From: Arnd Bergmann <arnd@arndb•de>
To: Olof Johansson <olof@lixom•net>
Cc: linuxppc-dev@ozlabs•org, paulus@samba•org
Subject: Re: [PATCH] powerpc: make ioport_map() handle already mapped ranges
Date: Sun, 13 May 2007 01:55:41 +0200 [thread overview]
Message-ID: <200705130155.42414.arnd@arndb.de> (raw)
In-Reply-To: <20070512223623.GA16045@lixom.net>
On Sunday 13 May 2007, Olof Johansson wrote:
> > We have a bug on cell that would be fixed with this patch, so it
> > might be the same problem, see the patch that I suggested for
> > this at http://patchwork.ozlabs.org/linuxppc/patch?id=10840 .
>
> Not in this case, but thanks for the pointer. Your case is still based
> on the fact that you only have one io space range, you're just making
> sure you're allocating out of that range. In my case, I have two distinct
> ranges, they're even on different busses...
There is a global io space range for all buses, which is maintained
by the reserve_phb_iospace() call. You should get your I/O ports in there
if you want them to just work. Note that while the reserve_phb_iospace()
logic works in practice, it does have a few shortcomings that should
eventually be resolved:
* There is no way to free these ranges, so you can't use this mechanism
to allocate space for hotpluggable buses, or you might run out of
space eventually
* there is no locking around the use of reserve_phb_iospace().
* Buses that are already hotplugged get an io port range above the
range maintained by reserve_phb_iospace(), but that may be larger
than 4GB, so that I/O port numbers allocated on thoses buses require
64 bit integers to store them.
* If you have registered primary PCI bus, the whole logic breaks down
and you always need 64 bit integers to store I/O port numbers, at best.
* Worse things happen if you try to use pci_iomap, which checks
PIO_MASK. This mask is currently defined for 30 bit addresses, while
the range managed by reserve_phb_iospace() is already 31 bits, not
to mention ports outside of that range.
* If you call reserve_phb_iospace() for a secondary bus before
setting pci_io_base to the primary bus, you actually get negative
I/O port numbers, and you crash when using a 32 bit number to store
it.
Arnd <><
next prev parent reply other threads:[~2007-05-13 0:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-12 14:32 [PATCH] powerpc: make ioport_map() handle already mapped ranges Olof Johansson
2007-05-12 22:18 ` Arnd Bergmann
2007-05-12 22:36 ` Olof Johansson
2007-05-12 23:55 ` Arnd Bergmann [this message]
2007-05-13 1:46 ` Benjamin Herrenschmidt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=200705130155.42414.arnd@arndb.de \
--to=arnd@arndb$(echo .)de \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=olof@lixom$(echo .)net \
--cc=paulus@samba$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox