Subject: Re: [PATCH/RFT] iwlagn: fix RX skb alignment
From: Johannes Berg <johannes@sipsolutions.net>
To: Tomas Winkler <tomasw@gmail.com>
Cc: John Linville <linville@tuxdriver.com>,
	reinette chatre <reinette.chatre@intel.com>,
	Marcel Holtmann <marcel@holtmann.org>,
	"Luis R. Rodriguez" <mcgrof@gmail.com>, Zhu Yi <yi.zhu@intel.com>,
	linux-wireless <linux-wireless@vger.kernel.org>
In-Reply-To: <1ba2fa240811190121h3ff51824o90b72a206192e793@mail.gmail.com> (sfid-20081119_102145_152719_5F0C41AF)
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Date: Wed, 19 Nov 2008 12:40:32 +0100
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On Wed, 2008-11-19 at 11:21 +0200, Tomas Winkler wrote:

> > Indeed. One would seem to be the buffer list itself, which also needs t=
o
> > fit within a 40-bit mask with 256 alignment (rxq->bd), the rb_stts need=
s
> > 16-byte alignment which probably is always satisfied, but I'm not sure,
> > you'll need to research the alignment guarantees.
>=20
> Note these are allocated using persistent calls and not kmalloc I hope
> at least does are page alignment.

Good point. On powerpc at least that uses alloc_pages internally.

> We have some alignment requirements also on TX side
>=20
> >
> > Another, different, question: I don't see where the driver tells the
> > hardware how large the buffers are it allocated. Can you point me to
> > that? You can switch 4k/8k ampdu but I don't see where you tell the
> > hardware.
>=20
> in iwl_rx_init
>  rb_size =3D
>  FH_RCSR_RX_CONFIG_REG_VAL_RB_SIZE_4K .. 8K .. can go up to 16K.
> This  amsdu size (not ampdu) influence the size of RB we choose

Thanks. Yeah, ampdus are deaggregated already, my mistake.

johannes

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