Messages in this thread | | | Subject | Re: [PATCH V2] ARM: cpuidle: Support asymmetric idle definition | From | Sudeep Holla <> | Date | Fri, 2 Jun 2017 10:39:21 +0100 |
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On 02/06/17 10:25, Daniel Lezcano wrote: > On 02/06/2017 11:20, Sudeep Holla wrote: >> >> >> On 01/06/17 12:39, Daniel Lezcano wrote: >>> Some hardware have clusters with different idle states. The current code does >>> not support this and fails as it expects all the idle states to be identical. >>> >>> Because of this, the Mediatek mtk8173 had to create the same idle state for a >>> big.Little system and now the Hisilicon 960 is facing the same situation. >>> >>> Solve this by simply assuming the multiple driver will be needed for all the >>> platforms using the ARM generic cpuidle driver which makes sense because of the >>> different topologies we can support with a single kernel for ARM32 or ARM64. >>> >>> Every CPU has its own driver, so every single CPU can specify in the DT the >>> idle states. >>> >>> This simple approach allows to support the future dynamIQ system, current SMP >>> and HMP. >>> >>> It is unoptimal from a memory point of view for a system with a large number of >>> CPUs but nowadays there is no such system with a cpuidle driver on ARM. >>> >> >> While I agree this may be simple solution, but just not necessary for >> systems with symmetric idle states especially one with large number of >> CPUs. I don't like to see 96 CPU Idle driver on say ThunderX. So we >> *must* have some basic distinction done here. >> >> IMO, we can't punish a large SMP systems just because they don't have >> asymmetric idle states. > > Can you point me in the upstream kernel a DTS with 96 cpus and using the > cpuidle-arm driver ? >
The bindings are upstream right. Not all DTS are upstream, firmware generate them especially for large systems.
Check arch/arm64/boot/dts/cavium/thunder{,2}-{88,99}xx.dtsi, it has supports PSCI and firmware can update DTB to add the idle states. They are systems with 96 and 128 CPUs.
-- Regards, Sudeep
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