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

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Message-ID: <ZqO9-ywEVvqdMRGF@pluto>
Date: Fri, 26 Jul 2024 16:17:15 +0100
From: Cristian Marussi <cristian.marussi@....com>
To: Florian Fainelli <f.fainelli@...il.com>
Cc: Cristian Marussi <cristian.marussi@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	arm-scmi@...r.kernel.org, sudeep.holla@....com,
	james.quinlan@...adcom.com, vincent.guittot@...aro.org,
	etienne.carriere@...com, peng.fan@....nxp.com, michal.simek@....com,
	quic_sibis@...cinc.com, quic_nkela@...cinc.com, ptosi@...gle.com,
	dan.carpenter@...aro.org, souvik.chakravarty@....com
Subject: Re: [PATCH 0/8] Make SCMI transport as standalone drivers

On Fri, Jul 12, 2024 at 02:02:32PM -0700, Florian Fainelli wrote:
> On 7/10/24 10:31, Cristian Marussi wrote:
> > 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.
> 
> Tested-by: Florian Fainelli <florian.fainelli@...adcom.com>

Thanks for testing this, Florian.
Cristian