From: Dan Malek <dan@embeddededge•com>
To: paulus@samba•org
Cc: Armin Kuster <akuster@mvista•com>,
ppcdevel <linuxppc-dev@lists•linuxppc.org>
Subject: Re: New API for non cache coherent ppc cpu's
Date: Thu, 22 Nov 2001 18:07:12 -0500 [thread overview]
Message-ID: <3BFD8520.5060105@embeddededge.com> (raw)
In-Reply-To: 15357.26322.107051.143144@cargo.ozlabs.ibm.com
Paul Mackerras wrote:
> If we have to have a consistent_sync_page, it should be purely a local
> function in our implementation of the official DMA mapping API - see
> Documentation/DMA-mapping.txt.
That's exactly what it is. We are not creating a new API, and it shouldn't
have been described as such.
> .... Drivers should be using functions such
> as pci_alloc_consistent, pci_map_single, pci_dma_sync_single,
> pci_unmap_single, etc. The implementation of those routines should do
> the correct cache flushing - if it doesn't then we need to fix it.
They do. Recently a pci_sync_page was added for some reason (because
Linux doesn't have a real VM implementation I guess :-). We just needed
to add the underlying function to support it. I think it popped up in
one of the SCSI drivers.
> If you're talking about non-PCI devices, use the pci DMA API but just
> pass NULL for the dev (we need to make sure that will work ok on the
> non-cache-coherent cpus).
Ummm....I don't normally do this because using these functions requires
the CONFIG_PCI option, which isn't supported or has bad effects when
requested on processors that don't have PCI. For non-PCI devices,
I call the consistent_* functions, which other architectures support
and do as well. So, we kind of have a common interface here for non-PCI
devices as well.
I stole all of this cache coherency stuff from ARM and Sparc (or MIPS,
I don't remember) when I did it the first time.
Thanks.
-- Dan
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2001-11-22 23:07 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-11-20 20:13 New API for non cache coherent ppc cpu's Armin Kuster
2001-11-21 11:15 ` Roman Zippel
2001-11-21 18:29 ` Armin Kuster
2001-11-21 20:20 ` Roman Zippel
2001-11-22 20:57 ` Paul Mackerras
2001-11-22 23:07 ` Dan Malek [this message]
2001-11-22 23:54 ` Roman Zippel
2001-11-23 1:32 ` Paul Mackerras
2001-11-23 16:08 ` Dan Malek
2001-11-22 23:50 ` Roman Zippel
2001-11-23 1:09 ` Paul Mackerras
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