linux-kernel - Re: Missing watchdog after ACPI watchdog creation failure

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Message-ID: <20180118102032.GJ27654@lahna.fi.intel.com>
Date:   Thu, 18 Jan 2018 12:20:32 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Missing watchdog after ACPI watchdog creation failure

On Wed, Jan 17, 2018 at 12:53:41PM +0100, Takashi Iwai wrote:
> Unfortunately we couldn't get approval yet, since it's a prototype
> machine.

In that case, I think the system itself and its ACPI tables should be
fixed if possible. Windows relies on that table as well so unless there
is something terribly wrong in how we allocate resources in Linux,
Windows should fail the same way. There is good reason why the WDAT
table is there in the first place so using iTCO to poke the hardware
directly might cause some other problems. Windows does not have iTCO
driver at all.

> Meanwhile, the reporter tested the patch below and confirmed to work.
> (It might be racy for acpi_has_watchdog() call during the probe, but
>  you see the idea.)

I would rather not to add any kinds of quirks for systems that are still
in development phase and the BIOS can be fixed. Basic idea is that if
the WDAT table is there we expect it to be correct and at least the
systems I'm aware of that's the case.

Of course if it turns out to be a problem in a real production system we
need to find out what the actual problem is (i.e why the resource
allocation fails in the first place) and fix it there.

That said, if Rafael says we should still add the check, I'll make a
patch that does it (based on yours) and send it upstream :)