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