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

From: "Ludvig Pärsson" <Ludvig.Parsson@axis.com>
To: "sumit.garg@linaro.org" <sumit.garg@linaro.org>,
	"sudeep.holla@arm.com" <sudeep.holla@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"jens.wiklander@linaro.org" <jens.wiklander@linaro.org>,
	"vincent.guittot@linaro.org" <vincent.guittot@linaro.org>,
	"Ludvig Pärsson" <Ludvig.Parsson@axis.com>,
	"etienne.carriere@linaro.org" <etienne.carriere@linaro.org>,
	"cristian.marussi@arm.com" <cristian.marussi@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] firmware: arm_scmi: Resolve dependency with TEE subsystem
Date: Fri, 11 Nov 2022 15:00:29 +0000	[thread overview]
Message-ID: <7a32a3694ffd6790e4e2a7c5896931cf8f1a7243.camel@axis.com> (raw)
In-Reply-To: <20221111143800.k7xje6g23ujefnye@bogus>

On Fri, 2022-11-11 at 14:38 +0000, Sudeep Holla wrote:
> 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)
> 
I have answered something similar in my submit [1]. Maybe I should have
CCed you, or atleast sent you this link when I told you I made the
submission.

[1] https://lkml.org/lkml/2022/11/9/803

BR,
Ludvig
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