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From: Dan Malek <dan@embeddededge•com>
To: "Fillod Stephane" <stephane.fillod@thomson•net>
Cc: linuxppc-dev@ozlabs•org
Subject: Re: [PATCH] invalid instructions in kernel mode
Date: Thu, 31 Mar 2005 22:45:39 -0500	[thread overview]
Message-ID: <12cdcb5f3594a4e2b4869f3666079a8e@embeddededge.com> (raw)
In-Reply-To: <1CFEB358338412458B21FAA0D78FE86D4F0D25@rennsmail02.eu.thmulti.com>


On Mar 31, 2005, at 2:17 PM, Fillod Stephane wrote:

> What I don't understand, is how the FP load/store operations
> in misc.S can "work" on a system with no FPU and *no* math-emu?

What should happen is to follow the example used by 8xx for
many years.  As I said, when math emulation is disabled, there is
still code that will emulate the load/store FP instructions.  These
instructions are used in may places even if user applications
are compiled without any FP usage.

> Many years? Allow me to doubt it's really used :).

I wrote it in 1998 for the 8xx.  I thought 4xx and e500 used the
same model.  If they don't, they should.

> Though, it does work for 8xx thanks to Soft_emulate_8xx, but doesn't
> for other FPU-less cores when CONFIG_MATH_EMULATION is disabled.

Well, then that should get fixed.

> So here is another patch,

The only patch I'm interested in is making the 4xx and e500 follow the
same path as 8xx.  All of the non-FP cores should work the same way.
The e500 is a special case because it doesn't have a classic FPU but
rather can utilize the SPE for floating point.  Put some thought into 
that.

Thanks.


	-- Dan

  reply	other threads:[~2005-04-01  3:45 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-03-31 19:17 [PATCH] invalid instructions in kernel mode Fillod Stephane
2005-04-01  3:45 ` Dan Malek [this message]
  -- strict thread matches above, loose matches on Subject: below --
2005-04-08 17:36 Fillod Stephane
2005-04-11 15:39 ` Kumar Gala
2005-04-05 12:25 Fillod Stephane
2005-04-05 12:24 Fillod Stephane
2005-04-05 16:16 ` Dan Malek
2005-03-31 17:47 Fillod Stephane
2005-03-31 18:15 ` Dan Malek
2005-04-01 10:04 ` Kumar Gala
2005-04-07 17:38 ` Tom Rini
2005-04-07 21:41   ` Kumar Gala
2005-04-07 22:14     ` Tom Rini
2005-04-07 22:29       ` Kumar Gala
2005-04-08 16:02         ` Kumar Gala

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