Re: [PATCH 1/6] MIPS: Loongson64: Do not write the read only field LPA of CP0_CONFIG3

[Jiaxun Yang]

在 2020/10/30 20:13, Jiaxun Yang 写道:
> 在 2020/10/30 14:22, Tiezhu Yang 写道:
> > On 10/30/2020 12:00 PM, Jiaxun Yang wrote:
> > > 在 2020/10/29 16:02, Tiezhu Yang 写道:
> > > > The field LPA of CP0_CONFIG3 register is read only for Loongson64, 
> > > > so the
> > > > write operations are meaningless, remove them.
> > > >
> > > > Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
> > > > ---
> > > >   arch/mips/include/asm/mach-loongson64/kernel-entry-init.h | 8 
> > > > --------
> > > >   arch/mips/loongson64/numa.c | 3 ---
> > > >   2 files changed, 11 deletions(-)
> > > Hi Tiezhu,
> > >
> > > AFAIK it's not read only on 3A1000.
> > > Have you check with hardware guys?
> >
> > Hi Jiaxun,
> >
> > Yes, I checked it before send this patch,  the field LPA of CP0_CONFIG3
> > on 3A1000 is also read only,  we can see the related description in the
> > chapter 3.22 of Loongson_3A1000_cpu_user_2.
>
> On page 36, it said:
> "能否写ELPA位依赖于Config3寄存器的LPA域 。当Config3的LPA位为0时，
> PageGrain的ELPA位被置位。"
>
> Don't know if it matters.
>
> @Huacai, Any comments? Do you know why it exists here?

Confirmed by another rev of the manual that it's only a tip for implementer.
I guess my assumption was wrong.
LPA should be read-only though.....

Thanks
- Jiaxun

> Thanks
>
> - Jiaxun