Messages in this thread | | | Date | Wed, 28 Aug 2013 12:01:22 +0200 | From | Thomas Petazzoni <> | Subject | Re: [PATCH v4 2/4] ARM: Add atomic_io_modify optimized routines |
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Dear Ezequiel Garcia,
On Wed, 28 Aug 2013 06:49:08 -0300, Ezequiel Garcia wrote:
> > Is this any different from the generic one introduced in patch 1/4? I > > would rather just use the generic definition. > > Well, according to Will Deacon (and as documented in the commit log) > we can optimize in ARM by using readl_relaxed instead of readl. > > Now, I'm sure you now better than me if that results (or not) in any > significant optimization. > > > Similarly, a generic > > atomic_io_modify_relaxed() but guarded with something like > > __HAVE_ARCH_RELAXED_IO. > > > > No, that's not possible. As far as I understand, there's no guarantee > of _relaxed variants to be available architecture-wide.
I think what Catalin was suggesting is that atomic_io_modify() should use readl() and writel() (i.e *not* the relaxed variants), and that a separate atomic_io_modify_relaxed() could be added on architectures that define __HAVE_ARCH_RELAXED_IO.
I think you misread Catalin's comment when you say there's no guarantee of _relaxed variants to be available architecture-wide, since Catalin precisely suggested to guard that with __HAVE_ARCH_RELAXED_IO, which indicates that _relaxed variants are available.
Thanks,
Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com
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