linux-kernel - [PATCH V2] arm64: add SCHED_CLUSTER's dependency on ACPI

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Date:   Mon, 25 Apr 2022 11:18:21 +0000
From:   王擎 <wangqing@...o.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "dietmar.eggemann@....com" <dietmar.eggemann@....com>
Subject: [PATCH V2] arm64: add SCHED_CLUSTER's dependency on ACPI


>> From: Wang Qing <wangqing@...o.com>
>> 
>> cluster sched_domain configured by cpu_topology[].cluster_sibling, 
>> which is set by cluster_id, cluster_id can only get from ACPI.
>> 
>> If the system does not enable ACPI, cluster_id is always -1, even enable
>> SCHED_CLUSTER is invalid, this is misleading. 
>> 
>> So we add SCHED_CLUSTER's dependency on ACPI here.
>>
>
>Any reason why this can't be extended to support DT based systems via
>cpu-map in the device tree. IMO we almost have everything w.r.t topology
>in DT and no reason to deviate this feature between ACPI and DT.
>
That's the problem, we parse out "cluster" info according to the
description in cpu-map, but do assign it to package_id, which used to
configure the MC sched domain, not cluster sched domain.

That is to say, "cluster" in cpu-map is used to describe the package_id.
We can't get cluster_id from DT.

Thanks,
Qing

>-- 
>Regards,
>Sudeep