linux-kernel - Re: [PATCH 17/18] arm64: dts: Convert to the hierarchical CPU topology layout for MSM8916

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Date:   Tue, 16 Jul 2019 14:36:31 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Raju P . L . S . S . S . N" <rplsssn@...eaurora.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Tony Lindgren <tony@...mide.com>,
        Kevin Hilman <khilman@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Souvik Chakravarty <souvik.chakravarty@....com>,
        linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Lina Iyer <lina.iyer@...aro.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>
Subject: Re: [PATCH 17/18] arm64: dts: Convert to the hierarchical CPU
 topology layout for MSM8916

On Tue, Jul 16 2019 at 08:47 -0600, Sudeep Holla wrote:
>On Mon, May 13, 2019 at 09:22:59PM +0200, Ulf Hansson wrote:
>> From: Lina Iyer <lina.iyer@...aro.org>
>>
>> In the hierarchical layout, we are creating power domains around each CPU
>> and describes the idle states for them inside the power domain provider
>> node. Note that, the CPU's idle states still needs to be compatible with
>> "arm,idle-state".
>>
>> Furthermore, represent the CPU cluster as a separate master power domain,
>> powering the CPU's power domains. The cluster node, contains the idle
>> states for the cluster and each idle state needs to be compatible with the
>> "domain-idle-state".
>>
>> If the running platform is using a PSCI FW that supports the OS initiated
>> CPU suspend mode, which likely should be the case unless the PSCI FW is
>> very old, this change triggers the PSCI driver to enable it.
>>
>> Cc: Andy Gross <andy.gross@...aro.org>
>> Cc: David Brown <david.brown@...aro.org>
>> Signed-off-by: Lina Iyer <lina.iyer@...aro.org>
>> Co-developed-by: Ulf Hansson <ulf.hansson@...aro.org>
>> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
>> ---
>
>[...]
>
>> @@ -166,12 +170,57 @@
>>  				min-residency-us = <2000>;
>>  				local-timer-stop;
>>  			};
>> +
>> +			CLUSTER_RET: cluster-retention {
>> +				compatible = "domain-idle-state";
>> +				arm,psci-suspend-param = <0x1000010>;
>> +				entry-latency-us = <500>;
>> +				exit-latency-us = <500>;
>> +				min-residency-us = <2000>;
>> +			};
>> +
>> +			CLUSTER_PWRDN: cluster-gdhs {
>> +				compatible = "domain-idle-state";
>> +				arm,psci-suspend-param = <0x1000030>;
>> +				entry-latency-us = <2000>;
>> +				exit-latency-us = <2000>;
>> +				min-residency-us = <6000>;
>> +			};
>>  		};
>>  	};
>
>I was trying to understand the composition of composite state parameters
>in this series and that made me look at these DT examples.
>
This was meant to depict a hierarchical state format for OSI.

>What format does the above platform use ? I tried matching them to
>both original as well as extended format and I fail to understand.
>Assuming original format:
>	State         power_state PowerLevel  StateType     StateID
>	SPC           0x40000002   0(core)    0(Retention)  0x2 (Res0 b[29]=1?)
>	CLUSTER_RET   0x1000010   1(clusters) 0(Retention)  0x10
>	CLUSTER_PWRDN 0x1000030   1(clusters) 0(Retention?) 0x30
>Now extended format:
>	State         power_state StateType     StateID
>	SPC           0x40000002  0(Retention)  0x40000002 (Res0 b[29]=1?)
>	CLUSTER_RET   0x1000010   0(Retention)  0x1000010
The composite state would comprise of CPU state and  Cluster state.
So for the last CPU entering idle -
(CLUSTER_RET | SPC)
0x41000012
>	CLUSTER_PWRDN 0x1000030   0(Retention?) 0x1000030
>
(CLUSTER_PWRDN | SPC)
0x41000032

Hope this helps.

Lina