Re: [PATCH v5 05/19] iommu/arm-smmu: Implement of_xlate() for SMMUv3

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

Hi Robin,

On Tue, Aug 23, 2016 at 08:05:16PM +0100, Robin Murphy wrote:
> Now that we can properly describe the mapping between PCI RIDs and
> stream IDs via "iommu-map", and have it fed it to the driver
> automatically via of_xlate(), rework the SMMUv3 driver to benefit from
> that, and get rid of the current misuse of the "iommus" binding.
> 
> Since having of_xlate wired up means that masters will now be given the
> appropriate DMA ops, we also need to make sure that default domains work
> properly. This necessitates dispensing with the "whole group at a time"
> notion for attaching to a domain, as devices which share a group get
> attached to the group's default domain one by one as they are initially
> probed.
> 
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
> ---
> 
> v5: Simplify init code, use firmware-agnostic (and more efficient)
>     driver-based instance lookup

I'm largely happy with this, just one question below...

> @@ -2649,7 +2602,14 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, smmu);
>  
>  	/* Reset the device */
> -	return arm_smmu_device_reset(smmu);
> +	ret = arm_smmu_device_reset(smmu);
> +	if (ret)
> +		return ret;

... if we fail the probe at this point, the drvdata remains set. Do you
need to clear it, or we can we guarantee that nobody is going to try
arm_smmu_get_by_node with the (failed) SMMU's device node?

Alternatively, we could postpone setting the drvdata until the very end
of probe.

Will