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can: dev: add can_tdc_get_relative_tdco() helper function

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struct can_tdc::tdco represents the absolute offset from TDCV. Some
controllers use instead an offset relative to the Sample Point (SP)
such that:
| SSP = TDCV + absolute TDCO
|     = TDCV + SP + relative TDCO

Consequently:
| relative TDCO = absolute TDCO - SP

The function can_tdc_get_relative_tdco() allow to retrieve this
relative TDCO value.

Link: https://lore.kernel.org/all/20210918095637.20108-7-mailhol.vincent@wanadoo.fr
CC: Stefan Mätje <Stefan.Maetje@esd.eu>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Vincent Mailhol 2021-09-18 18:56:37 +09:00 committed by Marc Kleine-Budde
parent e8060f08cd
commit fa759a9395
1 changed files with 29 additions and 0 deletions
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29
include/linux/can/dev.h
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@ -102,6 +102,35 @@ static inline bool can_tdc_is_enabled(const struct can_priv *priv)
return !!(priv->ctrlmode & CAN_CTRLMODE_TDC_MASK);
}
/*
* can_get_relative_tdco() - TDCO relative to the sample point
*
* struct can_tdc::tdco represents the absolute offset from TDCV. Some
* controllers use instead an offset relative to the Sample Point (SP)
* such that:
*
* SSP = TDCV + absolute TDCO
* = TDCV + SP + relative TDCO
*
* -+----------- one bit ----------+-- TX pin
* |<--- Sample Point --->|
*
* --+----------- one bit ----------+-- RX pin
* |<-------- TDCV -------->|
* |<------------------------>| absolute TDCO
* |<--- Sample Point --->|
* | |<->| relative TDCO
* |<------------- Secondary Sample Point ------------>|
*/
static inline s32 can_get_relative_tdco(const struct can_priv *priv)
{
const struct can_bittiming *dbt = &priv->data_bittiming;
s32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg +
dbt->phase_seg1) * dbt->brp;
return (s32)priv->tdc.tdco - sample_point_in_tc;
}
/* helper to define static CAN controller features at device creation time */
static inline void can_set_static_ctrlmode(struct net_device *dev,
u32 static_mode)