linux-kernel - Re: [PATCH 5/7] mmc_spi: allow higher timeouts for SPI mode

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Message-Id: <200903120916.27797.wolfgang.mues@auerswald.de>
Date:	Thu, 12 Mar 2009 09:16:27 +0100
From:	Wolfgang Mües <wolfgang.mues@...rswald.de>
To:	"David Brownell" <david-b@...bell.net>
Cc:	"Matt Fleming" <matt@...sole-pimps.org>,
	"Pierre Ossman" <drzeus@...eus.cx>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Mike Frysinger" <vapier.adi@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] mmc_spi: allow higher timeouts for SPI mode

David,

Am Mittwoch, 11. März 2009 schrieb David Brownell:
> I think you're confused.  A *delay() call will busy-wait.
> But a *sleep() call like msleep() will schedule.

Yes. You are right. I was confused. Sorry for that.

> (These speed concerns apply primarily to patch #6, not
> this one ...)

But I think the consequences of patch #6 are over-estimated. I have not noted 
a slowdown in filesystem I/O. Most responses are coming in while the loop is 
in busy-waiting. And for most embedded systems, it _is_ important to don't 
allow long periods of busy-waiting.

There are other problems which are more notable: I have found that SDHC cards 
(with FAT32, clustersize = 4 KByte) are much SLOWER than the older SD cards 
(with FAT16, clustersize = 16-32 KByte). I will do some investigation here.

best regards
 
i. A. Wolfgang Mües
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