On Tue, Mar 21, 2017 at 11:48:02AM +0800, Fu Wei wrote:
Hi Mark, Lurndal,
The base server system implements _a_ Generic Watchdog as specified in APPENDIX A: Generic Watchdog.It is a requirement of a conforming implementation that there be a generic watchdog (impl as per the appendix). That doesn't preclude an implmentation from providing additional watchdogs (for example, if the processor implements EL3, it is likely that an implementation will include a secure watchdog as well as a non-secure watchdog).
The SBSA describes the minimal hardware requirements for a compliant server.
So I think, for the SBSA watchdog:
(1) there maybe more then one non-secure watchdog in GTDT
I suppose a firmware vendor could chose to expose more than the platform minimum to linux. Not quite sure what linux would do with it :-)
(2) we may also need to skip secure watchdogs in GTDT, and only register non-secure watchdogs into platform resources.
The secure watchdog will, be definition, never be accessible to non-secure EL2 or non-secure EL1, so only in the case of a secure EL1 operating system would the secure watchdog ever be conveyed through ACPI. I don't think secure EL1 is in the scope of the SBSA, or something that needs to be accomodated in the GTDT at this time.
scott