netdev - Re: [PATCH] enc28j60: reduce the number of spi transfers in enc28j60_set

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Date:	Thu, 18 Dec 2008 19:39:24 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	baruch@...s.co.il
Cc:	lanconelli.claudio@...ar.com, netdev@...r.kernel.org
Subject: Re: [PATCH] enc28j60: reduce the number of spi transfers in
 enc28j60_set_bank()

From: Baruch Siach <baruch@...s.co.il>
Date: Thu, 18 Dec 2008 09:57:32 +0200

> A major source of overhead in the enc28j60 driver is the SPI transfers. Each 
> SPI transfer entails two kernel thread context switches. One major source of 
> SPI transfers is the enc28j60_set_bank() functions which runs before every 
> register access. This patch reduces the number of SPI transfers that 
> enc28j60_set_bank() performs in two ways:
> 
>   1. removes unnecessary bank switch for the registers that are present in all 
> 	 banks
> 
>   2. when switching from banks 0 or 3 to banks 1 or 2 (i.e. only one bit 
> 	 changes) enc28j60_set_bank() does only one SPI transfer instead of two
> 
> According to my tests these changes reduce the number of SPI transfers in 
> about 25%.
> 
> Signed-off-by: Baruch Siach <baruch@...s.co.il>

Applied, thanks Baruch.
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