Re: [PATCH] firmware: arm_scmi: Resolve dependency with TEE subsystem

From: Sudeep Holla <sudeep.holla@arm.com>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org, cristian.marussi@arm.com,
	Ludvig.Parsson@axis.com, jens.wiklander@linaro.org,
	etienne.carriere@linaro.org, vincent.guittot@linaro.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] firmware: arm_scmi: Resolve dependency with TEE subsystem
Date: Fri, 11 Nov 2022 14:38:00 +0000	[thread overview]
Message-ID: <20221111143800.k7xje6g23ujefnye@bogus> (raw)
In-Reply-To: <20221111095313.2010815-1-sumit.garg@linaro.org>

On Fri, Nov 11, 2022 at 03:23:13PM +0530, Sumit Garg wrote:
> The OP-TEE SCMI transport channel is dependent on TEE subsystem to be
> initialized first. But currently the Arm SCMI subsystem and TEE
> subsystem are invoked on the same initcall level as subsystem_init().
> 
> It is observed that the SCMI subsystem initcall is invoked prior to TEE
> subsystem initcall. This leads to unwanted error messages regarding TEE
> bus is not present yet. Although, -EPROBE_DEFER tries to workaround that
> problem.
> 
> Lets try to resolve inter subsystem dependency problem via shifting Arm
> SCMI subsystem to subsystem_init_sync() initcall level.
>

I would avoid doing that. We already have some implicit dependency with
subsys_initcall because this driver creates/registers bus and need to be
done early. Now in order to solve the dependency between SCMI and TEE,
both of which creates/registers bus and are at same subsys_initcall,
we are relying on subsys_initcall_sync.

Me and Ludvig discussed this in private and I suggested him to do something
like below patch snippet. He mentioned he did post a patch on the list but
I couldn't find it. For this the scmi node must be child node of OPTEE as
it is providing the transport.

@Ludvig, ?

Regards,
Sudeep

--

diff --git i/drivers/tee/optee/smc_abi.c w/drivers/tee/optee/smc_abi.c
index a1c1fa1a9c28..839feca0def4 100644
--- i/drivers/tee/optee/smc_abi.c
+++ w/drivers/tee/optee/smc_abi.c
@@ -1534,7 +1534,9 @@ static int optee_probe(struct platform_device *pdev)
                goto err_disable_shm_cache;

        pr_info("initialized driver\n");
-       return 0;
+
+       /* Populate any dependent child node(if any) */
+       return devm_of_platform_populate(&pdev->dev);

 err_disable_shm_cache:
        if (!optee->rpc_param_count)


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