On Thu, Apr 16, 2015 at 03:37:19PM +0100, Tomeu Vizoso wrote: [...] > >> I don't know what FIQs are. :-) > > > > In short, fast IRQs, it is a separate IRQ line handled as a separate > > exception source with some private (banked) registers that minimize registers > > saving/restoring. They are not identical to NMI on x86, since > > their behaviour (handling) may be overriden by platforms and they > > can be masked. > > > >> ->enter_freeze is entered with interrupts disabled on the local CPU. It is > >> not supposed to re-enable them. That is, while in the ->enter_freeze callback > >> routine, the CPU must not be interrupted aby anything other than NMI. > > > > It boils down to what FIQs handlers are allowed to do with tick frozen > > and what they are (may be) currently used for. > > > > Russell has more insights on this than I do, in particular what FIQs are > > currently used for on ARM and if we can leave them enabled safely with tick > > frozen. > > But even if it's currently safe to leave them enabled, is there any > reason for not disabling them? Ok, the point here is: either it is safe, and you leave them enabled, or it is not and we must disable them *before* enter_freeze() is entered. Disabling them in the platform enter_freeze() hook does not make sense, because this means we run with FIQs enabled with tick frozen, either it is safe or it is not, it can't be both. I would ask Russell opinion on this, before making any decision. Lorenzo -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
