netdev - Re: [MeeGo-Dev][PATCH] Topcliff: Update PCH

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Message-ID: <4C8F1F80.5050505@pengutronix.de>
Date:	Tue, 14 Sep 2010 09:08:48 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Masayuki Ohtake <masa-korg@....okisemi.com>
CC:	Wolfgang Grandegger <wg@...ndegger.com>, arjan@...ux.intel.com,
	meego-dev@...go.com, Morinaga <morinaga526@....okisemi.com>,
	socketcan-core@...ts.berlios.de, yong.y.wang@...el.com,
	gregkh@...e.de, netdev@...r.kernel.org, qi.wang@...el.com,
	andrew.chih.howe.khor@...el.com
Subject: Re: [MeeGo-Dev][PATCH] Topcliff: Update PCH_CAN driver to 2.6.35

On 09/14/2010 02:46 AM, Masayuki Ohtake wrote:

>>>> - implement NAPI
>>> Since Topcliff CAN HW register has only single rx buffer,
>>> I think NAPI is unnecessary.
> 
>> Doesn't matter. Please try to implement it.
> 
> Our CAN driver must pull received data from CAN-HW rx buffer as fast as it can
> so that the received data is not over-written by next received data.
> In case of implemented with NAPI,
> since NAPI has time-lagging after receiving first packet,
> probability of over-written(discarded) buffer is to be high.
> Thus, for our CAN HW, we should NOT implement with NAPI but normal "netif_rx".

Okay, point taken.

Regarding the one and only rx buffer. Is it a driver or a hardware
limitation?

BTW: Are the datasheets of this CAN core available somewhere?

cheers Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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