[PATCH v2 09/15] scsi: ufs: deprecate 'freq-table-hz' property
Krzysztof Kozlowski
krzysztof.kozlowski at canonical.com
Wed Feb 23 01:15:36 PST 2022
On 22/02/2022 19:16, Bjorn Andersson wrote:
> On Tue 22 Feb 06:58 PST 2022, Krzysztof Kozlowski wrote:
>
>> The 'freq-table-hz' is not correct in DT schema, because '-hz' suffix
>> defines uint32 type, not an array. Therefore deprecate 'freq-table-hz'
>> and use 'freq-table' instead.
>>
>
> Patch looks good in itself, but why don't we use opp-table to describe
> the performance states?
>
> In particular looking at the two columns of frequencies for various
> Qualcomm boards they require different performance-states.
>
> A concrete example is sm8350.dtsi, which specifies 75MHz and 300MHz as
> the first frequency pair. The lower level requires the VDD_CX power rail
> to be at least &rpmhpd_opp_low_svs, the higher frequency has a
> required-opps of &rpmhpd_opp_nom.
>
>
> As this isn't possible to express in the current binding we've just been
> forced to always run at a higher voltage level and kept this in the todo
> list.
>
> But rather than migrating freq-table-hz to freq-table and then having to
> introduce an opp table to express the power constraints, could we
> perhaps skip the intermediate step?
>
> Or would you have any other suggestion about how we can represent the
> required-opps level together with the freq-table (if that's what we want
> to stick with).
Usage of OPP tables is interesting solution. It would solve your problem
of power rail levels. This would need several opp-tables - one for each
clock, which is not a big problem.
The problem is that I do not have any UFS hardware (none of my Samsung
Exynos boards have UFS... I don't have even arm64 Exynos chips :( ), so
implementing it theoretically will be painful.
OTOH, I believe that having a working dtschema is very useful. Having
dtschema without errors/warnings is even worth some churn/intermediary work.
The intermediary work is also not that big. Once proper OPP is
implemented, we will have "just" two deprecated properties in the bindings.
Best regards,
Krzysztof
More information about the Linux-mediatek
mailing list