[Linaro-open-discussions] Notes on Linaro Open Discussions meeting 4 Nov 2020

Lorenzo Pieralisi lorenzo.pieralisi at arm.com
Tue Nov 24 11:13:11 UTC 2020


On Tue, Nov 24, 2020 at 09:58:23AM +0000, Mike Holmes wrote:
> Ok we have our usual timezone problem
> 
> How about one of the following?
> 
> 10.00 am GMT December 3rd ?
> 3.00 pm GMT December 3rd ?

I can only attend at 10am GMT on that day, not in the afternoon.

Or maybe beginning of that week (Dec 1st for instance ?) if we want
also to give access to people in Americas.

Thanks,
Lorenzo

> On Tue, Nov 24, 2020 at 1:13 AM Jammy Zhou via Linaro-open-discussions <
> linaro-open-discussions at op-lists.linaro.org> wrote:
> 
>     Some earlier slots can be better for potential attendees from Asia in the
>     early evening :-)
> 
>     Thanks,
>     Jammy
> 
>     On Tue, 24 Nov 2020 at 02:25, Lorenzo Pieralisi via Linaro-open-discussions
>     <linaro-open-discussions at op-lists.linaro.org> wrote:
> 
>     > On Mon, Nov 23, 2020 at 05:44:15PM +0000, Jonathan Cameron wrote:
>     >
>     > [...]
>     >
>     > > > > If possible 3PM GMT works
>     > > > > better for me;
>     > > >
>     > > >
>     > > > Linaro has a standing internal meeting with its members at 3.00 pm on
>     > > > December 2nd,  how is 4.30 pm GMT or retain the 2.00 pm slot?
>     > >
>     > > I have another call at 4.30 but any time before that works for me.
>     > > If that's a problem for Lorenzo, perhaps we can shift the day slightly
>     > > or go earlier in the day?
>     >
>     > The only slot I can in the afternoon is 3PM to 5PM on Wednesdays.
>     >
>     > Morning it is perfectly fine but it may be too early for some people.
>     >
>     > 2PM I really can't make it I am sorry. Maybe we can try in the morning ?
>     >
>     > Please let me know, thanks a lot,
>     > Lorenzo
>     >
>     > > > > the NUMA topic raised by Jonathan is another interesting
>     > > > > topic for debate. Other than that we can slot in the topics that
>     > > > > weren't discussed last time:
>     > > > >
>     > > > >
>     > https://collaborate.linaro.org/display/LOD/Linaro+Open+Discussions+Home
>     > > > >
>     > > > > even though those require a bit of preparation so the sooner we
>     > finalize
>     > > > > the schedule the better.
>     > > > >
>     > > > > Please let me know, thanks.
>     > > > >
>     > > >
>     > > > I think we should prepare any topic slides and have the call, does
>     > anyone
>     > > > have any additional agenda items?
>     > >
>     > > I'll chase up our end over the next few days,
>     > >
>     > > Thanks,
>     > >
>     > > Jonathan
>     > >
>     > > >
>     > > >
>     > > > >
>     > > > > Lorenzo
>     > > > >
>     > > > > > * DT alignment. Don't want different solutions for each firmware
>     > type.
>     > > > > > * Lorenzo / Sami to check IORT revision E is final.
>     > > > > >
>     > > > > > SVA
>     > > > > > ===
>     > > > > >
>     > > > > > Zangfei gave summary:
>     > > > > >  - Huawei has devices that are not PCIe but are presented as
>     such.
>     > > > > >  - They support stall mode for SVA (spec violation)
>     > > > > >  - Resistance from kernel maintainers to maintaining a white list
>     > for
>     > > > > any quirk. Fine to fix
>     > > > > >    it once (JPB), but not to keep doing so.
>     > > > > >  - Note that stall mode not yet supported at all (JPB to send out
>     > this
>     > > > > cycle).
>     > > > > >  - If longer term fix need add can't be done via PCISIG etc then
>     > need to
>     > > > > convince
>     > > > > >    PCI and SMMU maintainers.   Noted that quirk is very little
>     > code.
>     > > > > >
>     > > > > > * Other SVA topics.
>     > > > > >   - Mentioned virtual SVA (no actually problems just expressing
>     > > > > interest!)
