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SubjectRe: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach_dev
On Thu, Oct 01, 2020 at 12:56:46AM +0300, Dmitry Osipenko wrote:
> 01.10.2020 00:32, Nicolin Chen пишет:
> > On Thu, Oct 01, 2020 at 12:24:25AM +0300, Dmitry Osipenko wrote:
> >> ...
> >>>> It looks to me like the only reason why you need this new global API is
> >>>> because PCI devices may not have a device tree node with a phandle to
> >>>> the IOMMU. However, SMMU support for PCI will only be enabled if the
> >>>> root complex has an iommus property, right? In that case, can't we
> >>>> simply do something like this:
> >>>>
> >>>> if (dev_is_pci(dev))
> >>>> np = find_host_bridge(dev)->of_node;
> >>>> else
> >>>> np = dev->of_node;
> >>>>
> >>>> ? I'm not sure exactly what find_host_bridge() is called, but I'm pretty
> >>>> sure that exists.
> >>>>
> >>>> Once we have that we can still iterate over the iommus property and do
> >>>> not need to rely on this global variable.
> >>>
> >>> I agree that it'd work. But I was hoping to simplify the code
> >>> here if it's possible. Looks like we have an argument on this
> >>> so I will choose to go with your suggestion above for now.
> >>
> >> This patch removed more lines than were added. If this will be opposite
> >> for the Thierry's suggestion, then it's probably not a great suggestion.
> >
> > Sorry, I don't quite understand this comments. Would you please
> > elaborate what's this "it" being "not a great suggestion"?
> >
>
> I meant that you should try to implement Thierry's solution, but if the
> end result will be worse than the current patch, then you shouldn't make
> a v4, but get back to this discussion in order to choose the best option
> and make everyone agree on it.

I see. Thanks for the reply. And here is a sample implementation:

@@ -814,12 +815,15 @@ static struct tegra_smmu *tegra_smmu_find(struct device_node *np)
}

static int tegra_smmu_configure(struct tegra_smmu *smmu, struct device *dev,
- struct of_phandle_args *args)
+ struct of_phandle_args *args, struct fwnode_handle *fwnode)
{
const struct iommu_ops *ops = smmu->iommu.ops;
int err;

- err = iommu_fwspec_init(dev, &dev->of_node->fwnode, ops);
+ if (!fwnode)
+ return -ENOENT;
+
+ err = iommu_fwspec_init(dev, fwnode, ops);
if (err < 0) {
dev_err(dev, "failed to initialize fwspec: %d\n", err);
return err;
@@ -835,6 +839,19 @@ static int tegra_smmu_configure(struct tegra_smmu *smmu, struct device *dev,
return 0;
}

+static struct device_node *tegra_smmu_find_pci_np(struct pci_dev *pci_dev)
+{
+ struct pci_bus *bus = pci_dev->bus;
+ struct device *dev = &bus->dev;
+
+ while (!of_property_read_bool(dev->of_node, "iommus") && bus->parent) {
+ dev = &bus->parent->dev;
+ bus = bus->parent;
+ }
+
+ return dev->of_node;
+}
+
static struct iommu_device *tegra_smmu_probe_device(struct device *dev)
{
struct device_node *np = dev->of_node;
@@ -843,11 +860,14 @@ static struct iommu_device *tegra_smmu_probe_device(struct device *dev)
unsigned int index = 0;
int err;

+ if (dev_is_pci(dev))
+ np = tegra_smmu_find_pci_np(to_pci_dev(dev));
+
while (of_parse_phandle_with_args(np, "iommus", "#iommu-cells", index,
&args) == 0) {
smmu = tegra_smmu_find(args.np);
if (smmu) {
- err = tegra_smmu_configure(smmu, dev, &args);
+ err = tegra_smmu_configure(smmu, dev, &args, &np->fwnode);
of_node_put(args.np);

if (err < 0)
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