Watchdog Timer with x86 processor

Watchdog Timer with x86 processor

[Frederick Gotham]

I have an embedded Linux project with an x86_64 CPU.

I'm looking through the Barebox documentation and it seems that there's a lot 
of support for ARM, but I'm trying to find something that will work with my 
Intel processor.

When I go into the "menuconfig", I see the following symbols:

    WATCHDOG
    RAVE_SP_WATCHDOG
    WATCHDOG_AR9344
    WATCHDOG_BCM2835
    WATCHDOG_DAVINCI
    WATCHDOG_DW
    WATCHDOG_IMX
    WATCHDOG_IMX_RESET_SOURCE
    WATCHDOG_JZ4740
    WATCHDOG_MXS28
    WATCHDOG_OMAP
    WATCHDOG_ORION
    WATCHDOG_POLLER   	

Right now the only one that I have enabled is:WATCHDOG. I think the Intel 
Watchdog timer is referred to as iTCO_wdt, but I don't see it in the above 
list.

Is it possible to use the Barebox bootloader with a watchdog timer on an x86 
CPU?

Frederick




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Re: Watchdog Timer with x86 processor

[Rouven Czerwinski]

Hi Frederick,

On Mon, 2020-01-06 at 13:27 +0000, Frederick Gotham wrote:
> I have an embedded Linux project with an x86_64 CPU.
> 
> I'm looking through the Barebox documentation and it seems that
> there's a lot 
> of support for ARM, but I'm trying to find something that will work
> with my 
> Intel processor.
> 
> When I go into the "menuconfig", I see the following symbols:
> 
>     WATCHDOG
>     RAVE_SP_WATCHDOG
>     WATCHDOG_AR9344
>     WATCHDOG_BCM2835
>     WATCHDOG_DAVINCI
>     WATCHDOG_DW
>     WATCHDOG_IMX
>     WATCHDOG_IMX_RESET_SOURCE
>     WATCHDOG_JZ4740
>     WATCHDOG_MXS28
>     WATCHDOG_OMAP
>     WATCHDOG_ORION
>     WATCHDOG_POLLER

Your list is interesntigly missing WATCHDOG_EFI, which can be used on
x86_64 machines.

> Right now the only one that I have enabled is:WATCHDOG. I think the
> Intel 
> Watchdog timer is referred to as iTCO_wdt, but I don't see it in the
> above 
> list.
> Is it possible to use the Barebox bootloader with a watchdog timer on
> an x86 
> CPU?
https://www.barebox.org/doc/latest/boards/efi.html?highlight=watchdog#u-efi-watchdog

is probably the relevant documentation for this, the watchdog for efi
is implemented in drivers/watchdog/efi_wdt.c.

Regards,
Rouven



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Re: Watchdog Timer with x86 processor

[Ahmad Fatoum]

On 1/6/20 2:47 PM, Rouven Czerwinski wrote:
> Your list is interesntigly missing WATCHDOG_EFI, which can be used on
> x86_64 machines.

As described in the linked documentation, it's useless for monitoring Linux
boot, because it's a boot service and these are terminated very early in the
Linux boot process.

Only usable x86 watchdog we have at the moment is the Fintek Super I/O watchdog.
If you have another Super I/O, but your BIOS exports a WDAT ACPI table, barebox
v2019.01.0 will come with ACPI driver support, so you could write an ACPI driver on
top. Alternatively, you could turn on the watchdog in the BIOS and leave barebox
out of it altogether.

I've an iTCO patch series sitting on a local branch. I'll take a look and see
if it's usable. Main problem is that the iTCO is accessible over PCI, but we
have no EFI PCI support in barebox so far[1].

[1]: There's an incomplete patch series here:
     https://www.mail-archive.com/barebox@lists.infradead.org/msg33441.html

Cheers
Ahmad

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
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Re: Watchdog Timer with x86 processor

[Frederick Gotham]

Ahmad Fatoum <a.fatoum@pengutronix.de> wrote in
news:ee89e9f9-7ddf-ef42-0ad6-5881c74ebb48@pengutronix.de: 

> As described in the linked documentation, it's useless for monitoring
> Linux boot, because it's a boot service and these are terminated very
> early in the Linux boot process.
> 
> Only usable x86 watchdog we have at the moment is the Fintek Super I/O
> watchdog. If you have another Super I/O, but your BIOS exports a WDAT
> ACPI table, barebox v2019.01.0 will come with ACPI driver support, so
> you could write an ACPI driver on top. Alternatively, you could turn on
> the watchdog in the BIOS and leave barebox out of it altogether.



Just to be clear about what I'm doing.

I have an embedded Linux device whose CPU is 64-Bit quad-core.

Once the device has successfully booted up, there is a watchdog timer that 
makes sure everything keeps running smoothly. So if my device freezes AFTER 
it boots up successfully, then this eventuality is dealt with.

What I have NOT dealt with though, is the case of the device freezing mid-
boot. So let's say that Barebox tries to load the Linux kernel, and let's say 
the kernel get 15% loaded and then it freezes. If this happens, I need the 
device to reboot.

How would you go about this? Would you use the watchdog timer in the BIOS, or 
would you use the one in Barebox?


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Re: Watchdog Timer with x86 processor

[Ahmad Fatoum]

Hi,

On 1/7/20 12:23 PM, Frederick Gotham wrote:
> What I have NOT dealt with though, is the case of the device freezing mid-
> boot. So let's say that Barebox tries to load the Linux kernel, and let's say 
> the kernel get 15% loaded and then it freezes. If this happens, I need the 
> device to reboot.
> 
> How would you go about this? Would you use the watchdog timer in the BIOS, or 
> would you use the one in Barebox?

First you need to determine what watchdogs you have and determine which to choose
- Do you have a Super I/O chip? Does it have a watchdog?
- You have an iTCO watchdog. Are e.g. smbus devices correctly reset with an iTCO
  reset? A Super I/O reset might be more 'global'

Then you need to check what interfaces you have:
- Can the BIOS enable the watchdog?
- Can the BIOS provide a WDAT ACPI table for your watchdog?

Having the BIOS enable the watchdog is preferable, because then you can monitor
barebox execution reliably as well. If your BIOS can't do that, it exports
the wrong watchdog or you would like easy access to the barebox shell without
being reset all the time, you can then evaluate which driver would work
best for you:

- implement iTCO watchdog driver in barebox
- implement Super I/O watchdog in barebox (Porting over the Fintek Watchdog
  from Linux was quite straight-forward)
- implement WDAT watchdog in barebox

I've taken a look at my iTCO driver and it works mostly fine for iTCO version 3
(QEMU), but you'll probably need to port the missing parts for your particular
version from the kernel. I'll clean it up and send it to the list later this week. 

Cheers
Ahmad

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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