/* SPDX-License-Identifier: BSD-2-Clause */
/**
* @file
*
* @ingroup can
*
* @brief Common CAN baud-rate routines for OCCAN/GRCAN/GRCANFD controllers
*
* Implements common routines for calculating CAN baud-rate parameters from
* a user provided baud-rate speed.
*/
/*
* Copyright (C) 2019, 2020 Cobham Gailer AB
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <grlib/canbtrs.h>
/*#define GRLIB_CANBTRS_DEBUG*/
/* Calculate CAN baud-rate generation parameters from requested baud-rate */
int grlib_canbtrs_calc_timing(
unsigned int baud,
unsigned int core_hz,
unsigned int sampl_pt,
struct grlib_canbtrs_ranges *br,
struct grlib_canbtrs_timing *timing
)
{
int best_error = 2000000000, best_tseg=0, best_scaler=0;
int tseg=0, tseg1=0, tseg2=0, sc, tmp, error;
/* Default to 80% sample point */
if ((sampl_pt < 50) || (sampl_pt > 99))
sampl_pt = 80;
/* step though all TSEG1+TSEG2 values possible */
for (tseg = (br->min_tseg1 + br->min_tseg2);
tseg <= (br->max_tseg1 + br->max_tseg2);
tseg++) {
/* calculate scaler */
tmp = ((br->divfactor + tseg) * baud);
sc = (core_hz * 2)/ tmp - core_hz / tmp;
if (sc <= 0 || sc > br->max_scaler)
continue;
if (br->has_bpr &&
(((sc > 256 * 1) && (sc <= 256 * 2) && (sc & 0x1)) ||
((sc > 256 * 2) && (sc <= 256 * 4) && (sc & 0x3)) ||
((sc > 256 * 4) && (sc <= 256 * 8) && (sc & 0x7))))
continue;
error = baud - core_hz / (sc * (br->divfactor + tseg));
#ifdef GRLIB_CANBTRS_DEBUG
printf(" baud=%d, tseg=%d, sc=%d, error=%d\n",
baud, tseg, sc, error);
#endif
if (error < 0)
error = -error;
/* tseg is increasing, so we accept higher tseg with the same
* baudrate to get better sampling point.
*/
if (error <= best_error) {
best_error = error;
best_tseg = tseg;
best_scaler = sc;
#ifdef GRLIB_CANBTRS_DEBUG
printf(" ! best baud=%d\n",
core_hz/(sc * (br->divfactor + tseg)));
#endif
}
}
/* return an error if 5% off baud-rate */
if (best_error && (baud / best_error <= 5)) {
return -2;
} else if (!timing) {
return 0; /* nothing to store result in, but a valid bitrate can be calculated */
}
tseg2 = (best_tseg + br->divfactor) -
((sampl_pt * (best_tseg + br->divfactor)) / 100);
if (tseg2 < br->min_tseg2) {
tseg2 = br->min_tseg2;
} else if (tseg2 > br->max_tseg2) {
tseg2 = br->max_tseg2;
}
tseg1 = best_tseg - tseg2;
if (tseg1 > br->max_tseg1) {
tseg1 = br->max_tseg1;
tseg2 = best_tseg - tseg1;
} else if (tseg1 < br->min_tseg1) {
tseg1 = br->min_tseg1;
tseg2 = best_tseg - tseg1;
}
/* Get scaler and BPR from pseudo SCALER clock */
if (best_scaler <= 256) {
timing->scaler = best_scaler - 1;
timing->bpr = 0;
} else if (best_scaler <= 256 * 2) {
timing->scaler = ((best_scaler + 1) >> 1) - 1;
timing->bpr = 1;
} else if (best_scaler <= 256 * 4) {
timing->scaler = ((best_scaler + 1) >> 2) - 1;
timing->bpr = 2;
} else {
timing->scaler = ((best_scaler + 1) >> 3) - 1;
timing->bpr = 3;
}
timing->ps1 = tseg1;
timing->ps2 = tseg2;
timing->rsj = 1;
#ifdef GRLIB_CANBTRS_DEBUG
printf(" ! result: sc=%d,bpr=%d,ps1=%d,ps2=%d\n", timing->scaler, timing->bpr, timing->ps1, timing->ps2);
#endif
return 0;
}
