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 */
can_fixup_bittiming(const struct net_device * dev,struct can_bittiming * bt,const struct can_bittiming_const * btc)14 static 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 */
49 static int
can_validate_bitrate(const struct net_device * dev,const struct can_bittiming * bt,const u32 * bitrate_const,const unsigned int bitrate_const_cnt)50 can_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
can_get_bittiming(const struct net_device * dev,struct can_bittiming * bt,const struct can_bittiming_const * btc,const u32 * bitrate_const,const unsigned int bitrate_const_cnt)64 int 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 }
88
