From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: David Miller <davem@davemloft.net>
Cc: sfr@canb.auug.org.au, paulus@samba.org,
linuxppc-dev@lists.ozlabs.org, mika.westerberg@linux.intel.com,
netdev@vger.kernel.org, linux-next@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: linux-next: build failure after merge of the final tree (net-next tree related)
Date: Sat, 22 Sep 2012 07:46:40 +1000 [thread overview]
Message-ID: <1348264000.1132.63.camel@pasglop> (raw)
In-Reply-To: <20120920.185315.576326460331670020.davem@davemloft.net>
On Thu, 2012-09-20 at 18:53 -0400, David Miller wrote:
> 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.
Right, but on ppc, GFP_DMA is a nop (no separate ZONE_DMA, or rather all
of memory is ZONE_DMA). It's always been like that afaik.
We could support ISA device limited addressability using the iommu but
that would involve a map/unmap type API (which I remember we did support
in the old days by passing NULL to pci_map_*, but we dropped that along
the way).
> 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.
I will dig a bit. I think there might be some users of the ISA DMA
engine for legacy floppies and parport on some early pSeries and CHRP
machines (including Pegasos).
Cheers,
Ben.
next prev parent reply other threads:[~2012-09-21 21:47 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-20 7:36 linux-next: build failure after merge of the final tree (net-next tree related) Stephen Rothwell
2012-09-20 9:10 ` Mika Westerberg
2012-09-20 20:45 ` David Miller
2012-09-20 22:15 ` Stephen Rothwell
2012-09-20 22:22 ` Benjamin Herrenschmidt
2012-09-20 22:53 ` David Miller
2012-09-21 21:46 ` Benjamin Herrenschmidt [this message]
2012-09-22 20:00 ` David Miller
2012-09-22 21:20 ` Benjamin Herrenschmidt
2012-09-20 22:28 ` Stephen Rothwell
2012-09-21 1:37 ` Stephen Rothwell
-- strict thread matches above, loose matches on Subject: below --
2014-03-18 7:27 Stephen Rothwell
2014-03-19 3:13 ` David Miller
2014-03-17 10:21 Stephen Rothwell
2014-03-19 3:11 ` David Miller
2014-03-17 10:13 Stephen Rothwell
2013-09-02 9:11 Stephen Rothwell
2013-09-02 9:18 ` Cong Wang
2013-07-03 7:48 Stephen Rothwell
2013-07-03 7:51 ` Sedat Dilek
2013-07-03 8:45 ` Eliezer Tamir
2013-07-03 19:17 ` David Miller
2013-06-26 7:56 Stephen Rothwell
2013-06-26 8:07 ` Alexey Brodkin
2013-06-26 8:36 ` David Miller
2013-04-23 7:46 Stephen Rothwell
2013-04-23 17:10 ` David Miller
2013-04-23 23:44 ` David Rientjes
2013-04-12 6:00 Stephen Rothwell
2013-04-12 7:08 ` David Miller
2013-03-28 5:04 Stephen Rothwell
2013-03-28 5:19 ` David Miller
2013-01-03 3:23 Stephen Rothwell
2013-01-03 3:28 ` David Miller
2013-01-03 9:51 ` David Miller
2012-09-05 5:39 Stephen Rothwell
2012-09-05 21:46 ` David Miller
2012-09-04 6:58 Stephen Rothwell
2012-09-04 18:20 ` David Miller
2012-09-04 19:50 ` Jerry Chu
2012-07-22 6:34 Stephen Rothwell
2012-07-22 7:29 ` Jiri Pirko
2012-05-03 6:16 Stephen Rothwell
2012-05-03 6:26 ` David Miller
2012-04-30 5:58 Stephen Rothwell
2012-04-30 17:22 ` David Miller
2012-04-19 6:28 Stephen Rothwell
2012-04-19 6:40 ` David Miller
2012-04-10 5:29 Stephen Rothwell
2012-04-10 13:26 ` David Miller
2012-04-05 3:25 Stephen Rothwell
2012-04-05 3:59 ` David Miller
2012-04-06 7:09 ` Giuseppe CAVALLARO
2012-04-06 7:30 ` Giuseppe CAVALLARO
2012-02-20 5:15 Stephen Rothwell
2012-02-20 5:46 ` David Miller
2011-12-14 7:07 Stephen Rothwell
2011-12-14 18:35 ` David Miller
2011-11-23 4:00 Stephen Rothwell
2011-11-23 12:09 ` Neil Horman
2011-11-23 23:02 ` Andrew Morton
2011-11-23 23:44 ` David Miller
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