Messages in this thread | | | Subject | Re: [PATCH v3 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver | From | Daniel Lezcano <> | Date | Mon, 16 Apr 2018 15:57:03 +0200 |
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On 16/04/2018 14:30, Lorenzo Pieralisi wrote: > On Mon, Apr 16, 2018 at 02:10:30PM +0200, Daniel Lezcano wrote: >> On 16/04/2018 12:10, Viresh Kumar wrote: >>> On 16-04-18, 12:03, Daniel Lezcano wrote: >>>> On 16/04/2018 11:50, Viresh Kumar wrote: >>>>> On 16-04-18, 11:45, Daniel Lezcano wrote: >>>>>> Can you elaborate a bit ? I'm not sure to get the point. >>>>> >>>>> Sure. With your current code on Hikey960 (big/LITTLE), you end up >>>>> creating two cooling devices, one for the big cluster and one for >>>>> small cluster. Which is the right thing to do, as we also have two >>>>> cpufreq cooling devices. >>>>> >>>>> But with the change Sudeep is referring to, the helper you used to get >>>>> cluster id will return 0 (SoC id) for all the 8 CPUs. So your code >>>>> will end up creating a single cpuidle cooling device for all the CPUs. >>>>> Which would be wrong. >>>> >>>> Is the semantic of topology_physical_package_id changing ? >>> >>> That's what I understood from his email. >>> >>>> I don't >>>> understand the change Sudeep is referring to. >> >> Actually there is no impact with the change Sudeep is referring to. It >> is for ACPI, we are DT based. Confirmed with Jeremy. >> >> So AFAICT, it is not a problem. > > It is a problem - DT or ACPI alike. Sudeep was referring to the notion > of "cluster" that has no architectural meaning whatsoever and using > topology_physical_package_id() to detect a "cluster" was/is/will always > be the wrong thing to do. The notion of cluster must not appear in the > kernel at all, it has no architectural meaning. I understand you need > to group CPUs but that has to be done in a different way, through > cooling devices, thermal domains or power domains DT/ACPI bindings but > not by using topology masks.
I don't get it. What is the cluster concept defined in the ARM documentation?
ARM Cortex-A53 MPCore Processor Technical Reference Manual
4.5.2. Multiprocessor Affinity Register
I see the documentation says:
A cluster with two cores, three cores, ...
How the kernel can represent that if you kill the topology_physical_package_id() ?
> You should be able to figure out this week at OSPM the reasoning behind > what I am saying above.
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