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Re: [PATCH] MIPS: Define __arch_swab64 for all mips r2 cpus (v2).

To: Ralf Baechle <>
Subject: Re: [PATCH] MIPS: Define __arch_swab64 for all mips r2 cpus (v2).
From: "Maciej W. Rozycki" <>
Date: Wed, 1 Jul 2009 01:37:04 +0100 (BST)
Cc: David Daney <>,
In-reply-to: <>
Original-recipient: rfc822;
References: <> <>
User-agent: Alpine 2.00 (LFD 1167 2008-08-23)
On Mon, 29 Jun 2009, Ralf Baechle wrote:

> > Some CPUs implement mipsr2, but because they are a super-set of
> > mips64r2 do not define CONFIG_CPU_MIPS64_R2.  Cavium OCTEON falls into
> > this category.  We would still like to use the optimized
> > implementation, so since we have already checked for
> > CONFIG_CPU_MIPSR2, checking for CONFIG_64BIT instead of
> > CONFIG_CPU_MIPS64_R2 is sufficient.
> > 
> > Change from v1: Add comments about why the change is safe.
> Thanks, applied.  Though this sort of patch make me thing that maybe we
> rather should have treated the cnMIPS cores differently.

 This is a pure code generation option and it asks for "select 
CPU_MIPS64_R2" under CPU_OCTEON (or whatever option is used for that 
chip).  Or something like "select ISA_MIPS64_R2" actually, as we want to 
keep CPU_foo as the -march=, etc. designator.  IOW it looks like we lack 
ISA supersetting along the lines of how tools handle it.


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