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 software is released under the GPL-License.
22 #include <linux/types.h>
24 /* seems not to be defined in errno.h */
26 #define ENOTSUPP 524 /* Operation is not supported */
30 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
32 #define do_div(a,b) a = (a) / (b)
36 (__x < 0) ? -__x : __x; \
40 * clamp - return a value clamped to a given range with strict typechecking
42 * @min: minimum allowable value
43 * @max: maximum allowable value
45 * This macro does strict typechecking of min/max to make sure they are of the
46 * same type as val. See the unnecessary pointer comparisons.
48 #define clamp(val, min, max) ({ \
49 typeof(val) __val = (val); \
50 typeof(min) __min = (min); \
51 typeof(max) __max = (max); \
52 (void) (&__val == &__min); \
53 (void) (&__val == &__max); \
54 __val = __val < __min ? __min: __val; \
55 __val > __max ? __max: __val; })
57 /* we don't want to see these prints */
58 #define dev_err(dev, format, arg...) do { } while (0)
59 #define dev_warn(dev, format, arg...) do { } while (0)
61 /* define in-kernel-types */
67 * CAN bit-timing parameters
69 * For futher information, please read chapter "8 BIT TIMING
70 * REQUIREMENTS" of the "Bosch CAN Specification version 2.0"
71 * at http://www.semiconductors.bosch.de/pdf/can2spec.pdf.
73 struct can_bittiming {
74 __u32 bitrate; /* Bit-rate in bits/second */
75 __u32 sample_point; /* Sample point in one-tenth of a percent */
76 __u32 tq; /* Time quanta (TQ) in nanoseconds */
77 __u32 prop_seg; /* Propagation segment in TQs */
78 __u32 phase_seg1; /* Phase buffer segment 1 in TQs */
79 __u32 phase_seg2; /* Phase buffer segment 2 in TQs */
80 __u32 sjw; /* Synchronisation jump width in TQs */
81 __u32 brp; /* Bit-rate prescaler */
85 * CAN harware-dependent bit-timing constant
87 * Used for calculating and checking bit-timing parameters
89 struct can_bittiming_const {
90 char name[16]; /* Name of the CAN controller hardware */
91 __u32 tseg1_min; /* Time segement 1 = prop_seg + phase_seg1 */
93 __u32 tseg2_min; /* Time segement 2 = phase_seg2 */
95 __u32 sjw_max; /* Synchronisation jump width */
96 __u32 brp_min; /* Bit-rate prescaler */
100 /* added for can-calc-bit-timing utility */
101 __u32 ref_clk; /* CAN system clock frequency in Hz */
102 void (*printf_btr)(struct can_bittiming *bt, int hdr);
106 * CAN clock parameters
109 __u32 freq; /* CAN system clock frequency in Hz */
114 * minimal structs, just enough to be source level compatible
117 const struct can_bittiming_const *bittiming_const;
118 struct can_clock clock;
122 struct can_priv priv;
125 static inline void *netdev_priv(const struct net_device *dev)
127 return (void *)&dev->priv;
130 static void print_usage(char* cmd)
132 printf("Usage: %s [options] [<CAN-contoller-name>]\n"
134 "\t-q : don't print header line\n"
135 "\t-l : list all support CAN controller names\n"
136 "\t-b <bitrate> : bit-rate in bits/sec\n"
137 "\t-s <samp_pt> : sample-point in one-tenth of a percent\n"
138 "\t or 0 for CIA recommended sample points\n"
139 "\t-c <clock> : real CAN system clock in Hz\n",
145 static void printf_btr_sja1000(struct can_bittiming *bt, int hdr)
152 btr0 = ((bt->brp - 1) & 0x3f) | (((bt->sjw - 1) & 0x3) << 6);
