linux-kernel - Re: [PATCH v7 0/3] hwrng: add hwrng support for Rockchip RK3568

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Message-ID: <2451882.5D0I8gZW9r@bagend>
Date: Wed, 17 Jul 2024 10:22:18 +0200
From: Diederik de Haas <didi.debian@...ow.org>
To: Daniel Golle <daniel@...rotopia.org>, wens@...nel.org
Cc: linux-rockchip@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 linux-kernel@...r.kernel.org, Herbert Xu <herbert@...dor.apana.org.au>,
 Martin Kaiser <martin@...ser.cx>, Sascha Hauer <s.hauer@...gutronix.de>,
 Sebastian Reichel <sebastian.reichel@...labora.com>,
 Ard Biesheuvel <ardb@...nel.org>,
 Uwe Kleine-König <ukleinek@...ian.org>,
 devicetree@...r.kernel.org, linux-crypto@...r.kernel.org,
 Philipp Zabel <p.zabel@...gutronix.de>, Olivia Mackall <olivia@...enic.com>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Dragan Simic <dsimic@...jaro.org>,
 Aurelien Jarno <aurelien@...el32.net>, Heiko Stuebner <heiko@...ech.de>,
 Anand Moon <linux.amoon@...il.com>
Subject: Re: [PATCH v7 0/3] hwrng: add hwrng support for Rockchip RK3568

On Wednesday, 17 July 2024 04:58:51 CEST Chen-Yu Tsai wrote:
> On Wed, Jul 17, 2024 at 10:25 AM Daniel Golle <daniel@...rotopia.org> wrote:
> > On Tue, Jul 16, 2024 at 07:19:35PM +0200, Diederik de Haas wrote:
> > > On Tuesday, 16 July 2024 18:53:43 CEST Diederik de Haas wrote:
> > > > rngtest: FIPS 140-2(2001-10-10) Long run: 0
> > > 
> > > I don't know if it means something, but I noticed that I have
> > > ``Long run: 0`` with all my poor results,
> > > while Chen-Yu had ``Long run: 1``.
> > > 
> > > Different SoC (RK3399), but Anand had ``Long run: 0`` too on their
> > > very poor result (100% failure):
> > > https://lore.kernel.org/linux-rockchip/CANAwSgTTzZOwBaR9zjJ5VMpxm5BydtW6
> > > rB2S7jg+dnoX8hAoWg@...l.gmail.com/> 
> > The conclusions I draw from that rather ugly situation are:
> >  - The hwrng should not be enabled by default, but it should by done
> >  
> >    for each board on which it is known to work well.
> >  
> >  - RK_RNG_SAMPLE_CNT as well as the assumed rng quality should be
> >  
> >    defined in DT for each board:
> >    * introduce new 'rochchip,rng-sample-count' property
> >    * read 'quality' property already used for timeriomem_rng
> > 
> > I will prepare a follow-up patch taking those conclusions into account.
> > 
> > Just for completeness, here my test result on the NanoPi R5C:
> > root@...nWrt:~# cat /dev/hwrng | rngtest -c 1000
> > rngtest 6.15
> > Copyright (c) 2004 by Henrique de Moraes Holschuh
> > This is free software; see the source for copying conditions.  There is NO
> > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
> > PURPOSE.
> > 
> > rngtest: starting FIPS tests...
> > rngtest: bits received from input: 20000032
> > rngtest: FIPS 140-2 successes: 875
> > rngtest: FIPS 140-2 failures: 125
> > rngtest: FIPS 140-2(2001-10-10) Monobit: 123
> > rngtest: FIPS 140-2(2001-10-10) Poker: 5
> > rngtest: FIPS 140-2(2001-10-10) Runs: 4
> > rngtest: FIPS 140-2(2001-10-10) Long run: 0
> > rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
> > rngtest: input channel speed: (min=85.171; avg=141.102;
> > max=4882812.500)Kibits/s rngtest: FIPS tests speed: (min=17.809;
> > avg=19.494; max=60.169)Mibits/s rngtest: Program run time: 139628605
> > microseconds
> 
> I doubt this is per-board. The RNG is inside the SoC, so it could be a chip
> quality thing. 

I agree with ChenYu (and others) that this is isn't a per-board level thing.
I'd even go further: 's/I doubt/It can't be that/' (for the same reason 
though; this is inside the SoC).

Before I saw these latest emails, I was going to suggest:
1. Enable it only on RK3568 for now. I would be fine if this would be accepted 
by the maintainer

2. Ask that you make a special version (for me) where I could play with the 
params without having to compile a new kernel for each variant (it generally 
takes me more then 24h on my Q64-A). Either through kernel module properties 
or properties defined in the DeviceTree is fine with me.

3. Based on the results make  a choice to not enable it on rk3566 at all or 
(indeed) introduce DT properties to configure it differently per SoC.

4. Hope/Ask for more test results

> On the RK3399 we also saw wildly varying results.

On my Rock64('s) (RK3328) it doesn't work at all:

```
root@...1:~# cat /dev/hwrng | rngtest -c 1000
rngtest 5
...
rngtest: starting FIPS tests...
cat: /dev/hwrng: No such device
rngtest: entropy source drained
```

Cheers,
  Diederik
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