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

[Cristian Marussi <cristian.marussi@arm.com>]

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...

...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...

> 
> With this property set, such implementations which do not generate interrupts
> can be interacted with, until they are fixed to generate interrupts properly.
> 
> Note that, because the original base protocol exchange also requires some
> sort of completion mechanism, it is not possible to query SCMI itself for
> this property and it must be described in DT. While this does look a bit
> like policy, the SCMI provider is part of the hardware, hence DT.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

Thanks,
Cristian