linux-kernel - Re: [PATCH 1/2] arm64: dts: imx8mq: Correct OPP table according to latest datasheet

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Message-ID: <VI1PR04MB50553915C0D978A8019BDC5CEEFC0@VI1PR04MB5055.eurprd04.prod.outlook.com>
Date:   Fri, 28 Jun 2019 05:58:42 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     Anson Huang <anson.huang@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Jacky Bai <ping.bai@....com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        Daniel Baluta <daniel.baluta@....com>,
        Abel Vesa <abel.vesa@....com>,
        "andrew.smirnov@...il.com" <andrew.smirnov@...il.com>,
        "ccaione@...libre.com" <ccaione@...libre.com>,
        "angus@...ea.ca" <angus@...ea.ca>,
        "agx@...xcpu.org" <agx@...xcpu.org>,
        "devicetree@...r.kernel.org" <devicetree@...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>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 1/2] arm64: dts: imx8mq: Correct OPP table according to
 latest datasheet

On 28.06.2019 06:37, Anson.Huang@....com wrote:
> From: Anson Huang <Anson.Huang@....com>
> 
> According to latest datasheet (Rev.1, 10/2018) from below links,
> in the consumer datasheet, 1.5GHz is mentioned as highest opp but
> depends on speed grading fuse, and in the industrial datasheet,
> 1.3GHz is mentioned as highest opp but depends on speed grading
> fuse. 1.5GHz and 1.3GHz opp use same voltage, so no need for
> consumer part to support 1.3GHz opp, with same voltage, CPU should
> run at highest frequency in order to go into idle as quick as
> possible, this can save power.

I looked at the same datasheets and it's not clear to me that 1.3 Ghz 
should be disallowed for consumer parts. Power consumption increases 
with both voltage and frequency so having two OPPs with same voltage 
does make sense.

>   			opp-hz = /bits/ 64 <1300000000>;
>   			opp-microvolt = <1000000>;
> -			opp-supported-hw = <0xc>, <0x7>;
> +			/* Industrial only but rely on speed grading */
> +			opp-supported-hw = <0xc>, <0x4>;

Comment is false, you're explicitly excluding consumer parts via the 
second element.

>   			opp-hz = /bits/ 64 <1500000000>;
>   			opp-microvolt = <1000000>;
>   			/* Consumer only but rely on speed grading */
> -			opp-supported-hw = <0x8>, <0x7>;
> +			opp-supported-hw = <0x8>, <0x3>;

If you don't want to rely on the fact that only consumer parts should be 
fused for 1.5 Ghz then please delete the comment.