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From:   Doug Smythies <dsmythies@telus.net>
Date:   Fri, 26 Nov 2021 11:10:14 -0800
Message-ID: <CAAYoRsXLTYKGK_doqDqgerQ+uW3UhMYki7FfBy3cAhbfXiCrXA@mail.gmail.com>
Subject: Re: [PATCH v6 3/7] powercap/drivers/dtpm: Simplify the dtpm table
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Lukasz Luba <lukasz.luba@arm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        dsmythies <dsmythies@telus.net>
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On Fri, Nov 26, 2021 at 9:22 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> Hi Doug,
>
> On Fri, Nov 26, 2021 at 6:08 PM Doug Smythies <dsmythies@telus.net> wrote:
> >
> > Hi Daniel,
> >
> > This patch introduces a regression, at least on my test system.
> > I can no longer change CPU frequency scaling drivers, for example
> > from intel_cpufreq (A.K.A intel_pstate in passive mode) to intel_pstate
> > (A.K.A. active mode). The task just hangs forever.
> >
> > I bisected the kernel and got this commit as the result.
> > As a double check, I reverted this commit:
> > 7a89d7eacf8e84f2afb94db5ae9d9f9faa93f01c
> > on kernel 5.16-rc2 and the issue was resolved.
> >
> > While your email is fairly old, I observe that it was only included as of
> > kernel 5.16-rc1.
> >
> > Command Example that never completes:
> >
> > $ echo passive | sudo tee /sys/devices/system/cpu/intel_pstate/status
> >
> > syslog excerpt attached.
>
> This looks like it may be problematic:
>
> diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c
> index f6076de39540..98841524a782 100644
> --- a/drivers/powercap/dtpm_cpu.c
> +++ b/drivers/powercap/dtpm_cpu.c
> @@ -204,7 +204,7 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
>        return ret;
> }
>
> -int dtpm_register_cpu(struct dtpm *parent)
> +static int __init dtpm_cpu_init(void)
> {
>        int ret;
>
> so please try to remove the __init annotation from dtpm_cpu_init() and
> see if that helps.

Hi Rafael,

That did not fix the issue.
Just to be clear this is what I did, on top of 5.16-rc2:

$ git diff
diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c
index b740866b228d..26d1a87bdec6 100644
--- a/drivers/powercap/dtpm_cpu.c
+++ b/drivers/powercap/dtpm_cpu.c
@@ -231,7 +231,7 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
        return ret;
 }

-static int __init dtpm_cpu_init(void)
+static int dtpm_cpu_init(void)
 {
        int ret;