On Wed, Apr 15, 2020 at 03:29:29PM -0700, Julius Werner wrote: > > In addition, It looks more reasonable to use the "msec" as the unit of > > timeout parameter for the ATF fw interface with SMCWD_SET_TIMEOUT: > > > > - The fw interface will compatible with the uboot generic watchdog > > interface at [0], and there is no need to convert timeout from msec > > to sec. > > I think we're trying hard to keep this compatible to a Trusted > Firmware counterpart that we have already shipped, so we would prefer > to keep it at seconds if possible. That's what the Linux watchdog core > uses as well after all, so it just seems natural. I don't really see > how what U-Boot does would have anything to do with this. > > > - Some vendor's watchdog may be not support the "wdt_trigger_reset" > > reset operation, but they can use the method below to reset the system > > by the watchdog right now. > > > > watchdog_set_time(1); //1ms > > watchdog_enable(); > > They can still do that but they should do that on the Trusted Firmware > side. Emulating a missing reset functionality should be handled by the > hardware abstraction layer (in this case Trusted Firmware), not at the > Linux API level. So Linux would still send a PSCI_SYSTEM_RESET SMC, > but then Trusted Firmware can choose to implement that by setting the > watchdog to the smallest possible timeout (which it can because it's > accessing it directly, not through this SMC interface) and letting it > expire. I agree. Using a watchdog to implement reset functionality is always a means of last resort and should be avoided if possible. Guenter
