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can-utils/can-calc-bit-timing.c

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/* SPDX-License-Identifier: GPL-2.0-only */
/* can-calc-bit-timing.c: Calculate CAN bit timing parameters
*
* Copyright (C) 2008 Wolfgang Grandegger <wg@grandegger.com>
* Copyright (C) 2016 Marc Kleine-Budde <mkl@pengutronix.de>
*
* Derived from:
* can_baud.c - CAN baudrate calculation
* Code based on LinCAN sources and H8S2638 project
* Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
* Copyright 2005 Stanislav Marek
* email:pisa@cmp.felk.cvut.cz
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the version 2 of the GNU General Public License
* as published by the Free Software Foundation
*/
#include <errno.h>
#include <getopt.h>
#include <limits.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <libgen.h>
#include <string.h>
#include <linux/types.h>
#include <linux/can/netlink.h>
/* imported from kernel */
/**
* abs - return absolute value of an argument
* @x: the value. If it is unsigned type, it is converted to signed type first.
* char is treated as if it was signed (regardless of whether it really is)
* but the macro's return type is preserved as char.
*
* Return: an absolute value of x.
*/
#define abs(x) __abs_choose_expr(x, long long, \
__abs_choose_expr(x, long, \
__abs_choose_expr(x, int, \
__abs_choose_expr(x, short, \
__abs_choose_expr(x, char, \
__builtin_choose_expr( \
__builtin_types_compatible_p(typeof(x), char), \
(char)({ signed char __x = (x); __x<0?-__x:__x; }), \
((void)0)))))))
#define __abs_choose_expr(x, type, other) __builtin_choose_expr( \
__builtin_types_compatible_p(typeof(x), signed type) || \
__builtin_types_compatible_p(typeof(x), unsigned type), \
({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
/*
* min()/max()/clamp() macros that also do
* strict type-checking.. See the
* "unnecessary" pointer comparison.
*/
#define min(x, y) ({ \
typeof(x) _min1 = (x); \
typeof(y) _min2 = (y); \
(void) (&_min1 == &_min2); \
_min1 < _min2 ? _min1 : _min2; })
#define max(x, y) ({ \
typeof(x) _max1 = (x); \
typeof(y) _max2 = (y); \
(void) (&_max1 == &_max2); \
_max1 > _max2 ? _max1 : _max2; })
/**
* clamp - return a value clamped to a given range with strict typechecking
* @val: current value
* @lo: lowest allowable value
* @hi: highest allowable value
*
* This macro does strict typechecking of lo/hi to make sure they are of the
* same type as val. See the unnecessary pointer comparisons.
*/
#define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
# define do_div(n,base) ({ \
uint32_t __base = (base); \
uint32_t __rem; \
__rem = ((uint64_t)(n)) % __base; \
(n) = ((uint64_t)(n)) / __base; \
__rem; \
})
/* */
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
/* we don't want to see these prints */
#define netdev_err(dev, format, arg...) do { } while (0)
#define netdev_warn(dev, format, arg...) do { } while (0)
/* define in-kernel-types */
