From: khc@pm.waw.pl (Krzysztof Halasa)
To: linux-arm-kernel@lists.infradead.org
Subject: ixp4xx dmabounce
Date: Wed, 23 Sep 2009 16:40:41 +0200 [thread overview]
Message-ID: <m33a6dk9li.fsf@intrepid.localdomain> (raw)
In-Reply-To: <19129.24807.954274.688709@pilspetsen.it.uu.se> (Mikael Pettersson's message of "Wed, 23 Sep 2009 01:42:31 +0200")
Mikael Pettersson <mikpe@it.uu.se> writes:
> I strongly suspect that something on the USB or networking side
> is allocating I/O buffers without observing the correct DMA APIs.
At least the network stack allocates buffers ignoring the DMA masks.
The buffers may be allocated by one device (driver) and passed to
another device. The only plausible way to fix it is IMHO limiting all
skb allocations to the common mask (drivers would be free to either
handle or drop skbs outside of their mask).
This is relatively easy to implement and I'm going to try it, when time
permits.
> I think Krzysztof Halasa mentioned running ixp4xx devices with 128MB
> RAM and a kernel hacked so kernel-private allocations would always be
> served from memory below 64MB. I think he mentioned doing that because
> of networking components that would ignore PCI DMA mask constraints.
Right. This works fine for network buffers because they aren't that
large. The current patch is suboptimal, though.
--
Krzysztof Halasa
next prev parent reply other threads:[~2009-09-23 14:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-17 21:02 ixp4xx dmabounce Brian Walsh
2009-09-17 21:53 ` Russell King - ARM Linux
2009-09-22 22:02 ` Brian Walsh
2009-09-27 16:55 ` Russell King - ARM Linux
2009-09-29 15:16 ` Brian Walsh
2009-09-22 23:42 ` Mikael Pettersson
2009-09-23 14:40 ` Krzysztof Halasa [this message]
2009-09-24 16:02 ` Brian Walsh
2009-09-24 16:50 ` Mikael Pettersson
2009-09-24 22:15 ` Brian Walsh
2009-09-24 23:34 ` Mikael Pettersson
2009-09-24 23:43 ` Brian Walsh
2009-09-24 16:51 ` Krzysztof Halasa
2009-09-24 16:57 ` Brian Walsh
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