can: dev: add a helper function to calculate the duration of one bit
Rename macro CAN_CALC_SYNC_SEG to CAN_SYNC_SEG and make it available through include/linux/can/dev.h Add an helper function can_bit_time() which returns the duration (in time quanta) of one CAN bit. Rationale for this patch: the sync segment and the bit time are two concepts which are defined in the CAN ISO standard. Device drivers for CAN might need those. Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for additional information. Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> Link: https://lore.kernel.org/r/20201002154219.4887-6-mailhol.vincent@wanadoo.fr [mkl: Let can_bit_time() return an unsinged int, make argument const] Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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@ -60,7 +60,6 @@ EXPORT_SYMBOL_GPL(can_len2dlc);
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#ifdef CONFIG_CAN_CALC_BITTIMING
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#ifdef CONFIG_CAN_CALC_BITTIMING
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#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
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#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
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#define CAN_CALC_SYNC_SEG 1
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/* Bit-timing calculation derived from:
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/* Bit-timing calculation derived from:
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*
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*
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@ -86,8 +85,8 @@ can_update_sample_point(const struct can_bittiming_const *btc,
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int i;
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int i;
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for (i = 0; i <= 1; i++) {
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for (i = 0; i <= 1; i++) {
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tseg2 = tseg + CAN_CALC_SYNC_SEG -
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tseg2 = tseg + CAN_SYNC_SEG -
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(sample_point_nominal * (tseg + CAN_CALC_SYNC_SEG)) /
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(sample_point_nominal * (tseg + CAN_SYNC_SEG)) /
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1000 - i;
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1000 - i;
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tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
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tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
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tseg1 = tseg - tseg2;
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tseg1 = tseg - tseg2;
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@ -96,8 +95,8 @@ can_update_sample_point(const struct can_bittiming_const *btc,
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tseg2 = tseg - tseg1;
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tseg2 = tseg - tseg1;
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}
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}
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sample_point = 1000 * (tseg + CAN_CALC_SYNC_SEG - tseg2) /
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sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) /
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(tseg + CAN_CALC_SYNC_SEG);
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(tseg + CAN_SYNC_SEG);
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sample_point_error = abs(sample_point_nominal - sample_point);
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sample_point_error = abs(sample_point_nominal - sample_point);
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if (sample_point <= sample_point_nominal &&
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if (sample_point <= sample_point_nominal &&
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@ -145,7 +144,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
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/* tseg even = round down, odd = round up */
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/* tseg even = round down, odd = round up */
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for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
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for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
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tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
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tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
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tsegall = CAN_CALC_SYNC_SEG + tseg / 2;
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tsegall = CAN_SYNC_SEG + tseg / 2;
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/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
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/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
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brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
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brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
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@ -223,7 +222,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
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/* real bitrate */
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/* real bitrate */
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bt->bitrate = priv->clock.freq /
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bt->bitrate = priv->clock.freq /
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(bt->brp * (CAN_CALC_SYNC_SEG + tseg1 + tseg2));
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(bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2));
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return 0;
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return 0;
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}
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}
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@ -82,6 +82,21 @@ struct can_priv {
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#endif
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#endif
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};
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};
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#define CAN_SYNC_SEG 1
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/*
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* can_bit_time() - Duration of one bit
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*
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* Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
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* additional information.
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*
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* Return: the number of time quanta in one bit.
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*/
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static inline unsigned int can_bit_time(const struct can_bittiming *bt)
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{
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return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;
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}
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/*
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/*
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* get_can_dlc(value) - helper macro to cast a given data length code (dlc)
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* get_can_dlc(value) - helper macro to cast a given data length code (dlc)
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* to u8 and ensure the dlc value to be max. 8 bytes.
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* to u8 and ensure the dlc value to be max. 8 bytes.
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