Re: [Q] zynqmp-ipi-mailbox and SGI interrupts

[Shah, Tanmay]

Hello,

Thank you for your email, please find my response below:

On 10/15/2026 3:39 AM, Sebastian Andrzej Siewior wrote:
> Hi,
> 
> The ZynqMP IPI Mailbox driver supports two bindings of which
> xlnx,versal-ipi-mailbox is not present in any kernel dts file and

This new bindings are for Versal and later SoCs which has buffer-less
IPI. It supports only notification to the other core without any data
transfer. The device-tree nodes may not be available in the upstream
kernel yet, but it is used by other consumers. Here is an example:

https://github.com/Xilinx/u-boot-xlnx/blob/master/arch/arm/dts/versal-net-vn-x-b2197-01-revA.dts#L100


> xlnx,zynqmp-ipi-mailbox is used in two .dtsi files.
> For the per-CPU interrupts the irq-type should be 2 (which would
> correspond with GIC_ESPI in the dts, no?) which I can't find.
> Before the IPI_IRQ_TYPE_SGI it used to check for the value less than 16
> I also can't find this in the two available dts file.
> I did browse over the "AMD Versal Virt" but it also looks not present.
> 
> My question is whether this is used or just a development step that
> never got somewhere. 

No, it is the actual use case supported by the driver. Just the
device-tree node is not in the upstream kernel, because it is usually
project/vendor/consumer specific.

> My guess is that the device tree here is preconfigured from the boot
> firmware.

Yes.

> So is this SGI-IPI a thing or not?
> 

Yes it is. Ideally, TF-A and Linux can share the IPI. If the IPI
interrupt is used by the TF-A and the expectation is that Linux mailbox
work on the same IPI (because all other IPIs are busy) then the work
around is, TF-A will generate SGI for the linux mbox driver, and the
mbox driver will use that SGI via device-tree.

It is a vendor specific use case. So the dt-node for this use case, may
not be available in the usptream kernel, but can be enabled if correct
SGI is configured via the device-tree.

Thank you,
Tanmay

> Sebastian