diff options
| author | Vincent Mailhol <mailhol.vincent@wanadoo.fr> | 2020-10-03 00:41:49 +0900 |
|---|---|---|
| committer | Marc Kleine-Budde <mkl@pengutronix.de> | 2020-10-07 23:17:45 +0200 |
| commit | 1c47fa6b31c2683f03bc2f9174902bb7dcd35d83 (patch) | |
| tree | 6b23951a7d08219521f24875aaa6fc1f843f6bb3 /drivers/net/can/dev.c | |
| parent | f55a52bb2cdbc5a92ca209d0ada90a490a188f58 (diff) | |
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>
Diffstat (limited to 'drivers/net/can/dev.c')
| -rw-r--r-- | drivers/net/can/dev.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index 3c40bba71d5b..b70ded3760f2 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c @@ -60,7 +60,6 @@ EXPORT_SYMBOL_GPL(can_len2dlc); #ifdef CONFIG_CAN_CALC_BITTIMING #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */ -#define CAN_CALC_SYNC_SEG 1 /* Bit-timing calculation derived from: * @@ -86,8 +85,8 @@ can_update_sample_point(const struct can_bittiming_const *btc, int i; for (i = 0; i <= 1; i++) { - tseg2 = tseg + CAN_CALC_SYNC_SEG - - (sample_point_nominal * (tseg + CAN_CALC_SYNC_SEG)) / + tseg2 = tseg + CAN_SYNC_SEG - + (sample_point_nominal * (tseg + CAN_SYNC_SEG)) / 1000 - i; tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max); tseg1 = tseg - tseg2; @@ -96,8 +95,8 @@ can_update_sample_point(const struct can_bittiming_const *btc, tseg2 = tseg - tseg1; } - sample_point = 1000 * (tseg + CAN_CALC_SYNC_SEG - tseg2) / - (tseg + CAN_CALC_SYNC_SEG); + sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) / + (tseg + CAN_SYNC_SEG); sample_point_error = abs(sample_point_nominal - sample_point); if (sample_point <= sample_point_nominal && @@ -145,7 +144,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt, /* tseg even = round down, odd = round up */ for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1; tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) { - tsegall = CAN_CALC_SYNC_SEG + tseg / 2; + tsegall = CAN_SYNC_SEG + tseg / 2; /* Compute all possible tseg choices (tseg=tseg1+tseg2) */ brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2; @@ -223,7 +222,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt, /* real bitrate */ bt->bitrate = priv->clock.freq / - (bt->brp * (CAN_CALC_SYNC_SEG + tseg1 + tseg2)); + (bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2)); return 0; } |