1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
3 * Copyright (C) 2006 Andrey Volkov, Varma Electronics
4 * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
5 * Copyright (c) 2025 Vincent Mailhol <mailhol@kernel.org>
6 */
7
8#include <linux/can/dev.h>
9
10void can_sjw_set_default(struct can_bittiming *bt)
11{
12 if (bt->sjw)
13 return;
14
15 /* If user space provides no sjw, use sane default of phase_seg2 / 2 */
16 bt->sjw = max(1U, min(bt->phase_seg1, bt->phase_seg2 / 2));
17}
18
19int can_sjw_check(const struct net_device *dev, const struct can_bittiming *bt,
20 const struct can_bittiming_const *btc, struct netlink_ext_ack *extack)
21{
22 if (bt->sjw > btc->sjw_max) {
23 NL_SET_ERR_MSG_FMT(extack, "sjw: %u greater than max sjw: %u",
24 bt->sjw, btc->sjw_max);
25 return -EINVAL;
26 }
27
28 if (bt->sjw > bt->phase_seg1) {
29 NL_SET_ERR_MSG_FMT(extack,
30 "sjw: %u greater than phase-seg1: %u",
31 bt->sjw, bt->phase_seg1);
32 return -EINVAL;
33 }
34
35 if (bt->sjw > bt->phase_seg2) {
36 NL_SET_ERR_MSG_FMT(extack,
37 "sjw: %u greater than phase-seg2: %u",
38 bt->sjw, bt->phase_seg2);
39 return -EINVAL;
40 }
41
42 return 0;
43}
44
45/* Checks the validity of the specified bit-timing parameters prop_seg,
46 * phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
47 * prescaler value brp. You can find more information in the header
48 * file linux/can/netlink.h.
49 */
50static int can_fixup_bittiming(const struct net_device *dev, struct can_bittiming *bt,
51 const struct can_bittiming_const *btc,
52 struct netlink_ext_ack *extack)
53{
54 const unsigned int tseg1 = bt->prop_seg + bt->phase_seg1;
55 const struct can_priv *priv = netdev_priv(dev);
56 u64 brp64;
57 int err;
58
59 if (tseg1 < btc->tseg1_min) {
60 NL_SET_ERR_MSG_FMT(extack, "prop-seg + phase-seg1: %u less than tseg1-min: %u",
61 tseg1, btc->tseg1_min);
62 return -EINVAL;
63 }
64 if (tseg1 > btc->tseg1_max) {
65 NL_SET_ERR_MSG_FMT(extack, "prop-seg + phase-seg1: %u greater than tseg1-max: %u",
66 tseg1, btc->tseg1_max);
67 return -EINVAL;
68 }
69 if (bt->phase_seg2 < btc->tseg2_min) {
70 NL_SET_ERR_MSG_FMT(extack, "phase-seg2: %u less than tseg2-min: %u",
71 bt->phase_seg2, btc->tseg2_min);
72 return -EINVAL;
73 }
74 if (bt->phase_seg2 > btc->tseg2_max) {
75 NL_SET_ERR_MSG_FMT(extack, "phase-seg2: %u greater than tseg2-max: %u",
76 bt->phase_seg2, btc->tseg2_max);
77 return -EINVAL;
78 }
79
80 can_sjw_set_default(bt);
81
82 err = can_sjw_check(dev, bt, btc, extack);
83 if (err)
84 return err;
85
86 brp64 = (u64)priv->clock.freq * (u64)bt->tq;
87 if (btc->brp_inc > 1)
88 do_div(brp64, btc->brp_inc);
89 brp64 += 500000000UL - 1;
90 do_div(brp64, 1000000000UL); /* the practicable BRP */
91 if (btc->brp_inc > 1)
92 brp64 *= btc->brp_inc;
93 bt->brp = (u32)brp64;
94
95 if (bt->brp < btc->brp_min) {
96 NL_SET_ERR_MSG_FMT(extack, "resulting brp: %u less than brp-min: %u",
97 bt->brp, btc->brp_min);
98 return -EINVAL;
99 }
100 if (bt->brp > btc->brp_max) {
101 NL_SET_ERR_MSG_FMT(extack, "resulting brp: %u greater than brp-max: %u",
102 bt->brp, btc->brp_max);
103 return -EINVAL;
104 }
105
106 bt->bitrate = priv->clock.freq / (bt->brp * can_bit_time(bt));
107 bt->sample_point = ((CAN_SYNC_SEG + tseg1) * 1000) / can_bit_time(bt);
108 bt->tq = DIV_U64_ROUND_CLOSEST(mul_u32_u32(bt->brp, NSEC_PER_SEC),
109 priv->clock.freq);
110
111 return 0;
112}
113
114/* Checks the validity of predefined bitrate settings */
115static int
116can_validate_bitrate(const struct net_device *dev, const struct can_bittiming *bt,
117 const u32 *bitrate_const,
118 const unsigned int bitrate_const_cnt,
119 struct netlink_ext_ack *extack)
120{
121 unsigned int i;
122
123 for (i = 0; i < bitrate_const_cnt; i++) {
124 if (bt->bitrate == bitrate_const[i])
125 return 0;
126 }
127
128 NL_SET_ERR_MSG_FMT(extack, "bitrate %u bps not supported",
129 bt->brp);
130
131 return -EINVAL;
132}
133
134int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
135 const struct can_bittiming_const *btc,
136 const u32 *bitrate_const,
137 const unsigned int bitrate_const_cnt,
138 struct netlink_ext_ack *extack)
139{
140 /* Depending on the given can_bittiming parameter structure the CAN
141 * timing parameters are calculated based on the provided bitrate OR
142 * alternatively the CAN timing parameters (tq, prop_seg, etc.) are
143 * provided directly which are then checked and fixed up.
