Re: [PATCH 3/3] iommu/arm-smmu: Error out only if not enough context interrupts

[Vivek Gautam]

Hi Will,


On 7/24/2018 2:06 PM, Will Deacon wrote:
> On Thu, Jul 19, 2018 at 11:23:56PM +0530, Vivek Gautam wrote:
> > Currently we check if the number of context banks is not equal to
> > num_context_interrupts. However, there are booloaders such as, one
> > on sdm845 that reserves few context banks and thus kernel views
> > less than the total available context banks.
> > So, although the hardware definition in device tree would mention
> > the correct number of context interrupts, this number can be
> > greater than the number of context banks visible to smmu in kernel.
> > We should therefore error out only when the number of context banks
> > is greater than the available number of context interrupts.
> >
> > Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
> > Suggested-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>
> > Cc: Robin Murphy <robin.murphy@xxxxxxx>
> > Cc: Will Deacon <will.deacon@xxxxxxx>
> > ---
> >   drivers/iommu/arm-smmu.c | 19 +++++++++++++------
> >   1 file changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> > index 7c69736a30f8..4cb53bf4f423 100644
> > --- a/drivers/iommu/arm-smmu.c
> > +++ b/drivers/iommu/arm-smmu.c
> > @@ -2229,12 +2229,19 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
> >   	if (err)
> >   		return err;
> >   
> > -	if (smmu->version == ARM_SMMU_V2 &&
> > -	    smmu->num_context_banks != smmu->num_context_irqs) {
> > -		dev_err(dev,
> > -			"found only %d context interrupt(s) but %d required\n",
> > -			smmu->num_context_irqs, smmu->num_context_banks);
> > -		return -ENODEV;
> > +	if (smmu->version == ARM_SMMU_V2) {
> > +		if (smmu->num_context_banks > smmu->num_context_irqs) {
> > +			dev_err(dev,
> > +			      "found only %d context irq(s) but %d required\n",
> > +			      smmu->num_context_irqs, smmu->num_context_banks);
> > +			return -ENODEV;
> > +		} else if (smmu->num_context_banks < smmu->num_context_irqs) {
> > +			/* loose extra context interrupts */
> > +			dev_notice(dev,
> > +			      "found %d context irq(s) but only %d required\n",
> > +			      smmu->num_context_irqs, smmu->num_context_banks);
> > +			smmu->num_context_irqs = smmu->num_context_banks;
> > +		}
> I don't see the utility in the new message. Can you simplify with the patch
> below on top? It's a bit weird that we only decide to ignore the extra irqs
> after calling platform_get_irq() on them, but that seems to be harmless.

Thanks. I will modify as suggested below and respin.

Best regards
Vivek

> Will
>
> --->8
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index aa46c1ed5bf9..5349e22b5c78 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -2109,13 +2109,10 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>   			      "found only %d context irq(s) but %d required\n",
>   			      smmu->num_context_irqs, smmu->num_context_banks);
>   			return -ENODEV;
> -		} else if (smmu->num_context_banks < smmu->num_context_irqs) {
> -			/* loose extra context interrupts */
> -			dev_notice(dev,
> -			      "found %d context irq(s) but only %d required\n",
> -			      smmu->num_context_irqs, smmu->num_context_banks);
> -			smmu->num_context_irqs = smmu->num_context_banks;
>   		}
> +
> +		/* Ignore superfluous interrupts */
> +		smmu->num_context_irqs = smmu->num_context_banks;
>   	}
>   
>   	for (i = 0; i < smmu->num_global_irqs; ++i) {
> --
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