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Re: [PATCH V2 3/8] MIPS: BMIPS: Add CFLAGS, Makefile entries for BMIPS

To: Kevin Cernekee <cernekee@gmail.com>
Subject: Re: [PATCH V2 3/8] MIPS: BMIPS: Add CFLAGS, Makefile entries for BMIPS
From: Ralf Baechle <ralf@linux-mips.org>
Date: Fri, 11 Nov 2011 17:20:39 +0000
Cc: linux-mips@linux-mips.org
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On Fri, Nov 11, 2011 at 08:57:39AM -0800, Kevin Cernekee wrote:

> At a high level, the CONFIG_CPU_BMIPS* settings are used to make
> compile-time decisions that differentiate BMIPS from standard MIPS32,
> and that differentiate the BMIPS CPUs from one another.
> 
> 
> Present and future uses include:
> 
> Figuring out which set of proprietary BMIPS CP0 registers / core
> registers to use, where they are located, bit fields, etc.
> 
> Per-BMIPS SMP operations and capabilities
> 
> Per-BMIPS performance counter access
> 
> cpu-feature-overrides.h
> 
> HIGHMEM, SMP, and other basic features
> 
> eDSP instruction set (different on each BMIPS, and BMIPS-specific)
> 
> Cache architecture and BMIPS-specific cache optimizations
> 
> 
> Some of these could potentially be replaced with a "switch
> (current_cpu_type())" but others are a little trickier (i.e. they show
> up in low-level PM resume code, exception vectors, or other sensitive
> places).
> 
> 
> It is true that BMIPS uses -mips32 for compilation.  If the criteria
> for adding a new CONFIG_CPU_* choice is whether it selects a new
> instruction set or compilation flags, do you think it makes sense to
> remove BMIPS* from the "CPU selection" menu, enable
> CONFIG_CPU_MIPS32_R1 for BMIPS platforms, and call our options
> something different?  e.g.
> 
> CONFIG_BMIPS
> CONFIG_BMIPS3300
> CONFIG_BMIPS4350
> CONFIG_BMIPS4380
> CONFIG_BMIPS5000

Fair enough; sorting that kind of thing will need some effort across
the tree at some point in the future.

I notice there seems to be only CPU core support; are you planning
to submit board support code as well?

  Ralf

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