Re: [microblaze-uclinux] RE: CONFIG_OPT_LIB_FUNCTION crashes kernel without a barrel shifter

["Steven J. Magnani" <steve@xxxxxxxxxxxxxxx>]

On Mon, 2009-10-26 at 08:35 +0100, Michal Simek wrote:
> 
> John Linn wrote:
> >> -----Original Message-----
> >> From: John Linn
> >> Sent: Friday, October 23, 2009 1:01 PM
> >> To: microblaze-uclinux@xxxxxxxxxxxxxx
> >> Subject: CONFIG_OPT_LIB_FUNCTION crashes kernel without a barrel
> > shifter
> >> On an MMU kernel, I see that when this feature is enabled in the
> > kernel config, and there is no
> >> barrel shifter in h/w, the kernel won't boot.
> >>
> >> I believe the lack of barrel shifter is the cause, but not 100%
> > confident.
> > 
> > It looks like you have to have both of these for the failure to boot.
> > 
> > CONFIG_OPT_LIB_FUNCTION=y
> > CONFIG_OPT_LIB_ASM=y
> 
> yes, you are right - asm implementation use barrel-shifter instruction.
> 
> Thanks,
> Michal

Aha. This explains the problems I had earlier in the year getting the
assembly memcpy() to work (ref:
http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/archive/2009/05/msg00197.html).

At the time I was working with an EDK that didn't have the barrel
shifter. I withdraw my claim that the implementation is buggy.

--Steve

> 
> > 
> >> The help in the kernel config indicates it might be sub-optimal, but
> > not crashing.  The mmu_defconfig
> >> uses this option.
> >>
> >> Thanks,
> >> John
> > 
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