Re: [Buildroot] [PATCH 1/1] configs/raspberrypi*: stop setting powersave as the default CPU governor

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Carlos, All,

On 2023-10-20 15:20 +0100, Carlos Alberto Lopez Perez spake thusly:
> * The defconfigs from the RPi Kernel set `powersave` as the default
>   CPU governor, which is a bad idea as that reduces performance by
>   setting the CPU frequency to the minimum one.
> 
> * In case of a buildroot build user-space is not configured by default
>   to change the CPU governor, so `powersave` will remain the CPU
>   governor and it will slow down everything.
> 
> * I submitted a fix for those defconfigs to upstream here:
>   https://github.com/raspberrypi/linux/pull/5666
>   However, we shouldn't wait until that is accepted and backported
>   to all the stable branches (if ever is).

Unfortunately, the rpi folks have rejected this change:

    https://github.com/raspberrypi/linux/pull/5666#issuecomment-1772531097

    We're not changing it.

So, as much as I understand the situation, we're are not going to go
counter the upstream decision.

Besides, it is not proper kconfig syntax, see below.

[--SNIP--]
> diff --git a/board/raspberrypi/default-cpu-governor.fragment b/board/raspberrypi/default-cpu-governor.fragment
> new file mode 100644
> index 0000000000..e2e201d71d
> --- /dev/null
> +++ b/board/raspberrypi/default-cpu-governor.fragment
> @@ -0,0 +1,9 @@
> +# The defconfigs from the RPi Kernel set "powersave" as the default CPU governor.
> +# That is a bad idea as it reduces performance, so we unset that default option here.
> +# The option to build the powersave governor (but not as the default) is also enabled.
> +# A fix for this was sent to upstream: https://github.com/raspberrypi/linux/pull/5666
> +# However, we need to carry this option override until those defconfigs are fixed on
> +# *all* the kernel branches that we support. So that can be a long time depending
> +# on wheter the above PR gets accepted and/or backported to the stable branches.
> +CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE=n

In kconfig, a symbol is never set to 'n'; rather it is not set as a
comment, e.g."

    # CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE is not set

Regards,
Yann E. MORIN.

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