Re: [PATCH v2 3/6] arm64: cpufeature: Extend bbml2_noabort support list

[Anshuman Khandual]

On 08/07/26 8:23 PM, Suzuki K Poulose wrote:
> On 08/07/2026 15:43, Linu Cherian wrote:
>> Add below cpus to the midr list, which supports
>> BBML2_NOABORT.
>>
>> Cortex A520(AE)
>> Cortex A715
>> Cortex A720(AE)
>> Cortex A725
>> Neoverse N3
>> C1-Nano
>> C1-Pro
>> C1-Ultra
>> C1-Premium
>>
>> C1-Ultra and C1-Premium both suffer from erratum 3683289,
>> where Break-Before-Make must be followed to avoid a livelock.
>> For both CPUs, the erratum is fixed from r1p1.
>> Hence we do not enable BBML2_NOABORT for CPU revisions <= r1p0.
> 
> Please could you also update the list of errata here :
> 
> Documentation/arch/arm64/silicon-errata.rst

Agreed. There are existing errata entries for C1-Ultra
and C1-Premimum although this errata will not have any
corresponding ARM64_ERRATUM_ associated for now.
> 
>>
>> The relevant SDENs are:
>> * C1-Ultra: https://developer.arm.com/documentation/111077/9-00/
>> * C1-Premium: https://developer.arm.com/documentation/111078/9-00/
>>
>> Signed-off-by: Linu Cherian <linu.cherian@xxxxxxx>
>> ---
>>   arch/arm64/kernel/cpufeature.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index 9a22df0c5120..adcabea80fcb 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -2152,6 +2152,15 @@ bool cpu_supports_bbml2_noabort(void)
>>           MIDR_ALL_VERSIONS(MIDR_NVIDIA_OLYMPUS),
>>           MIDR_ALL_VERSIONS(MIDR_AMPERE1),
>>           MIDR_ALL_VERSIONS(MIDR_AMPERE1A),
>> +        MIDR_ALL_VERSIONS(MIDR_CORTEX_A520AE),
>> +        MIDR_ALL_VERSIONS(MIDR_CORTEX_A715),
>> +        MIDR_ALL_VERSIONS(MIDR_CORTEX_A720AE),
>> +        MIDR_ALL_VERSIONS(MIDR_CORTEX_A725),
>> +        MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N3),
>> +        MIDR_ALL_VERSIONS(MIDR_C1_NANO),
>> +        MIDR_ALL_VERSIONS(MIDR_C1_PRO),
> 
> And mention it here, so that it is evident from the code alone ?
> 
>> +        MIDR_REV_RANGE(MIDR_C1_ULTRA, 1, 1, 0xf),
>> +        MIDR_REV_RANGE(MIDR_C1_PREMIUM, 1, 1, 0xf),
> 
> 
> Suzuki
> 
> 
>>           {}
>>       };
>>   
>