[RFC PATCH 3/7] iommu/arm-smmu-v3: Introduce smmu option USE_SHARED_IRQS for Silicon errata

Will Deacon
2017-04-11T16:21:24Z

On Tue, Apr 11, 2017 at 04:54:26PM +0100, Robin Murphy wrote:
> On 11/04/17 15:42, linucherian at gmail.com wrote:
> > From: Geetha <gakula@cavium.com>
> >
> > Cavium 99xx SMMU implementation doesn't not support unique irq lines for
> > gerror, eventq and cmdq-sync. USE_SHARED_IRQS option enables to use single
> > irq line for all three interrupts.
>
> AFAICS, there's nothing actually wrong with using shared wired IRQs -
> the architecture spec doesn't appear to say anything about it. I think
> it might suffice to simply add IRQF_SHARED if we can see the SMMU
> doesn't support MSIs anyway - it doesn't really seem like something we
> need to treat as a specific quirk.

No, this is not permitted by the spec. See 3.18.2 ("Interrupt sources"),
where it's clear that each source asserts a *unique* wired interrupt.

Geetha: does your implementation support MSIs?

Will