Re: [PATCH 1/2] dt-bindings: firmware: arm,scmi: Document arm,poll-transport property

[Marek Vasut <marek.vasut@mailbox.org>]

On 10/23/25 3:45 PM, Cristian Marussi wrote:

Hello Cristian,

> On Thu, Oct 23, 2025 at 02:35:57PM +0200, Marek Vasut wrote:
>> Document new property arm,poll-transport, which sets all SCMI operation into
>> poll mode. This is meant to work around uncooperative SCP implementations,
>> which do not generate completion interrupts. This applies primarily on mbox
>> based implementations, but does also cover SMC and VirtIO ones.
> 
> Hi,
> 
> ..indeed I was thinking a while ago about exposing the existing force-polling
> switch but in my case it was purely a testing-scenario configuration, so a
> no-no for the DT, things are different if you have to describe an HW that has
> no completion IRQ also on the a2p channel...

Correct, at least until the SCP on this hardware is updated.

> ...having said that, though, usually polling-mode is reserved to a few
> selected commands in a few chosen scenarios (as you may have seen),
> 'carpet-polling' non-for-testing for all the commands on A2P seems a lot
> inefficient and heavy...is it really a viable solution ? or these
> systems use such a low rate of SCMI messages that polling after each and
> every message is negligible ?
> 
> ..just to understand the context...

These systems are early in development and it is likely that the SCP 
will be updated to generate interrupts properly. Currently, this is not 
the case, hence the carpet-polling, until this is resolved.

-- 
Best regards,
Marek Vasut