typedef __u64 u64;
typedef __u32 u32;
struct calc_ref_clk {
__u32 clk; /* CAN system clock frequency in Hz */
char *name;
};
struct calc_bittiming_const {
struct can_bittiming_const bittiming_const;
const struct calc_ref_clk ref_clk[16];
void (*printf_btr)(struct can_bittiming *bt, bool hdr);
};
/*
* minimal structs, just enough to be source level compatible
*/
struct can_priv {
struct can_clock clock;
};
struct net_device {
struct can_priv priv;
};
static inline void *netdev_priv(const struct net_device *dev)
{
return (void *)&dev->priv;
}
static void print_usage(char *cmd)
{
printf("%s - calculate CAN bit timing parameters.\n", cmd);
printf("Usage: %s [options] [<CAN-contoller-name>]\n"
"Options:\n"
"\t-q don't print header line\n"
"\t-l list all support CAN controller names\n"
"\t-b <bitrate> bit-rate in bits/sec\n"
"\t-s <samp_pt> sample-point in one-tenth of a percent\n"
"\t or 0 for CIA recommended sample points\n"
"\t-c <clock> real CAN system clock in Hz\n",
cmd);
}
static void printf_btr_sja1000(struct can_bittiming *bt, bool hdr)
{
uint8_t btr0, btr1;
if (hdr) {
printf("BTR0 BTR1");
} else {
btr0 = ((bt->brp - 1) & 0x3f) | (((bt->sjw - 1) & 0x3) << 6);
btr1 = ((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) |
(((bt->phase_seg2 - 1) & 0x7) << 4);
printf("0x%02x 0x%02x", btr0, btr1);
}
}
static void printf_btr_at91(struct can_bittiming *bt, bool hdr)
{
if (hdr) {
printf("%10s", "CAN_BR");
} else {
uint32_t br = ((bt->phase_seg2 - 1) |
((bt->phase_seg1 - 1) << 4) |
((bt->prop_seg - 1) << 8) |
((bt->sjw - 1) << 12) |
((bt->brp - 1) << 16));
printf("0x%08x", br);
}
}
static void printf_btr_flexcan(struct can_bittiming *bt, bool hdr)
{
if (hdr) {
printf("%10s", "CAN_CTRL");
} else {
uint32_t ctrl = (((bt->brp - 1) << 24) |
((bt->sjw - 1) << 22) |
((bt->phase_seg1 - 1) << 19) |
((bt->phase_seg2 - 1) << 16) |
((bt->prop_seg - 1) << 0));
printf("0x%08x", ctrl);
}
}
static void printf_btr_mcp251x(struct can_bittiming *bt, bool hdr)
{
uint8_t cnf1, cnf2, cnf3;
if (hdr) {
printf("CNF1 CNF2 CNF3");
} else {
cnf1 = ((bt->sjw - 1) << 6) | (bt->brp - 1);
cnf2 = 0x80 | ((bt->phase_seg1 - 1) << 3) | (bt->prop_seg - 1);
cnf3 = bt->phase_seg2 - 1;
printf("0x%02x 0x%02x 0x%02x", cnf1, cnf2, cnf3);
}
}
static void printf_btr_ti_hecc(struct can_bittiming *bt, bool hdr)
{
if (hdr) {
printf("%10s", "CANBTC");
} else {
uint32_t can_btc;
can_btc = (bt->phase_seg2 - 1) & 0x7;
can_btc |= ((bt->phase_seg1 + bt->prop_seg - 1)
& 0xF) << 3;
can_btc |= ((bt->sjw - 1) & 0x3) << 8;
can_btc |= ((bt->brp - 1) & 0xFF) << 16;
printf("0x%08x", can_btc);
}
}
#define RCAR_CAN_BCR_TSEG1(x) (((x) & 0x0f) << 20)
#define RCAR_CAN_BCR_BPR(x) (((x) & 0x3ff) << 8)
#define RCAR_CAN_BCR_SJW(x) (((x) & 0x3) << 4)
#define RCAR_CAN_BCR_TSEG2(x) ((x) & 0x07)
static void printf_btr_rcar_can(struct can_bittiming *bt, bool hdr)
{
if (hdr) {
printf("%10s", "CiBCR");
} else {
uint32_t bcr;
bcr = RCAR_CAN_BCR_TSEG1(bt->phase_seg1 + bt->prop_seg - 1) |
