Re: [PATCH v2 2/3] power: reset: pscrr: add watchdog pretimeout reason tracking

[Matti Vaittinen <mazziesaccount@gmail.com>]

On 30/07/2026 18:02, Guenter Roeck wrote:
> On 7/29/26 22:24, Oleksij Rempel wrote:
>> Hi Matti,
>>
>> On Thu, Jul 30, 2026 at 07:49:41AM +0300, Matti Vaittinen wrote:
>>> On 22/07/2026 18:13, Faruque Ansari wrote:
>>>> Watchdog pretimeout resets are not recorded with a dedicated reset
>>>> reason, causing subsequent boots to report PSCR_UNKNOWN and making it
>>>> difficult to distinguish them from other unexpected resets.
>>>>
>>>> Add PSCR_WATCHDOG_PRETIMEOUT as a dedicated reset reason code and
>>>> prevent the panic notifier from overwriting a watchdog pretimeout
>>>> reason with PSCR_KERNEL_PANIC when the pretimeout governor triggers a
>>>> panic.
>>>>
>>>> Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>
>>>> ---
>>>>    drivers/power/reset/pscrr.c           | 7 ++++++-
>>>>    include/linux/power/power_on_reason.h | 1 +
>>>>    include/linux/reboot.h                | 1 +
>>>>    kernel/reboot.c                       | 1 +
>>>>    4 files changed, 9 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/power/reset/pscrr.c b/drivers/power/reset/pscrr.c
>>>> index b5906f127e88..5b107c62fe82 100644
>>>> --- a/drivers/power/reset/pscrr.c
>>>> +++ b/drivers/power/reset/pscrr.c
>>>> @@ -149,7 +149,12 @@ static int pscrr_panic_notifier(struct 
>>>> notifier_block *nb,
>>>>        if (!backend || !backend->ops || !backend->ops->write_reason)
>>>>            return NOTIFY_OK;
>>>> -    set_psc_reason(PSCR_KERNEL_PANIC);
>>>> +    /*
>>>> +     * Do not overwrite a previously recorded watchdog pretimeout 
>>>> reason
>>>> +     * during panic handling.
>>>> +     */
>>>> +    if (get_psc_reason() != PSCR_WATCHDOG_PRETIMEOUT)
>>>> +        set_psc_reason(PSCR_KERNEL_PANIC);
>>>
>>> Hi Faruque,
>>>
>>> I like the idea of adding WDG pretimeout resets in pscrr. I am just
>>> wondering what makes WDG reason so special, that it shouldn't be 
>>> overwritten
>>> while other reasons can be? Can this notifier be called (now or in the
>>> future) so, that there are other reasons getting overwritten? For some
>>> reason I think the PSCRR was designed to be able to store multiple
>>> reasons(?)
>>
>> It depends on the backed. A simple nvmem cell, would be able to hold
>> only one reason.

Thanks for the explanation Oleksij :)

> That makes me wonder: Shouldn't the priority be a back-end decision, not a
> front-end decision ?

I have no strong opinion on that but even if the priority was decided by 
front, the decision whether to store multiple or single reason should 
perhaps be left for (or depend on) the backend.

Yours,
	-- Matti

-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~