc->cc, ns);
84 spin_unlock(&phc->lock);
85
86 return 0;
87 }
88
mock_phc_gettime64(struct ptp_clock_info * info,struct timespec64 * ts)89 static int mock_phc_gettime64(struct ptp_clock_info *info, struct timespec64 *ts)
90 {
91 struct mock_phc *phc = info_to_phc(info);
92 u64 ns;
93
94 spin_lock(&phc->lock);
95 ns = timecounter_read(&phc->tc);
96 spin_unlock(&phc->lock);
97
98 *ts = ns_to_timespec64(ns);
99
100 return 0;
101 }
102
mock_phc_refresh(struct ptp_clock_info * info)103 static long mock_phc_refresh(struct ptp_clock_info *info)
104 {
105 struct timespec64 ts;
106
107 mock_phc_gettime64(info, &ts);
108
109 return MOCK_PHC_REFRESH_INTERVAL;
110 }
111
mock_phc_index(struct mock_phc * phc)112 int mock_phc_index(struct mock_phc *phc)
113 {
114 return ptp_clock_index(phc->clock);
115 }
116 EXPORT_SYMBOL_GPL(mock_phc_index);
117
mock_phc_create(struct device * dev)118 struct mock_phc *mock_phc_create(struct device *dev)
119 {
120 struct mock_phc *phc;
121 int err;
122
123 phc = kzalloc(sizeof(*phc), GFP_KERNEL);
124 if (!phc) {
125 err = -ENOMEM;
126 goto out;
127 }
128
129 phc->info = (struct ptp_clock_info) {
130 .owner = THIS_MODULE,
131 .name = "Mock-up PTP clock",
132 .max_adj = MOCK_PHC_MAX_ADJ_PPB,
133 .adjfine = mock_phc_adjfine,
134 .adjtime = mock_phc_adjtime,
135 .gettime64 = mock_phc_gettime64,
136 .settime64 = mock_phc_settime64,
137 .do_aux_work = mock_phc_refresh,
138 };
139
140 phc->cc = (struct cyclecounter) {
141 .read = mock_phc_cc_read,
142 .mask = CYCLECOUNTER_MASK(64),
143 .mult = MOCK_PHC_CC_MULT,
144 .shift = MOCK_PHC_CC_SHIFT,
145 };
146
147 spin_lock_init(&phc->lock);
148 timecounter_init(&phc->tc, &phc->cc, 0);
149
150 phc->clock = ptp_clock_register(&phc->info, dev);
151 if (IS_ERR(phc->clock)) {
152 err = PTR_ERR(phc->clock);
153 goto out_free_phc;
154 }
155
156 ptp_schedule_worker(phc->clock, MOCK_PHC_REFRESH_INTERVAL);
157
158 return phc;
159
160 out_free_phc:
161 kfree(phc);
162 out:
163 return ERR_PTR(err);
164 }
165 EXPORT_SYMBOL_GPL(mock_phc_create);
166
mock_phc_destroy(struct mock_phc * phc)167 void mock_phc_destroy(struct mock_phc *phc)
168 {
169 ptp_clock_unregister(phc->clock);
170 kfree(phc);
171 }
172 EXPORT_SYMBOL_GPL(mock_phc_destroy);
173
174 MODULE_DESCRIPTION("Mock-up PTP Hardware Clock driver");
175 MODULE_LICENSE("GPL");
176