>     > > > > >   - Would need Eric Auger, wasn't on topic list so Eric not on
>     > call.
>     > > > > >
>     > > > > > AI: Nothing planned until after JPB has upstreamed stall mode.
>     > Hard to
>     > > > > have discussion before that.
>     > > > > >
>     > > > > > DVFS
>     > > > > > ====
>     > > > > >
>     > > > > > guohanjun
>     > > > > >
>     > > > > > Solutions exist for
>     > > > > > * CPU DVFS (voltage + frequency scaling)
>     > > > > > * PCIe device power states etc
>     > > > > >
>     > > > > > No standard way of controlling Uncore voltage and frequency for
>     > ACPI
>     > > > > based systems.
>     > > > > >
>     > > > > > 3 options:
>     > > > > > 1. MMIO / kernel driver.
>     > > > > > 2. PSCI via trusted firmware and system management controller.
>     > > > > > 3. ACPI (wrapping up an op region and SCMI)
>     > > > > >
>     > > > > > Clarifications / discussions.
>     > > > > >  * Vincent G: Power states, or voltage frequency of interest? Ans
>     > > > > Voltage Freq
>     > > > > >  * Considered SCMI?  Ans: Works only for DT as SCMI under ACPI is
>     > > > > wrapped up in AML
>     > > > > >    so looks like an ACPI interface.
>     > > > > >  * Sudeep H: Necessary to trace CPU freq?  Yes.
>     > > > > >  * Sudeep H: Why not do it in firmware entirely?  Ans. Not just
>     > CPU.
>     > > > > For example PCI device accessing
>     > > > > >    memory may well need the ring bus to be fast.
>     > > > > >  * Vincent G: Bandwidth affected?  Yes. VG: mobile does this by
>     > > > > specifying a BW requirement (via SCMI.-
>     > > > > >  * Sudeep H Observed need to expose it via ACPI spec. (option 3
>     > above).
>     > > > > >  * Sudeep H: Does PCI also need fine-grain control? We might need
>     > to add
>     > > > > to the spec.
>     > > > > >  * Sudeep H:  What are the requirements? gaohanjun: Now we just
>     > > > > frequency scaling.
>     > > > > >  * Jonathan C: Noted PCI power state is not enough.  It's
>     > workload
>     > > > > dependent.
>     > > > > >  * Sudeep H: We need to gather all the info, need to talk in ASWG
>     > about
>     > > > > DVFS
>     > > > > >  * Jonathan C:  For now direct control probably makes sense.
>     > Whilst it
>     > > > > would be nice to have
>     > > > > >    a detailed enough system description in a standard way to make
>     > > > > general software that is a
>     > > > > >    big spec job.
>     > > > > >  * Jonathan C: Seems like true standard SW will not happen any
>     > time soon.
>     > > > > >
>     > > > > > AI: RFC to the linux-pm / linux-acpi Rafael and those in this
>     > discussion
>     > > > > to ask about
>     > > > > >     interest in adding per device DVFS to ACPI spec.  Possibly
>     > pursue
>     > > > > code first ACPI
>     > > > > >     approach.
>     > > > > >
>     > > > > > If I've miss listed or "volunteered" anyone for AIs they didn't
>     > agree to
>     > > > > then please
>     > > > > > correct that.
>     > > > > >
>     > > > > > Thanks all for contributions. I for one found it a very useful
>     > call!
>     > > > > >
>     > > > > > Jonathan
>     > > > > >
>     > > > > >
>     > > > > > --
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>     > > > > >
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>     > > > > >
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>     > > > > --
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>     linaro-open-discussions
>     > > > >
>     > > >
>     > > >
>     > >
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> 
> 
> --
>  Mike Holmes | Director, Foundation Technologies, Linaro
>  Mike.Holmes at linaro.org 
>   "Work should be fun and collaborative, the rest follows"
> 


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