Hi Yann,
You are right, the RSE comms is basically a custom RPC protocol between the application processor and RSE which is coupled
with MHUs (acting as the data link layer). The RSE comms sounds like it’s specific to this platform component (RSE) but the protocol
itself could be extended to other platforms as well I believe. The platform dependency here is the MHU, how the data is transferred.
Your approach could work, adding an extra data layer between the abstract MHU communication (include/drivers/arm/mhu.h) and the RSE comms
protocol – hiding the platform specifics of the data transfer. However, setting
PLAT_MHU_VERSION to 0 would be misleading to some extent I think.
I would rather introduce a new build option for clarity.
What others think?
Regards,
David
From:
Olivier Deprez <Olivier.Deprez@arm.com>
Date: Monday, 23 September 2024 at 14:14
To: tf-a@lists.trustedfirmware.org <tf-a@lists.trustedfirmware.org>, Yann Gautier <yann.gautier@foss.st.com>
Cc: Tamas Ban <Tamas.Ban@arm.com>, Raef Coles <Raef.Coles@arm.com>, David Vincze <David.Vincze@arm.com>, Manish Badarkhe <Manish.Badarkhe@arm.com>
Subject: Re: [TF-A] PSA calls with RSE comms and MHU
From: Yann Gautier via TF-A <tf-a@lists.trustedfirmware.org>
Sent: 23 September 2024 11:28
To: tf-a@lists.trustedfirmware.org <tf-a@lists.trustedfirmware.org>
Subject: [TF-A] PSA calls with RSE comms and MHU
Hello,
I would like to use PSA calls for an application on STM32MP2 platform.
I've seen the psa_call() API that I could use, in
drivers/arm/rse/rse_comms.c.
The problem is that it is based on MHU mailbox, which I don't have on
STM32MP2.
So I was planning plan to disentangle RSE comms and MHU, having a new
file in the same directory to manage MHU.
This code should then be under a flag, I could re-use PLAT_MHU_VERSION.
Setting it to 0, would mean no MHU.
AFAICT TF-M uses that split with a dedicated file:
rse_comms_hal.c: Abstracts MHU message sending and receiving.
(see
https://tf-m-user-guide.trustedfirmware.org/platform/arm/rse/rse_comms.html).
Do you think this approach sounds right?
Thanks,
Yann
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