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

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Message-ID: <20201005200744.robd42nkt6ahg52x@bogus>
Date:   Mon, 5 Oct 2020 21:07:44 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
Cc:     Michal Simek <michal.simek@...inx.com>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Raja Subramanian, Lakshmi Bai" 
        <lakshmi.bai.raja.subramanian@...el.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "Wan Mohamad, Wan Ahmad Zainie" 
        <wan.ahmad.zainie.wan.mohamad@...el.com>
Subject: Re: [PATCH v2 2/3] firmware: Keem Bay: Add support for Arm Trusted
 Firmware Service call

On Mon, Oct 05, 2020 at 05:04:10PM +0000, Zulkifli, Muhammad Husaini wrote:

> To be clarify keembay_sd_voltage_selection function as Michal's prefers is
> actually using the firmware driver. This function located in firmware
> driver.

OK, it can be just one function place it in any file you think is more
appropriate need not be arasan controller driver. Any reasons why this
can't work ? Can even be in some header.

int keembay_sd_voltage_selection(int volt)
{
	int res;

	arm_smccc_1_1_invoke(KEEMBAY_SET_SD_VOLTAGE_FUNC_ID, volt, &res)

	/* appropriate error check if needed here */

	return res;
}

> I will call this func during voltage switching from arasan controller. I
> believe this implementation require DT to specify the compatible name and
> method use either smc/hvc.

No, use the standard one as detected by arm_smccc_1_1_invoke
(It calls arm_smccc_get_conduit internally and use SMC/HVC based on that)

> 
> Are you saying that by using simple smcc based function library I should
> call below func() in arasan controller. For example
> 1) arm_smccc_get_version(void)
> 2) arm_smccc_version_init(arm_smccc_get_version(), SMCCC_CONDUIT_SMC);

Nope

> 3) arm_smccc_1_1_invoke(KEEMBAY_SET_SD_VOLTAGE_FUNC_ID, voltage_value ,  &res);

Just this.

-- 
Regards,
Sudeep