1/* SPDX-License-Identifier: GPL-2.0-only */
2/* Copyright (c) 2020 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
3 * Copyright (c) 2021 Vincent Mailhol <mailhol.vincent@wanadoo.fr>
4 */
5
6#ifndef _CAN_BITTIMING_H
7#define _CAN_BITTIMING_H
8
9#include <linux/netdevice.h>
10#include <linux/can/netlink.h>
11
12#define CAN_SYNC_SEG 1
13
14#define CAN_BITRATE_UNSET 0
15#define CAN_BITRATE_UNKNOWN (-1U)
16
17#define CAN_CTRLMODE_TDC_MASK					\
18	(CAN_CTRLMODE_TDC_AUTO | CAN_CTRLMODE_TDC_MANUAL)
19
20/*
21 * struct can_tdc - CAN FD Transmission Delay Compensation parameters
22 *
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.
26 *
27 * To solve this issue, ISO 11898-1 introduces in section 11.3.3
28 * "Transmitter delay compensation" a SSP (Secondary Sample Point)
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.
31 *
32 * This structure contains the parameters to calculate that SSP.
33 *
34 * -+----------- one bit ----------+-- TX pin
35 *  |<--- Sample Point --->|
36 *
37 *                         --+----------- one bit ----------+-- RX pin
38 *  |<-------- TDCV -------->|
39 *                           |<------- TDCO ------->|
40 *  |<----------- Secondary Sample Point ---------->|
41 *
42 * To increase precision, contrary to the other bittiming parameters
43 * which are measured in time quanta, the TDC parameters are measured
44 * in clock periods (also referred as "minimum time quantum" in ISO
45 * 11898-1).
46 *
47 * @tdcv: Transmitter Delay Compensation Value. The time needed for
48 *	the signal to propagate, i.e. the distance, in clock periods,
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:
51 *
52 *	  CAN_CTRLMODE_TDC_AUTO is set: The transceiver dynamically
53 *	  measures @tdcv for each transmitted CAN FD frame and the
54 *	  value provided here should be ignored.
55 *
56 *	  CAN_CTRLMODE_TDC_MANUAL is set: use the fixed provided @tdcv
57 *	  value.
58 *
59 *	N.B. CAN_CTRLMODE_TDC_AUTO and CAN_CTRLMODE_TDC_MANUAL are
60 *	mutually exclusive. Only one can be set at a time. If both
61 *	CAN_TDC_CTRLMODE_AUTO and CAN_TDC_CTRLMODE_MANUAL are unset,
62 *	TDC is disabled and all the values of this structure should be
63 *	ignored.
64 *
65 * @tdco: Transmitter Delay Compensation Offset. Offset value, in
66 *	clock periods, defining the distance between the start of the
67 *	bit reception on the RX pin of the transceiver and the SSP
68 *	position such that SSP = @tdcv + @tdco.
69 *
70 * @tdcf: Transmitter Delay Compensation Filter window. Defines the
71 *	minimum value for the SSP position in clock periods. If the
72 *	SSP position is less than @tdcf, then no delay compensations
73 *	occur and the normal sampling point is used instead. The
74 *	feature is enabled if and only if @tdcv is set to zero
75 *	(automatic mode) and @tdcf is configured to a value greater
76 *	than @tdco.
77 */
78struct can_tdc {
79	u32 tdcv;
80	u32 tdco;
81	u32 tdcf;
82};
83
84/*
85 * struct can_tdc_const - CAN hardware-dependent constant for
86 *	Transmission Delay Compensation
87 *
88 * @tdcv_min: Transmitter Delay Compensation Value minimum value. If
89 *	the controller does not support manual mode for tdcv
90 *	(c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is
91 *	ignored.
92 * @tdcv_max: Transmitter Delay Compensation Value maximum value. If
93 *	the controller does not support manual mode for tdcv
94 *	(c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is
95 *	ignored.
96 *
97 * @tdco_min: Transmitter Delay Compensation Offset minimum value.
98 * @tdco_max: Transmitter Delay Compensation Offset maximum value.
99 *	Should not be zero. If the controller does not support TDC,
100 *	then the pointer to this structure should be NULL.
101 *
102 * @tdcf_min: Transmitter Delay Compensation Filter window minimum
103 *	value. If @tdcf_max is zero, this value is ignored.
104 * @tdcf_max: Transmitter Delay Compensation Filter window maximum
105 *	value. Should be set to zero if the controller does not
106 *	support this feature.
107 */
108struct can_tdc_const {
109	u32 tdcv_min;
110	u32 tdcv_max;
111	u32 tdco_min;
112	u32 tdco_max;
113	u32 tdcf_min;
114	u32 tdcf_max;
115};
116
117#ifdef CONFIG_CAN_CALC_BITTIMING
118int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
119		       const struct can_bittiming_const *btc, struct netlink_ext_ack *extack);
120
121void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
122		   const struct can_bittiming *dbt,
123		   u32 *ctrlmode, u32 ctrlmode_supported);
124#else /* !CONFIG_CAN_CALC_BITTIMING */
125static inline int
126can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
127		   const struct can_bittiming_const *btc, struct netlink_ext_ack *extack)
128{
129	netdev_err(dev, "bit-timing calculation not available\n");
130	return -EINVAL;
131}
132
133static inline void
134can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
135	      const struct can_bittiming *dbt,
136	      u32 *ctrlmode, u32 ctrlmode_supported)
137{
138}
139#endif /* CONFIG_CAN_CALC_BITTIMING */
140
141void can_sjw_set_default(struct can_bittiming *bt);
142
143int can_sjw_check(const struct net_device *dev, const struct can_bittiming *bt,
144		  const struct can_bittiming_const *btc, struct netlink_ext_ack *extack);
145
146int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
147		      const struct can_bittiming_const *btc,
148		      const u32 *bitrate_const,
149		      const unsigned int bitrate_const_cnt,
150		      struct netlink_ext_ack *extack);
151
152/*
153 * can_bit_time() - Duration of one bit
154 *
155 * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
156 * additional information.
157 *
158 * Return: the number of time quanta in one bit.
159 */
160static inline unsigned int can_bit_time(const struct can_bittiming *bt)
161{
162	return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;
163}
164
165#endif /* !_CAN_BITTIMING_H */
166