From: David Miller <davem@davemloft.net>
To: benh@kernel.crashing.org
Cc: sfr@canb.auug.org.au, mika.westerberg@linux.intel.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-next@vger.kernel.org, paulus@samba.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: linux-next: build failure after merge of the final tree (net-next tree related)
Date: Thu, 20 Sep 2012 18:53:15 -0400 (EDT) [thread overview]
Message-ID: <20120920.185315.576326460331670020.davem@davemloft.net> (raw)
In-Reply-To: <1348179764.1132.35.camel@pasglop>
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 21 Sep 2012 08:22:44 +1000
> Hrm, that's ancient gunk, I'll have to dig. We potentially can support
> ISA devices DMA'ing from an ISA bridge... but via the iommu, which means
> isa_virt_to_bus is a non-starter.
>
> But then, do we really care ? IE. Is there single device that actually
> requires ISA_DMA_API and that is expected to work on any currently
> supported powerpc hw ? :-)
>
> We don't even support PReP anymore, so that leaves us with what ?
ISA_DMA_API implies a fixed window of addresses which are <= 32-bits
on the bus, which is a hardware requirement of these devices.
isa_virt_to_bus() goes to that physical address, and the expection is
that you use GFP_DMA and thus the physical addresses fit inside of
an unsigned int.
isa_virt_to_bus() basically amounts to a virt-->phys plus a cast.
> Anybody has an objection to turning ISA_DMA_API off ?
Then you can remove all of the DMA api stuff in powerpc's asm/dma.h
but some of it looks like it might be in use.
next prev parent reply other threads:[~2012-09-20 22:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120920173622.2aa7209cd241a3945f4384d4@canb.auug.org.au>
[not found] ` <20120920091013.GV15548@intel.com>
[not found] ` <20120920.164558.2281417114805373564.davem@davemloft.net>
2012-09-20 22:15 ` linux-next: build failure after merge of the final tree (net-next tree related) Stephen Rothwell
2012-09-20 22:22 ` Benjamin Herrenschmidt
2012-09-20 22:53 ` David Miller [this message]
2012-09-21 21:46 ` Benjamin Herrenschmidt
2012-09-22 20:00 ` David Miller
2012-09-22 21:20 ` Benjamin Herrenschmidt
2012-09-20 22:28 ` Stephen Rothwell
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