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From:   Leonard Crestez <leonard.crestez@nxp.com>
To:     Anson Huang <anson.huang@nxp.com>, Jacky Bai <ping.bai@nxp.com>,
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Subject: Re: [PATCH 1/2] arm64: dts: imx8mq: Correct OPP table according to
 latest datasheet
Thread-Topic: [PATCH 1/2] arm64: dts: imx8mq: Correct OPP table according to
 latest datasheet
Thread-Index: AQHVLWLGEgwa/2nQ4E+GYs5uFNg8hw==
Date:   Fri, 28 Jun 2019 06:45:07 +0000
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On 6/28/2019 9:16 AM, Anson Huang wrote:=0A=
>> From: Leonard Crestez=0A=
>>> From: Anson Huang <Anson.Huang@nxp.com>=0A=
>>>=0A=
>>> According to latest datasheet (Rev.1, 10/2018) from below links, in=0A=
>>> the consumer datasheet, 1.5GHz is mentioned as highest opp but depends=
=0A=
>>> on speed grading fuse, and in the industrial datasheet, 1.3GHz is=0A=
>>> mentioned as highest opp but depends on speed grading fuse. 1.5GHz and=
=0A=
>>> 1.3GHz opp use same voltage, so no need for consumer part to support=0A=
>>> 1.3GHz opp, with same voltage, CPU should run at highest frequency in=
=0A=
>>> order to go into idle as quick as possible, this can save power.=0A=
>>=0A=
>> I looked at the same datasheets and it's not clear to me that 1.3 Ghz sh=
ould=0A=
>> be disallowed for consumer parts. Power consumption increases with both=
=0A=
>> voltage and frequency so having two OPPs with same voltage does make=0A=
>> sense.=0A=
> =0A=
> The consumer part datasheet does NOT mention 1.3GHz at all, so consumer p=
art ONLY=0A=
> support 1GHz/1.5GHz, and industrial part ONLY support 800MHz/1.3GHz, this=
 is what=0A=
> we did in our internal tree and NPI release, so better to make them align=
ed, otherwise,=0A=
> we have to change it when kernel upgrade.=0A=
=0A=
Datasheet seems ambiguous: it mentions "max freq for volt" so my =0A=
understanding is that any lower freqs should also work at that voltage.=0A=
=0A=
This also seems to be the understanding behind commit 8cfd813c7307 =0A=
("arm64: dts: imx8mq: fix higher CPU operating point") by Lucas.=0A=
=0A=
On datasheet page 7 it mentions that product code can have "JZ" or "HZ" =0A=
for 1.3Ghz or 1.5Ghz. Are you saying that only industrial parts can be "JZ"=
?=0A=
=0A=
>>>    			opp-hz =3D /bits/ 64 <1500000000>;=0A=
>>>    			opp-microvolt =3D <1000000>;=0A=
>>>    			/* Consumer only but rely on speed grading */=0A=
>>> -			opp-supported-hw =3D <0x8>, <0x7>;=0A=
>>> +			opp-supported-hw =3D <0x8>, <0x3>;=0A=
>>=0A=
>> If you don't want to rely on the fact that only consumer parts should be=
=0A=
>> fused for 1.5 Ghz then please delete the comment.=0A=
> =0A=
> Don't quite understand, 1.5GHz is indeed consumer ONLY, but if the consum=
er=0A=
> part is fused to 1GHz, then 1.5GHz is also NOT available, so it also rely=
 on speed=0A=
> grading. So keep the comment there is OK?=0A=
=0A=
What I meant with that comment is that 1.5Ghz is only mentioned for =0A=
consumer parts but instead of explicitly banning it on industrial parts =0A=
we rely on MFG never fusing industrial parts for 1.5Ghz.=0A=
=0A=
Now you're explicitly banning it on industrial parts.=0A=
=0A=
This comment is indeed confusing so better to just remove all instances.=0A=