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Date:   Tue, 13 Aug 2019 22:38:43 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Christophe Leroy <christophe.leroy@c-s.fr>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, npiggin@gmail.com,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 02/10] powerpc/mm: rework io-workaround invocation.
Message-ID: <20190814053843.GB27497@infradead.org>
References: <6bc35eca507359075528bc0e55938bc1ce8ee485.1565726867.git.christophe.leroy@c-s.fr>
 <d6049aee232029c01c7569975d49455058c945fe.1565726867.git.christophe.leroy@c-s.fr>
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On Tue, Aug 13, 2019 at 08:11:34PM +0000, Christophe Leroy wrote:
> ppc_md.ioremap() is only used for I/O workaround on CELL platform,
> so indirect function call can be avoided.
> 
> This patch reworks the io-workaround and ioremap() functions to
> use static keys for the activation of io-workaround.
> 
> When CONFIG_PPC_IO_WORKAROUNDS or CONFIG_PPC_INDIRECT_MMIO are not
> selected, the I/O workaround ioremap() voids and the static key is
> not used at all.

Why bother with the complex static key?  ioremap isn't exactly a fast
path.  Just make it a normal branch if enabled, with the option to
compile it out entirely as in your patch.