linux-kernel - Re: [PATCH v1 5/9] firmware: keembay: Add support for Trusted Firmware Service call

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Date:   Mon, 18 Jan 2021 11:19:29 +0000
From:   Mark Brown <broonie@...nel.org>
To:     "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
        "A, Rashmi" <rashmi.a@...el.com>,
        "Vaidya, Mahesh R" <mahesh.r.vaidya@...el.com>
Subject: Re: [PATCH v1 5/9] firmware: keembay: Add support for Trusted
 Firmware Service call

On Mon, Jan 18, 2021 at 10:28:33AM +0000, Zulkifli, Muhammad Husaini wrote:

> >> There is a SCMI voltage domain protocol intended for just this use
> >> case of controlling regulators managed by the firmware, why are you
> >> not using that for these systems?  See drivers/firmware/arm_scmi/voltage.c.

> From mmc maintainer's perspective, I should use the common modelling either using 
> regulator framework or pinctrl to perform voltage operation. Not just directly invoke 
> smccc call in the mmc driver. That is why I came up with this regulator driver to perform 
> voltage operation. 

The above is a standard way of controlling regulators via SMCCC which
already has a regulator driver, you're duplicating this functionality.

> >Indeed. Please switch to using the new voltage protocol added for this without
> >any extra code. You just need to wire up DT for this.

> May I know even if I wire up the DT, how should I call this from the mmc driver
> For set/get voltage operation? Any example?

There's one in the binding document for the driver.

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