| // 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 can_tdc *tdc, const struct can_tdc_const *tdc_const, |
| const struct can_bittiming *dbt, |
| u32 *ctrlmode, u32 ctrlmode_supported) |
| |
| { |
| if (!tdc_const || !(ctrlmode_supported & CAN_CTRLMODE_TDC_AUTO)) |
| return; |
| |
| *ctrlmode &= ~CAN_CTRLMODE_TDC_MASK; |
| |
| /* 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) { |
| /* Sample point in clock periods */ |
| u32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg + |
| dbt->phase_seg1) * dbt->brp; |
| |
| if (sample_point_in_tc < tdc_const->tdco_min) |
| return; |
| tdc->tdco = min(sample_point_in_tc, tdc_const->tdco_max); |
| *ctrlmode |= CAN_CTRLMODE_TDC_AUTO; |
| } |
| } |
| #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; |
| } |
