linux-kernel - Re: sdio: set the functions' block size

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Date:	Mon, 06 Aug 2007 11:04:30 +0100
From:	David Vrabel <david.vrabel@....com>
To:	Pierre Ossman <drzeus-list@...eus.cx>
CC:	linux-kernel@...r.kernel.org
Subject: Re: sdio: set the functions' block size

Pierre Ossman wrote:
> On Tue, 31 Jul 2007 16:36:32 +0100
> David Vrabel <david.vrabel@....com> wrote:
> 
>> Prior to calling the driver's probe(), set the functions' block size
>> to the largest that's supported by both the card and the driver.
>>
>> Signed-off-by: David Vrabel <david.vrabel@....com>
>>
> 
> Why a maximum size for the driver?

For efficient use of the bus it is useful to pad transfers to a multiple
of the block size.  I reckoned it was potentially beneficial for drivers
to use smaller blocks so less padding was required.  However, after
looking at some figures the per block overhead (28 clocks for a write)
really does limit the transfer sizes where small block sizes is beneficial.

I'll remove this.  Drivers can still override the block size by calling
sdio_set_block_size() directly.

David
-- 
David Vrabel, Software Engineer, Drivers group  Tel: +44 (0)1223 692562
CSR plc, Churchill House, Cambridge Business Park, Cowley Road, CB4 0WZ

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