Re: [PATCH] of/irq: Add msi-parent check to of_msi_xlate()

Lorenzo Pieralisi
2025-09-18T15:21:33Z

On Thu, Sep 18, 2025 at 08:55:55AM -0500, Rob Herring wrote:
> On Tue, Sep 16, 2025 at 11:18:58AM +0200, Lorenzo Pieralisi wrote:
> > In some legacy platforms the MSI controller for a PCI host
> > bridge is identified by an msi-parent property whose phandle
> > points at an MSI controller node with no #msi-cells property,
> > that implicitly means #msi-cells == 0.
> >
> > For such platforms, mapping a device ID and retrieving the
> > MSI controller node becomes simply a matter of checking
> > whether in the device hierarchy there is an msi-parent property
> > pointing at an MSI controller node with such characteristics.
> >
> > Add a helper function to of_msi_xlate() to check the msi-parent
> > property in addition to msi-map and retrieve the MSI controller
> > node (with a 1:1 ID deviceID-IN<->deviceID-OUT mapping) to
> > provide support for deviceID mapping and MSI controller node
> > retrieval for such platforms.
>
> Your line wrapping is a bit short.
>
> I had a look at who is parsing "msi-parent" themselves as that's
> typically a recipe for doing it incorrectly ('interrupt-map' anyone).
> Can we make iproc_pcie_msi_enable() use this? It's quite ugly reaching
> into the GICv3 node...

I am not sure I get what you mean here. Possibly iproc_pcie_msi_enable()
can reuse this patch's code if I extend it and make it a global function,
yes and somehow use that function to carry out the check for an
msi-parent property with no #msi-cells property or an #msi-cells == 0.

Don't get what GICv3 node has to do with that though, sorry.

> And perhaps irq-gic-its-msi-parent.c could use this?

Yes and I have to fix leaks there too (and there are other
of_phandle_with_args() calls in the kernel that don't put the args.np
pointer on success - though not to retrieve msi-parent).
>
> And looks like pcie-layerscape-gen4 is leaking a node reference...

It looks like it is in good company I am afraid :(

Thanks,
Lorenzo

> >
> > Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> > Cc: Sascha Bischoff <sascha.bischoff@arm.com>
> > Cc: Rob Herring <robh@kernel.org>
> > Cc: Marc Zyngier <maz@kernel.org>
> > ---
> > drivers/of/irq.c | 38 +++++++++++++++++++++++++++++++++++---
> > 1 file changed, 35 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> > index e7c12abd10ab..d0e2dfd0ee28 100644
> > --- a/drivers/of/irq.c
> > +++ b/drivers/of/irq.c
> > @@ -670,6 +670,35 @@ void __init of_irq_init(const struct of_device_id *matches)
> > }
> > }
> >
> > +static int of_check_msi_parent(struct device_node *dev_node, struct device_node **msi_node)
> > +{
> > + struct of_phandle_args msi_spec;
> > + int ret;
> > +
> > + /*
> > + * An msi-parent phandle with a missing or == 0 #msi-cells
> > + * property identifies a 1:1 ID translation mapping.
> > + *
> > + * Set the msi controller node if the firmware matches this
> > + * condition.
> > + */
> > + ret = of_parse_phandle_with_optional_args(dev_node, "msi-parent", "#msi-cells",
> > + 0, &msi_spec);
> > + if (!ret) {
> > + if ((*msi_node && *msi_node != msi_spec.np) || msi_spec.args_count != 0)
> > + ret = -EINVAL;
> > +
> > + if (!ret) {
> > + /* Return with a node reference held */
> > + *msi_node = msi_spec.np;
> > + return 0;
> > + }
> > + of_node_put(msi_spec.np);
> > + }
> > +
> > + return ret;
> > +}
> > +
> > /**
> > * of_msi_xlate - map a MSI ID and find relevant MSI controller node
> > * @dev: device for which the mapping is to be done.
> > @@ -677,7 +706,7 @@ void __init of_irq_init(const struct of_device_id *matches)
> > * @id_in: Device ID.
> > *
> > * Walk up the device hierarchy looking for devices with a "msi-map"
> > - * property. If found, apply the mapping to @id_in.
> > + * or "msi-parent" property. If found, apply the mapping to @id_in.
> > * If @msi_np points to a non-NULL device node pointer, only entries targeting
> > * that node will be matched; if it points to a NULL value, it will receive the
> > * device node of the first matching target phandle, with a reference held.
> > @@ -691,12 +720,15 @@ u32 of_msi_xlate(struct device *dev, struct device_node **msi_np, u32 id_in)
> >
> > /*
> > * Walk up the device parent links looking for one with a
> > - * "msi-map" property.
> > + * "msi-map" or an "msi-parent" property.
> > */
> > - for (parent_dev = dev; parent_dev; parent_dev = parent_dev->parent)
> > + for (parent_dev = dev; parent_dev; parent_dev = parent_dev->parent) {
> > if (!of_map_id(parent_dev->of_node, id_in, "msi-map",
> > "msi-map-mask", msi_np, &id_out))
> > break;
> > + if (!of_check_msi_parent(parent_dev->of_node, msi_np))
> > + break;
> > + }
> > return id_out;
> > }
> >
> > --
> > 2.48.0
> >