> Yes. Most 64bit MIPS processors cannot access 64bit content
> of registers when it is in 32bit mode.
For clarity, there is no 32/64-bit mode in MIPS processors. There is a
mode in which 64-bit OPERATIONS are enabled (that is, those instructions
which operate on the full width of the registers) - See the definition
of 64-bit Operations Enable in the MIPS64 Architecture for Programmers,
volume III. Note that such operations are always enabled while the
processor is running in Kernel Mode.
The patch is a little short on context, but if you've got a 64-bit
kernel, I had always assumed that save/restore of context is always done
with LD/SD, not by figuring out whether a process has 64-bit operations
enabled, then doing a conditional LD/SD or LW/SW.
/gmu
---
Michael Uhler, Chief Technology Officer
MIPS Technologies, Inc. Email: uhler AT mips.com
1225 Charleston Road Voice: (650)567-5025 FAX: (650)567-5225
Mountain View, CA 94043
> -----Original Message-----
> From: linux-mips-bounce@linux-mips.org
> [mailto:linux-mips-bounce@linux-mips.org] On Behalf Of Fuxin Zhang
> Sent: Wednesday, April 18, 2007 6:32 AM
> To: Ralf Baechle
> Cc: tiansm@lemote.com; linux-mips@linux-mips.org; Fuxin Zhang
> Subject: Re: [PATCH 3/16] Kconfig update for lemote fulong mini-PC
>
>
> >> +
> >>
> >
> > Is there anything in implementation of this option
> Loongson2-specific?
> >
> Yes. Most 64bit MIPS processors cannot access 64bit content
> of registers when it is in 32bit mode.
>
> Loongson2 has no 32/64 mode bit in fact.
>
> And the usage arise from Loongson2's multimedia extension,
> which is also uniq.
> > If not then I suggest we make this option loook like:
> >
> > bool "Save 64bit integer registers" if
> CPU_SUPPORTS_64BIT_KERNEL &&
> > 32BIT
> >
> > Somebody else might have a use for it!
> >
> > Ralf
> >
> >
> >
> >
> >
>
>
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