linux-kernel - Re: [PATCH v2 2/3] firmware: Keem Bay: Add support for Arm Trusted Firmware Service call

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Message-ID: <20201002105840.GE906@bogus>
Date:   Fri, 2 Oct 2020 11:58:40 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Michal Simek <michal.simek@...inx.com>
Cc:     muhammad.husaini.zulkifli@...el.com, adrian.hunter@...el.com,
        ulf.hansson@...aro.org, linux-mmc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        lakshmi.bai.raja.subramanian@...el.com, arnd@...db.de,
        wan.ahmad.zainie.wan.mohamad@...el.com
Subject: Re: [PATCH v2 2/3] firmware: Keem Bay: Add support for Arm Trusted
 Firmware Service call

Hi Michal,

On Fri, Oct 02, 2020 at 10:23:02AM +0200, Michal Simek wrote:
> Hi Sudeep,
> 
> On 01. 10. 20 17:35, Sudeep Holla wrote:

[...]

> > 
> > What are the other uses of this KEEMBAY_SIP_* ?
> > For now I tend to move this to the driver making use of it using
> > arm_smccc_1_1_invoke directly if possible. I don't see the need for this
> > to be separate driver. But do let us know the features implemented in the
> > firmware. If it is not v1.1+, reasons for not upgrading as you need v1.1
> > for some CPU errata implementation.
> 
> This driver has been created based on my request to move it out the mmc
> driver. It looks quite hacky to have arm_smccc_res and call
> arm_smccc_smc() also with some IDs where it is visible that the part of
> ID is just based on any spec.

OK, driver is fine but no dt-bindings as it is discoverable. It can
also be just a wrapper library instead as it needs no explicit
initialisation like drivers to setup.

> Also in v1 he is just calling SMC. But maybe there is going a need to
> call HVC instead which is something what device driver shouldn't decide
> that's why IMHO doing step via firmware driver is much better approach.

Agreed and one must use arm_smccc_get_conduit or something similar. No
additional bindings for each and ever platform and driver that uses SMCCC
please.

> Of course if there is a better/cleaner way how this should be done I am
> happy to get more information about it.
> 

Let me know what you think about my thoughts stated above.

-- 
Regards,
Sudeep