124 lines
3.9 KiB
C
124 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/* Copyright (c) 2020 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
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* Copyright (c) 2021 Vincent Mailhol <mailhol.vincent@wanadoo.fr>
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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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/* Kilobits and Megabits per second */
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#define CAN_KBPS 1000UL
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#define CAN_MBPS 1000000UL
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/* Megahertz */
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#define CAN_MHZ 1000000UL
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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, in time quanta, from the start of the bit
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* time on the TX pin 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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* @tdcv: Transmitter Delay Compensation Value. Distance, in time
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* quanta, from when the bit is sent on the TX pin to when it is
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* received on the RX pin of the transmitter. Possible options:
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*
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* O: automatic mode. The controller dynamically measure @tdcv
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* for each transmitted CAN FD frame.
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*
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* Other values: manual mode. Use the fixed provided value.
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*
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* @tdco: Transmitter Delay Compensation Offset. Offset value, in time
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* quanta, defining the distance between the start of the bit
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* reception on the RX pin of the transceiver and the SSP
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* position such as SSP = @tdcv + @tdco.
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*
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* If @tdco is zero, then TDC is disabled and both @tdcv and
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* @tdcf should be ignored.
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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 time quanta. If SSP is
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* less than @tdcf, then no delay compensations occur and the
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* normal sampling point is used instead. The feature is enabled
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* if and only if @tdcv is set to zero (automatic mode) and @tdcf
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* is configured to a value greater 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_max: Transmitter Delay Compensation Value maximum value.
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* Should be set to zero if the controller does not support
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* manual mode for tdcv.
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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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* @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_max;
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u32 tdco_max;
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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(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 net_device *dev);
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#else /* !CONFIG_CAN_CALC_BITTIMING */
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static inline int
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can_calc_bittiming(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 can_calc_tdco(struct net_device *dev)
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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(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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