144 */
145 if (!bt->tq && bt->bitrate && btc)
146 return can_calc_bittiming(dev, bt, btc, extack);
147 if (bt->tq && !bt->bitrate && btc)
148 return can_fixup_bittiming(dev, bt, btc, extack);
149 if (!bt->tq && bt->bitrate && bitrate_const)
150 return can_validate_bitrate(dev, bt, bitrate_const,
151 bitrate_const_cnt, extack);
152
153 return -EINVAL;
154}
155
156int can_validate_pwm_bittiming(const struct net_device *dev,
157 const struct can_pwm *pwm,
158 struct netlink_ext_ack *extack)
159{
160 const struct can_priv *priv = netdev_priv(dev);
161 u32 xl_bit_time_tqmin = can_bit_time_tqmin(bt: &priv->xl.data_bittiming);
162 u32 nom_bit_time_tqmin = can_bit_time_tqmin(bt: &priv->bittiming);
163 u32 pwms_ns = can_tqmin_to_ns(tqmin: pwm->pwms, clock_freq: priv->clock.freq);
164 u32 pwml_ns = can_tqmin_to_ns(tqmin: pwm->pwml, clock_freq: priv->clock.freq);
165
166 if (pwms_ns + pwml_ns > CAN_PWM_NS_MAX) {
167 NL_SET_ERR_MSG_FMT(extack,
168 "The PWM symbol duration: %u ns may not exceed %u ns",
169 pwms_ns + pwml_ns, CAN_PWM_NS_MAX);
170 return -EINVAL;
171 }
172
173 if (pwms_ns < CAN_PWM_DECODE_NS) {
174 NL_SET_ERR_MSG_FMT(extack,
175 "PWMS: %u ns shall be at least %u ns",
176 pwms_ns, CAN_PWM_DECODE_NS);
177 return -EINVAL;
178 }
179
180 if (pwm->pwms >= pwm->pwml) {
181 NL_SET_ERR_MSG_FMT(extack,
182 "PWMS: %u tqmin shall be smaller than PWML: %u tqmin",
183 pwm->pwms, pwm->pwml);
184 return -EINVAL;
185 }
186
187 if (pwml_ns - pwms_ns < 2 * CAN_PWM_DECODE_NS) {
188 NL_SET_ERR_MSG_FMT(extack,
189 "At least %u ns shall separate PWMS: %u ns from PMWL: %u ns",
190 2 * CAN_PWM_DECODE_NS, pwms_ns, pwml_ns);
191 return -EINVAL;
192 }
193
194 if (xl_bit_time_tqmin % (pwm->pwms + pwm->pwml) != 0) {
195 NL_SET_ERR_MSG_FMT(extack,
196 "PWM duration: %u tqmin does not divide XL's bit time: %u tqmin",
197 pwm->pwms + pwm->pwml, xl_bit_time_tqmin);
198 return -EINVAL;
199 }
200
201 if (pwm->pwmo >= pwm->pwms + pwm->pwml) {
202 NL_SET_ERR_MSG_FMT(extack,
203 "PWMO: %u tqmin can not be greater than PWMS + PWML: %u tqmin",
204 pwm->pwmo, pwm->pwms + pwm->pwml);
205 return -EINVAL;
206 }
207
208 if (nom_bit_time_tqmin % (pwm->pwms + pwm->pwml) != pwm->pwmo) {
209 NL_SET_ERR_MSG_FMT(extack,
210 "Can not assemble nominal bit time: %u tqmin out of PWMS + PMWL and PWMO",
211 nom_bit_time_tqmin);
212 return -EINVAL;
213 }
214
215 return 0;
216}
217

source code of linux/drivers/net/can/dev/bittiming.c