From: Leif Lindholm <leif.lindholm@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org, nico@linaro.org,
patches@linaro.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org,
Russell King - ARM Linux <linux@arm.linux.org.uk>
Subject: Re: [PATCH 0/2] arm: add early_ioremap() support
Date: Wed, 26 Jun 2013 23:34:10 +0200 [thread overview]
Message-ID: <20130626213409.GA18151@rocoto.smurfnet.nu> (raw)
In-Reply-To: <201306262323.50691.arnd@arndb.de>
On Wed, Jun 26, 2013 at 11:23:50PM +0200, Arnd Bergmann wrote:
> > Is this an issue here, since (unlike x86) this early_ioremap only works
> > before paging_init()?
>
> The main problem is that the total fixmap size is only around 900kb,
> and we want to reserve at least 64kb per cpu for kmap_atomic.
> If you want to fit multiple 128kb mappings in there, you run out of
> space really fast.
Sorry, I still don't get it. Are you saying that kmap_atomic is
available before kmap_init() (in paging_init())?
If not, all of my mappings are discarded (well, abandoned to be more
correct), so I don't see how it affects kmap.
> > > Extending the iotable mechanism on ARM would be the convenient
> > > solution for us I think.
> >
> > Could that easily be extended to give similar semantics sufficiently
> > that we can progress with merging more of the UEFI and ACPI support
> > together as common code with x86/ia64?
>
> I don't know what the requirements are, but the idea with iotable
> is that the mappings stay around at run time, while it seems you want
> to discard them at some point.
Indeed - almost immediately.
x86 early_ioremap can coexist with kmap; the intent of my
implementation is to use the kmap region only before kmap is available.
/
Leif
next prev parent reply other threads:[~2013-06-26 21:34 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-25 17:46 [PATCH 0/2] arm: add early_ioremap() support Leif Lindholm
2013-06-25 17:46 ` [PATCH 1/2] Documentation: arm: early_ioremap Leif Lindholm
2013-06-30 3:14 ` Rob Landley
2013-06-25 17:46 ` [PATCH 2/2] arm: add early_ioremap support Leif Lindholm
2013-06-26 18:52 ` [PATCH 0/2] arm: add early_ioremap() support Arnd Bergmann
2013-06-26 19:23 ` Leif Lindholm
2013-06-26 21:23 ` Arnd Bergmann
2013-06-26 21:34 ` Leif Lindholm [this message]
2013-06-26 22:13 ` Arnd Bergmann
2013-06-26 23:25 ` Leif Lindholm
2013-06-27 8:47 ` Arnd Bergmann
2013-06-27 9:29 ` Leif Lindholm
2013-06-27 11:55 ` Arnd Bergmann
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