linux-kernel - Re: [PATCH] mips: Remove q-accessors from non-64bit platforms

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Date:   Mon, 24 Jun 2019 21:16:10 +0000
From:   Paul Burton <paul.burton@...s.com>
To:     Serge Semin <fancer.lancer@...il.com>
CC:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <pburton@...ecomp.com>,
        James Hogan <jhogan@...nel.org>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        Arnd Bergmann <arnd@...db.de>,
        "Vadim V . Vlasov" <vadim.vlasov@...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] mips: Remove q-accessors from non-64bit platforms

Hello,

Serge Semin wrote:
> There are some generic drivers in the kernel, which make use of the
> q-accessors or their derivatives. While at current asm/io.h the accessors
> are defined, their implementation is only applicable either for 64bit
> systems, or for systems with cpu_has_64bits flag set. Obviously there
> are MIPS systems which are neither of these, but still need to have
> those drivers supported. In this case the solution is to define some
> generic versions of the q-accessors, but with a limitation to be
> non-atomic. Such accessors are defined in the
> io-64-nonatomic-{hi-lo,lo-hi}.h file. The drivers which utilize the
> q-suffixed IO-methods are supposed to include the header file, so
> in case if these accessors aren't defined for the platform, the generic
> non-atomic versions are utilized. Currently the MIPS-specific asm/io.h
> file provides the q-accessors for any MIPS system even for ones, which
> in fact don't support them and raise BUG() in case if any of them is
> called. Due to this the generic versions of the accessors are never
> used while an attempt to call the IO-methods causes the kernel BUG().
> In order to fix this we need to define the q-accessors only for
> the MIPS systems, which actually support them, and don't define them
> otherwise, so to let the corresponding drivers to use the non-atomic
> q-suffixed accessors.
> 
> Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Cc: Vadim V. Vlasov <vadim.vlasov@...latforms.ru>

Applied to mips-next.

Thanks,
    Paul

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