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.

---

v2: Resend due to wrong mail address header encoding.
v3: - Detected malformed patch format due to line break in function name
- Added Acked-by: from Wolfgang Grandegger

index 9bf1116..25695bd 100644
@@ -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));

From: Oliver Hartkopp <[email protected]>
Date: Wed, 28 Sep 2011 14:50:11 +0200

Applied.