RCAR_CAN_BCR_BPR(bt->brp - 1) |
RCAR_CAN_BCR_SJW(bt->sjw - 1) |
RCAR_CAN_BCR_TSEG2(bt->phase_seg2 - 1);
printf("0x%08x", bcr << 8);
}
}
static struct calc_bittiming_const can_calc_consts[] = {
{
.bittiming_const = {
.name = "sja1000",
.tseg1_min = 1,
.tseg1_max = 16,
.tseg2_min = 1,
.tseg2_max = 8,
.sjw_max = 4,
.brp_min = 1,
.brp_max = 64,
.brp_inc = 1,
},
.ref_clk = {
{ .clk = 8000000, },
},
.printf_btr = printf_btr_sja1000,
}, {
.bittiming_const = {
.name = "mscan",
.tseg1_min = 4,
.tseg1_max = 16,
.tseg2_min = 2,
.tseg2_max = 8,
.sjw_max = 4,
.brp_min = 1,
.brp_max = 64,
.brp_inc = 1,
},
.ref_clk = {
{ .clk = 32000000, },
{ .clk = 33000000, },
{ .clk = 33300000, },
{ .clk = 33333333, },
{ .clk = 66660000, .name = "mpc5121", },
{ .clk = 66666666, .name = "mpc5121" },
},
.printf_btr = printf_btr_sja1000,
}, {
.bittiming_const = {
.name = "at91",
.tseg1_min = 4,
.tseg1_max = 16,
.tseg2_min = 2,
.tseg2_max = 8,
.sjw_max = 4,
.brp_min = 2,
.brp_max = 128,
.brp_inc = 1,
},
.ref_clk = {
{ .clk = 99532800, .name = "ronetix PM9263", },
{ .clk = 100000000, },
},
.printf_btr = printf_btr_at91,
}, {
.bittiming_const = {
.name = "flexcan",
.tseg1_min = 4,
.tseg1_max = 16,
.tseg2_min = 2,
.tseg2_max = 8,
.sjw_max = 4,
.brp_min = 1,
.brp_max = 256,
.brp_inc = 1,
},
.ref_clk = {
{ .clk = 24000000, .name = "mx28" },
{ .clk = 30000000, .name = "mx6" },
{ .clk = 49875000, },
{ .clk = 66000000, },
{ .clk = 66500000, },
{ .clk = 66666666, },
{ .clk = 83368421, .name = "vybrid" },
},
.printf_btr = printf_btr_flexcan,
}, {
.bittiming_const = {
.name = "mcp251x",
.tseg1_min = 3,
.tseg1_max = 16,
.tseg2_min = 2,
.tseg2_max = 8,
.sjw_max = 4,
.brp_min = 1,
.brp_max = 64,
.brp_inc = 1,
},
.ref_clk = {
{ .clk = 8000000, },
{ .clk = 16000000, },
},
.printf_btr = printf_btr_mcp251x,
}, {
.bittiming_const = {
.name = "ti_hecc",
.tseg1_min = 1,
.tseg1_max = 16,
.tseg2_min = 1,
.tseg2_max = 8,
.sjw_max = 4,
.brp_min = 1,
.brp_max = 256,
.brp_inc = 1,
},
.ref_clk = {
{ .clk = 13000000, },
},
.printf_btr = printf_btr_ti_hecc,
}, {
.bittiming_const = {
.name = "rcar_can",
.tseg1_min = 4,
.tseg1_max = 16,
.tseg2_min = 2,
.tseg2_max = 8,
.sjw_max = 4,
.brp_min = 1,
.brp_max = 1024,
.brp_inc = 1,
},
.ref_clk = {
{ .clk = 65000000, },
},
.printf_btr = printf_btr_rcar_can,
},
};
static long common_bitrates[] = {
1000000,
800000,
500000,
250000,
125000,
100000,
50000,
20000,
10000,
};
#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
#define CAN_CALC_SYNC_SEG 1
/*
* Bit-timing calculation derived from:
*
* Code based on LinCAN sources and H8S2638 project
* Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
* Copyright 2005 Stanislav Marek
* email: pisa@cmp.felk.cvut.cz
*
* Calculates proper bit-timing parameters for a specified bit-rate
* and sample-point, which can then be used to set the bit-timing
* registers of the CAN controller. You can find more information
* in the header file linux/can/netlink.h.
