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.
CC: Stefan Mätje <Stefan.Maetje@xxxxxx>
Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
---
include/linux/can/dev.h | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 0be982fd22fb..fa75e29182a3 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -93,6 +93,35 @@ 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)
--
2.31.1
