[PATCH] qe_ic: Do a sync when masking interrupts.

[Paul Mackerras]

Scott Wood writes:

> This patch causes a sync do be done after masking a QE interrupt, to
> ensure that the masking has completed before interrupts are enabled.
> This allows the masking of the cascade IRQ to be removed without causing
> spurious interrupts.

Hmmm.  In general a sync having completed doesn't mean that previous
MMIO stores have actually got to the device.  Reading from a device
register generally does ensure that previous writes have actually got
to the device though - could you do that instead?  I'm concerned that
adding the sync is not a robust fix and is possibly only working due
to fortuitous timing.

Paul.