libflash questions mostly relating to P9 bringup

[Benjamin Herrenschmidt]

On Tue, 2016-10-11 at 18:45 +1100, Cyril Bur wrote:
> > Hacky. Not really supported.
> 
> I should apologise, if we're talking about https://github.com/open-powe
> r/skiboot/blob/master/external/pflash/powerpc_io.c, we shouldn't. That
> code isn't used anymore and I doubt it will work. I'll send patches to
> remove it!
> 
> Currently updating PNOR from the host, Joel is correct, it isn't really
> supported by openbmc. Of course it can be done through /dev/mtd exposed
> by host linux (https://github.com/open-power/linux/blob/master/drivers/
> mtd/devices/powernv_flash.c) and backed by a driver in skiboot. I
> really hope that all pflash binaries around today know how to do this.

I dont know if that was mentioned earlier in the thread but we are
working on a mailbox based protocol for flash access to avoid accessing
the flash controller registers from any other entity than the BMC, in
order to be able to cut off the iLPC->AHB backdoor completely.

This should support having the flash either access directly for reads
or via an in-memory image in the BMC (aka memboot) and writes will be
done to an in-memory window on the LPC and "committed" to flash via
mbox commands.

We can get you details when we have a bit more sorted out on our side,
hopefully in a few days.

Cheers,
Ben.