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candev: allow SJW user setting for bittiming calculation 

This patch adds support for SJW user settings to not set the synchronization
jump width (SJW) to 1 in any case when using the in-kernel bittiming
calculation.

The ip-tool from iproute2 already supports to pass the user defined SJW
value. The given SJW value is sanitized with the controller specific sjw_max
and the calculated tseg2 value. As the SJW can have values up to 4 providing
this value will lead to the maximum possible SJW automatically. A higher SJW
allows higher controller oscillator tolerances.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Oliver Hartkopp 2011-09-28 02:50:11 +00:00 committed by David S. Miller
parent d4fa0e35fd
commit 2e11437427
1 changed files with 13 additions and 1 deletions
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14
drivers/net/can/dev.c
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@ -150,7 +150,19 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt)
bt->prop_seg = tseg1 / 2;
bt->phase_seg1 = tseg1 - bt->prop_seg;
bt->phase_seg2 = tseg2;
bt->sjw = 1;
/* check for sjw user settings */
if (!bt->sjw || !btc->sjw_max)
bt->sjw = 1;
else {
/* bt->sjw is at least 1 -> sanitize upper bound to sjw_max */
if (bt->sjw > btc->sjw_max)
bt->sjw = btc->sjw_max;
/* bt->sjw must not be higher than tseg2 */
if (tseg2 < bt->sjw)
bt->sjw = tseg2;
}
bt->brp = best_brp;
/* real bit-rate */
bt->bitrate = priv->clock.freq / (bt->brp * (tseg1 + tseg2 + 1));