linux-kernel - Re: [PATCH v2 27/45] mfd: ntxec: Use devm_register_power

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Date:   Sun, 7 Nov 2021 20:16:44 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Jonathan Neuschäfer <j.neuschaefer@....net>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Lee Jones <lee.jones@...aro.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@...linux.org.uk>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
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        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
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Subject: Re: [PATCH v2 27/45] mfd: ntxec: Use devm_register_power_handler()

07.11.2021 20:08, Guenter Roeck пишет:
> On 11/7/21 8:53 AM, Dmitry Osipenko wrote:
>> 06.11.2021 23:54, Jonathan Neuschäfer пишет:
>>> Hi,
>>>
>>> On Thu, Oct 28, 2021 at 12:16:57AM +0300, Dmitry Osipenko wrote:
>>>> Use devm_register_power_handler() that replaces global pm_power_off
>>>> variable and allows to register multiple power-off handlers. It also
>>>> provides restart-handler support, i.e. all in one API.
>>>>
>>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>>> ---
>>>
>>> When I boot with (most of) this patchset applied, I get the warning at
>>> kernel/reboot.c:187:
>>>
>>>     /*
>>>      * Handler must have unique priority. Otherwise call order is
>>>      * determined by registration order, which is unreliable.
>>>      */
>>>     WARN_ON(!atomic_notifier_has_unique_priority(&restart_handler_list,
>>> nb));
>>>
>>> As the NTXEC driver doesn't specify a priority, I think this is an issue
>>> to be fixed elsewhere.
>>>
>>> Other than that, it works and looks good, as far as I can tell.
>>>
>>>
>>> For this patch:
>>>
>>> Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@....net>
>>> Tested-by: Jonathan Neuschäfer <j.neuschaefer@....net>
>>
>> Thank you. You have conflicting restart handlers, apparently NTXEC
>> driver should have higher priority than the watchdog driver. It should
>> be a common problem for the watchdog drivers, I will lower watchdog's
>> default priority to fix it.
>>
> 
> The watchdog subsystem already uses "0" as default priority, which was
> intended as priority of last resort for restart handlers. I do not see
> a reason to change that.

Right, I meant that watchdog drivers which use restart handler set the
level to the default 128 [1]. Although, maybe it's a problem only for
i.MX drivers in practice, I'll take a closer look at the other drivers.

[1]
https://elixir.bootlin.com/linux/latest/source/drivers/watchdog/imx2_wdt.c#L318