linux-kernel - Re: [PATCH] FDDI: defza: Include linux/io-64-nonatomic-lo-hi.h

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Message-ID: <MWHPR2201MB1277792136FAB29E384E2152C1E00@MWHPR2201MB1277.namprd22.prod.outlook.com>
Date:   Mon, 24 Jun 2019 21:16:08 +0000
From:   Paul Burton <paul.burton@...s.com>
To:     Paul Burton <pburton@...ecomp.com>
CC:     "Maciej W. Rozycki" <macro@...ux-mips.org>,
        "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Paul Burton <pburton@...ecomp.com>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>
Subject: Re: [PATCH] FDDI: defza: Include linux/io-64-nonatomic-lo-hi.h

Hello,

Paul Burton wrote:
> 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>
> Cc: Serge Semin <Sergey.Semin@...latforms.ru>
> Cc: "Maciej W. Rozycki" <macro@...ux-mips.org>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: netdev@...r.kernel.org
> Cc: linux-mips@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Acked-by: Maciej W. Rozycki <macro@...ux-mips.org>
> Acked-by: David S. Miller <davem@...emloft.net>

Applied to mips-next.

Thanks,
    Paul

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