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

[Shah, Tanmay]

On 10/16/2026 11:23 AM, Sebastian Andrzej Siewior wrote:
> On 2026-10-16 11:10:29 [-0500], Shah, Tanmay wrote:
>> Hello,
> Hello,
> 
>> Thank you for your email, please find my response below:
> 
> Thank you for your email, too.
> 
>>> 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.
> 
> And it has to be a per-CPU interrupt? It can't become a regular
> interrupt which is not per-CPU? Does the driver at some point access
> per-CPU registers?
> 

As per my understanding, it has to be a per-CPU interrupt.

Driver access those registers via percpu APIs, for example:
xlnx_mbox_cpuhp_start() uses enable_percpu_irq(). It is called for each CPU.

>> Thank you,
>> Tanmay
>>
> Sebastian