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>
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 9bf1116..25695bd 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -150,7 +150,19 @@
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));