Message-ID: <CADvTj4rmPdWqf2ohJenzxXupFq5gpwr4dofjS3vU=q0wTtoFNQ@mail.gmail.com>
Date: Fri, 18 Oct 2024 09:18:44 -0600
From: James Hilliard <james.hilliard1@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: linux-watchdog@...r.kernel.org, Wim Van Sebroeck <wim@...ux-watchdog.org>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: it87_wdt: add quirks for some Qotom IT8786 boards

On Fri, Oct 18, 2024 at 4:09 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On 10/17/24 21:29, James Hilliard wrote:
> > On Thu, Oct 17, 2024 at 9:59 PM Guenter Roeck <linux@...ck-us.net> wrote:
> >>
> >> On 10/17/24 20:09, James Hilliard wrote:
> >>> For the watchdog timer to work properly on the QCML04 board we need to
> >>> set PWRGD enable in the Environment Controller Configuration Registers
> >>> Special Configuration Register 1 when it is not already set, this may
> >>> be the case when the watchdog is not enabled from within the BIOS.
> >>>
> >>> For the Qotom QGLK02 board the vendor indicates that the IT8786
> >>> watchdog hardware is not functional due to a conflict with the BIOS
> >>> power-on function, with PWRGD set the watchdog will trigger but the
> >>> board will poweroff rather than restart as expected. Disable the
> >>> it87 driver on this broken hardware.
> >>>
> >>
> >> This shouldn't be done in drivers, and it doesn't scale. The driver needs
> >> to be disabled with the mechanism supported by the distribution, for example
> >> in /etc/modprobe.d/blacklist-watchdog.conf, or by whatever other mechanism
> >> the distribution supports for that purpose.
> >
> > There isn't really a good way that I've found with my setup since I use common
> > images for both of these boards. I'm also worried that it's much easier to mess
> > something critical like this up if user space is involved in hardware detection.
> >
> > Many other watchdog drivers do this sort of thing so I'm a bit confused why we
> > would want to not do that here as well, for example:
> > https://github.com/torvalds/linux/blob/v6.11/drivers/watchdog/renesas_wdt.c#L176-L207
> > https://github.com/torvalds/linux/blob/v6.11/drivers/watchdog/ebc-c384_wdt.c#L125
> > https://github.com/torvalds/linux/blob/v6.11/drivers/watchdog/lenovo_se10_wdt.c#L242-L285
> > https://github.com/torvalds/linux/blob/v6.11/drivers/watchdog/sbc_fitpc2_wdt.c#L203-L206
> >
>
> Those are specialty watchdog drivers, which only work on a very limited number of boards
> to start with. For the most part they use DMI data to determine if the watchdog is supported
> on a board, not to determine if a watchdog isn't supported.
>
> The it87 driver works on thousands of boards, and is not wired up on a substantial percentage
> of them. In many cases, systems with ITE Super-IO chips have two Super-IO chips installed
> (one of them typically being an IT8786), and only one of those (or none) will have the watchdog
> wired up. Many boards with Intel CPUs use the iTCO watchdog and don't have the Super-IO
> watchdog wired up at all. Trying to maintain a deny-list for all boards where the watchdog
> isn't wired up would not scale.

Hmm, so what would scale then? I mean obviously having every user manually
configure watchdog drivers scales even worse than trying to maintain a deny-list
as users are generally going to expect drivers to work properly without manual
configuration.

Maybe something like hid-quirks would work better here for matching the
correct watchdog driver on systems where multiple watchdog drivers
otherwise detect a watchdog as being present?:
https://github.com/torvalds/linux/blob/v6.11/drivers/hid/hid-quirks.c

>
> Guenter
>

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