Re: FOR COMMENT: void __iomem * and similar casts are Bad News

[David Brownell <david-b@pacbell.net>]

On Wednesday 03 September 2008, Woodruff, Richard wrote:
> Fixed translations do have some benefits.  You can ensure that you
> are using section or super section descriptors to cover large areas.
> This does result in better TLB usage.  Along with freeing up TLB
> entries you also generally avoid TLB misses on IO calls which
> touch a variety of internal spaces as part of the IRQ sequence.    

... which is exactly why some linux/arch/... code makes sure ioremap()
can return fixed mappings instead of always requiring dynamic ones.


> Frankly I've never been convinced that a multi OMAP1/2/3 image makes much
> sense apart forcing better code structure

Which is actually a pretty big thing.  Along with "structure", it
helps avoid #define collisions ... and also ensures that test
builds can cover increasing fractions of the code base, giving a
big win for maintainability.

Maintainability is a *big thing* ... without it, you ensure that
lots of code will begin bitrotting long before it needs to.


>		 and being kind of cool.  Each 
> chip has very different performance targets and is really better built with
> an optimized tool chain (ARMv5, ARMv6, ARMv7).  Doing multi-boots with in
> the same architecture family seems really good but across seems less so.

True enough, but that decision can be in the hands of whoever
builds a kernel.  If you want to deploy an A8-optimized system,
the kernel will be only one part of the equation.

- Dave
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