linux-kernel - Re: [PATCH] arm64: dts: ti: k3-am62p-j722s: add rng node

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Message-ID: <e2a37e72-d9c8-4329-8a5a-f2c9865cdb5d@ti.com>
Date: Tue, 1 Apr 2025 15:32:31 +0530
From: "Kumar, Udit" <u-kumar1@...com>
To: Michael Walle <mwalle@...nel.org>, Nishanth Menon <nm@...com>,
        Vignesh
 Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>, Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>, <u-kumar1@...com>
CC: <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: ti: k3-am62p-j722s: add rng node

Hi Michael

On 4/1/2025 11:50 AM, Michael Walle wrote:
> Hi Udit,
>
>>>>> --- a/arch/arm64/boot/dts/ti/k3-am62p-j722s-common-main.dtsi
>>>>> [..]
>>>> For completeness , this is ok to add this node but should be kept disabled
>>> Shouldn't it be "reserved" then, see [1].
>> yes, should be reserved.
>>
>> With marking status as reserved.
>>
>> Please use Reviewed-by: Udit Kumar <u-kumar1@...com>
> Thanks.
>
>>>> similar to
>>>>
>>>> https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/ti/k3-j7200-mcu-wakeup.dtsi#L662
>>> j784s4, j721e and j721s2 have them enabled. What is the rule here?
>> J784s4, j721e and j721s2 SOCs has two TRNG blocks,
>>
>> example for j721e, one is used by kernel [0] and another by optee [1].
>>
>>
>>> You also disable the hwrng in optee in your evm according to [2]:
>>> CFG_WITH_SOFTWARE_PRNG=y
>> We are planning to use this hardware block by secure firmware.
>>
>> Therefore request not to use by optee as well
> How will you be able to access the RNG from linux and u-boot? I'm
> asking because I'll need it in u-boot for the lwip stack and the
> HTTPS protocol.

For now,  If you need TRNG then I can suggest to use optee TRNG (ie 
build optee with HW TRNG).


>
> -michael