diff options
Diffstat (limited to 'drivers/net/can/dev/calc_bittiming.c')
| -rw-r--r-- | drivers/net/can/dev/calc_bittiming.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/drivers/net/can/dev/calc_bittiming.c b/drivers/net/can/dev/calc_bittiming.c new file mode 100644 index 000000000000..cc4022241553 --- /dev/null +++ b/drivers/net/can/dev/calc_bittiming.c @@ -0,0 +1,262 @@ +// 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> + * Copyright (C) 2021-2025 Vincent Mailhol <mailhol@kernel.org> + */ + +#include <linux/units.h> +#include <linux/can/dev.h> + +#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */ + +/* CiA recommended sample points for Non Return to Zero encoding. */ +static int can_calc_sample_point_nrz(const struct can_bittiming *bt) +{ + if (bt->bitrate > 800 * KILO /* BPS */) + return 750; + + if (bt->bitrate > 500 * KILO /* BPS */) + return 800; + + return 875; +} + +/* Sample points for Pulse-Width Modulation encoding. */ +static int can_calc_sample_point_pwm(const struct can_bittiming *bt) +{ + if (bt->bitrate > 15 * MEGA /* BPS */) + return 625; + + if (bt->bitrate > 9 * MEGA /* BPS */) + return 600; + + if (bt->bitrate > 4 * MEGA /* BPS */) + return 560; + + return 520; +} + +/* 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, + const unsigned int sample_point_reference, const 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_reference * (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_reference - sample_point); + + if (sample_point <= sample_point_reference && + 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(const struct net_device *dev, struct can_bittiming *bt, + const struct can_bittiming_const *btc, struct netlink_ext_ack *extack) +{ + struct can_priv *priv = netdev_priv(dev); + unsigned int bitrate; /* current bitrate */ + unsigned int bitrate_error; /* diff between calculated and reference value */ + unsigned int best_bitrate_error = UINT_MAX; + unsigned int sample_point_error; /* diff between calculated and reference value */ + unsigned int best_sample_point_error = UINT_MAX; + unsigned int sample_point_reference; /* reference 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; + int err; + + if (bt->sample_point) + sample_point_reference = bt->sample_point; + else if (btc == priv->xl.data_bittiming_const && + (priv->ctrlmode & CAN_CTRLMODE_XL_TMS)) + sample_point_reference = can_calc_sample_point_pwm(bt); + else + sample_point_reference = can_calc_sample_point_nrz(bt); + + /* 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_reference, 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-hundredth of a percent */ + v64 = (u64)best_bitrate_error * 10000; + do_div(v64, bt->bitrate); + bitrate_error = (u32)v64; + /* print at least 0.01% if the error is smaller */ + bitrate_error = max(bitrate_error, 1U); + if (bitrate_error > CAN_CALC_MAX_ERROR) { + NL_SET_ERR_MSG_FMT(extack, + "bitrate error: %u.%02u%% too high", + bitrate_error / 100, + bitrate_error % 100); + return -EINVAL; + } + NL_SET_ERR_MSG_FMT(extack, + "bitrate error: %u.%02u%%", + bitrate_error / 100, bitrate_error % 100); + } + + /* real sample point */ + bt->sample_point = can_update_sample_point(btc, sample_point_reference, + 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; + + can_sjw_set_default(bt); + + err = can_sjw_check(dev, bt, btc, extack); + if (err) + return err; + + bt->brp = best_brp; + + /* real bitrate */ + bt->bitrate = priv->clock.freq / + (bt->brp * can_bit_time(bt)); + + return 0; +} + +void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const, + const struct can_bittiming *dbt, + u32 tdc_mask, u32 *ctrlmode, u32 ctrlmode_supported) + +{ + u32 tdc_auto = tdc_mask & CAN_CTRLMODE_TDC_AUTO_MASK; + + if (!tdc_const || !(ctrlmode_supported & tdc_auto)) + return; + + *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 |= tdc_auto; + } +} + +int can_calc_pwm(struct net_device *dev, struct netlink_ext_ack *extack) +{ + struct can_priv *priv = netdev_priv(dev); + const struct can_pwm_const *pwm_const = priv->xl.pwm_const; + struct can_pwm *pwm = &priv->xl.pwm; + u32 xl_tqmin = can_bit_time_tqmin(&priv->xl.data_bittiming); + u32 xl_ns = can_tqmin_to_ns(xl_tqmin, priv->clock.freq); + u32 nom_tqmin = can_bit_time_tqmin(&priv->bittiming); + int pwm_per_bit_max = xl_tqmin / (pwm_const->pwms_min + pwm_const->pwml_min); + int pwm_per_bit; + u32 pwm_tqmin; + + /* For 5 MB/s databitrate or greater, xl_ns < CAN_PWM_NS_MAX + * giving us a pwm_per_bit of 1 and the loop immediately breaks + */ + for (pwm_per_bit = DIV_ROUND_UP(xl_ns, CAN_PWM_NS_MAX); + pwm_per_bit <= pwm_per_bit_max; pwm_per_bit++) + if (xl_tqmin % pwm_per_bit == 0) + break; + + if (pwm_per_bit > pwm_per_bit_max) { + NL_SET_ERR_MSG_FMT(extack, + "Can not divide the XL data phase's bit time: %u tqmin into multiple PWM symbols", + xl_tqmin); + return -EINVAL; + } + + pwm_tqmin = xl_tqmin / pwm_per_bit; + pwm->pwms = DIV_ROUND_UP_POW2(pwm_tqmin, 4); + pwm->pwml = pwm_tqmin - pwm->pwms; + pwm->pwmo = nom_tqmin % pwm_tqmin; + + return 0; +} |