linux-kernel - Re: [PATCH v4 0/11] Introduce a unified API for SCMI Server testing

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Message-ID: <20221103112147.rq2v7dwte577kmb4@bogus>
Date:   Thu, 3 Nov 2022 11:21:47 +0000
From:   Sudeep Holla <sudeep.holla@....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,
        james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com,
        etienne.carriere@...aro.org, vincent.guittot@...aro.org,
        souvik.chakravarty@....com, wleavitt@...vell.com,
        peter.hilber@...nsynergy.com, nicola.mazzucato@....com,
        tarek.el-sherbiny@....com, quic_kshivnan@...cinc.com,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v4 0/11] Introduce a unified API for SCMI Server testing

On Fri, Oct 28, 2022 at 07:38:25PM -0700, Florian Fainelli wrote:
> Hi Christian,
> 
> On 10/19/2022 1:46 PM, Cristian Marussi wrote:
> [snip]
> 
> > In V2 the runtime enable/disable switching capability has been removed
> > (for now) since still not deemed to be stable/reliable enough: as a
> > consequence when SCMI Raw support is compiled in, the regular SCMI stack
> > drivers are now inhibited permanently for that Kernel.
> 
> For our platforms (ARCH_BRCMSTB) we would need to have the ability to start
> with the regular SCMI stack to satisfy if nothing else, all clock consumers
> otherwise it makes it fairly challenging for us to boot to a prompt as we
> purposely turn off all unnecessary peripherals to conserve power. We could
> introduce a "full on" mode to remove the clock provider dependency, but I
> suspect others on "real" silicon may suffer from the same short comings.
>

Fair enough. But if we are doing SCMI firmware testing or conformance via
the $subject proposed way, can these drivers survive if the userspace do
a random or a torture test changing the clock configurations ? Not sure
how to deal with that as the intention here is to do the testing from the
user-space and anything can happen. How do we avoid bring the entire system
down while doing this testing. Can we unbind all the drivers using scmi on
your platform ? I guess no. Let me know.

> Once user-space is reached, I suppose we could find a way to unbind from all
> SCMI consumers, and/or ensure that runtime PM is disabled, cpufreq is in a
> governor that won't do any active frequency switching etc.
>
> What do you think?

Yes, Cristian always wanted to support that but I am the one trying to
convince him not to unless there is a strong requirement for it. You seem
to suggest that you have such a requirement, but that just opens loads of
questions and how to we deal with that. Few of them are as stated above, I
need to recall all the conversations I had with Cristian around that and why
handling it may be bit complex.

--
Regards,
Sudeep