[PATCH] powerpc: Merge align.c

Kumar Gala galak at kernel.crashing.org
Thu Nov 17 02:15:09 EST 2005

On Nov 16, 2005, at 3:36 AM, Gabriel Paubert wrote:

> On Tue, Nov 15, 2005 at 08:19:58PM -0600, Becky Bruce wrote:
>> Ben,
>> Yeah,  I clearly shouldn't run testcases at 11pm, because I got in a
>> rush and only confirmed that lmw/stmw were actually taking the
>> exception.  Those 2 are working beautifully.  To test the others, I
>> need to run on a different board which, of course,  isn't bootable at
>> the moment.  As soon as I can get that up and running, I'll try  
>> some of
>> the other cases and let you know how it goes......
>> BTW, Based on the pile of docs I have here, I think the list of
>> alignment-exception-causing events on FSL's current parts (603, 603e,
>> 750, 74x, 74xx, e500) is:
> The 603 is still in production? And is the upcoming 8641 exactly
> the same as the 74xx series in this respect?

603 is used in all 82xx/83xx processors from Freescale. The 8641 is  
the same core as 7448.

>> - single and double precision floating point ld/st ops (non-E500, non
>> data size aligned)
> Hmm, you can load a double from any 4 byte aligned address AFAIR.

This is only because every processor handles the misalignment for  
you.  Its completely valid for someone to build a PPC that has an  
alignment exception in this case.

>> - dcbz to WT or CI memory (all procs)
>> - dcbz with cache disabled (all procs but 603e?)
>> - misaligned little endian accesses (603e)
> I understand that you mention it for completeness since we
> don't care about LE mode AFAICT. But I believe that there
> were some differences between 603 and 603e in this area.
> However we do care about byte reversal instructions, which
> probably believe like the corresponding normal instruction
> (i.e., lwbrx has the same rules as lwzx, etc.)
>> - lwarx/stwcx (all procs)
> And ldarx/stdcx. on 64 bit, but these ones should not
> be emulated. So it's easy ;-)
>> - multiple/string with LE set (750, 603e, 7450, 7400)
> Again LE mode is probably irrelevant.

Agree with that. We dont support LE on classic.

>> - eciwx/ecowx (750, 7450, 7400)
> Have these instructions ever been used for something
> under Linux?

I dont believe so.

>> - a couple of others related to vector processing
> Which ones? The Altivec load and store instructions
> simply mask the low order bits AFAIR.

SPE misalignment is something to look at.

>> If anybody knows offhand of something missing there, let me know.
> Nothing, but did you check when crossing a segment (256MB) boundary.
> I seem to remember that some processors performed misaligned
> load/store across pages but not across segments.

- kumar

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