Re: [PATCH 3/5] iommu/tegra-smmu: Use iommu_fwspec in .probe_/.attach_device()

Nicolin Chen
2020-09-28T23:43:47Z

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().