linux-kernel - Re: [PATCH] riscv: Update MIPS vendor id to 0x127.

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Message-ID: <8ccb619c-69ba-4a53-9d47-15f276d64f9f@htecgroup.com>
Date: Thu, 13 Nov 2025 16:07:29 +0000
From: Aleksa Paunovic <aleksa.paunovic@...cgroup.com>
To: "conor.dooley@...rochip.com" <conor.dooley@...rochip.com>
CC: Djordje Todorovic <Djordje.Todorovic@...cgroup.com>, Aleksa Paunovic
	<aleksa.paunovic@...cgroup.com>, "alex@...ti.fr" <alex@...ti.fr>,
	"aou@...s.berkeley.edu" <aou@...s.berkeley.edu>, "cfu@...ecomp.com"
	<cfu@...ecomp.com>, "conor@...nel.org" <conor@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"palmer@...belt.com" <palmer@...belt.com>, "pjw@...nel.org" <pjw@...nel.org>
Subject: Re: [PATCH] riscv: Update MIPS vendor id to 0x127.

On 11/4/25 15:09, Conor Dooley wrote:
> On Tue, Nov 04, 2025 at 02:06:31PM +0000, Aleksa Paunovic wrote:
>> On 11/4/25 14:18, Conor Dooley wrote:
>>
>>> On Tue, Nov 04, 2025 at 11:53:49AM +0000, Aleksa Paunovic wrote:
>>>> On 11/3/25 23:07, Conor Dooley wrote:
>>>>> On Mon, Nov 03, 2025 at 04:05:48PM +0100, Aleksa Paunovic wrote:
>>>>>> From: Chao-ying Fu <cfu@...ecomp.com>
> While I am here, you have a From: header with Chao-ying it it, but the
> patch has not been signed off by them.
>
>>>>>> [1] defines MIPS vendor id as 0x127.
>>>>>>
>>>>>> [1] https://mips.com/wp-content/uploads/2025/06/P8700_Programmers_Reference_Manual_Rev1.84_5-31-2025.pdf
>>>>>>
>>>>>> Fixes: a8fed1bc03ace27902338e4f0d318335883ac847 ("riscv: Add xmipsexectl as a vendor extension")
>>>>> Incorrect format for fixes tags!
>>>> Will fix that in v2.
>>>>
>>>>>> Signed-off-by: Aleksa Paunovic <aleksa.paunovic@...cgroup.com>
>>>>>> ---
>>>>>>  arch/riscv/include/asm/vendorid_list.h | 2 +-
>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/arch/riscv/include/asm/vendorid_list.h b/arch/riscv/include/asm/vendorid_list.h
>>>>>> index 3b09874d7a6dfb8f8aa45b0be41c20711d539e78..55205f7938055ba2b744dba5118bba935bcac008 100644
>>>>>> --- a/arch/riscv/include/asm/vendorid_list.h
>>>>>> +++ b/arch/riscv/include/asm/vendorid_list.h
>>>>>> @@ -9,6 +9,6 @@
>>>>>>  #define MICROCHIP_VENDOR_ID	0x029
>>>>>>  #define SIFIVE_VENDOR_ID	0x489
>>>>>>  #define THEAD_VENDOR_ID		0x5b7
>>>>>> -#define MIPS_VENDOR_ID		0x722
>>>>>> +#define MIPS_VENDOR_ID		0x127
>>>>> How was this ever wrong? Do devices exist with this old ID? Do we need
>>>>> to support both as vendor IDs for MIPS?
>>>> I'm not sure how it first started, but since we worked on qemu as well, we never noticed any issues while testing. 
>>>> It shouldn't cause any problems in the future though.
>>> So all the hardware uses the 0x127 id? Where did 0x722 come from?
>>> I recall qemu defaults to 0x0, so were none of the mips code paths
>>> tested, or were they tested with a qemu modified to use 0x722?
>>
>> That is correct, all hardware uses the 0x127 id. 
>>
>> I'm not sure where we got 0x722 from - perhaps I or someone else misread the value 
>>
>> (0x27 and 0x2 are both mentioned in the Programmer's Guide mvendorid bit descriptions).
>>
>>
>> Everything was tested with qemu modified to use 0x722. Please see [1], for example.
>>
>>
>> [1] https://patchew.org/QEMU/20250717093833.402237-1-djordje.todorovic@htecgroup.com/20250717093833.402237-4-djordje.todorovic@htecgroup.com/
> Okay, cool. Can you put this information into the commit message? It
> should really explain what went wrong and what is impacted by the
> change.
Will do. Thanks again!