linux-kernel - Re: [PATCH v3 5/9] firmware: arm_scmi: Make use of FastChannels configurable

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Date:   Fri, 1 Jul 2022 15:03:07 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Cristian Marussi <cristian.marussi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com,
        f.fainelli@...il.com, etienne.carriere@...aro.org,
        vincent.guittot@...aro.org, daniel.lezcano@...aro.org,
        tarek.el-sherbiny@....com, adrian.slatineanu@....com,
        souvik.chakravarty@....com, wleavitt@...vell.com,
        wbartczak@...vell.com
Subject: Re: [PATCH v3 5/9] firmware: arm_scmi: Make use of FastChannels
 configurable

On Mon, Jun 27, 2022 at 01:30:34PM +0100, Cristian Marussi wrote:
> Add a Kernel configuration entry used to optionally disable, globally, the
> usage of SCMI FastChannels even on platforms where they are available.
> 
> Make such option default-no to preserve the original SCMI system behaviour
> of using any available FC.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi@....com>
> ---
> v2 --> v3
> - fixed wording in Kconfig
> - reverted Kconfig logic _USE_ -> _AVOID_
> ---
>  drivers/firmware/arm_scmi/Kconfig  | 13 +++++++++++++
>  drivers/firmware/arm_scmi/driver.c |  6 ++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig
> index 1e7b7fec97d9..3fb34db01014 100644
> --- a/drivers/firmware/arm_scmi/Kconfig
> +++ b/drivers/firmware/arm_scmi/Kconfig
> @@ -42,6 +42,19 @@ config ARM_SCMI_HAVE_MSG
>  	  This declares whether a message passing based transport for SCMI is
>  	  available.
>  
> +config ARM_SCMI_AVOID_FASTCHANNELS
> +	bool "Avoid using SCMI FastChannels even when available"

Without default, won't this prompt user now ? I would have explicit default n
if we are adding this. But why do we need this is my question ? This would
be a quirk IMO on systems where FC is broken. I don't want people to enable
this during testing and ship f/w with FC broken(or not developed yet).

We can add this if some platforms really need this as a quirk in the future.
Thoughts ?

-- 
Regards,
Sudeep