Re: [PATCH v3 2/2] mailbox: Add Broadcom STB mailbox driver
From: Florian Fainelli
Date: Fri Oct 09 2020 - 13:03:32 EST
On 10/9/2020 9:38 AM, Sudeep Holla wrote:
On Sat, Sep 19, 2020 at 03:22:30PM -0400, Jim Quinlan wrote:
only implements the agent-to-platform channel;
In that case any reason why you can't reuse the existing smc transport
for SCMI. It was added recently in case you haven't checked the latest
kernel version(v5.8 or above). Check out for drivers/firmware/arm_scmi/smc.c
IIUC rather vaguely Florian was cc-ed on those patches.
Our firmware completes all commands by posting an interrupt and we
already have platforms in the field with this mailbox driver. I was
hoping we could make use of the SMC transport, but the current firmware
implementation completes commands by raising an interrupt. The reason
why we did that was that we could support synchronous and asynchronous
calls the same way.
we may implement the platform-to-agent channel in the future.
This is not yet support with that transport, it is hard to generalise
as different vendors have their own solutions there.
An unusual aspect of this driver is how the completion of an SCMI message
is indicated. An SCMI message is initiated with an ARM SMC call, but the
return of this call does not indicate the execution or completion of the
message. Rather, the message's completion is signaled by an interrupt.
So are these not fast SMC/HVC calls then ? If so we may need some changes
to that driver. I just rejected multiple message support as we had assumed
fast smc/hvc.
--
Florian