Subject: Re: Revision K strongarms ...
To: Tony Houghton <tonyh@tcp.co.uk>
From: Neil A. Carson <neil@causality.com>
List: port-arm32
Date: 05/02/1998 14:10:07
Tony Houghton wrote:

> I don't know the exact details of the bug, and the superficial details
> I've seen here have two conflicting views. Most people seem to think
> that the problem is caused by the LDM instruction itself lying on a page
> boundary, but at least one posting says it's if the data it's loading is
> on a page boundary. If the latter, it rules out one possible solution ie
> replacing LDM with LDM followed by a noop and getting the linker to swap
> them if necessary. That wouldn't be popular with the porting team
> anyway, requiring the compiler and linker to be patched and most
> binaries to be recompiled.

It's if the instruction is on the end of a page, not the data.

> Another solution is to replace all LDMs with a set of LDRs, which I
> gather gcc already has an option before. Although the resulting code is
> theoretically just as fast on StrongARMs, I guess it would be
> unacceptably detrimental to code density, and hence cache misses to some
> extent. Still, not as bad as the pre-shared library versions I should
> think, and it would be something that affected users could manage for
> ourselves, although I think certain sources would have to be made more
> available in ready-to-compile-for-arm32 form.

I didn't know gcc had that option.

> As for getting StrongARM's replaced, I've spoken to someone (well before
> this thread blew up) who thinks he could get the "raw" devices from a
> supplier as a private customer even in quantities of one for probably
> better than the 50ukp suggested here. And from personal experience I

Yeah, they cost about 30 quid these days.

> think the likes of IFEL and Simtec wouldn't charge more than 30ukp for
> the remount work. If Neil still has close ties with Simtec perhaps he
> could arrange something.

Simtec (I think) would be happy to remount if a big enough chunk of guys
got together.

> OTOH the Clan has started promoting Linux and NetBSD to some extent [1],
> so maybe we could put a bit of pressure on Acorn after all ;-).
> 
> [1] The latest mailing is reasonably sensible, unlike the utter bollocks
> about ARMLinux ("the UNIX-like programming language") a while ago.

Yeah, I wrote it :-)

Did they not put my name by it? I'm not actually in the clan, and wasn't
sent a free copy :-(

	Neil