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
