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

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Date:   Thu, 18 Jan 2018 12:28:26 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Missing watchdog after ACPI watchdog creation failure

On Thu, 18 Jan 2018 12:26:37 +0100,
Mika Westerberg wrote:
> 
> On Thu, Jan 18, 2018 at 12:20:32PM +0200, Mika Westerberg wrote:
> > 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 :)
> 
> However, we can still check if the WDAT is actually enabled and prevent
> creation of the device in that case. It may be that the BIOS always
> exposes the table but the device itself is disabled.
> 
> Can you ask the reporter to try the below patch and see if it helps?

OK, will provide a test kernel and ask for testing with it.


thanks,

Takashi