linux-kernel - Re: [PATCH v6 3/7] powercap/drivers/dtpm: Simplify the dtpm table

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Message-ID: <acb3ac6c-d6e6-c3f7-6b04-12d3a1fbf0a1@linaro.org>
Date:   Fri, 26 Nov 2021 18:43:24 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Doug Smythies <dsmythies@...us.net>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lukasz Luba <lukasz.luba@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v6 3/7] powercap/drivers/dtpm: Simplify the dtpm table

On 26/11/2021 18:21, Rafael J. Wysocki wrote:
> Hi Doug,
> 
> On Fri, Nov 26, 2021 at 6:08 PM Doug Smythies <dsmythies@...us.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.

Yes, actually that should be called only if it is configured properly.
The dtpm_cpu just initializes itself unconditionally, I did not figured
out there is the usually allyesconfig used by default by the distros.

That should be fixed with a proper DT configuration [1]

[1]
https://lore.kernel.org/all/20211124125506.2971069-3-daniel.lezcano@linaro.org/

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