From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: RFC on writel and writel_relaxed
Date: Wed, 28 Mar 2018 08:24:41 +1100
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To: Sinan Kaya <okaya@codeaurora.org>, Will Deacon <will.deacon@arm.com>, Arnd Bergmann <arnd@arndb.de>
Cc: Jonathan Corbet <corbet@lwn.net>, "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>, Jason Gunthorpe <jgg@ziepe.ca>, Peter Zijlstra <peterz@infradead.org>, David Laight <David.Laight@aculab.com>, Oliver <oohall@gmail.com>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, "open list:LINUX FOR POWERPC (32-BIT AND
 64-BIT)" <linuxppc-dev@lists.ozlabs.org>, Ingo Molnar <mingo@redhat.com>
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On Tue, 2018-03-27 at 09:46 -0400, Sinan Kaya wrote:
> On 3/27/2018 7:02 AM, Will Deacon wrote:
> > -     See Documentation/DMA-API.txt for more information on consistent memory.
> > +     can see it now has ownership.  Note that, when using writel(), a prior
> > +     wmb() is not needed to guarantee that the cache coherent memory writes
> > +     have completed before writing to the MMIO region.  The cheaper
> > +     writel_relaxed() does not provide this guarantee and must not be used
> > +     here.
> 
> Can we say the same thing for iowrite32() and iowrite32be(). I also see wmb()
> in front of these.

Yes, they should have the same semantics as writel

Cheers,
Ben.