linux-kernel - Re: [PATCH 0/8] sdhci: Move real work out of an atomic context

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Message-ID: <87oce9z3hs.fsf@linux-g6p1.site>
Date:	Thu, 15 Jul 2010 07:02:55 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Anton Vorontsov <avorontsov@...sta.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Albert Herranz <albert_herranz@...oo.es>,
	Ben Dooks <ben-linux@...ff.org>,
	Pierre Ossman <pierre@...man.eu>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [PATCH 0/8] sdhci: Move real work out of an atomic context

On Wed, 14 Jul 2010 17:07:28 +0400, Anton Vorontsov <avorontsov@...sta.com> wrote:
> Hi all,
> 
> Currently the sdhci driver does everything in the atomic context.
> And what is worse, PIO transfers are made from the IRQ handler.
> 
> This causes huge latencies (up to 120 ms). On some P2020 SOCs,
> DMA and card detection is broken, which means that kernel polls
> for the card via PIO transfers every second. Needless to say
> that this is quite bad.
> 
> So, this patch set reworks sdhci code to avoid atomic context,
> almost completely. We only do two device memory operations
> in the atomic context, and all the rest is threaded.
> 
> I noticed no throughput drop neither with PIO transfers nor
> with DMA (tested on MPC8569E CPU), while latencies should be
> greatly improved.

I haven't had time to read these patches in detail yet but they all seem
to be sensible changes. A very nice series!
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