netdev - Re: [PATCH] net: can: Remodel FlexCAN register read/write APIs for BE instances

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Message-ID: <53AAA5AC.5070707@pengutronix.de>
Date:	Wed, 25 Jun 2014 12:34:20 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	David Laight <David.Laight@...LAB.COM>,
	"'bhupesh.sharma@...escale.com'" <bhupesh.sharma@...escale.com>,
	"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
CC:	"wg@...ndegger.com" <wg@...ndegger.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: can: Remodel FlexCAN register read/write APIs for
 BE instances

On 06/25/2014 12:29 PM, David Laight wrote:
>> Ok. Or should I create two functions for read and write - one does it in LE way and the other
>> in BE way and parse the DT to understand which endianness the module supports.
> 
> An indirect call is likely to be slower than a conditional.
> The conditional inside a non-inlined function is likely to get
> predicted correctly on any code paths that matter.
> Unfortunately using a real function increases register pressure.
> 
> Maybe a compile-time option for BE, LE or both.
> So a 'generic' kernel can work, but a SoC specific one will be faster.
> Then have the driver load/attach/init fail if it is the wrong endianness.

Don't overengineer, CAN is max 1 MiB/s.

Marc

-- 
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