Re: [RFC] PPC: MPIC: necessary readback after EOI?

On Wed, 2015-01-07 at 15:44 +0100, Benjamin Herrenschmidt wrote:

On Mon, 2015-01-05 at 12:10 -0600, Scott Wood wrote:

quoted

It would have been nice if a code comment explained why it was doing the
readback...  I don't see any particular need to wait for EOI completion
here (unlike when masking).

The EOI is what causes the MPIC to drop it's EE output to the CPU, if the
EOI is processed too slowly & asynchronously (posted write + 33Mhz MPIC)
we observe cases of spurrious interrupts. We had some macs basically getting
a spurrious irq for every MPIC interrupts...

Shouldn't reading INTACK be what causes the MPIC to drop its EE output?

-Scott