153 btr1 = ((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) |
154 (((bt->phase_seg2 - 1) & 0x7) << 4);
155 printf("0x%02x 0x%02x", btr0, btr1);
159 static void printf_btr_at91(struct can_bittiming *bt, int hdr)
162 printf("%10s", "CAN_BR");
164 uint32_t br = ((bt->phase_seg2 - 1) |
165 ((bt->phase_seg1 - 1) << 4) |
166 ((bt->prop_seg - 1) << 8) |
167 ((bt->sjw - 1) << 12) |
168 ((bt->brp - 1) << 16));
169 printf("0x%08x", br);
173 static void printf_btr_flexcan(struct can_bittiming *bt, int hdr)
176 printf("%10s", "CAN_CTRL");
178 uint32_t ctrl = (((bt->brp - 1) << 24) |
179 ((bt->sjw - 1) << 22) |
180 ((bt->phase_seg1 - 1) << 19) |
181 ((bt->phase_seg2 - 1) << 16) |
182 ((bt->prop_seg - 1) << 0));
184 printf("0x%08x", ctrl);
188 static void printf_btr_mcp251x(struct can_bittiming *bt, int hdr)
190 uint8_t cnf1, cnf2, cnf3;
193 printf("CNF1 CNF2 CNF3");
195 cnf1 = ((bt->sjw - 1) << 6) | bt->brp;
196 cnf2 = 0x80 | ((bt->phase_seg1 - 1) << 3) | (bt->prop_seg - 1);
197 cnf3 = bt->phase_seg2 - 1;
198 printf("0x%02x 0x%02x 0x%02x", cnf1, cnf2, cnf3);
202 static struct can_bittiming_const can_calc_consts[] = {
215 .printf_btr = printf_btr_sja1000,
229 .printf_btr = printf_btr_sja1000,
243 .printf_btr = printf_btr_sja1000,
257 .printf_btr = printf_btr_sja1000,
271 .printf_btr = printf_btr_sja1000,
284 .ref_clk = 100000000,
285 .printf_btr = printf_btr_at91,
298 /* real world clock as found on the ronetix PM9263 */
300 .printf_btr = printf_btr_at91,
314 .printf_btr = printf_btr_flexcan,
328 .printf_btr = printf_btr_flexcan,
342 .printf_btr = printf_btr_mcp251x,
356 .printf_btr = printf_btr_mcp251x,
360 static long common_bitrates[] = {
372 #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
374 static int can_update_spt(const struct can_bittiming_const *btc,
375 int sampl_pt, int tseg, int *tseg1, int *tseg2)
377 *tseg2 = tseg + 1 - (sampl_pt * (tseg + 1)) / 1000;
378 if (*tseg2 < btc->tseg2_min)
379 *tseg2 = btc->tseg2_min;
380 if (*tseg2 > btc->tseg2_max)
381 *tseg2 = btc->tseg2_max;
382 *tseg1 = tseg - *tseg2;
383 if (*tseg1 > btc->tseg1_max) {
384 *tseg1 = btc->tseg1_max;
385 *tseg2 = tseg - *tseg1;
387 return 1000 * (tseg + 1 - *tseg2) / (tseg + 1);
390 static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt)
392 struct can_priv *priv = netdev_priv(dev);
393 const struct can_bittiming_const *btc = priv->bittiming_const;
394 long rate, best_rate = 0;
395 long best_error = 1000000000, error = 0;
396 int best_tseg = 0, best_brp = 0, brp = 0;
397 int tsegall, tseg = 0, tseg1 = 0, tseg2 = 0;
398 int spt_error = 1000, spt = 0, sampl_pt;
401 if (!priv->bittiming_const)
404 /* Use CIA recommended sample points */
405 if (bt->sample_point) {
406 sampl_pt = bt->sample_point;
408 if (bt->bitrate > 800000)
410 else if (bt->bitrate > 500000)
416 /* tseg even = round down, odd = round up */
417 for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
418 tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
419 tsegall = 1 + tseg / 2;
420 /* Compute all possible tseg choices (tseg=tseg1+tseg2) */
421 brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
422 /* chose brp step which is possible in system */
423 brp = (brp / btc->brp_inc) * btc->brp_inc;
