From: Oliver Hartkopp <socketcan-fJ+pQTUTwRTk1uMJSBkQmQ@public•gmane.org>
To: David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public•gmane.org>
Cc: SocketCAN Core Mailing List
<socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public•gmane.org>,
Linux Netdev List
<netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org>,
Wolfgang Grandegger <wg-5Yr1BZd7O62+XT7JhA+gdA@public•gmane.org>
Subject: [PATCH net-next v3] candev: allow SJW user setting for bittiming calculation
Date: Wed, 28 Sep 2011 14:50:11 +0200 [thread overview]
Message-ID: <4E831803.7020409@hartkopp.net> (raw)
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-fJ+pQTUTwRTk1uMJSBkQmQ@public•gmane.org>
Acked-by: Wolfgang Grandegger <wg-5Yr1BZd7O62+XT7JhA+gdA@public•gmane.org>
---
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
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 @@ 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));
next reply other threads:[~2011-09-28 12:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-28 12:50 Oliver Hartkopp [this message]
2011-09-28 17:43 ` [PATCH net-next v3] candev: allow SJW user setting for bittiming calculation David Miller
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