leon,can: introduce common CAN baud-rate calculation function

Reimplemented the baud-rate algorithm from scratch to cope with
GRCAN, GRCANFD and OC_CAN devices.

Update #4323.

1 files changed, 144 insertions, 0 deletions

diff --git a/bsps/shared/grlib/can/canbtrs.c b/bsps/shared/grlib/can/canbtrs.c
new file mode 100644
index 0000000000..307547475c
--- /dev/null
+++ b/bsps/shared/grlib/can/canbtrs.c
@@ -0,0 +1,144 @@
+/* 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;
+}