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
15 /* Kilobits and Megabits per second */
16 #define CAN_KBPS 1000UL
17 #define CAN_MBPS 1000000UL
18
19 /* Megahertz */
20 #define CAN_MHZ 1000000UL
21
22 #define CAN_CTRLMODE_TDC_MASK \
23 (CAN_CTRLMODE_TDC_AUTO | CAN_CTRLMODE_TDC_MANUAL)
24
25 /*
26 * struct can_tdc - CAN FD Transmission Delay Compensation parameters
27 *
28 * At high bit rates, the propagation delay from the TX pin to the RX
29 * pin of the transceiver causes measurement errors: the sample point
30 * on the RX pin might occur on the previous bit.
31 *
32 * To solve this issue, ISO 11898-1 introduces in section 11.3.3
33 * "Transmitter delay compensation" a SSP (Secondary Sample Point)
34 * equal to the distance from the start of the bit time on the TX pin
35 * to the actual measurement on the RX pin.
36 *
37 * This structure contains the parameters to calculate that SSP.
38 *
39 * -+----------- one bit ----------+-- TX pin
40 * |<--- Sample Point --->|
41 *
42 * --+----------- one bit ----------+-- RX pin
43 * |<-------- TDCV -------->|
44 * |<------- TDCO ------->|
45 * |<----------- Secondary Sample Point ---------->|
46 *
47 * To increase precision, contrary to the other bittiming parameters
48 * which are measured in time quanta, the TDC parameters are measured
49 * in clock periods (also referred as "minimum time quantum" in ISO
50 * 11898-1).
51 *
52 * @tdcv: Transmitter Delay Compensation Value. The time needed for
53 * the signal to propagate, i.e. the distance, in clock periods,
54 * from the start of the bit on the TX pin to when it is received
55 * on the RX pin. @tdcv depends on the controller modes:
56 *
57 * CAN_CTRLMODE_TDC_AUTO is set: The transceiver dynamically
58 * measures @tdcv for each transmitted CAN FD frame and the
59 * value provided here should be ignored.
60 *
61 * CAN_CTRLMODE_TDC_MANUAL is set: use the fixed provided @tdcv
62 * value.
63 *
64 * N.B. CAN_CTRLMODE_TDC_AUTO and CAN_CTRLMODE_TDC_MANUAL are
65 * mutually exclusive. Only one can be set at a time. If both
66 * CAN_TDC_CTRLMODE_AUTO and CAN_TDC_CTRLMODE_MANUAL are unset,
67 * TDC is disabled and all the values of this structure should be
68 * ignored.
69 *
70 * @tdco: Transmitter Delay Compensation Offset. Offset value, in
71 * clock periods, defining the distance between the start of the
72 * bit reception on the RX pin of the transceiver and the SSP
73 * position such that SSP = @tdcv + @tdco.
74 *
75 * @tdcf: Transmitter Delay Compensation Filter window. Defines the
76 * minimum value for the SSP position in clock periods. If the
77 * SSP position is less than @tdcf, then no delay compensations
78 * occur and the normal sampling point is used instead. The
79 * feature is enabled if and only if @tdcv is set to zero
80 * (automatic mode) and @tdcf is configured to a value greater
81 * than @tdco.
82 */
83 struct can_tdc {
84 u32 tdcv;
85 u32 tdco;
86 u32 tdcf;
87 };
88
89 /*
90 * struct can_tdc_const - CAN hardware-dependent constant for
91 * Transmission Delay Compensation
92 *
93 * @tdcv_min: Transmitter Delay Compensation Value minimum value. If
94 * the controller does not support manual mode for tdcv
95 * (c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is
96 * ignored.
97 * @tdcv_max: Transmitter Delay Compensation Value maximum value. If
98 * the controller does not support manual mode for tdcv
99 * (c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is
100 * ignored.
101 *
102 * @tdco_min: Transmitter Delay Compensation Offset minimum value.
103 * @tdco_max: Transmitter Delay Compensation Offset maximum value.
104 * Should not be zero. If the controller does not support TDC,
105 * then the pointer to this structure should be NULL.
106 *
107 * @tdcf_min: Transmitter Delay Compensation Filter window minimum
108 * value. If @tdcf_max is zero, this value is ignored.
109 * @tdcf_max: Transmitter Delay Compensation Filter window maximum
110 * value. Should be set to zero if the controller does not
111 * support this feature.
112 */
113 struct can_tdc_const {
114 u32 tdcv_min;
115 u32 tdcv_max;
116 u32 tdco_min;
117 u32 tdco_max;
118 u32 tdcf_min;
119 u32 tdcf_max;
120 };
121
122 #ifdef CONFIG_CAN_CALC_BITTIMING
123 int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
124 const struct can_bittiming_const *btc);
125
126 void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
127 const struct can_bittiming *dbt,
128 u32 *ctrlmode, u32 ctrlmode_supported);
129 #else /* !CONFIG_CAN_CALC_BITTIMING */
130 static inline int
can_calc_bittiming(struct net_device * dev,struct can_bittiming * bt,const struct can_bittiming_const * btc)131 can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
132 const struct can_bittiming_const *btc)
133 {
134 netdev_err(dev, "bit-timing calculation not available\n");
135 return -EINVAL;
136 }
137
138 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)139 can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
140 const struct can_bittiming *dbt,
141 u32 *ctrlmode, u32 ctrlmode_supported)
142 {
143 }
144 #endif /* CONFIG_CAN_CALC_BITTIMING */
145
146 int can_get_bittiming(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
151 /*
152 * can_bit_time() - Duration of one bit
153 *
154 * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
155 * additional information.
156 *
157 * Return: the number of time quanta in one bit.
158 */
can_bit_time(const struct can_bittiming * bt)159 static inline unsigned int can_bit_time(const struct can_bittiming *bt)
160 {
161 return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;
162 }
163
164 #endif /* !_CAN_BITTIMING_H */
165