diff options
| -rw-r--r-- | drivers/net/can/dev/bittiming.c | 9 | ||||
| -rw-r--r-- | include/linux/can/bittiming.h | 28 |
2 files changed, 22 insertions, 15 deletions
diff --git a/drivers/net/can/dev/bittiming.c b/drivers/net/can/dev/bittiming.c index 9dda44c0ae9d..0ccf982ca301 100644 --- a/drivers/net/can/dev/bittiming.c +++ b/drivers/net/can/dev/bittiming.c @@ -193,12 +193,13 @@ void can_calc_tdco(struct net_device *dev) * one or two. */ if (dbt->brp == 1 || dbt->brp == 2) { - /* Reuse "normal" sample point and convert it to time quanta */ - u32 sample_point_in_tq = can_bit_time(dbt) * dbt->sample_point / 1000; + /* Sample point in clock periods */ + u32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg + + dbt->phase_seg1) * dbt->brp; - if (sample_point_in_tq < tdc_const->tdco_min) + if (sample_point_in_tc < tdc_const->tdco_min) return; - tdc->tdco = min(sample_point_in_tq, tdc_const->tdco_max); + tdc->tdco = min(sample_point_in_tc, tdc_const->tdco_max); priv->ctrlmode |= CAN_CTRLMODE_TDC_AUTO; } } diff --git a/include/linux/can/bittiming.h b/include/linux/can/bittiming.h index 9e20260611cc..aebbe65dab7e 100644 --- a/include/linux/can/bittiming.h +++ b/include/linux/can/bittiming.h @@ -31,8 +31,8 @@ * * To solve this issue, ISO 11898-1 introduces in section 11.3.3 * "Transmitter delay compensation" a SSP (Secondary Sample Point) - * equal to the distance, in time quanta, from the start of the bit - * time on the TX pin to the actual measurement on the RX pin. + * equal to the distance from the start of the bit time on the TX pin + * to the actual measurement on the RX pin. * * This structure contains the parameters to calculate that SSP. * @@ -44,8 +44,13 @@ * |<------- TDCO ------->| * |<----------- Secondary Sample Point ---------->| * + * To increase precision, contrary to the other bittiming parameters + * which are measured in time quanta, the TDC parameters are measured + * in clock periods (also referred as "minimum time quantum" in ISO + * 11898-1). + * * @tdcv: Transmitter Delay Compensation Value. The time needed for - * the signal to propagate, i.e. the distance, in time quanta, + * the signal to propagate, i.e. the distance, in clock periods, * from the start of the bit on the TX pin to when it is received * on the RX pin. @tdcv depends on the controller modes: * @@ -62,17 +67,18 @@ * TDC is disabled and all the values of this structure should be * ignored. * - * @tdco: Transmitter Delay Compensation Offset. Offset value, in time - * quanta, defining the distance between the start of the bit - * reception on the RX pin of the transceiver and the SSP + * @tdco: Transmitter Delay Compensation Offset. Offset value, in + * clock periods, defining the distance between the start of the + * bit reception on the RX pin of the transceiver and the SSP * position such that SSP = @tdcv + @tdco. * * @tdcf: Transmitter Delay Compensation Filter window. Defines the - * minimum value for the SSP position in time quanta. If the SSP - * position is less than @tdcf, then no delay compensations occur - * and the normal sampling point is used instead. The feature is - * enabled if and only if @tdcv is set to zero (automatic mode) - * and @tdcf is configured to a value greater than @tdco. + * minimum value for the SSP position in clock periods. If the + * SSP position is less than @tdcf, then no delay compensations + * occur and the normal sampling point is used instead. The + * feature is enabled if and only if @tdcv is set to zero + * (automatic mode) and @tdcf is configured to a value greater + * than @tdco. */ struct can_tdc { u32 tdcv; |