1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix 3 * Copyright (C) 2006 Andrey Volkov, Varma Electronics 4 * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com> 5 * Copyright (C) 2021-2025 Vincent Mailhol <mailhol@kernel.org> 6 */ 7 8 #include <linux/units.h> 9 #include <linux/can/dev.h> 10 11 #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */ 12 13 /* CiA recommended sample points for Non Return to Zero encoding. */ 14 static int can_calc_sample_point_nrz(const struct can_bittiming *bt) 15 { 16 if (bt->bitrate > 800 * KILO /* BPS */) 17 return 750; 18 19 if (bt->bitrate > 500 * KILO /* BPS */) 20 return 800; 21 22 return 875; 23 } 24 25 /* Sample points for Pulse-Width Modulation encoding. */ 26 static int can_calc_sample_point_pwm(const struct can_bittiming *bt) 27 { 28 if (bt->bitrate > 15 * MEGA /* BPS */) 29 return 625; 30 31 if (bt->bitrate > 9 * MEGA /* BPS */) 32 return 600; 33 34 if (bt->bitrate > 4 * MEGA /* BPS */) 35 return 560; 36 37 return 520; 38 } 39 40 /* Bit-timing calculation derived from: 41 * 42 * Code based on LinCAN sources and H8S2638 project 43 * Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz 44 * Copyright 2005 Stanislav Marek 45 * email: pisa@cmp.felk.cvut.cz 46 * 47 * Calculates proper bit-timing parameters for a specified bit-rate 48 * and sample-point, which can then be used to set the bit-timing 49 * registers of the CAN controller. You can find more information 50 * in the header file linux/can/netlink.h. 51 */ 52 static int 53 can_update_sample_point(const struct can_bittiming_const *btc, 54 const unsigned int sample_point_reference, const unsigned int tseg, 55 unsigned int *tseg1_ptr, unsigned int *tseg2_ptr, 56 unsigned int *sample_point_error_ptr) 57 { 58 unsigned int sample_point_error, best_sample_point_error = UINT_MAX; 59 unsigned int sample_point, best_sample_point = 0; 60 unsigned int tseg1, tseg2; 61 int i; 62 63 for (i = 0; i <= 1; i++) { 64 tseg2 = tseg + CAN_SYNC_SEG - 65 (sample_point_reference * (tseg + CAN_SYNC_SEG)) / 66 1000 - i; 67 tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max); 68 tseg1 = tseg - tseg2; 69 if (tseg1 > btc->tseg1_max) { 70 tseg1 = btc->tseg1_max; 71 tseg2 = tseg - tseg1; 72 } 73 74 sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) / 75 (tseg + CAN_SYNC_SEG); 76 sample_point_error = abs(sample_point_reference - sample_point); 77 78 if (sample_point <= sample_point_reference && 79 sample_point_error < best_sample_point_error) { 80 best_sample_point = sample_point; 81 best_sample_point_error = sample_point_error; 82 *tseg1_ptr = tseg1; 83 *tseg2_ptr = tseg2; 84 } 85 } 86 87 if (sample_point_error_ptr) 88 *sample_point_error_ptr = best_sample_point_error; 89 90 return best_sample_point; 91 } 92 93 int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt, 94 const struct can_bittiming_const *btc, struct netlink_ext_ack *extack) 95 { 96 struct can_priv *priv = netdev_priv(dev); 97 unsigned int bitrate; /* current bitrate */ 98 unsigned int bitrate_error; /* diff between calculated and reference value */ 99 unsigned int best_bitrate_error = UINT_MAX; 100 unsigned int sample_point_error; /* diff between calculated and reference value */ 101 unsigned int best_sample_point_error = UINT_MAX; 102 unsigned int sample_point_reference; /* reference sample point */ 103 unsigned int best_tseg = 0; /* current best value for tseg */ 104 unsigned int best_brp = 0; /* current best value for brp */ 105 unsigned int brp, tsegall, tseg, tseg1 = 0, tseg2 = 0; 106 u64 v64; 107 int err; 108 109 if (bt->sample_point) 110 sample_point_reference = bt->sample_point; 111 else if (btc == priv->xl.data_bittiming_const && 112 (priv->ctrlmode & CAN_CTRLMODE_XL_TMS)) 113 sample_point_reference = can_calc_sample_point_pwm(bt); 114 else 115 sample_point_reference = can_calc_sample_point_nrz(bt); 116 117 /* tseg even = round down, odd = round up */ 118 for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1; 119 tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) { 120 tsegall = CAN_SYNC_SEG + tseg / 2; 121 122 /* Compute all possible tseg choices (tseg=tseg1+tseg2) */ 123 brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2; 124 125 /* choose