From: Ben Hutchings <bhutchings@solarflare.com>
Date: Thu, 17 May 2012 17:40:54 +0000 (+0100)
Subject: sfc: Simplify TSO header buffer allocation
X-Git-Tag: omap-for-v3.7-rc1/fixes-cpufreq-signed~47^2~277^2~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f7251a9ce936f1006fbfdef63dbe42ae5e0fee7c;p=pandora-kernel.git

sfc: Simplify TSO header buffer allocation

TSO header buffers contain a control structure immediately followed by
the packet headers, and are kept on a free list when not in use.  This
complicates buffer management and tends to result in cache read misses
when we recycle such buffers (particularly if DMA-coherent memory
requires caches to be disabled).

Replace the free list with a simple mapping by descriptor index.  We
know that there is always a payload descriptor between any two
descriptors with TSO header buffers, so we can allocate only one
such buffer for each two descriptors.

While we're at it, use a standard error code for allocation failure,
not -1.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
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