Re: [PATCH 1/2] arm64: dts: qcom: sdm630: Drop the cluster idle states

[Konrad Dybcio]

On 10/20/26 6:15 PM, Fabricio Akio wrote:
> On 10/15/26 3:51 PM, Konrad Dybcio wrote:
>> I threw an LLM at the downstream tree and it decoded the states to:
>>
>> C2D, no cluster state    2        0x00000002
>> C3, no cluster state    3        0x40000003
>> pwr/perf L2 D2D + C2D    L2 2        0x01000022
>> pwr/perf L2 D2D + C3    L2 2        0x41000023
>> pwr/perf L2 D2E + C3    L2 3        0x41000033
>> pwr/perf L2 D4 + C3    L2 4        0x41000043
>> System PC + L2 D4 + C3    sys3, L2 4    0x42000343
>>
>> sorry for getting it wrong years ago!
> 
> Thanks! I had decoded the same values, but I didn't just put them in
> place of the old ones. This firmware supports OS-initiated mode and
> refuses platform-coordinated mode ("psci: [Firmware Bug]: failed to
> set PC mode: -3", PSCI DENIED). In OS-initiated mode a cluster state
> may only be requested by the last running CPU of the cluster, which a
> flat cpu-idle-states list cannot express. I tried it: with 0x41000043
> in the flat list the firmware returns DENIED to nearly every request,
> accepting only the few that come from a cluster's last running CPU,
> and the idle CPUs spin on it again, at about twice the battery current.
> Linux runs OSI only with the CPUs described as PSCI power domains,
> with 0x41000043 as each cluster's domain-idle-state and 0x42000343 for
> system power collapse above them. I'm working on that, but I'm not
> sure yet when it will be ready, so this is not a placeholder for a
> replacement coming right behind it.

See:

https://lore.kernel.org/linux-arm-msm/20261015-b4-shikra_lpm_addition-v2-0-ac7f1a0d5638@xxxxxxxxxxxxxxxx/

https://lore.kernel.org/lkml/20261005-s2idle_state-v1-0-3c402c66f388@xxxxxxxxxxxxxxxx/

> Dropping the states is not the complete fix, but it helps now, because
> as they are they do harm: cpuidle records no successful entry into any
> of them, and since the deepest of them is what an idle CPU picks, each
> failed request is retried instead of sleeping. On the Moto X4
> that is about 133,000 failed entries per second with the screen off,
> and the battery current goes from 277 mA to about 115 mA without them.
> 
> Is dropping them first OK with you?

Temporarily, yes

Konrad