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