xref: /openbmc/linux/drivers/net/can/dev/bittiming.c (revision e724e7aa)
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  */
6 
7 #include <linux/can/dev.h>
8 
9 void can_sjw_set_default(struct can_bittiming *bt)
10 {
11 	if (bt->sjw)
12 		return;
13 
14 	/* If user space provides no sjw, use sane default of phase_seg2 / 2 */
15 	bt->sjw = max(1U, min(bt->phase_seg1, bt->phase_seg2 / 2));
16 }
17 
18 int can_sjw_check(const struct net_device *dev, const struct can_bittiming *bt,
19 		  const struct can_bittiming_const *btc, struct netlink_ext_ack *extack)
20 {
21 	if (bt->sjw > btc->sjw_max) {
22 		NL_SET_ERR_MSG_FMT(extack, "sjw: %u greater than max sjw: %u",
23 				   bt->sjw, btc->sjw_max);
24 		return -EINVAL;
25 	}
26 
27 	if (bt->sjw > bt->phase_seg1) {
28 		NL_SET_ERR_MSG_FMT(extack,
29 				   "sjw: %u greater than phase-seg1: %u",
30 				   bt->sjw, bt->phase_seg1);
31 		return -EINVAL;
32 	}
33 
34 	if (bt->sjw > bt->phase_seg2) {
35 		NL_SET_ERR_MSG_FMT(extack,
36 				   "sjw: %u greater than phase-seg2: %u",
37 				   bt->sjw, bt->phase_seg2);
38 		return -EINVAL;
39 	}
40 
41 	return 0;
42 }
43 
44 /* Checks the validity of the specified bit-timing parameters prop_seg,
45  * phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
46  * prescaler value brp. You can find more information in the header
47  * file linux/can/netlink.h.
48  */
49 static int can_fixup_bittiming(const struct net_device *dev, struct can_bittiming *bt,
50 			       const struct can_bittiming_const *btc,
51 			       struct netlink_ext_ack *extack)
52 {
53 	const unsigned int tseg1 = bt->prop_seg + bt->phase_seg1;
54 	const struct can_priv *priv = netdev_priv(dev);
55 	u64 brp64;
56 	int err;
57 
58 	if (tseg1 < btc->tseg1_min) {
59 		NL_SET_ERR_MSG_FMT(extack, "prop-seg + phase-seg1: %u less than tseg1-min: %u",
60 				   tseg1, btc->tseg1_min);
61 		return -EINVAL;
62 	}
63 	if (tseg1 > btc->tseg1_max) {
64 		NL_SET_ERR_MSG_FMT(extack, "prop-seg + phase-seg1: %u greater than tseg1-max: %u",
65 				   tseg1, btc->tseg1_max);
66 		return -EINVAL;
67 	}
68 	if (bt->phase_seg2 < btc->tseg2_min) {
69 		NL_SET_ERR_MSG_FMT(extack, "phase-seg2: %u less than tseg2-min: %u",
70 				   bt->phase_seg2, btc->tseg2_min);
71 		return -EINVAL;
72 	}
73 	if (bt->phase_seg2 > btc->tseg2_max) {
74 		NL_SET_ERR_MSG_FMT(extack, "phase-seg2: %u greater than tseg2-max: %u",
75 				   bt->phase_seg2, btc->tseg2_max);
76 		return -EINVAL;
77 	}
78 
79 	can_sjw_set_default(bt);
80 
81 	err = can_sjw_check(dev, bt, btc, extack);
82 	if (err)
83 		return err;
84 
85 	brp64 = (u64)priv->clock.freq * (u64)bt->tq;
86 	if (btc->brp_inc > 1)
87 		do_div(brp64, btc->brp_inc);
88 	brp64 += 500000000UL - 1;
89 	do_div(brp64, 1000000000UL); /* the practicable BRP */
90 	if (btc->brp_inc > 1)
91 		brp64 *= btc->brp_inc;
92 	bt->brp = (u32)brp64;
93 
94 	if (bt->brp < btc->brp_min) {
95 		NL_SET_ERR_MSG_FMT(extack, "resulting brp: %u less than brp-min: %u",
96 				   bt->brp, btc->brp_min);
97 		return -EINVAL;
98 	}
99 	if (bt->brp > btc->brp_max) {
100 		NL_SET_ERR_MSG_FMT(extack, "resulting brp: %u greater than brp-max: %u",
101 				   bt->brp, btc->brp_max);
102 		return -EINVAL;
103 	}
104 
105 	bt->bitrate = priv->clock.freq / (bt->brp * can_bit_time(bt));
106 	bt->sample_point = ((CAN_SYNC_SEG + tseg1) * 1000) / can_bit_time(bt);
107 	bt->tq = DIV_U64_ROUND_CLOSEST(mul_u32_u32(bt->brp, NSEC_PER_SEC),
108 				       priv->clock.freq);
109 
110 	return 0;
111 }
112 
113 /* Checks the validity of predefined bitrate settings */
114 static int
115 can_validate_bitrate(const struct net_device *dev, const struct can_bittiming *bt,
116 		     const u32 *bitrate_const,
117 		     const unsigned int bitrate_const_cnt,
118 		     struct netlink_ext_ack *extack)
119 {
120 	unsigned int i;
121 
122 	for (i = 0; i < bitrate_const_cnt; i++) {
123 		if (bt->bitrate == bitrate_const[i])
124 			return 0;
125 	}
126 
127 	NL_SET_ERR_MSG_FMT(extack, "bitrate %u bps not supported",
128 			   bt->brp);
129 
130 	return -EINVAL;
131 }
132 
133 int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
134 		      const struct can_bittiming_const *btc,
135 		      const u32 *bitrate_const,
136 		      const unsigned int bitrate_const_cnt,
137 		      struct netlink_ext_ack *extack)
138 {
139 	/* Depending on the given can_bittiming parameter structure the CAN
140 	 * timing parameters are calculated based on the provided bitrate OR
141 	 * alternatively the CAN timing parameters (tq, prop_seg, etc.) are
142 	 * provided directly which are then checked and fixed up.
143 	 */
144 	if (!bt->tq && bt->bitrate && btc)
145 		return can_calc_bittiming(dev, bt, btc, extack);
146 	if (bt->tq && !bt->bitrate && btc)
147 		return can_fixup_bittiming(dev, bt, btc, extack);
148 	if (!bt->tq && bt->bitrate && bitrate_const)
149 		return can_validate_bitrate(dev, bt, bitrate_const,
150 					    bitrate_const_cnt, extack);
151 
152 	return -EINVAL;
153 }
154