Re: [PATCH v3 2/3] iommu/arm-smmu-v3: Detect Tegra264 erratum

[Ashish Mhetre <amhetre@nvidia.com>]

On 6/5/2026 7:40 PM, Jason Gunthorpe wrote:
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> On Fri, Jun 05, 2026 at 07:35:35PM +0530, Ashish Mhetre wrote:
>>>> +{
>>>> +     if (!(smmu->options & ARM_SMMU_OPT_TLBI_TWICE))
>>>> +             return false;
>>> Maybe we should make this a static key?
>> Okay. Shall I add just static key and remove option bit, or
>> have static key alongside existing option bit such that
>> static_branch_unlikely will precede the option bit check?
> You'd have the static key and the options. Keep it simple, enable the
> static key once if any driver probes to set TWICE. Check the key
> before options to get the best code gen

Okay, I'll incorporate this in V4 and send.

> But IDK if it is really worth it, there are already lots of branches
> on the performance tlbi flow, and we didn't do this for other tlbi
> affecting errata..
>
> IDK if we really care about branches we should also be doing things
> like disabling the range/non-range paths and ATC based on what is
> actually in use..
>
> Jason