brp step which is possible in system */ 126 brp = (brp / btc->brp_inc) * btc->brp_inc; 127 if (brp < btc->brp_min || brp > btc->brp_max) 128 continue; 129 130 bitrate = priv->clock.freq / (brp * tsegall); 131 bitrate_error = abs(bt->bitrate - bitrate); 132 133 /* tseg brp biterror */ 134 if (bitrate_error > best_bitrate_error) 135 continue; 136 137 /* reset sample point error if we have a better bitrate */ 138 if (bitrate_error < best_bitrate_error) 139 best_sample_point_error = UINT_MAX; 140 141 can_update_sample_point(btc, sample_point_reference, tseg / 2, 142 &tseg1, &tseg2, &sample_point_error); 143 if (sample_point_error >= best_sample_point_error) 144 continue; 145 146 best_sample_point_error = sample_point_error; 147 best_bitrate_error = bitrate_error; 148 best_tseg = tseg / 2; 149 best_brp = brp; 150 151 if (bitrate_error == 0 && sample_point_error == 0) 152 break; 153 } 154 155 if (best_bitrate_error) { 156 /* Error in one-hundredth of a percent */ 157 v64 = (u64)best_bitrate_error * 10000; 158 do_div(v64, bt->bitrate); 159 bitrate_error = (u32)v64; 160 /* print at least 0.01% if the error is smaller */ 161 bitrate_error = max(bitrate_error, 1U); 162 if (bitrate_error > CAN_CALC_MAX_ERROR) { 163 NL_SET_ERR_MSG_FMT(extack, 164 "bitrate error: %u.%02u%% too high", 165 bitrate_error / 100, 166 bitrate_error % 100); 167 return -EINVAL; 168 } 169 NL_SET_ERR_MSG_FMT(extack, 170 "bitrate error: %u.%02u%%", 171 bitrate_error / 100, bitrate_error % 100); 172 } 173 174 /* real sample point */ 175 bt->sample_point = can_update_sample_point(btc, sample_point_reference, 176 best_tseg, &tseg1, &tseg2, 177 NULL); 178 179 v64 = (u64)best_brp * 1000 * 1000 * 1000; 180 do_div(v64, priv->clock.freq); 181 bt->tq = (u32)v64; 182 bt->prop_seg = tseg1 / 2; 183 bt->phase_seg1 = tseg1 - bt->prop_seg; 184 bt->phase_seg2 = tseg2; 185 186 can_sjw_set_default(bt); 187 188 err = can_sjw_check(dev, bt, btc, extack); 189 if (err) 190 return err; 191 192 bt->brp = best_brp; 193 194 /* real bitrate */ 195 bt->bitrate = priv->clock.freq / 196 (bt->brp * can_bit_time(bt)); 197 198 return 0; 199 } 200 201 void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const, 202 const struct can_bittiming *dbt, 203 u32 tdc_mask, u32 *ctrlmode, u32 ctrlmode_supported) 204 205 { 206 u32 tdc_auto = tdc_mask & CAN_CTRLMODE_TDC_AUTO_MASK; 207 208 if (!tdc_const || !(ctrlmode_supported & tdc_auto)) 209 return; 210 211 *ctrlmode &= ~tdc_mask; 212 213 /* As specified in ISO 11898-1 section 11.3.3 "Transmitter 214 * delay compensation" (TDC) is only applicable if data BRP is 215 * one or two. 216 */ 217 if (dbt->brp == 1 || dbt->brp == 2) { 218 /* Sample point in clock periods */ 219 u32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg + 220 dbt->phase_seg1) * dbt->brp; 221 222 if (sample_point_in_tc < tdc_const->tdco_min) 223 return; 224 tdc->tdco = min(sample_point_in_tc, tdc_const->tdco_max); 225 *ctrlmode |= tdc_auto; 226 } 227 } 228 229 int can_calc_pwm(struct net_device *dev, struct netlink_ext_ack *extack) 230 { 231 struct can_priv *priv = netdev_priv(dev); 232 const struct can_pwm_const *pwm_const = priv->xl.pwm_const; 233 struct can_pwm *pwm = &priv->xl.pwm; 234 u32 xl_tqmin = can_bit_time_tqmin(&priv->xl.data_bittiming); 235 u32 xl_ns = can_tqmin_to_ns(xl_tqmin, priv->clock.freq); 236 u32 nom_tqmin = can_bit_time_tqmin(&priv->bittiming); 237 int pwm_per_bit_max = xl_tqmin / (pwm_const->pwms_min + pwm_const->pwml_min); 238 int pwm_per_bit; 239 u32 pwm_tqmin; 240 241 /* For 5 MB/s databitrate or greater, xl_ns < CAN_PWM_NS_MAX 242 * giving us a pwm_per_bit of 1 and the loop immediately breaks 243 */ 244 for (pwm_per_bit = DIV_ROUND_UP(xl_ns, CAN_PWM_NS_MAX); 245 pwm_per_bit <= pwm_per_bit_max; pwm_per_bit++) 246 if (xl_tqmin % pwm_per_bit == 0) 247 break; 248 249 if (pwm_per_bit > pwm_per_bit_max) { 250 NL_SET_ERR_MSG_FMT(extack, 251 "Can not divide the XL data phase's bit time: %u tqmin into multiple PWM symbols", 252 xl_tqmin); 253 return -EINVAL; 254 } 255 256 pwm_tqmin = xl_tqmin / pwm_per_bit; 257 pwm->pwms = DIV_ROUND_UP_POW2(pwm_tqmin, 4); 258 pwm->pwml = pwm_tqmin - pwm->pwms; 259 pwm->pwmo = nom_tqmin % pwm_tqmin; 260 261 return 0; 262 } 263