Re: Prevent Nand page writes on Power failure

[Richard Weinberger <richard@xxxxxx>]

Am Donnerstag, 21. Februar 2019, 09:39:14 CET schrieb Sascha Hauer:
> > Regarding important data, users that care need to use fsync() anyway, so
> > there is no need to trigger whatever writeback upon power failure.
> > Or what else important data do you have in mind?
> 
> What you want to do on a power failure probably depends on the time
> you have left. When you have a second left then you get other ideas than
> when you have just a few milliseconds. If you have enough time then you
> maybe even want to do an ordered shutdown which would include writing to
> the nand.

Well, these are two distinct use cases. Both are sane but have different goals.
If you have a signal that tells "I'm out of power supply and have plenty of time"
you can notify/wake userspace and it is no big deal if the userspace action takes too
long and the board browns out.

But for the NAND stuff you need something that tells you "I'm out of of power
and you need to take action immediately".
Here the action needs to happen in any case because the hardware requires so.

Thanks,
//richard




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