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Groups > linux.debian.kernel > #69843

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

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Le 2021-03-17 15:49, Wookey a écrit :
> On 2021-03-17 14:52 +0100, Vincent Blut wrote:
> > Control: tags -1 moreinfo
> >
> > Hi Wookey,
> >
> > Le 2021-01-27 12:57, Wookey a écrit :
> > > Source: linux
> > > Version: Please enable ARM CMN-600 power management on arm64
> > > Severity: normal
> > > Tags: patch
> > >
> > > Current arm hardware such as graviton2 (AWS arm64 hardware) has
> > > 'Coherent Mesh Network' interconnect (between components in a
> > > soc). It's important that support for this is built in the kernel so
> > > it can be used.
> > >
> > > 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 just did it like this because the other settings here are set as
> built-ins too and this seemed less disruptive. (If we make it a module
> we'll need to make sure it gets included in the right module package -
> I'm not sure if that need tweaking somewhere else in the build system)
> 
> 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.

> […]

> 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.

> 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?

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Bug#981186: linux: Enable CMN-600 interconnect on arm64 Wookey <wookey@debian.org> - 2021-01-27 14:10 +0100
  Bug#981186: linux: Enable CMN-600 interconnect on arm64 Noah Meyerhans <noahm@debian.org> - 2021-02-02 22:40 +0100
  Bug#981186: linux: Enable CMN-600 interconnect on arm64 Wookey <wookey@wookware.org> - 2021-03-17 03:30 +0100
  Processed: Re: Bug#981186: linux: Enable CMN-600 interconnect on  arm64 "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-03-17 15:00 +0100
  Processed: Re: Bug#981186: linux: Enable CMN-600 interconnect on  arm64 "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-03-17 15:00 +0100
  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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