1 /* can-calc-bit-timing.c: Calculate CAN bit timing parameters
3 * Copyright (C) 2008 Wolfgang Grandegger <wg@grandegger.com>
6 * can_baud.c - CAN baudrate calculation
7 * Code based on LinCAN sources and H8S2638 project
8 * Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
9 * Copyright 2005 Stanislav Marek
10 * email:pisa@cmp.felk.cvut.cz
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
26 #include <linux/types.h>
28 /* seems not to be defined in errno.h */
30 #define ENOTSUPP 524 /* Operation is not supported */
34 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
36 #define do_div(a,b) a = (a) / (b)
40 (__x < 0) ? -__x : __x; \
44 * clamp - return a value clamped to a given range with strict typechecking
46 * @min: minimum allowable value
47 * @max: maximum allowable value
49 * This macro does strict typechecking of min/max to make sure they are of the
50 * same type as val. See the unnecessary pointer comparisons.
52 #define clamp(val, min, max) ({ \
53 typeof(val) __val = (val); \
54 typeof(min) __min = (min); \
55 typeof(max) __max = (max); \
56 (void) (&__val == &__min); \
57 (void) (&__val == &__max); \
58 __val = __val < __min ? __min: __val; \
59 __val > __max ? __max: __val; })
61 /* we don't want to see these prints */
62 #define dev_err(dev, format, arg...) do { } while (0)
63 #define dev_warn(dev, format, arg...) do { } while (0)
65 /* define in-kernel-types */
71 * CAN bit-timing parameters
73 * For futher information, please read chapter "8 BIT TIMING
74 * REQUIREMENTS" of the "Bosch CAN Specification version 2.0"
75 * at http://www.semiconductors.bosch.de/pdf/can2spec.pdf.
77 struct can_bittiming {
78 __u32 bitrate; /* Bit-rate in bits/second */
79 __u32 sample_point; /* Sample point in one-tenth of a percent */
80 __u32 tq; /* Time quanta (TQ) in nanoseconds */
81 __u32 prop_seg; /* Propagation segment in TQs */
82 __u32 phase_seg1; /* Phase buffer segment 1 in TQs */
83 __u32 phase_seg2; /* Phase buffer segment 2 in TQs */
84 __u32 sjw; /* Synchronisation jump width in TQs */
85 __u32 brp; /* Bit-rate prescaler */
89 * CAN harware-dependent bit-timing constant
91 * Used for calculating and checking bit-timing parameters
93 struct can_bittiming_const {
94 char name[16]; /* Name of the CAN controller hardware */
95 __u32 tseg1_min; /* Time segement 1 = prop_seg + phase_seg1 */
97 __u32 tseg2_min; /* Time segement 2 = phase_seg2 */
99 __u32 sjw_max; /* Synchronisation jump width */
100 __u32 brp_min; /* Bit-rate prescaler */
104 /* added for can-calc-bit-timing utility */
105 __u32 ref_clk; /* CAN system clock frequency in Hz */
106 void (*printf_btr)(struct can_bittiming *bt, bool hdr);
110 * CAN clock parameters
113 __u32 freq; /* CAN system clock frequency in Hz */
118 * minimal structs, just enough to be source level compatible
121 const struct can_bittiming_const *bittiming_const;
122 struct can_clock clock;
126 struct can_priv priv;
129 static inline void *netdev_priv(const struct net_device *dev)
131 return (void *)&dev->priv;
134 static void print_usage(char *cmd)
136 printf("Usage: %s [options] [<CAN-contoller-name>]\n"
138 "\t-q : don't print header line\n"
139 "\t-l : list all support CAN controller names\n"
140 "\t-b <bitrate> : bit-rate in bits/sec\n"
141 "\t-s <samp_pt> : sample-point in one-tenth of a percent\n"
142 "\t or 0 for CIA recommended sample points\n"
143 "\t-c <clock> : real CAN system clock in Hz\n",
149 static void printf_btr_sja1000(struct can_bittiming *bt, bool hdr)
156 btr0 = ((bt->brp - 1) & 0x3f) | (((bt->sjw - 1) & 0x3) << 6);
157 btr1 = ((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) |
158 (((bt->phase_seg2 - 1) & 0x7) << 4);
159 printf("0x%02x 0x%02x", btr0, btr1);
163 static void printf_btr_at91(struct can_bittiming *bt, bool hdr)
