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

[Michael Walle]

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@xxxxxx>
> > 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).

I'll be using an uboot TRNG driver. But how will that work in
the future if the RNG is used by the secure firmware?

-michael