From: Ulrich Hecht <uli@fpond.eu>
To: Guenter Roeck <linux@roeck-us.net>,
Ulrich Hecht <uli+renesas@fpond.eu>,
linux-renesas-soc@vger.kernel.org
Cc: wsa@the-dreams.de, geert@linux-m68k.org,
linux-i2c@vger.kernel.org, linux-watchdog@vger.kernel.org
Subject: Re: [PATCH] watchdog: da9063: wake up parent ahead of reboot
Date: Mon, 7 Sep 2020 23:19:59 +0200 (CEST) [thread overview]
Message-ID: <919936154.542022.1599513599331@webmail.strato.com> (raw)
In-Reply-To: <a89b6ee3-4b69-422c-4a48-d105ff8807ed@roeck-us.net>
> On 09/01/2020 6:48 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
>
> On 9/1/20 9:17 AM, Ulrich Hecht wrote:
> > This patch ensures our parent is awake before a reboot takes place. This
> > prevents situations in which the I2C host has been suspended and cannot
> > be safely woken up anymore when it needs to talk to us.
> >
>
> Why not call pm_runtime_get_sync() in da9063_wdt_restart() ?
It's no longer safe to do so at that point because the restart handler runs in atomic context. The unpleasant details can be found at https://www.spinics.net/lists/linux-i2c/msg46367.html
> What
> guarantees that the local notifier is called before the watchdog core's
> restart notifier ?
It would seem to me that a reboot notifier that triggers after the restart notifier (which, if successfully handled, does not return) would be rather pointless.
> And what is the point of using the watchdog core's
> reboot handler if it is bypassed anyway ?
I don't think it's bypassed, it should be possible to register several reboot notifiers per device.
It would also be possible to do this stuff in the core's reboot handler, but I have chosen not to do so because the core seems to avoid dealing with PM, which I assume is a design decision. Also, it would affect all other drivers with a restart handler, with (to me) unforeseeable effects. What do you think?
> Also, why is it not necessary to call pm functions when the watchdog is
> started, when it is stopped, and during suspend/resume ?
These cases are handled automatically, AFAIK.
CU
Uli
prev parent reply other threads:[~2020-09-07 21:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 16:17 [PATCH] watchdog: da9063: wake up parent ahead of reboot Ulrich Hecht
2020-09-01 16:48 ` Guenter Roeck
2020-09-07 21:19 ` Ulrich Hecht [this message]
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