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
  9void 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
 18int 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 */
 49static 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 */
114static int
115can_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
133int 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}