linux-kernel - Re: [PATCH 1/6] MIPS: Loongson64: Do not write the read only field LPA of CP0

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Date:   Fri, 30 Oct 2020 14:22:21 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhc@...ote.com>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH 1/6] MIPS: Loongson64: Do not write the read only field
 LPA of CP0_CONFIG3

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@...ngson.cn>
>> ---
>>   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.

And also we can see the following description in the chapter
"9.45 Configuration Register 3 (CP0 Register 16, Select 3)" of
MD00091-2B-MIPS64PRA-AFP-05.04:
"The Config3 register encodes additional capabilities.
All fields in the Config3 register are read-only."

Thanks,
Tiezhu

>
> Thanks.
>
> - Jiaxun