linux-kernel - Re: [PATCH] arm64/sysreg: Update ID_AA64MMFR2

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Date: Mon, 22 Apr 2024 08:38:40 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Will Deacon <will@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
 Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/sysreg: Update ID_AA64MMFR2_EL1 register



On 4/19/24 19:16, Will Deacon wrote:
> On Fri, Apr 19, 2024 at 07:43:25AM +0530, Anshuman Khandual wrote:
>> This updates ID_AA64MMFR2_EL1.VARange register fields as per the definition
>> based on DDI0601 2024-03.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Mark Brown <broonie@...nel.org>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>> This applies on v6.9-rc4
>>
>>  arch/arm64/tools/sysreg | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
>> index a4c1dd4741a4..6d7213dcbeb5 100644
>> --- a/arch/arm64/tools/sysreg
>> +++ b/arch/arm64/tools/sysreg
>> @@ -1739,6 +1739,7 @@ EndEnum
>>  UnsignedEnum	19:16	VARange
>>  	0b0000	48
>>  	0b0001	52
>> +	0b0010	56
> 
> Is anybody using this? I'm not sure there's a lot of value in adding
> these fields one-by-one for the sake of completeness.

This is not being used currently but will be required for upcoming
features. I was under the impression that register fields (atleast
for the ID registers) should be kept updated, with latest released
spec ? Besides lately arch/arm64/tools/sysreg serves as very good
reference for all necessary register fields.

https://developer.arm.com/documentation/ddi0601/2024-03/AArch64-Registers/ID-AA64MMFR2-EL1--AArch64-Memory-Model-Feature-Register-2