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Bug#981186: linux: Enable CMN-600 interconnect on arm64

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Le 2021-03-17 19:24, Wookey a écrit :
> On 2021-03-17 19:43 +0100, Vincent Blut wrote:
> > Le 2021-03-17 15:49, Wookey a écrit :
> > > On 2021-03-17 14:52 +0100, Vincent Blut wrote:
> > > > Le 2021-01-27 12:57, Wookey a écrit :
> > > > > Version: Please enable ARM CMN-600 power management on arm64
> > > > >
> > > > > This requires CONFIG_ARM_CMN=y
> > > >
> > > > Does it really have to be built-in instead of being provided as a module? Last I
> > > > checked, Fedora and Ubuntu provide it as a module.
> > > 
> > > No it should really be a module. Perf is driven from userspace so you
> > > never need to use it before modules can be loaded.
> > 
> > Agreed.
> 
> > > I see that
> > > CONFIG_THUNDERX2_PMU=y
> > > CONFIG_ARM_SMMU_V3_PMU=y
> > > are also set as builtins. That's probably wrong too.
> > 
> > It seems your arm64 kernel config deviates from the one we provide in Debian.
> > CONFIG_THUNDERX2_PMU is compiled as a module while CONFIG_ARM_SMMU_V3_PMU is
> > not set, at least in linux 5.10.19-1.
> 
> Hmm. I was looking at the (built, with CONFIG_ARM_CMN=y) sources for
> 5.10.9-1 and the (unbuilt) sources for 5.10.19-1. So yes, slightly
> different and the built version is not up to date any more.
> 
> If we already have CONFIG_THUNDERX2_PMU=m already then that's great
> (Ah yes - that's the upstream default).  Adding
> CONFIG_ARM_SMMU_V3_PMU=m would be good too. Adding it as a module
> should be pretty harmless then at least it's available? I'll set off a
> build now to check it works.

Enabling ARM_SMMU_V3_PMU as a module should be harmless, indeed.

> > > […]
> > 
> > > I also checked the state of the other perf configs with the arm kernel team
> > > and got feedback that we have all the ones that should sensibly be set set once
> > > CONFIG_ARM_CMN=m
> > > and
> > > CONFIG_THUNDERX2_PMU=m
> > > is added
> > 
> > This means updating the arm64 kernel config to only include ARM_CMN as a module.
> > To me it is acceptable for Bullseye as this seems uncontroversial, but note that
> > I can't speak for the kernel team.
> 
> Will you ask them, or should I?

I can send merge requests to enable ARM_CMN and ARM_SMMU_V3_PMU if you wish.

> It seems like prodding someone would be good as this was filed back on 27th
> jan and there have been uploads since, so I guess no-one has noticed till now.

I have been contributing for some time to help the kernel team, but I must admit
I didn't notice this one (and probably many others).

> > > Upstream enables
> > > CONFIG_FSL_IMX8_DDR_PMU=m
> > > by default too. IMX8 hardware is available so we should probably turn this on too
>
> > Contrary to Ubuntu, we do not provide support for the i.MX8M SoC family,
> > so enabling this option in the arm64 kernel config is not an option, right?
> 
> Ah OK. I didn't realise IMX8 was not enabled in the debian kernel (A
> subject for a different bug). In that case, no this is not
> appropriate.

I wanted to work on this a few months ago, but sadly I was unable to obtain a
i.MX8 SBC.

> Wookey
> -- 
> Principal hats:  Linaro, Debian, Wookware, ARM
> http://wookware.org/

Cheers,
Vincent

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Thread

Bug#981186: linux: Enable CMN-600 interconnect on arm64 Vincent Blut <vincent.debian@free.fr> - 2021-03-17 15:00 +0100
  Bug#981186: linux: Enable CMN-600 interconnect on arm64 Wookey <wookey@wookware.org> - 2021-03-17 17:00 +0100
    Bug#981186: linux: Enable CMN-600 interconnect on arm64 Vincent Blut <vincent.debian@free.fr> - 2021-03-17 19:50 +0100
      Bug#981186: linux: Enable CMN-600 interconnect on arm64 Wookey <wookey@wookware.org> - 2021-03-17 20:30 +0100
        Bug#981186: linux: Enable CMN-600 interconnect on arm64 Vincent Blut <vincent.debian@free.fr> - 2021-03-17 22:10 +0100
          Bug#981186: linux: Enable CMN-600 interconnect on arm64 Salvatore Bonaccorso <carnil@debian.org> - 2021-03-19 10:00 +0100

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