Re: [PATCH 0/8] Make SCMI transport as standalone drivers

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

On Thu, Jul 11, 2024 at 01:26:16PM +0000, Peng Fan wrote:
> > Subject: [PATCH 0/8] Make SCMI transport as standalone drivers
> 
> You may need use V2 here :)

...oh damn :P

> > 
> > Hi all,
> > 
> > Till now the SCMI transport layer was being built embedded into in the
> > core SCMI stack.
> > 
> > Some of these transports, despite being currently part of the main
> > SCMI module, are indeed also registered with different subsystems like
> > optee or virtio, and actively probed also by those: this led to a few
> > awkward and convoluted tricks to properly handle such interactions at
> > boot time in the SCMI stack.
> > 
> > Moreover some partner expressed the desire to be able to fully
> > modularize the transports components.
> > 
> > This series aim to make all such transports as standalone drivers that
> > can be optionally loaded as modules.
> > 
> > In order to do this, at first some new mechanism is introduced to
> > support this new capability while maintaining, in parallel, the old
> > legacy embedded transports; then each transport, one by one, is
> > transitioned to be a standalone driver and finally the old legacy
> > support for embedded transport is removed.
> > 
> > Patch [1/8] is a mostly unrelated (but much needed) clean-up from
> > Peng, which I included in this series to avoid conflicts at merge.
> > 
> > Patch [2/8] simply collects the existing datagram manipulation helpers
> > in a pair of function pointers structures, in preparation for later reworks.
> > 
> > Patch [3/8] adds the bulk of the new logic to the core SCMI stack and
> > then each existing transport is transitioned to be a standalone driver in
> > patches 4,5,6,7 while shuffling around the compatibles. (no DT change
> > is needed of curse for backward compatibility) While doing this I kept
> > the module authorship in line with the main
> > author(S) as spitted out by git-blame.
> > 
> > Finally patch [8/8] removes all the legacy dead code from the core
> > SCMI stack.
> > 
> > No new symbol EXPORT has been added.
> > 
> > The new transport drivers have been tested, as built-in and LKM, as
> > follows:
> > 
> > - mailbox on JUNO
> > - virtio on emulation
> > - optee on QEMU/optee using Linaro setup
> > 
> > Exercised using the regular SCMI drivers stack and the SCMI ACS suite,
> > testing commands, replies, delayed responses and notification.
> > 
> > Multiple virtual SCMI instances support has been tested too.
> > 
> > SMC has NOT been tested/exercised at run-time, only compile-tested.
> > (due to lack of hardware)
> > 
> > Note that in this new setup, all the probe deferral and retries between
> > the SCMI core stack and the transports has been removed, since no
> > more needed.
> > 
> > Moreover the new drivers have been tested also with a fully
> > modularized SCMI stack, i.e.:
> > 
> >   scmi-core.ko + scmi-module.ko + scmi_transport_*.ko [ + vendor
> > modules ]
> > 
> > ToBeDone:
> >  - completely remove any dependency at build time at the Kconfig level
> > between
> >    the SCMI core and the transport drivers: so that the transports will be
> >    dependent only on the related subsystems (optee/virtio/mailbox/smc)
> >    (easy to be done but maybe it is not worth...)
> >  - integrate per-platform transport configuration capabilities
> >    (max_rx_timeout_ms & friends..)
> > 
> > Based on sudeep/for-next/scmi/updates.
> > 
> > Any feedback, and especially testing (:D) is welcome.
> > 
> 
> For the v2 patchset:
> Tested-by: Peng Fan <peng.fan@nxp.com>  #i.MX95-19x19-EVK
> 

Thanks a lot for the review and testing,

Cristian