424 if ((brp < btc->brp_min) || (brp > btc->brp_max))
426 rate = priv->clock.freq / (brp * tsegall);
427 error = bt->bitrate - rate;
428 /* tseg brp biterror */
431 if (error > best_error)
435 spt = can_update_spt(btc, sampl_pt, tseg / 2,
437 error = sampl_pt - spt;
440 if (error > spt_error)
444 best_tseg = tseg / 2;
452 /* Error in one-tenth of a percent */
453 error = (best_error * 1000) / bt->bitrate;
454 if (error > CAN_CALC_MAX_ERROR) {
455 dev_err(dev->dev.parent,
456 "bitrate error %ld.%ld%% too high\n",
457 error / 10, error % 10);
460 dev_warn(dev->dev.parent, "bitrate error %ld.%ld%%\n",
461 error / 10, error % 10);
465 /* real sample point */
466 bt->sample_point = can_update_spt(btc, sampl_pt, best_tseg,
469 v64 = (u64)best_brp * 1000000000UL;
470 do_div(v64, priv->clock.freq);
472 bt->prop_seg = tseg1 / 2;
473 bt->phase_seg1 = tseg1 - bt->prop_seg;
474 bt->phase_seg2 = tseg2;
479 bt->bitrate = priv->clock.freq / (bt->brp * (tseg1 + tseg2 + 1));
484 static __u32 get_cia_sample_point(__u32 bitrate)
488 if (bitrate > 800000)
490 else if (bitrate > 500000)
498 static void print_bit_timing(const struct can_bittiming_const *btc,
499 __u32 bitrate, __u32 sample_point, __u32 ref_clk,
502 struct net_device dev = {
503 .priv.bittiming_const = btc,
504 .priv.clock.freq = ref_clk,
506 struct can_bittiming bt = {
508 .sample_point = sample_point,
510 long rate_error, spt_error;
513 printf("Bit timing parameters for %s with %.6f MHz ref clock\n"
514 "nominal real Bitrt nom real SampP\n"
515 "Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP SampP Error ",
517 ref_clk / 1000000.0);
519 btc->printf_btr(&bt, 1);
523 if (can_calc_bittiming(&dev, &bt)) {
524 printf("%7d ***bitrate not possible***\n", bitrate);
528 /* get nominal sample point */
530 sample_point = get_cia_sample_point(bitrate);
532 rate_error = abs((__s32)(bitrate - bt.bitrate));
533 spt_error = abs((__s32)(sample_point - bt.sample_point));
539 "%4.1f%% %4.1f%% %4.1f%% ",
541 bt.tq, bt.prop_seg, bt.phase_seg1, bt.phase_seg2,
545 100.0 * rate_error / bitrate,
548 bt.sample_point / 10.0,
549 100.0 * spt_error / sample_point);
551 btc->printf_btr(&bt, 0);
555 static void do_list(void)
559 for (i = 0; i < ARRAY_SIZE(can_calc_consts); i++)
560 printf("%s\n", can_calc_consts[i].name);
563 int main(int argc, char *argv[])
566 __u32 opt_ref_clk = 0, ref_clk;
574 const struct can_bittiming_const *btc = NULL;
576 while ((opt = getopt(argc, argv, "b:c:lps:")) != -1) {
579 bitrate = atoi(optarg);
583 opt_ref_clk = atoi(optarg);
595 sampl_pt = atoi(optarg);
599 print_usage(argv[0]);
604 if (argc > optind + 1)
605 print_usage(argv[0]);
607 if (argc == optind + 1)
615 if (sampl_pt && (sampl_pt >= 1000 || sampl_pt < 100))
616 print_usage(argv[0]);
618 for (i = 0; i < ARRAY_SIZE(can_calc_consts); i++) {
619 if (name && strcmp(can_calc_consts[i].name, name))
623 btc = &can_calc_consts[i];
626 ref_clk = opt_ref_clk;
628 ref_clk = btc->ref_clk;
631 print_bit_timing(btc, bitrate, sampl_pt, ref_clk, quiet);
633 for (j = 0; j < ARRAY_SIZE(common_bitrates); j++)
634 print_bit_timing(btc, common_bitrates[j],
635 sampl_pt, ref_clk, j);
641 printf("error: unknown CAN controller '%s', try one of these:\n\n", name);