166 printf("%10s", "CAN_BR");
168 uint32_t br = ((bt->phase_seg2 - 1) |
169 ((bt->phase_seg1 - 1) << 4) |
170 ((bt->prop_seg - 1) << 8) |
171 ((bt->sjw - 1) << 12) |
172 ((bt->brp - 1) << 16));
173 printf("0x%08x", br);
177 static void printf_btr_flexcan(struct can_bittiming *bt, bool hdr)
180 printf("%10s", "CAN_CTRL");
182 uint32_t ctrl = (((bt->brp - 1) << 24) |
183 ((bt->sjw - 1) << 22) |
184 ((bt->phase_seg1 - 1) << 19) |
185 ((bt->phase_seg2 - 1) << 16) |
186 ((bt->prop_seg - 1) << 0));
188 printf("0x%08x", ctrl);
192 static void printf_btr_mcp251x(struct can_bittiming *bt, bool hdr)
194 uint8_t cnf1, cnf2, cnf3;
197 printf("CNF1 CNF2 CNF3");
199 cnf1 = ((bt->sjw - 1) << 6) | (bt->brp - 1);
200 cnf2 = 0x80 | ((bt->phase_seg1 - 1) << 3) | (bt->prop_seg - 1);
201 cnf3 = bt->phase_seg2 - 1;
202 printf("0x%02x 0x%02x 0x%02x", cnf1, cnf2, cnf3);
206 static void printf_btr_ti_hecc(struct can_bittiming *bt, bool hdr)
209 printf("%10s", "CANBTC");
213 can_btc = (bt->phase_seg2 - 1) & 0x7;
214 can_btc |= ((bt->phase_seg1 + bt->prop_seg - 1)
216 can_btc |= ((bt->sjw - 1) & 0x3) << 8;
217 can_btc |= ((bt->brp - 1) & 0xFF) << 16;
219 printf("0x%08x", can_btc);
223 #define RCAR_CAN_BCR_TSEG1(x) (((x) & 0x0f) << 20)
224 #define RCAR_CAN_BCR_BPR(x) (((x) & 0x3ff) << 8)
225 #define RCAR_CAN_BCR_SJW(x) (((x) & 0x3) << 4)
226 #define RCAR_CAN_BCR_TSEG2(x) ((x) & 0x07)
228 static void printf_btr_rcar_can(struct can_bittiming *bt, bool hdr)
231 printf("%10s", "CiBCR");
235 bcr = RCAR_CAN_BCR_TSEG1(bt->phase_seg1 + bt->prop_seg - 1) |
236 RCAR_CAN_BCR_BPR(bt->brp - 1) |
237 RCAR_CAN_BCR_SJW(bt->sjw - 1) |
238 RCAR_CAN_BCR_TSEG2(bt->phase_seg2 - 1);
240 printf("0x%08x", bcr << 8);
244 static struct can_bittiming_const can_calc_consts[] = {
257 .printf_btr = printf_btr_sja1000,
271 .printf_btr = printf_btr_sja1000,
285 .printf_btr = printf_btr_sja1000,
299 .printf_btr = printf_btr_sja1000,
313 .printf_btr = printf_btr_sja1000,
326 .ref_clk = 66660000, /* mpc5121 */
327 .printf_btr = printf_btr_sja1000,
340 .ref_clk = 66666666, /* mpc5121 */
341 .printf_btr = printf_btr_sja1000,
354 .ref_clk = 100000000,
355 .printf_btr = printf_btr_at91,
368 /* real world clock as found on the ronetix PM9263 */
370 .printf_btr = printf_btr_at91,
383 .ref_clk = 24000000, /* mx28 */
384 .printf_btr = printf_btr_flexcan,
397 .ref_clk = 30000000, /* mx6 */
398 .printf_btr = printf_btr_flexcan,
412 .printf_btr = printf_btr_flexcan,
426 .printf_btr = printf_btr_flexcan,
440 .printf_btr = printf_btr_flexcan,
454 .printf_btr = printf_btr_flexcan,
468 .printf_btr = printf_btr_flexcan, /* vybrid */
482 .printf_btr = printf_btr_mcp251x,
496 .printf_btr = printf_btr_mcp251x,
510 .printf_btr = printf_btr_ti_hecc,
524 .printf_btr = printf_btr_rcar_can,
528 static long common_bitrates[] = {
540 #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
542 static int can_update_spt(const struct can_bittiming_const *btc,
543 int sampl_pt, int tseg, int *tseg1, int *tseg2)
545 *tseg2 = tseg + 1 - (sampl_pt * (tseg + 1)) / 1000;
546 if (*tseg2 < btc->tseg2_min)
547 *tseg2 = btc->tseg2_min;
548 if (*tseg2 > btc->tseg2_max)
549 *tseg2 = btc->tseg2_max;
550 *tseg1 = tseg - *tseg2;
551 if (*tseg1 > btc->tseg1_max) {
552 *tseg1 = btc->tseg1_max;
553 *tseg2 = tseg - *tseg1;
555 return 1000 * (tseg + 1 - *tseg2) / (tseg + 1);
558 static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt)
560 struct can_priv *priv = netdev_priv(dev);
561 const struct can_bittiming_const *btc = priv->bittiming_const;
563 long best_error = 1000000000, error = 0;
564 int best_tseg = 0, best_brp = 0, brp = 0;
565 int tsegall, tseg = 0, tseg1 = 0, tseg2 = 0;
566 int spt_error = 1000, spt = 0, sampl_pt;
569 if (!priv->bittiming_const)
572 /* Use CIA recommended sample points */
573 if (bt->sample_point) {
