Commit 2e114374 authored Sep 28, 2011 by Oliver Hartkopp Committed by David S. Miller Sep 28, 2011

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>

parent d4fa0e35

drivers/net/can/dev.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -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;

		/* 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));