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 <20210401183654.27214-3-daniel.lezcano@linaro.org> <CAAYoRsURO1tf03nfiki1uaXYEmTKQyYKUeTyKW+vefrVzCO7jg@mail.gmail.com>
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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Fri, 26 Nov 2021 18:21:57 +0100
Message-ID: <CAJZ5v0hcuq0qriHbc=XHbCo8fJMAV1dbCBws3M9GktN17aCE_g@mail.gmail.com>
Subject: Re: [PATCH v6 3/7] powercap/drivers/dtpm: Simplify the dtpm table
To:     Doug Smythies <dsmythies@telus.net>
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>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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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.