Re: [microblaze-uclinux] [PATCH] microblaze: Fix unaligned accesses

["Steve Magnani" <steve@xxxxxxxxxxxxxxx>]

Michal Simek <michal.simek@xxxxxxxxxxxxx> wrote:

> Hi,
> 
> John did the similar patch some month ago and it is in mmu and master
> branch
> http://developer.petalogix.com/git/gitweb.cgi?p=linux-2.6-microblaze.gi
> t;a=commit;h=c6c26dce3f0944971c6bfb76e6667369bec3c210
> 
> I added his patch to for-linus too (+ change the commit message a
> little bit)
> http://developer.petalogix.com/git/gitweb.cgi?p=linux-2.6-microblaze.gi
> t;a=commit;h=3447ef29a7f3b1fd0d8d58376950e695e04f6f8b
> 
> Do you have any reason why to include <linux/unaligned/be_byteshift.h>
> and use shifts instead of struct? 

I included only one of <be_byteshift.h> and <le_byteshift.h> and 
something wouldn't compile. The other arches seem to include something 
for both BE and LE so I followed suit.

> Do you have any investigation that shifts are faster?

No, although it occurred to me that performance could be platform-
dependent, based on whether the Microblaze is built with a barrel shifter 
or not. I expected that someone with more knowledge than I would critique 
the decision; my main goal was to point out the issue and set some kind 
of fix in motion.

> Anyway one patch is there and we should do more tests and of course we
> can add this patch later in rc.
> 
> + I wanted to sync header style with adding indentation. Please do not
> revert it.
> 
> Thanks,
> Michal
> 
> Steven.J.Magnani@xxxxxxxxxxxxxxxxxx wrote:
> > Microblaze requires special handling of unaligned accesses.
> > 
> > Signed-off-by: Steven J. Magnani <steve@xxxxxxxxxxxxxxx>
> > ---
> > There may be more efficient choices than byteshift, 
> > but access_ok is incorrect.
> > 
> > diff -uprN a/arch/microblaze/include/asm/unaligned.h
> b/arch/microblaze/include/asm/unaligned.h
> > --- a/arch/microblaze/include/asm/unaligned.h	2009-06-01
> 18:17:48.000000000 -0500
> > +++ b/arch/microblaze/include/asm/unaligned.h	2009-06-01
> 18:18:32.000000000 -0500
> > @@ -10,13 +10,14 @@
> >  #ifndef _ASM_MICROBLAZE_UNALIGNED_H
> >  #define _ASM_MICROBLAZE_UNALIGNED_H
> >  
> > -# ifdef __KERNEL__
> > +#ifdef __KERNEL__
> >  
> > -# include <linux/unaligned/access_ok.h>
> > -# include <linux/unaligned/generic.h>
> > +#include <linux/unaligned/le_byteshift.h>
> > +#include <linux/unaligned/be_byteshift.h>
> > +#include <linux/unaligned/generic.h>
> >  
> > -# define get_unaligned	__get_unaligned_be
> > -# define put_unaligned	__put_unaligned_be
> > +#define get_unaligned	__get_unaligned_be
> > +#define put_unaligned	__put_unaligned_be
> >  
> > -# endif	/* __KERNEL__ */
> > +#endif	/* __KERNEL__ */
> >  #endif /* _ASM_MICROBLAZE_UNALIGNED_H */
> > 
> > ___________________________
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> > microblaze-uclinux@xxxxxxxxxxxxxx
> > Project Home Page :
> http://www.itee.uq.edu.au/~jwilliams/mblaze-uclinux
> > Mailing List Archive :
> http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/
> > 
> > 
> 
> -- 
> Michal Simek, Ing. (M.Eng)
> PetaLogix - Linux Solutions for a Reconfigurable World
> w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f:
> +61-7-30090663
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> 


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