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

Sunil Kovvuri
2017-04-11T16:34:41Z

On Tue, Apr 11, 2017 at 9:51 PM, Will Deacon <will.deacon@arm.com> wrote:
> 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

No, this silicon doesn't support MSIs.

Thanks,
Sunil.