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/* 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
/* Kilobits and Megabits per second */
#define CAN_KBPS 1000UL
#define CAN_MBPS 1000000UL
/* Megahertz */
#define CAN_MHZ 1000000UL
#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(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(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(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 */
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