Re: [PATCH v2] firmware: arm_scmi: Give SMC transport precedence over mailbox

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

On Mon, Oct 07, 2024 at 04:54:13PM -0700, Florian Fainelli wrote:
> Broadcom STB platforms have for historical reasons included both
> "arm,scmi-smc" and "arm,scmi" in their SCMI Device Tree node compatible
> string, in that order.
> 
> After the commit cited in the Fixes tag and with a kernel configuration
> that enables both the SMC and the Mailbox transports, we would probe
> the mailbox transport, but fail to complete since we would not have a
> mailbox driver available. With each SCMI transport being a platform
> driver with its own set of compatible strings to match, rather than an
> unique platform driver entry point, we no longer match from most
> specific to least specific. There is also no simple way for the mailbox
> driver to return -ENODEV and let another platform driver attempt
> probing. This leads to a platform with no SCMI provider, therefore all
> drivers depending upon SCMI resources are put on deferred probe forever.
> 
> By keeping the SMC transport objects linked first, we can let the
> platform driver match the compatible string and probe successfully with
> no adverse effects on platforms using the mailbox transport.
> 
> Fixes: b53515fa177c ("firmware: arm_scmi: Make MBOX transport a standalone driver")
> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>

I was hoping to find some way to avoid this workaround....
...but I failed :P ... so

LGTM.
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>

Thanks,
Cristian