/* SPDX-License-Identifier: GPL-2.0-only */ /* Copyright (c) 2020 Pengutronix, Marc Kleine-Budde <[email protected]> * Copyright (c) 2021 Vincent Mailhol <[email protected]> */ #ifndef _CAN_BITTIMING_H #define _CAN_BITTIMING_H #include <linux/netdevice.h> #include <linux/can/netlink.h> #define CAN_SYNC_SEG … #define CAN_BITRATE_UNSET … #define CAN_BITRATE_UNKNOWN … #define CAN_CTRLMODE_TDC_MASK … /* * 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 { … }; /* * 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 { … }; #ifdef CONFIG_CAN_CALC_BITTIMING int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt, const struct can_bittiming_const *btc, struct netlink_ext_ack *extack); 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, struct netlink_ext_ack *extack) { 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 */ void can_sjw_set_default(struct can_bittiming *bt); int can_sjw_check(const struct net_device *dev, const struct can_bittiming *bt, const struct can_bittiming_const *btc, struct netlink_ext_ack *extack); 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, struct netlink_ext_ack *extack); /* * 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) { … } #endif /* !_CAN_BITTIMING_H */
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