*/
static int can_update_spt(const struct can_bittiming_const *btc,
unsigned int spt_nominal, unsigned int tseg,
unsigned int *tseg1_ptr, unsigned int *tseg2_ptr,
unsigned int *spt_error_ptr)
{
unsigned int spt_error, best_spt_error = UINT_MAX;
unsigned int spt, best_spt = 0;
unsigned int tseg1, tseg2;
int i;
for (i = 0; i <= 1; i++) {
tseg2 = tseg + CAN_CALC_SYNC_SEG - (spt_nominal * (tseg + CAN_CALC_SYNC_SEG)) / 1000 - i;
tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
tseg1 = tseg - tseg2;
if (tseg1 > btc->tseg1_max) {
tseg1 = btc->tseg1_max;
tseg2 = tseg - tseg1;
}
spt = 1000 * (tseg + CAN_CALC_SYNC_SEG - tseg2) / (tseg + CAN_CALC_SYNC_SEG);
spt_error = abs(spt_nominal - spt);
if ((spt <= spt_nominal) && (spt_error < best_spt_error)) {
best_spt = spt;
best_spt_error = spt_error;
*tseg1_ptr = tseg1;
*tseg2_ptr = tseg2;
}
}
if (spt_error_ptr)
*spt_error_ptr = best_spt_error;
return best_spt;
}
static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
const struct can_bittiming_const *btc)
{
struct can_priv *priv = netdev_priv(dev);
unsigned int rate; /* current bitrate */
unsigned int rate_error; /* difference between current and nominal value */
unsigned int best_rate_error = UINT_MAX;
unsigned int spt_error; /* difference between current and nominal value */
unsigned int best_spt_error = UINT_MAX;
unsigned int spt_nominal; /* nominal sample point */
unsigned int best_tseg = 0; /* current best value for tseg */
unsigned int best_brp = 0; /* current best value for brp */
unsigned int brp, tsegall, tseg, tseg1 = 0, tseg2 = 0;
u64 v64;
/* Use CiA recommended sample points */
if (bt->sample_point) {
spt_nominal = bt->sample_point;
} else {
if (bt->bitrate > 800000)
spt_nominal = 750;
else if (bt->bitrate > 500000)
spt_nominal = 800;
else
spt_nominal = 875;
}
/* tseg even = round down, odd = round up */
for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
tsegall = CAN_CALC_SYNC_SEG + tseg / 2;
/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
/* choose brp step which is possible in system */
brp = (brp / btc->brp_inc) * btc->brp_inc;
if ((brp < btc->brp_min) || (brp > btc->brp_max))
continue;
rate = priv->clock.freq / (brp * tsegall);
rate_error = abs(bt->bitrate - rate);
/* tseg brp biterror */
if (rate_error > best_rate_error)
continue;
/* reset sample point error if we have a better bitrate */
if (rate_error < best_rate_error)
best_spt_error = UINT_MAX;
can_update_spt(btc, spt_nominal, tseg / 2, &tseg1, &tseg2, &spt_error);
if (spt_error > best_spt_error)
continue;
best_spt_error = spt_error;
best_rate_error = rate_error;
best_tseg = tseg / 2;
best_brp = brp;
if (rate_error == 0 && spt_error == 0)
break;
}
if (best_rate_error) {
/* Error in one-tenth of a percent */
rate_error = (best_rate_error * 1000) / bt->bitrate;
if (rate_error > CAN_CALC_MAX_ERROR) {
netdev_err(dev,
"bitrate error %ld.%ld%% too high\n",
rate_error / 10, rate_error % 10);
return -EDOM;
}
netdev_warn(dev, "bitrate error %ld.%ld%%\n",
rate_error / 10, rate_error % 10);
}
/* real sample point */
bt->sample_point = can_update_spt(btc, spt_nominal, best_tseg,
&tseg1, &tseg2, NULL);
v64 = (u64)best_brp * 1000 * 1000 * 1000;
do_div(v64, priv->clock.freq);
bt->tq = (u32)v64;
bt->prop_seg = tseg1 / 2;
bt->phase_seg1 = tseg1 - bt->prop_seg;
bt->phase_seg2 = tseg2;
/* check for sjw user settings */
if (!bt->sjw || !btc->sjw_max) {
bt->sjw = 1;
} else {
/* bt->sjw is at least 1 -> sanitize upper bound to sjw_max */
if (bt->sjw > btc->sjw_max)
bt->sjw = btc->sjw_max;
/* bt->sjw must not be higher than tseg2 */
if (tseg2 < bt->sjw)
bt->sjw = tseg2;
}
bt->brp = best_brp;
/* real bit-rate */
