From: Wolfgang Grandegger <wg-5Yr1BZd7O62+XT7JhA+gdA@public•gmane.org>
To: Masayuki Ohtake <masa-korg-ECg8zkTtlr0C6LszWs/t0g@public•gmane.org>
Cc: andrew.chih.howe.khor-ral2JQCrhuEAvxtiuMwx3w@public•gmane.org,
sameo-VuQAYsv1563Yd54FQh9/CA@public•gmane.org,
margie.foster-ral2JQCrhuEAvxtiuMwx3w@public•gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
yong.y.wang-ral2JQCrhuEAvxtiuMwx3w@public•gmane.org,
socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public•gmane.org,
mkl-bIcnvbaLZ9MEGnE8C9+IrQ@public•gmane.org,
chripell-VaTbYqLCNhc@public•gmane.org,
morinaga526-ECg8zkTtlr0C6LszWs/t0g@public•gmane.org,
kok.howg.ewe-ral2JQCrhuEAvxtiuMwx3w@public•gmane.org,
David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public•gmane.org>,
joel.clark-ral2JQCrhuEAvxtiuMwx3w@public•gmane.org,
qi.wang-ral2JQCrhuEAvxtiuMwx3w@public•gmane.org
Subject: Re: [MeeGo-Dev][PATCH v3] Topcliff: Update PCH_CAN driver to 2.6.35
Date: Tue, 12 Oct 2010 09:42:52 +0200 [thread overview]
Message-ID: <4CB4117C.4070207@grandegger.com> (raw)
In-Reply-To: <000c01cb69dc$5d2aaab0$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>
Hi Ohtake,
On 10/12/2010 09:09 AM, Masayuki Ohtake wrote:
> Hi Wolfgang,
>
> We have implemented our CAN driver with FIFO mode, and
> We are testing our CAN driver with FIFO mode.
> However, we have found Our CAN hardware spec is different from our anticipated.
> Our CAN HW FIFO is not common FIFO.
> Using FIFO mode, there is possibility received packets are out-of-order.
>
> e.g.
> Recv packet-A from NW and set to FIFO.
> |A|
>
> Recv packet-B from NW and set to FIFO.
> |A|B|
>
> Recv packet-C is about to set to FIFO
> |A|B|(C)|
>
> Userspace Copies A from Driver
OK, let's say the CPU or software starts processing the message FIFO.
> Userspace Copies B from Driver
> | | |(C)|
>
> packet-C set to FIFO (C is not head.)
> Recv packet-D from NW(Next packet is set to head)
> |D| |C|
>
> Userspace Copies D from Driver
The software could continues searching the FIFO for valid messages. Then
it would find C first.
> Userspace Copies C from Driver
> Userspace raceived packet order is like below
> A-B-D-C
I'm still optimistic that it could be handled properly by software, it
might be tricky though.
> So, I think normal-mode is better than FIFO-mode.
To be clear. Out-of-order reception is not allowed!
> I will revert like the following spec.
> Rx 1 Message Object
> Tx 1 Message Object
>
> Could you agree the above ?
See above. I agree if the software cannot assure in-order reception. But
it's not yet obvious to me that it cannot be achieved. I will have a
closer look to the manual. Just one RX message object without any
further buffering is really bad as message losses are likely to happen.
Wolfgang.
next prev parent reply other threads:[~2010-10-12 7:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4C9C7C6F.1000003@dsn.okisemi.com>
[not found] ` <4C9C7C6F.1000003-ECg8zkTtlr0C6LszWs/t0g@public.gmane.org>
2010-09-27 8:38 ` [MeeGo-Dev][PATCH v3] Topcliff: Update PCH_CAN driver to 2.6.35 Wolfgang Grandegger
2010-09-30 9:10 ` Wolfgang Grandegger
[not found] ` <4CA4541F.5040804-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2010-09-30 18:50 ` David Miller
2010-10-01 10:02 ` Masayuki Ohtake
[not found] ` <000401cb614f$c932c750$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>
2010-10-01 12:40 ` Wolfgang Grandegger
2010-10-05 10:21 ` Masayuki Ohtake
2010-10-05 11:08 ` Marc Kleine-Budde
2010-10-05 12:09 ` Masayuki Ohtake
[not found] ` <002e01cb6486$2ed72cc0$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>
2010-10-05 18:45 ` David Miller
2010-10-06 3:07 ` Masayuki Ohtake
[not found] ` <000b01cb6503$962bc7f0$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>
2010-10-06 3:09 ` David Miller
[not found] ` <20101005.200904.71120150.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
2010-10-06 9:12 ` Wolfgang Grandegger
2010-10-12 7:09 ` Masayuki Ohtake
[not found] ` <000c01cb69dc$5d2aaab0$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>
2010-10-12 7:42 ` Wolfgang Grandegger [this message]
2010-10-12 7:56 ` Marc Kleine-Budde
2010-10-13 4:23 ` Masayuki Ohtake
[not found] ` <000701cb6a8e$60de6900$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>
2010-10-13 7:38 ` Marc Kleine-Budde
2010-10-13 10:09 ` Masayuki Ohtake
[not found] ` <004a01cb6abe$c41a9cc0$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>
2010-10-13 11:08 ` Wolfgang Grandegger
2010-10-13 12:05 ` Masayuki Ohtake
2010-09-24 10:24 Masayuki Ohtak
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