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/* Checks the validity of the specified bit-timing parameters prop_seg,
10 * phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
11 * prescaler value brp. You can find more information in the header
12 * file linux/can/netlink.h.
13 */
14static int can_fixup_bittiming(const struct net_device *dev, struct can_bittiming *bt,
15			       const struct can_bittiming_const *btc)
16{
17	const struct can_priv *priv = netdev_priv(dev);
18	unsigned int tseg1, alltseg;
19	u64 brp64;
20
21	tseg1 = bt->prop_seg + bt->phase_seg1;
22	if (!bt->sjw)
23		bt->sjw = 1;
24	if (bt->sjw > btc->sjw_max ||
25	    tseg1 < btc->tseg1_min || tseg1 > btc->tseg1_max ||
26	    bt->phase_seg2 < btc->tseg2_min || bt->phase_seg2 > btc->tseg2_max)
27		return -ERANGE;
28
29	brp64 = (u64)priv->clock.freq * (u64)bt->tq;
30	if (btc->brp_inc > 1)
31		do_div(brp64, btc->brp_inc);
32	brp64 += 500000000UL - 1;
33	do_div(brp64, 1000000000UL); /* the practicable BRP */
34	if (btc->brp_inc > 1)
35		brp64 *= btc->brp_inc;
36	bt->brp = (u32)brp64;
37
38	if (bt->brp < btc->brp_min || bt->brp > btc->brp_max)
39		return -EINVAL;
40
41	alltseg = bt->prop_seg + bt->phase_seg1 + bt->phase_seg2 + 1;
42	bt->bitrate = priv->clock.freq / (bt->brp * alltseg);
43	bt->sample_point = ((tseg1 + 1) * 1000) / alltseg;
44
45	return 0;
46}
47
48/* Checks the validity of predefined bitrate settings */
49static int
50can_validate_bitrate(const struct net_device *dev, const struct can_bittiming *bt,
51		     const u32 *bitrate_const,
52		     const unsigned int bitrate_const_cnt)
53{
54	unsigned int i;
55
56	for (i = 0; i < bitrate_const_cnt; i++) {
57		if (bt->bitrate == bitrate_const[i])
58			return 0;
59	}
60
61	return -EINVAL;
62}
63
64int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
65		      const struct can_bittiming_const *btc,
66		      const u32 *bitrate_const,
67		      const unsigned int bitrate_const_cnt)
68{
69	int err;
70
71	/* Depending on the given can_bittiming parameter structure the CAN
72	 * timing parameters are calculated based on the provided bitrate OR
73	 * alternatively the CAN timing parameters (tq, prop_seg, etc.) are
74	 * provided directly which are then checked and fixed up.
75	 */
76	if (!bt->tq && bt->bitrate && btc)
77		err = can_calc_bittiming(dev, bt, btc);
78	else if (bt->tq && !bt->bitrate && btc)
79		err = can_fixup_bittiming(dev, bt, btc);
80	else if (!bt->tq && bt->bitrate && bitrate_const)
81		err = can_validate_bitrate(dev, bt, bitrate_const,
82					   bitrate_const_cnt);
83	else
84		err = -EINVAL;
85
86	return err;
87}