linux-kernel - Re: [PATCH 3/5] iommu/tegra-smmu: Use iommu_fwspec in .probe_/.attach

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Date:   Mon, 28 Sep 2020 15:18:29 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     joro@...tes.org, krzk@...nel.org, vdumpa@...dia.com,
        jonathanh@...dia.com, linux-tegra@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] iommu/tegra-smmu: Use iommu_fwspec in
 .probe_/.attach_device()

On Mon, Sep 28, 2020 at 09:52:12AM +0200, Thierry Reding wrote:
> On Sat, Sep 26, 2020 at 01:07:17AM -0700, Nicolin Chen wrote:
> > @@ -13,6 +13,7 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/slab.h>
> >  #include <linux/spinlock.h>
> > +#include <linux/dma-iommu.h>
> 
> Why is this needed? I don't see any of the symbols declared in that file
> used here.

Hmm..I think I mixed with some other change that needs this header
file. Removing it....

> >  #include <linux/dma-mapping.h>
> >  
> >  #include <soc/tegra/ahb.h>
> > @@ -61,6 +62,8 @@ struct tegra_smmu_as {
> >  	u32 attr;
> >  };
> >  
> > +static const struct iommu_ops tegra_smmu_ops;
> > +
> >  static struct tegra_smmu_as *to_smmu_as(struct iommu_domain *dom)
> >  {
> >  	return container_of(dom, struct tegra_smmu_as, domain);
> > @@ -484,60 +487,49 @@ static void tegra_smmu_as_unprepare(struct tegra_smmu *smmu,
> >  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;
> > -		}
> > +	int index, err = 0;
> >  
> > -		of_node_put(args.np);
> > +	if (!fwspec || fwspec->ops != &tegra_smmu_ops)
> > +		return -ENOENT;
> >  
> > +	for (index = 0; index < fwspec->num_ids; index++) {
> >  		err = tegra_smmu_as_prepare(smmu, as);
> > -		if (err < 0)
> > -			return err;
> > +		if (err)
> > +			goto err_disable;
> 
> I'd personally drop the err_ prefix here because it's pretty obvious
> that we're going to do this as a result of an error happening.

Changing to "goto disable".

> > @@ -845,10 +837,25 @@ static int tegra_smmu_configure(struct tegra_smmu *smmu, struct device *dev,
> >  	return 0;
> >  }
> >  
> > +static struct tegra_smmu *tegra_smmu_get_by_fwnode(struct fwnode_handle *fwnode)
> > +{
> > +	struct device *dev = driver_find_device_by_fwnode(&tegra_mc_driver.driver, fwnode);
> > +	struct tegra_mc *mc;
> > +
> > +	if (!dev)
> > +		return NULL;
> > +
> > +	put_device(dev);
> > +	mc = dev_get_drvdata(dev);
> > +
> > +	return mc->smmu;
> > +}
> > +
> 
> As I mentioned in another reply, I think tegra_smmu_find() should be all
> you need in this case.

This function is used by .probe_device() where its dev pointer is
an SMMU client. IIUC, tegra_smmu_find() needs np pointer of "mc".
For a PCI device that doesn't have a DT node with iommus property,
not sure how we can use tegra_smmu_find().