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Diffstat (limited to 'include/linux/can/bittiming.h')
| -rw-r--r-- | include/linux/can/bittiming.h | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/include/linux/can/bittiming.h b/include/linux/can/bittiming.h new file mode 100644 index 000000000000..ef0a77173e3c --- /dev/null +++ b/include/linux/can/bittiming.h @@ -0,0 +1,159 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* Copyright (c) 2020 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de> + * Copyright (c) 2021 Vincent Mailhol <mailhol.vincent@wanadoo.fr> + */ + +#ifndef _CAN_BITTIMING_H +#define _CAN_BITTIMING_H + +#include <linux/netdevice.h> +#include <linux/can/netlink.h> + +#define CAN_SYNC_SEG 1 + +#define CAN_BITRATE_UNSET 0 +#define CAN_BITRATE_UNKNOWN (-1U) + +#define CAN_CTRLMODE_TDC_MASK \ + (CAN_CTRLMODE_TDC_AUTO | CAN_CTRLMODE_TDC_MANUAL) + +/* + * struct can_tdc - CAN FD Transmission Delay Compensation parameters + * + * At high bit rates, the propagation delay from the TX pin to the RX + * pin of the transceiver causes measurement errors: the sample point + * on the RX pin might occur on the previous bit. + * + * To solve this issue, ISO 11898-1 introduces in section 11.3.3 + * "Transmitter delay compensation" a SSP (Secondary Sample Point) + * equal to the distance from the start of the bit time on the TX pin + * to the actual measurement on the RX pin. + * + * This structure contains the parameters to calculate that SSP. + * + * -+----------- one bit ----------+-- TX pin + * |<--- Sample Point --->| + * + * --+----------- one bit ----------+-- RX pin + * |<-------- TDCV -------->| + * |<------- TDCO ------->| + * |<----------- Secondary Sample Point ---------->| + * + * To increase precision, contrary to the other bittiming parameters + * which are measured in time quanta, the TDC parameters are measured + * in clock periods (also referred as "minimum time quantum" in ISO + * 11898-1). + * + * @tdcv: Transmitter Delay Compensation Value. The time needed for + * the signal to propagate, i.e. the distance, in clock periods, + * from the start of the bit on the TX pin to when it is received + * on the RX pin. @tdcv depends on the controller modes: + * + * CAN_CTRLMODE_TDC_AUTO is set: The transceiver dynamically + * measures @tdcv for each transmitted CAN FD frame and the + * value provided here should be ignored. + * + * CAN_CTRLMODE_TDC_MANUAL is set: use the fixed provided @tdcv + * value. + * + * N.B. CAN_CTRLMODE_TDC_AUTO and CAN_CTRLMODE_TDC_MANUAL are + * mutually exclusive. Only one can be set at a time. If both + * CAN_TDC_CTRLMODE_AUTO and CAN_TDC_CTRLMODE_MANUAL are unset, + * TDC is disabled and all the values of this structure should be + * ignored. + * + * @tdco: Transmitter Delay Compensation Offset. Offset value, in + * clock periods, defining the distance between the start of the + * bit reception on the RX pin of the transceiver and the SSP + * position such that SSP = @tdcv + @tdco. + * + * @tdcf: Transmitter Delay Compensation Filter window. Defines the + * minimum value for the SSP position in clock periods. If the + * SSP position is less than @tdcf, then no delay compensations + * occur and the normal sampling point is used instead. The + * feature is enabled if and only if @tdcv is set to zero + * (automatic mode) and @tdcf is configured to a value greater + * than @tdco. + */ +struct can_tdc { + u32 tdcv; + u32 tdco; + u32 tdcf; +}; + +/* + * struct can_tdc_const - CAN hardware-dependent constant for + * Transmission Delay Compensation + * + * @tdcv_min: Transmitter Delay Compensation Value minimum value. If + * the controller does not support manual mode for tdcv + * (c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is + * ignored. + * @tdcv_max: Transmitter Delay Compensation Value maximum value. If + * the controller does not support manual mode for tdcv + * (c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is + * ignored. + * + * @tdco_min: Transmitter Delay Compensation Offset minimum value. + * @tdco_max: Transmitter Delay Compensation Offset maximum value. + * Should not be zero. If the controller does not support TDC, + * then the pointer to this structure should be NULL. + * + * @tdcf_min: Transmitter Delay Compensation Filter window minimum + * value. If @tdcf_max is zero, this value is ignored. + * @tdcf_max: Transmitter Delay Compensation Filter window maximum + * value. Should be set to zero if the controller does not + * support this feature. + */ +struct can_tdc_const { + u32 tdcv_min; + u32 tdcv_max; + u32 tdco_min; + u32 tdco_max; + u32 tdcf_min; + u32 tdcf_max; +}; + +#ifdef CONFIG_CAN_CALC_BITTIMING +int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt, + const struct can_bittiming_const *btc); + +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); +#else /* !CONFIG_CAN_CALC_BITTIMING */ +static inline int +can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt, + const struct can_bittiming_const *btc) +{ + netdev_err(dev, "bit-timing calculation not available\n"); + return -EINVAL; +} + +static inline 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) +{ +} +#endif /* CONFIG_CAN_CALC_BITTIMING */ + +int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt, + const struct can_bittiming_const *btc, + const u32 *bitrate_const, + const unsigned int bitrate_const_cnt); + +/* + * can_bit_time() - Duration of one bit + * + * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for + * additional information. + * + * Return: the number of time quanta in one bit. + */ +static inline unsigned int can_bit_time(const struct can_bittiming *bt) +{ + return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2; +} + +#endif /* !_CAN_BITTIMING_H */ |