Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

[Jon Masters]

On 06/03/2015 02:53 PM, Timur Tabi wrote:
> On 06/03/2015 01:25 PM, Guenter Roeck wrote:
>> In general the idea here would be to use a crashdump kernel, which,
>> when loaded, would reset the watchdog before it fires. This kernel
>> would then write a core dump to a specified location.
> 
> What is the mechanism for resetting the watchdog?  The only code that 
> knows about the hardware registers is this driver.  Does the crashdump 
> kernel call the watchdog stop function?
> 
>> If arm64 doesn't support a crashdump kernel, it might still be possible
>> to log the backtrace somewhere (eg in nvram using pstore if that is
>> supported via acpi or efi).

Just to go back and explicitly answer this, arm64 does have support for
crashdump, using the standard kexec/kdump approach, exactly as on x86.
There's still some more work to be done to get the ACPI case fully
upstream (e.g. on X-Gene platforms such as the HP ProLiant Moonshot m400
we need non-PSCI CPU parking protocol offlining when booting in
UEFI/ACPI mode), but it's what we are doing in RHEL(SA) and the goal is
to help clean up the remaining pieces upstream there.

Jon.

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