linux-kernel - Re: [PATCH] cpuidle: tegra: add ARCH_SUSPEND

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Date:   Wed, 13 Oct 2021 23:55:35 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thierry Reding <treding@...dia.com>,
        Arnd Bergmann <arnd@...db.de>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        He Ying <heying24@...wei.com>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpuidle: tegra: add ARCH_SUSPEND_POSSIBLE dependency

On Wed, Oct 13, 2021 at 10:49 PM Dmitry Osipenko <digetx@...il.com> wrote:
> > diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
> > index 2cc3c208a180..af97992eaa82 100644
> > --- a/drivers/cpuidle/Kconfig.arm
> > +++ b/drivers/cpuidle/Kconfig.arm
> > @@ -100,6 +100,7 @@ config ARM_MVEBU_V7_CPUIDLE
> >  config ARM_TEGRA_CPUIDLE
> >       bool "CPU Idle Driver for NVIDIA Tegra SoCs"
> >       depends on (ARCH_TEGRA || COMPILE_TEST) && !ARM64 && MMU
> > +     depends on ARCH_SUSPEND_POSSIBLE
> >       select ARCH_NEEDS_CPU_IDLE_COUPLED if SMP
> >       select ARM_CPU_SUSPEND
> >       help
> >
>
> Arnd, thank you for the patch!
>
> Apparently ARM_QCOM_SPM_CPUIDLE doesn't have that problem visible
> because it selects QCOM_SPM, which depends on ARCH_QCOM, and thus
> ARCH_QCOM should be auto-selected(?).

No, that's not how it works. In fact ARM_QCOM_SPM_CPUIDLE has the
exact same problem. I tried to check if there are other drivers affected
by this problem before I sent my patch, but I did something wrong and
missed this one.

> I'm curious whether this needs to
> be corrected, otherwise (ARCH_QCOM || COMPILE_TEST) doesn't make much
> sense for that driver. And then it will need the same Kconfig fix as well.
>
> I assume this problem wasn't caught by regular kernel build bots because
> they don't test randconfig, don't they?

They do test randconfig builds, but only a few of them. This one is
rather hard to hit, it probably took me 100 builds before I hit the first
one and I haven't run into the QCOM one yet, though I did see a
different issue for ARM_QCOM_SPM_CPUIDLE:

WARNING: unmet direct dependencies detected for QCOM_SPM
  Depends on [n]: ARCH_QCOM [=n]
  Selected by [y]:
  - ARM_QCOM_SPM_CPUIDLE [=y] && CPU_IDLE [=y] && (ARM [=y] || ARM64)
&& (ARCH_QCOM [=n] || COMPILE_TEST [=y]) && !ARM64 && MMU [=y]

       Arnd