[openib-general] Re: Disabling IRQ #201 message

[Grant Grundler]

On Wed, Feb 02, 2005 at 03:37:05PM +0200, Michael S. Tsirkin wrote:
> Pls consider:
> 
> EQ0 drives interrupt (low)
> IRQ handler clears interrupt (high)
> EQ1 drives interrupt (low)
> IRQ handler reads ECR
> IRQ handler serves EQ0 and EQ1
> IRQ handler responds with IRQ handled

I think a step is missing here.

> 
> all EQs are now empty, but interrupt line is low (asserted).

If the IRQ line is asserted and we get another interrupt for
something we've already handled, then it means the regular
interrupt code really hasn't cleaned up sufficiently.
There has to be some way to tell the card what work has
been done *OR* flush all inflight DMA (MMIO read - Ouch!).
The interrupt handler needs to guarantee it has handled
pending work and communicatied that back to the card so
IRQ line is not asserted.

> I propose returning IRQ_HANDLED *always* in regular interrupt.

This totally breaks Shared IRQ support.
If the driver asserts it must have a private IRQ line
in it's request_irq() call, then I would be ok with this.

grant