574 sampl_pt = bt->sample_point;
576 if (bt->bitrate > 800000)
578 else if (bt->bitrate > 500000)
584 /* tseg even = round down, odd = round up */
585 for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
586 tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
587 tsegall = 1 + tseg / 2;
588 /* Compute all possible tseg choices (tseg=tseg1+tseg2) */
589 brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
590 /* chose brp step which is possible in system */
591 brp = (brp / btc->brp_inc) * btc->brp_inc;
592 if ((brp < btc->brp_min) || (brp > btc->brp_max))
594 rate = priv->clock.freq / (brp * tsegall);
595 error = bt->bitrate - rate;
596 /* tseg brp biterror */
599 if (error > best_error)
603 spt = can_update_spt(btc, sampl_pt, tseg / 2,
605 error = sampl_pt - spt;
608 if (error > spt_error)
612 best_tseg = tseg / 2;
619 /* Error in one-tenth of a percent */
620 error = (best_error * 1000) / bt->bitrate;
621 if (error > CAN_CALC_MAX_ERROR) {
622 dev_err(dev->dev.parent,
623 "bitrate error %ld.%ld%% too high\n",
624 error / 10, error % 10);
627 dev_warn(dev->dev.parent, "bitrate error %ld.%ld%%\n",
628 error / 10, error % 10);
632 /* real sample point */
633 bt->sample_point = can_update_spt(btc, sampl_pt, best_tseg,
636 v64 = (u64)best_brp * 1000000000UL;
637 do_div(v64, priv->clock.freq);
639 bt->prop_seg = tseg1 / 2;
640 bt->phase_seg1 = tseg1 - bt->prop_seg;
641 bt->phase_seg2 = tseg2;
646 bt->bitrate = priv->clock.freq / (bt->brp * (tseg1 + tseg2 + 1));
651 static __u32 get_cia_sample_point(__u32 bitrate)
655 if (bitrate > 800000)
657 else if (bitrate > 500000)
665 static void print_bit_timing(const struct can_bittiming_const *btc,
666 __u32 bitrate, __u32 sample_point, __u32 ref_clk,
669 struct net_device dev = {
670 .priv.bittiming_const = btc,
671 .priv.clock.freq = ref_clk,
673 struct can_bittiming bt = {
675 .sample_point = sample_point,
677 long rate_error, spt_error;
680 printf("Bit timing parameters for %s with %.6f MHz ref clock\n"
681 "nominal real Bitrt nom real SampP\n"
682 "Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP SampP Error ",
684 ref_clk / 1000000.0);
686 btc->printf_btr(&bt, true);
690 if (can_calc_bittiming(&dev, &bt)) {
691 printf("%7d ***bitrate not possible***\n", bitrate);
695 /* get nominal sample point */
697 sample_point = get_cia_sample_point(bitrate);
699 rate_error = abs((__s32)(bitrate - bt.bitrate));
700 spt_error = abs((__s32)(sample_point - bt.sample_point));
706 "%4.1f%% %4.1f%% %4.1f%% ",
708 bt.tq, bt.prop_seg, bt.phase_seg1, bt.phase_seg2,
712 100.0 * rate_error / bitrate,
715 bt.sample_point / 10.0,
716 100.0 * spt_error / sample_point);
718 btc->printf_btr(&bt, false);
722 static void do_list(void)
726 for (i = 0; i < ARRAY_SIZE(can_calc_consts); i++)
727 printf("%s\n", can_calc_consts[i].name);
730 int main(int argc, char *argv[])
733 __u32 opt_ref_clk = 0, ref_clk;
735 bool quiet = false, list = false, found = false;
740 const struct can_bittiming_const *btc = NULL;
742 while ((opt = getopt(argc, argv, "b:c:lps:")) != -1) {
745 bitrate = atoi(optarg);
749 opt_ref_clk = atoi(optarg);
761 sampl_pt = atoi(optarg);
765 print_usage(argv[0]);
770 if (argc > optind + 1)
771 print_usage(argv[0]);
773 if (argc == optind + 1)
781 if (sampl_pt && (sampl_pt >= 1000 || sampl_pt < 100))
782 print_usage(argv[0]);
784 for (i = 0; i < ARRAY_SIZE(can_calc_consts); i++) {
785 if (name && strcmp(can_calc_consts[i].name, name))
789 btc = &can_calc_consts[i];
792 ref_clk = opt_ref_clk;
794 ref_clk = btc->ref_clk;
797 print_bit_timing(btc, bitrate, sampl_pt, ref_clk, quiet);
799 for (j = 0; j < ARRAY_SIZE(common_bitrates); j++)
800 print_bit_timing(btc, common_bitrates[j],
801 sampl_pt, ref_clk, j);
807 printf("error: unknown CAN controller '%s', try one of these:\n\n", name);