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Date: Thu, 19 Mar 2009 21:22:25 -0400
Message-ID: <c4d76b3b0903191822l5494f268h395acc4a14608239@mail.gmail.com> (sfid-20090320_022231_904381_2FD27C7F)
Subject: Re: kernel BUG at drivers/net/wireless/iwlwifi/iwl3945-base.c:3127!
From: Jason Andryuk <jandryuk@gmail.com>
To: reinette chatre <reinette.chatre@intel.com>
Cc: Samuel Ortiz <samuel@sortiz.org>, Tomas Winkler <tomasw@gmail.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
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Sender: linux-wireless-owner@vger.kernel.org
List-ID: <linux-wireless.vger.kernel.org>

There is a bug related to the use of DMA.  Using wireless-testing
2.6.29-rc7 from ~3/15, and booting with "iommu=off mem=2G" gives me a
working iwl3945.  I also confirmed
78bb4a96d0d4ab2860df5f0fdfde58cd7a3ad642 "iwl3945: use iwl3945_tx_cmd
instead of iwl_tx_cmd" plus previously posted "rb_stts and BUG to
WARN" patch as working when iommu is disabled.

So swiotlb exposes iwl3945 dma breakage.

>From 78bb4a96d0d4ab2860df5f0fdfde58cd7a3ad642 "iwl3945: use
iwl3945_tx_cmd instead of iwl_tx_cmd" the most obvious problem is the
change to pci_map_single from pci_alloc_consistent.

As previously noted, problems brought along by that include the
modification of data to be DMAed after the _map_single call.  The lack
of associated un-mapping of memory may also be a problem.

For testing, swiotlb use can be forced with "swiotlb=force" which
should reproduce the error.

Jason