From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: memcpy alignment for DEVICE_nGnRnE
Date: Tue, 8 Apr 2014 12:49:49 +0100 [thread overview]
Message-ID: <20140408114949.GB21054@arm.com> (raw)
In-Reply-To: <20140408003547.GA18321@codeaurora.org>
On Tue, Apr 08, 2014 at 01:35:47AM +0100, Michael Bohan wrote:
> On Fri, Feb 21, 2014 at 10:53:08AM +0000, Catalin Marinas wrote:
> > On Fri, Feb 21, 2014 at 09:58:27AM +0000, Zhou Zhu wrote:
> > > We faced one issue using memcpy for memory type DEVICE_nGnRnE
> > > (pgprot_noncached). If the address is not aligned, exception would
> > > happen due to the alignment of this type could not be handled by hardware.
> >
> > Indeed, that's expected. This memory type is the equivalent of Strongly
> > Ordered.
> >
> > > Is there any plan and ongoing patch to support this or we need to keep
> > > address aligned for memcpy using pgprot_noncached memory in drivers?
> >
> > You either change the memory type to pgprot_writecombine() or use the
> > right API (memcpy_toio/memcpy_fromio, these could be further optimised,
> > similar to powerpc for example, but I didn't get there yet).
>
> How should we handle Device Memory with copy_from_user / copy_to_user?
> Should we follow the same scheme and create
> copy_from_user_io / copy_to_user_io, or rather enforce that the stock
> routines handle alignment?
We have generic copy_from_user_toio() and copy_to_user_fromio(). Are
these what you need? As with the memcpy_(to|from)io, they can be further
optimised.
--
Catalin
next prev parent reply other threads:[~2014-04-08 11:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <53072343.4080505@marvell.com>
2014-02-21 10:53 ` memcpy alignment for DEVICE_nGnRnE Catalin Marinas
2014-04-08 0:35 ` Michael Bohan
2014-04-08 11:49 ` Catalin Marinas [this message]
2014-04-08 23:39 ` Michael Bohan
2014-04-09 8:17 ` Catalin Marinas
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