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Date:   Sun, 23 Jun 2019 11:25:02 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     paul.burton@...s.com
Cc:     macro@...ux-mips.org, netdev@...r.kernel.org, pburton@...ecomp.com,
        Sergey.Semin@...latforms.ru, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] FDDI: defza: Include linux/io-64-nonatomic-lo-hi.h

From: Paul Burton <paul.burton@...s.com>
Date: Thu, 20 Jun 2019 22:13:58 +0000

> Currently arch/mips/include/asm/io.h provides 64b memory accessor
> functions such as readq & writeq even on MIPS32 platforms where those
> accessors cannot actually perform a 64b memory access. They instead
> BUG(). This is unfortunate for drivers which either #ifdef on the
> presence of these accessors, or can function with non-atomic
> implementations of them found in either linux/io-64-nonatomic-lo-hi.h or
> linux/io-64-nonatomic-hi-lo.h. As such we're preparing to remove the
> definitions of these 64b accessor functions for MIPS32 kernels.
> 
> In preparation for this, include linux/io-64-nonatomic-lo-hi.h in
> defza.c in order to provide a non-atomic implementation of the
> readq_relaxed & writeq_relaxed functions that are used by this code. In
> practice this will have no runtime effect, since use of the 64b accessor
> functions is conditional upon sizeof(unsigned long) == 8, ie. upon
> CONFIG_64BIT=y. This means the calls to these non-atomic readq & writeq
> implementations will be optimized out anyway, but we need their
> definitions to keep the compiler happy.
> 
> For 64bit kernels using this code this change should also have no effect
> because asm/io.h will continue to provide the definitions of
> readq_relaxed & writeq_relaxed, which linux/io-64-nonatomic-lo-hi.h
> checks for before defining itself.
> 
> Signed-off-by: Paul Burton <paul.burton@...s.com>
 ...
> Maciej, David, if you'd be happy to provide an Ack so that I can take
> this through the mips-next branch that would be great; that'll let me
> apply it prior to the asm/io.h change.

Acked-by: David S. Miller <davem@...emloft.net>

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