From: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
To: Marc Kleine-Budde <mkl@pengutronix.de>,
"wg@grandegger.com" <wg@grandegger.com>,
"robh+dt@kernel.org" <robh+dt@kernel.org>,
"pawel.moll@arm.com" <pawel.moll@arm.com>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
"ijc+devicetree@hellion.org.uk" <ijc+devicetree@hellion.org.uk>,
"galak@codeaurora.org" <galak@codeaurora.org>,
"corbet@lwn.net" <corbet@lwn.net>
Cc: "linux-renesas-soc@vger.kernel.org"
<linux-renesas-soc@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-can@vger.kernel.org" <linux-can@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"geert+renesas@glider.be" <geert+renesas@glider.be>,
Chris Paterson <Chris.Paterson2@renesas.com>
Subject: RE: [PATCH] can: rcar_canfd: Add Renesas R-Car CAN FD driver
Date: Thu, 3 Mar 2016 13:48:14 +0000 [thread overview]
Message-ID: <SG2PR06MB1038ABE33F06BCCA9EB072B7C3BD0@SG2PR06MB1038.apcprd06.prod.outlook.com> (raw)
In-Reply-To: <56D6BEAC.10408@pengutronix.de>
Hi Marc,
Sorry for the late response.
> On 03/02/2016 11:08 AM, Ramesh Shanmugasundaram wrote:
> >>>> I see no locking for the tx-path.
> >>>
> >>> I am not sure why locking is needed in tx-path?
> >>
> >> If the tx-path is shared between both channels you need locking as
> >> the networking subsystem may send one frame to each controller at the
> >> same time.
> >
> > Yes. Tx completion interrupt is shared by both channels but the Tx
> > FIFO, echo skbs, head, tail are maintained on a per channel basis.
> > Yes, net subsystem can send one frame to each channel at the same time
> > and the tx completion interrupt handler will traverse each channel &
> > update per channel context accordingly.
>
> Ok. Which instruction starts the transmit? Please add a comment to the
> code.
Please see
---<snip>---
+ /* Start Tx: Write 0xff to CFPC to increment the CPU-side
+ * pointer for the Common FIFO
+ */
+ rcar_canfd_write(priv, RCANFD_CFPCTR(ch, RCANFD_CFFIFO_IDX), 0xff);
---<snip>---
> You stop the tx_queue after this, so your code is racy, as the
> interrupt might happen in between.
It is a very good point. Thank you.
I managed to reproduce this issue once with 50Kbps rate and ignoring -ENOBUFS in user space. It also exposed another subtle issue in the echo skb management where the tx_done loop pushes the skb before the actual ACK for that index happens. Fixed both issues.
As you mentioned, I have introduced a lock to protect this critical section. I'll send the updates in the next v2 patch.
Thanks,
Ramesh
next prev parent reply other threads:[~2016-03-03 13:48 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-01 9:34 [PATCH] can: rcar_canfd: Add Renesas R-Car CAN FD driver Ramesh Shanmugasundaram
[not found] ` <1456824849-7987-1-git-send-email-ramesh.shanmugasundaram-kTT6dE0pTRh9uiUsa/gSgQ@public.gmane.org>
2016-03-01 20:41 ` Marc Kleine-Budde
2016-03-02 8:41 ` Ramesh Shanmugasundaram
2016-03-02 9:20 ` Marc Kleine-Budde
2016-03-02 10:08 ` Ramesh Shanmugasundaram
2016-03-02 10:21 ` Marc Kleine-Budde
2016-03-03 13:48 ` Ramesh Shanmugasundaram [this message]
2016-03-01 21:07 ` Oliver Hartkopp
2016-03-02 8:45 ` Ramesh Shanmugasundaram
2016-03-03 15:38 ` [PATCH v2] " Ramesh Shanmugasundaram
2016-03-05 4:30 ` Rob Herring
2016-03-07 9:33 ` Ramesh Shanmugasundaram
2016-03-06 11:32 ` Oliver Hartkopp
2016-03-07 8:02 ` Ramesh Shanmugasundaram
2016-03-07 8:08 ` Marc Kleine-Budde
2016-03-07 8:32 ` Ramesh Shanmugasundaram
2016-03-08 7:46 ` Oliver Hartkopp
2016-03-08 8:57 ` Ramesh Shanmugasundaram
2016-03-08 12:25 ` Oliver Hartkopp
2016-03-08 12:48 ` Ramesh Shanmugasundaram
2016-03-08 17:16 ` Oliver Hartkopp
2016-03-11 7:14 ` Ramesh Shanmugasundaram
2016-03-12 18:49 ` Oliver Hartkopp
2016-03-15 9:48 ` [PATCH v3] " Ramesh Shanmugasundaram
2016-03-15 12:51 ` Marc Kleine-Budde
2016-03-15 14:26 ` Ramesh Shanmugasundaram
2016-03-18 21:07 ` Rob Herring
2016-03-21 16:45 ` [PATCH v4 0/2] Add CAN FD driver support to r8a7795 SoC Ramesh Shanmugasundaram
2016-03-21 16:45 ` [PATCH 1/2] can: rcar_canfd: Add Renesas R-Car CAN FD driver Ramesh Shanmugasundaram
2016-03-21 16:45 ` [PATCH 2/2] can: rcar_can: Move Renesas CAN driver to rcar dir Ramesh Shanmugasundaram
2016-03-31 20:51 ` [PATCH v2] can: rcar_canfd: Add Renesas R-Car CAN FD driver Marc Kleine-Budde
2016-04-01 12:48 ` Ramesh Shanmugasundaram
2016-04-13 6:25 ` Ramesh Shanmugasundaram
2016-04-28 6:27 ` Oliver Hartkopp
2016-04-28 12:31 ` Ramesh Shanmugasundaram
2016-04-28 12:23 ` [PATCH v5 0/2] Add CAN FD driver support to r8a7795 SoC Ramesh Shanmugasundaram
2016-04-28 12:23 ` [PATCH v5 1/2] can: rcar_canfd: Add Renesas R-Car CAN FD driver Ramesh Shanmugasundaram
2016-05-03 16:47 ` Rob Herring
2016-05-04 6:23 ` Ramesh Shanmugasundaram
2016-04-28 12:23 ` [PATCH v5 2/2] can: rcar_can: Move Renesas CAN driver to rcar dir Ramesh Shanmugasundaram
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=SG2PR06MB1038ABE33F06BCCA9EB072B7C3BD0@SG2PR06MB1038.apcprd06.prod.outlook.com \
--to=ramesh.shanmugasundaram@bp.renesas.com \
--cc=Chris.Paterson2@renesas.com \
--cc=corbet@lwn.net \
--cc=devicetree@vger.kernel.org \
--cc=galak@codeaurora.org \
--cc=geert+renesas@glider.be \
--cc=ijc+devicetree@hellion.org.uk \
--cc=linux-can@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mkl@pengutronix.de \
--cc=netdev@vger.kernel.org \
--cc=pawel.moll@arm.com \
--cc=robh+dt@kernel.org \
--cc=wg@grandegger.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).