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

Kumar Gala galak at kernel.crashing.org
Tue Oct 24 03:52:26 EST 2006

On Oct 23, 2006, at 10:19 AM, Scott Wood wrote:

> Paul Mackerras wrote:
>> 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.
> Possibly -- but the only problem on the rare occasions where the  
> timing
> is not fortuitous is a spurious interrupt; the only reason the sync
> needs to be there at all is to avoid the overhead of the extra  
> interrupt
> (and to avoid user complaints that they're getting "BAD" interrupts).

Why wouldn't the read accomplish the same thing in a more robust way  
than the sync?

- k

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