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

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Message-ID: <bb3a2237-6dde-4231-a016-faf190f9a877@htecgroup.com>
Date: Tue, 4 Nov 2025 14:06:31 +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 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>
>>>>
>>>> [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/


I apologize for the confusion.