Re: [PATCH v7 00/38] SCMI vendor protocols and modularization

Florian Fainelli
2021-03-26T04:12:54Z

On 3/16/2021 5:48 AM, Cristian Marussi wrote:
> Hi all,
>
> The current SCMI implementation does not provide an interface to easily
> develop and include a custom vendor protocol implementation as prescribed
> by the SCMI standard, also because, there is not currently any custom
> protocol in the upstream to justify the development of a custom interface
> and its maintenance.
>
> Moreover the current interface exposes protocol operations to the SCMI
> driver users attaching per-protocol operations directly to the handle
> structure, which, in this way, tends to grow indefinitely for each new
> protocol addition.
>
> Beside this, protocols private data are also exposed via handle *_priv
> pointers, making such private data accessible also to the SCMI drivers
> even if neither really needed nor advisable.
>
> This series wants to address this by simplifying the SCMI protocols
> interface and reducing it, roughly, to these common generic operations:
>
> - handle->devm_protocol_get()
> - handle->devm_protocol_put()
> - handle->notify_ops->*
>
> All protocols' private data pointers are removed from handle too and made
> accessible only to the protocols code through dedicated internal helpers.
>
> The concept of protocol handle is also introduced in the SCMI protocol code
> to represent a protocol instance initialized against a specific SCMI
> instance (handle), so that all the new protocol code uses such protocol
> handles wherever previously SCMI handle was used: this enable tighter
> control of what is exposed to the protocol code vs the SCMI drivers.
>
> Moreover protocol initialization is moved away from device probe and now
> happens on demand when the first user shows up (first .protocol_get), while
> de-initialization is performed once the last user of the protocol, even in
> terms of registered notifications callback, is gone, with the SCMI core
> taking care to perform all the needed underlying resource accounting.
>
> This way any new future standard or custom protocol implementation will
> expose a common unified interface which does not need to be extended
> endlessly: no need to maintain a custom interface only for vendor protos.
> SCMI drivers written on top of standard or custom protocols will use this
> same common interface to access any protocol operations.
>
> All existent upstream SCMI drivers are converted to this new interface.
>
> In order to make this migration painless and to avoid the need of a big
> un-mergeable jumbo patch touching all over the protocols and drivers (like
> it was in v2), since v3 the migration process has been heavily split with a
> bit of transient code added along the way (to preserve bisectability) and
> finally removed towards the ends of the series.
> Protocols and SCMI drivers migration to the new interface happens along
> patches 10->30.
>
> Leveraging this new centralized and common initialization flow we took
> care also to refactor and simplify protocol-events registration and remove
> *notify_priv from the handle interface making it accessible only to the
> notification core.
>
> Patch 37 builds on top of this new interface and introduces a mechanism to
> define an SCMI protocol as a full blown module (possibly loadable) while
> leaving the core dealing with proper resource accounting.
> Standard protocols are still kept as builtins in this series, though.
>
> Finally, patch 38 introduces dynamic SCMI devices creation to avoid having
> to update the static module device table in the core each time a new driver
> is added.
>
> The whole SCMI stack can still be built alternatively as a module, with all
> the standard protocols included in scmi-module.ko in such a case.
>
> On top of this series an example SCMI Custom protocol 0x99 and related
> SCMI Custom Dummy driver has been built and it is available at [1] as a
> series of DEBUG patches on top this same series.
>
> The series is currently based on sudeep/for-next/scmi [2] on top of:
>
> commit 908a4f778dc7 ("Merge branch 'ib-iio-scmi-5.12-rc2-take3' of
> git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio into
> for-next/scmi")
>
> Any feedback welcome.

You copied me on each round and thanks for doing that, I did not have
time to go look at each change, but sensors, clocks and cpufreq still
worked on ARCH_BRCMSTB with both 32-bit and 64-bit kernels, so:

Tested-by: Florian Fainelli <f.fainelli@gmail.com>

Thanks!
--
Florian