bt->bitrate = priv->clock.freq / (bt->brp * (CAN_CALC_SYNC_SEG + tseg1 + tseg2));
return 0;
}
static __u32 get_cia_sample_point(__u32 bitrate)
{
__u32 sampl_pt;
if (bitrate > 800000)
sampl_pt = 750;
else if (bitrate > 500000)
sampl_pt = 800;
else
sampl_pt = 875;
return sampl_pt;
}
static void print_bit_timing(const struct calc_bittiming_const *btc,
const struct calc_ref_clk *ref_clk,
unsigned int bitrate_nominal,
unsigned int spt_nominal,
bool quiet)
{
struct net_device dev = {
.priv.clock.freq = ref_clk->clk,
};
struct can_bittiming bt = {
.bitrate = bitrate_nominal,
.sample_point = spt_nominal,
};
long rate_error, spt_error;
if (!quiet) {
printf("Bit timing parameters for %s%s%s%s with %.6f MHz ref clock\n"
"nominal real Bitrt nom real SampP\n"
"Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP SampP Error ",
btc->bittiming_const.name,
ref_clk->name ? " (" : "",
ref_clk->name ? ref_clk->name : "",
ref_clk->name ? ")" : "",
ref_clk->clk / 1000000.0);
btc->printf_btr(&bt, true);
printf("\n");
}
if (can_calc_bittiming(&dev, &bt, &btc->bittiming_const)) {
printf("%7d ***bitrate not possible***\n", bitrate_nominal);
return;
}
/* get nominal sample point */
if (!spt_nominal)
spt_nominal = get_cia_sample_point(bitrate_nominal);
rate_error = abs(bitrate_nominal - bt.bitrate);
spt_error = abs(spt_nominal - bt.sample_point);
printf("%7d "
"%6d %3d %4d %4d "
"%3d %3d "
"%7d %4.1f%% "
"%4.1f%% %4.1f%% %4.1f%% ",
bitrate_nominal,
bt.tq, bt.prop_seg, bt.phase_seg1, bt.phase_seg2,
bt.sjw, bt.brp,
bt.bitrate,
100.0 * rate_error / bitrate_nominal,
spt_nominal / 10.0,
bt.sample_point / 10.0,
100.0 * spt_error / spt_nominal);
btc->printf_btr(&bt, false);
printf("\n");
}
static void do_list(void)
{
unsigned int i;
for (i = 0; i < ARRAY_SIZE(can_calc_consts); i++)
printf("%s\n", can_calc_consts[i].bittiming_const.name);
}
int main(int argc, char *argv[])
{
__u32 bitrate_nominal = 0;
struct calc_ref_clk opt_ref_clk = {
.name = "cmd-line",
};
const struct calc_ref_clk *ref_clk;
unsigned int spt_nominal = 0;
bool quiet = false, list = false, found = false;
char *name = NULL;
unsigned int i, j, k;
int opt;
const struct calc_bittiming_const *btc;
while ((opt = getopt(argc, argv, "b:c:lqs:?")) != -1) {
switch (opt) {
case 'b':
bitrate_nominal = atoi(optarg);
break;
case 'c':
opt_ref_clk.clk = strtoul(optarg, NULL, 10);
break;
case 'l':
list = true;
break;
case 'q':
quiet = true;
break;
case 's':
spt_nominal = strtoul(optarg, NULL, 10);
break;
case '?':
print_usage(basename(argv[0]));
exit(EXIT_SUCCESS);
break;
default:
print_usage(basename(argv[0]));
exit(EXIT_FAILURE);
break;
}
}
if (argc > optind + 1) {
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
if (argc == optind + 1)
name = argv[optind];
if (list) {
do_list();
exit(EXIT_SUCCESS);
}
if (spt_nominal && (spt_nominal >= 1000 || spt_nominal < 100)) {
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
for (i = 0; i < ARRAY_SIZE(can_calc_consts); i++) {
if (name && strcmp(can_calc_consts[i].bittiming_const.name, name))
continue;
found = true;
btc = &can_calc_consts[i];
for (j = 0; j < ARRAY_SIZE(btc->ref_clk); j++) {
if (opt_ref_clk.clk)
ref_clk = &opt_ref_clk;
else
ref_clk = &btc->ref_clk[j];
if (!ref_clk->clk)
break;
if (bitrate_nominal) {
print_bit_timing(btc, ref_clk, bitrate_nominal,
spt_nominal, quiet);
} else {
for (k = 0; k < ARRAY_SIZE(common_bitrates); k++)
print_bit_timing(btc, ref_clk,
common_bitrates[k],
spt_nominal, k);
}
printf("\n");
if (opt_ref_clk.clk)
break;
}
}
if (!found) {
printf("error: unknown CAN controller '%s', try one of these:\n\n", name);
do_list();
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
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