linux-kernel - Re: [PATCH] arm64: dts: rockchip: Describe why is HWRNG disabled in RK356x base dtsi

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Message-ID: <a6eaa2ca428abe2bedf10cc8c213513b@manjaro.org>
Date: Mon, 02 Dec 2024 19:33:18 +0100
From: Dragan Simic <dsimic@...jaro.org>
To: Diederik de Haas <didi.debian@...ow.org>
Cc: linux-rockchip@...ts.infradead.org, heiko@...ech.de,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, marcin.juszkiewicz@...aro.org
Subject: Re: [PATCH] arm64: dts: rockchip: Describe why is HWRNG disabled in
 RK356x base dtsi

Hello Diederik,

On 2024-12-02 18:05, Diederik de Haas wrote:
> I'd have swapped 'is' and 'HWRNG' in the subject, but otherwise ...

Ah, I'd actually write it as "Describe why the HWRNG is disabled
in the RK356x base SoC dtsi", but that's way too long for a patch
summary, so I went with something shorter that also makes it sound
more like a question than a statement. :)

> On Mon Dec 2, 2024 at 3:44 PM CET, Dragan Simic wrote:
>> Despite the presence of the hardware random number generator (HWRNG) 
>> in the
>> different Rockchip RK356x SoC variants, it remains disabled for the 
>> RK3566
>> SoC because testing showed [1] that it produces unacceptably low 
>> quality of
>> random data, for some yet unknown reason.  The HWRNG is enabled for 
>> the RK3568
>> SoC, on which the testing showed good quality of the generated random 
>> data.
>> 
>> To avoid possible confusion in the future, [2] let's have this 
>> described
>> briefly in the RK356x base SoC dtsi.
>> 
>> [1] 
>> https://lore.kernel.org/linux-rockchip/cover.1720969799.git.daniel@makrotopia.org/T/#u
>> [2] 
>> https://lore.kernel.org/linux-rockchip/20241201234613.52322-1-pbrobinson@gmail.com/T/#u
>> 
>> Signed-off-by: Dragan Simic <dsimic@...jaro.org>
>> ---
>>  arch/arm64/boot/dts/rockchip/rk356x-base.dtsi | 5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> diff --git a/arch/arm64/boot/dts/rockchip/rk356x-base.dtsi 
>> b/arch/arm64/boot/dts/rockchip/rk356x-base.dtsi
>> index 62be06f3b863..ab8f42c0a843 100644
>> --- a/arch/arm64/boot/dts/rockchip/rk356x-base.dtsi
>> +++ b/arch/arm64/boot/dts/rockchip/rk356x-base.dtsi
>> @@ -1032,6 +1032,11 @@ sdhci: mmc@...10000 {
>>  		status = "disabled";
>>  	};
>> 
>> +	/*
>> +	 * Testing showed that the HWRNG found in RK3566 produces 
>> unacceptably
>> +	 * low quality of random data, so the HWRNG isn't enabled for all 
>> RK356x
>> +	 * SoC variants despite its presence.
>> +	 */
>>  	rng: rng@...88000 {
>>  		compatible = "rockchip,rk3568-rng";
>>  		reg = <0x0 0xfe388000 0x0 0x4000>;
> 
> Reviewed-by: Diederik de Haas <didi.debian@...ow.org>
> 
> Thanks for this :-)

Thanks. :)