"Guilherme G. Piccoli" [off-list ref] writes:

During a kdump kernel boot in PowerPC, we request a reset of the
PHBs to the FW. It makes sense, since if we are booting a kdump
kernel it means we had some trouble before and we cannot rely in
the adapters' health; they could be in a bad state, hence the
reset is needed.

But not only in a kdump kernel we could use this reset - there are
situations, specially when debugging drivers, that we could break
an adapter in a way it requires such reset. One can tell to just
go ahead and reboot the machine, but happens that many times doing
kexec is much faster, and so preferable than a full power cycle.
Also, we could have situations in which adapters are in bad state
due to adapter's FW issue, and only a PHB Fundamental Reset could
revive them.

This patch enables the reset_devices parameter to perform such reset.
The parameter is barely used - only few drivers make use of it.
This is a PowerPC-only change.

Signed-off-by: Guilherme G. Piccoli <redacted>
---
This patch was built/tested against powerpc/next branch.

We recently had a situation in which i40e driver couldn't start,
even after a full power cycle, due to a bug in its FW triggered
by a DCB condition in switch (thanks Mauro for narrowing this).
This patch enabled us to revive the adapter and use network
while debugging.

I really dislike this.

You're basically saying the kernel can't work out how to get a device
working, so let's leave it up to the user.

The driver should be fixed to detect that the device is not responding
and request a reset.

cheers