From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
David Woodhouse <dwmw2@infradead.org>,
Alan <alan@lxorguk.ukuu.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] libata-sff: Don't call bmdma_stop on non DMA capable controllers
Date: Mon, 29 Jan 2007 09:57:19 +1100 [thread overview]
Message-ID: <1170025039.26655.96.camel@localhost.localdomain> (raw)
In-Reply-To: <45B95D3A.10108@pobox.com>
> On sparc64, for example, after I pointed this out to DaveM, he was able
> to implement the new iomap interface without the 'if (pio-mem-area)'
> branch present on x86.
Yup, we did that from day 1 on powerpc :-) However, I don't totally
agree with adding some other remapping layer here, I think if we want
PIO 0 to be illegal, then make it illegal at the HW level too.
The reason is in fact the same as Linus invoked for remapping it in the
first place -> make things look like an x86 :-)
That is, quite a few non-x86 machines do have some kind of superIO chip
or other set of legacy devices around. They also commonly have VGA cards
hard decoding VGA PIO addresses.
So here's a very simplified version on how most non-x86 platforms do
PIO :
at boot:
pci_io_base = ioremap(MAGIC_PIO_REGION);
and then
#define inb(port) (readb(pci_io_base + (port)))
The nice thing with that approach is that all those legacy x86 drivers
for bits in your SuperIO chip or for VGA do actually still work when they
do
inb(STUPID_HARD_CODED_IO_PORT);
While if we now add some magic remapping to make 0 illegal, that will break
and all those legacy drivers would have to be fixed, which nobody wants
to do.
So I do stand firm there. I don't necessarily mind deciding that 0 is an
illegal PIO address, but if we're going to do that, we should make it
illegal as a HW PIO address, not by adding a remapping trick to something
that really doesn't want more than it already has :-)
Ben.
next prev parent reply other threads:[~2007-01-28 22:58 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-25 15:09 [PATCH] libata-sff: Don't call bmdma_stop on non DMA capable controllers Alan
2007-01-25 16:14 ` David Woodhouse
2007-01-25 16:17 ` Jeff Garzik
2007-01-25 16:19 ` David Woodhouse
2007-01-25 16:22 ` Russell King
2007-01-25 16:26 ` David Woodhouse
2007-01-25 17:27 ` Alan
2007-01-25 17:56 ` Linus Torvalds
2007-01-26 0:23 ` David Woodhouse
2007-01-26 1:28 ` Linus Torvalds
2007-01-26 1:45 ` Jeff Garzik
2007-01-26 2:01 ` Linus Torvalds
2007-01-26 2:11 ` Jeff Garzik
2007-01-26 10:37 ` Alan
2007-01-28 23:01 ` Benjamin Herrenschmidt
2007-01-28 22:57 ` Benjamin Herrenschmidt [this message]
2007-01-26 2:23 ` David Woodhouse
2007-01-26 2:58 ` Linus Torvalds
2007-01-26 3:28 ` David Woodhouse
2007-01-26 4:00 ` Linus Torvalds
2007-01-26 4:19 ` David Woodhouse
2007-01-26 4:48 ` Linus Torvalds
2007-01-26 5:09 ` David Woodhouse
2007-01-26 6:01 ` Linus Torvalds
2007-01-26 6:18 ` Linus Torvalds
2007-01-26 8:17 ` David Miller
2007-01-26 8:20 ` David Miller
2007-01-26 4:53 ` Jeff Garzik
2007-01-26 15:32 ` Mark Lord
2007-01-26 15:29 ` Mark Lord
2007-01-28 23:04 ` Benjamin Herrenschmidt
2007-01-28 22:49 ` Benjamin Herrenschmidt
2007-01-25 23:36 ` Jeff Garzik
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