Re: [PATCH 2/2] iommu: arm-smmu-qcom: add sdm670 compatible

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 21/09/2022 23:14, Konrad Dybcio wrote:
>> Unfortunately I don't get this explanation... you mean some other
>> firmware requires Linux drivers to use specific compatibles instead of
>> one fallback?
> No, perhaps I misunderstood you.
> 
>>
>> All of these do not have driver data, so they are essentially compatible
>> for Linux driver. Growing this list in the driver seems pointless. What
>> is the benefit of growing driver with same entries, except more patches?
> Compatible lists in smmu-impl files allow matching driver quirks for SMMUs themselves
> and consumer devices (such as MDSS). The situation is more complicated, because some
> qcom SMMUs also require more quirks than others (think 8974 vs 8994 vs 8996/pro&660&8998
> vs 845+ vs adreno smmu in various flavours), so all qcom SMMUs need to use
> `qcom_smmu_impl` and some others need even more quirks on top of that (that generally
> hurt performance or functionality, so we don't want them when they're unnecessary).
> If all generations of qcom SMMU implementation that bear the same name behaved anywhere
> near consistent, there would be no need for keeping this around, instead requiring only
> "qcom,broken-smmu" or something".

So where are the quirks? Again: driver data is empty.

Best regards,
Krzysztof