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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 | // SPDX-License-Identifier: GPL-2.0-only /* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix * Copyright (C) 2006 Andrey Volkov, Varma Electronics * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com> */ #include <linux/can/dev.h> #ifdef CONFIG_CAN_CALC_BITTIMING #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */ /* 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_sample_point(const struct can_bittiming_const *btc, unsigned int sample_point_nominal, unsigned int tseg, unsigned int *tseg1_ptr, unsigned int *tseg2_ptr, unsigned int *sample_point_error_ptr) { unsigned int sample_point_error, best_sample_point_error = UINT_MAX; unsigned int sample_point, best_sample_point = 0; unsigned int tseg1, tseg2; int i; for (i = 0; i <= 1; i++) { tseg2 = tseg + CAN_SYNC_SEG - (sample_point_nominal * (tseg + CAN_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; } sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) / (tseg + CAN_SYNC_SEG); sample_point_error = abs(sample_point_nominal - sample_point); if (sample_point <= sample_point_nominal && sample_point_error < best_sample_point_error) { best_sample_point = sample_point; best_sample_point_error = sample_point_error; *tseg1_ptr = tseg1; *tseg2_ptr = tseg2; } } if (sample_point_error_ptr) *sample_point_error_ptr = best_sample_point_error; return best_sample_point; } 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 bitrate; /* current bitrate */ unsigned int bitrate_error; /* difference between current and nominal value */ unsigned int best_bitrate_error = UINT_MAX; unsigned int sample_point_error; /* difference between current and nominal value */ unsigned int best_sample_point_error = UINT_MAX; unsigned int sample_point_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) { sample_point_nominal = bt->sample_point; } else { if (bt->bitrate > 800 * CAN_KBPS) sample_point_nominal = 750; else if (bt->bitrate > 500 * CAN_KBPS) sample_point_nominal = 800; else sample_point_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_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; bitrate = priv->clock.freq / (brp * tsegall); bitrate_error = abs(bt->bitrate - bitrate); /* tseg brp biterror */ if (bitrate_error > best_bitrate_error) continue; /* reset sample point error if we have a better bitrate */ if (bitrate_error < best_bitrate_error) best_sample_point_error = UINT_MAX; can_update_sample_point(btc, sample_point_nominal, tseg / 2, &tseg1, &tseg2, &sample_point_error); if (sample_point_error > best_sample_point_error) continue; best_sample_point_error = sample_point_error; best_bitrate_error = bitrate_error; best_tseg = tseg / 2; best_brp = brp; if (bitrate_error == 0 && sample_point_error == 0) break; } if (best_bitrate_error) { /* Error in one-tenth of a percent */ v64 = (u64)best_bitrate_error * 1000; do_div(v64, bt->bitrate); bitrate_error = (u32)v64; if (bitrate_error > CAN_CALC_MAX_ERROR) { netdev_err(dev, "bitrate error %d.%d%% too high\n", bitrate_error / 10, bitrate_error % 10); return -EDOM; } netdev_warn(dev, "bitrate error %d.%d%%\n", bitrate_error / 10, bitrate_error % 10); } /* real sample point */ bt->sample_point = can_update_sample_point(btc, sample_point_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 bitrate */ bt->bitrate = priv->clock.freq / (bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2)); return 0; } void can_calc_tdco(struct net_device *dev) { struct can_priv *priv = netdev_priv(dev); const struct can_bittiming *dbt = &priv->data_bittiming; struct can_tdc *tdc = &priv->tdc; const struct can_tdc_const *tdc_const = priv->tdc_const; if (!tdc_const) return; /* As specified in ISO 11898-1 section 11.3.3 "Transmitter * delay compensation" (TDC) is only applicable if data BRP is * one or two. */ if (dbt->brp == 1 || dbt->brp == 2) { /* Reuse "normal" sample point and convert it to time quanta */ u32 sample_point_in_tq = can_bit_time(dbt) * dbt->sample_point / 1000; tdc->tdco = min(sample_point_in_tq, tdc_const->tdco_max); } else { tdc->tdco = 0; } } #endif /* CONFIG_CAN_CALC_BITTIMING */ /* Checks the validity of the specified bit-timing parameters prop_seg, * phase_seg1, phase_seg2 and sjw and tries to determine the bitrate * prescaler value brp. You can find more information in the header * file linux/can/netlink.h. */ static int can_fixup_bittiming(struct net_device *dev, struct can_bittiming *bt, const struct can_bittiming_const *btc) { struct can_priv *priv = netdev_priv(dev); unsigned int tseg1, alltseg; u64 brp64; tseg1 = bt->prop_seg + bt->phase_seg1; if (!bt->sjw) bt->sjw = 1; if (bt->sjw > btc->sjw_max || tseg1 < btc->tseg1_min || tseg1 > btc->tseg1_max || bt->phase_seg2 < btc->tseg2_min || bt->phase_seg2 > btc->tseg2_max) return -ERANGE; brp64 = (u64)priv->clock.freq * (u64)bt->tq; if (btc->brp_inc > 1) do_div(brp64, btc->brp_inc); brp64 += 500000000UL - 1; do_div(brp64, 1000000000UL); /* the practicable BRP */ if (btc->brp_inc > 1) brp64 *= btc->brp_inc; bt->brp = (u32)brp64; if (bt->brp < btc->brp_min || bt->brp > btc->brp_max) return -EINVAL; alltseg = bt->prop_seg + bt->phase_seg1 + bt->phase_seg2 + 1; bt->bitrate = priv->clock.freq / (bt->brp * alltseg); bt->sample_point = ((tseg1 + 1) * 1000) / alltseg; return 0; } /* Checks the validity of predefined bitrate settings */ static int can_validate_bitrate(struct net_device *dev, struct can_bittiming *bt, const u32 *bitrate_const, const unsigned int bitrate_const_cnt) { struct can_priv *priv = netdev_priv(dev); unsigned int i; for (i = 0; i < bitrate_const_cnt; i++) { if (bt->bitrate == bitrate_const[i]) break; } if (i >= priv->bitrate_const_cnt) return -EINVAL; return 0; } int can_get_bittiming(struct net_device *dev, struct can_bittiming *bt, const struct can_bittiming_const *btc, const u32 *bitrate_const, const unsigned int bitrate_const_cnt) { int err; /* Depending on the given can_bittiming parameter structure the CAN * timing parameters are calculated based on the provided bitrate OR * alternatively the CAN timing parameters (tq, prop_seg, etc.) are * provided directly which are then checked and fixed up. */ if (!bt->tq && bt->bitrate && btc) err = can_calc_bittiming(dev, bt, btc); else if (bt->tq && !bt->bitrate && btc) err = can_fixup_bittiming(dev, bt, btc); else if (!bt->tq && bt->bitrate && bitrate_const) err = can_validate_bitrate(dev, bt, bitrate_const, bitrate_const_cnt); else err = -EINVAL; return err; } |