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Groups > linux.debian.kernel > #69842

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

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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.

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.
This should be a module (whic is the upstream default - I'm not sure why
it's coming out as a built-in in the debian build):
CONFIG_THUNDERX2_PMU=m

I'm not sure about CONFIG_ARM_SMMU_V3_PMU=y as it's an architectureal
feature. Best to leave it as a built-in for now.

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

Upstream enables
CONFIG_FSL_IMX8_DDR_PMU=m
by default too. IMX8 hardware is available so we should probably turn this on too

Do you want me to knock up a patch for this or is that enough info?

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

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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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