Re: [PATCH] iommu/arm-smmu: Only return IRQ_NONE if FSR is not set

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

Hi Mitch,

On Sat, Sep 26, 2015 at 01:12:05AM +0100, Mitchel Humpherys wrote:
> Currently we return IRQ_NONE from the context fault handler if the FSR
> doesn't actually have the fault bit set (some sort of miswired
> interrupt?) or if the client doesn't register an IOMMU fault handler.
> However, registering a client fault handler is optional, so telling the
> interrupt framework that the interrupt wasn't for this device if the
> client doesn't register a handler isn't exactly accurate.  Fix this by
> returning IRQ_HANDLED even if the client doesn't register a handler.
> 
> Signed-off-by: Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> ---
>  drivers/iommu/arm-smmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 48a39dfa9777..95560d447a54 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -653,7 +653,7 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
>  		dev_err_ratelimited(smmu->dev,
>  		    "Unhandled context fault: iova=0x%08lx, fsynr=0x%x, cb=%d\n",
>  		    iova, fsynr, cfg->cbndx);
> -		ret = IRQ_NONE;
> +		ret = IRQ_HANDLED;
>  		resume = RESUME_TERMINATE;

Hmm, but if we haven't actually done anything to rectify the cause of the
fault, what means that we won't take it again immediately? I guess I'm not
understanding the use-case that triggered you to write this patch...

Will