Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach_dev

[Nicolin Chen]

On Wed, Sep 30, 2020 at 06:09:43PM +0300, Dmitry Osipenko wrote:
> ...
> >  static int tegra_smmu_attach_dev(struct iommu_domain *domain,
> >  				 struct device *dev)
> >  {
> > +	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> >  	struct tegra_smmu *smmu = dev_iommu_priv_get(dev);
> >  	struct tegra_smmu_as *as = to_smmu_as(domain);
> > -	struct device_node *np = dev->of_node;
> > -	struct of_phandle_args args;
> >  	unsigned int index = 0;
> >  	int err = 0;
> >  
> > -	while (!of_parse_phandle_with_args(np, "iommus", "#iommu-cells", index,
> > -					   &args)) {
> > -		unsigned int swgroup = args.args[0];
> > -
> > -		if (args.np != smmu->dev->of_node) {
> > -			of_node_put(args.np);
> > -			continue;
> > -		}
> > -
> > -		of_node_put(args.np);
> > +	if (!fwspec || fwspec->ops != &tegra_smmu_ops)
> > +		return -ENOENT;
> 
> In previous reply you said that these fwspec checks are borrowed from
> the arm-smmu driver, but I'm now looking at what other drivers do and I
> don't see them having this check.
> 
> Hence I'm objecting the need to have this check here. You either should
> give a rational to having the check or it should be removed.
> 
> Please never blindly copy foreign code, you should always double-check it.

I will give a test and remove it upon positive result.