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 | */ |
78 | struct 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 | */ |
108 | struct 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 |
118 | int 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 | |
121 | void 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 */ |
125 | static inline int |
126 | can_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 | |
133 | static inline void |
134 | can_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 | |
141 | void can_sjw_set_default(struct can_bittiming *bt); |
142 | |
143 | int 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 | |
146 | int 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 | */ |
160 | static 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 | |