netdev - Re: [PATCH v3] Fix SJA1000 command register writes on SMP systems

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Message-Id: <20100518.140319.257494929.davem@davemloft.net>
Date:	Tue, 18 May 2010 14:03:19 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	socketcan@...tkopp.net
Cc:	wg@...ndegger.com, netdev@...r.kernel.org,
	socketcan-core@...ts.berlios.de
Subject: Re: [PATCH v3] Fix SJA1000 command register writes on SMP systems

From: Oliver Hartkopp <socketcan@...tkopp.net>
Date: Tue, 18 May 2010 21:05:54 +0200

> The SJA1000 command register is concurrently written in the rx-path to free
> the receive buffer _and_ in the tx-path to start the transmission.
> 
> The SJA1000 data sheet, 6.4.4 COMMAND REGISTER (CMR) states:
> "Between two commands at least one internal clock cycle is needed in
> order to proceed. The internal clock is half of the external oscillator
> frequency."
> 
> On SMP systems the current implementation leads to a write stall in the
> tx-path, which can be solved by adding some general locking and some time
> to settle the write_reg() operation for the command register.
> 
> Thanks to Klaus Hitschler for the original fix and detailed problem
> description.
> 
> This patch applies on net-2.6 and (with some offsets) on net-next-2.6 .
> 
> Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
> Acked-by: Wolfgang Grandegger <wg@...ndegger.com>

Applied, thanks.
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