linux/can/bittiming.h

1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /* Copyright (c) 2020 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
15 #define CAN_BITRATE_UNKNOWN (-1U)
21  * struct can_tdc - CAN FD Transmission Delay Compensation parameters
23  * At high bit rates, the propagation delay from the TX pin to the RX
24  * pin of the transceiver causes measurement errors: the sample point
25  * on the RX pin might occur on the previous bit.
27  * To solve this issue, ISO 11898-1 introduces in section 11.3.3
29  * equal to the distance from the start of the bit time on the TX pin
30  * to the actual measurement on the RX pin.
34  * -+----------- one bit ----------+-- TX pin
35  *  |<--- Sample Point --->|
37  *                         --+----------- one bit ----------+-- RX pin
38  *  |<-------- TDCV -------->|
39  *                           |<------- TDCO ------->|
40  *  |<----------- Secondary Sample Point ---------->|
45  * 11898-1).
49  *	from the start of the bit on the TX pin to when it is received
50  *	on the RX pin. @tdcv depends on the controller modes:
67  *	bit reception on the RX pin of the transceiver and the SSP
85  * struct can_tdc_const - CAN hardware-dependent constant for
129 	netdev_err(dev, "bit-timing calculation not available\n");  in can_calc_bittiming()
130 	return -EINVAL;  in can_calc_bittiming()
153  * can_bit_time() - Duration of one bit
155  * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
162 	return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;  in can_bit_time()