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can-calc-bit-timing: introduce CAN_CALC_SYNC_SEG 

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
pull/17/head
Marc Kleine-Budde 2016-04-12 16:27:54 +02:00
parent 94e40d3c2d
commit e36391c7d9
1 changed files with 7 additions and 4 deletions
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11
can-calc-bit-timing.c
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@ -530,6 +530,7 @@ static long common_bitrates[] = {
};
#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
#define CAN_CALC_SYNC_SEG 1
/*
* Bit-timing calculation derived from:
@ -547,7 +548,8 @@ static long common_bitrates[] = {
static int can_update_spt(const struct can_bittiming_const *btc,
int sampl_pt, int tseg, int *tseg1, int *tseg2)
{
*tseg2 = tseg + 1 - (sampl_pt * (tseg + 1)) / 1000;
*tseg2 = tseg + CAN_CALC_SYNC_SEG -
(sampl_pt * (tseg + CAN_CALC_SYNC_SEG)) / 1000;
if (*tseg2 < btc->tseg2_min)
*tseg2 = btc->tseg2_min;
if (*tseg2 > btc->tseg2_max)
@ -557,7 +559,7 @@ static int can_update_spt(const struct can_bittiming_const *btc,
*tseg1 = btc->tseg1_max;
*tseg2 = tseg - *tseg1;
}
return 1000 * (tseg + 1 - *tseg2) / (tseg + 1);
return 1000 * (tseg + CAN_CALC_SYNC_SEG - *tseg2) / (tseg + CAN_CALC_SYNC_SEG);
}
static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
@ -586,7 +588,8 @@ 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 = 1 + tseg / 2;
tsegall = CAN_CALC_SYNC_SEG + tseg / 2;
/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
/* chose brp step which is possible in system */
@ -655,7 +658,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
bt->brp = best_brp;
/* real bit-rate */
bt->bitrate = priv->clock.freq / (bt->brp * (tseg1 + tseg2 + 1));
bt->bitrate = priv->clock.freq / (bt->brp * (CAN_CALC_SYNC_SEG + tseg1 + tseg2));
return 0;
}