linux-kernel - Re: [RFC] ARM: omap3: Enable HWMODS for HW Random Number Generator

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Date:   Tue, 22 Oct 2019 07:13:00 -0500
From:   Adam Ford <aford173@...il.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Pali Rohár <pali.rohar@...il.com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        Tero Kristo <t-kristo@...com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Adam Ford <adam.ford@...icpd.com>,
        Benoît Cousson <bcousson@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Paul Walmsley <paul@...an.com>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC] ARM: omap3: Enable HWMODS for HW Random Number Generator

On Mon, Sep 9, 2019 at 11:35 AM Tony Lindgren <tony@...mide.com> wrote:
>
> * Pali Rohár <pali.rohar@...il.com> [190909 13:41]:
> > On Monday 09 September 2019 08:37:09 Adam Ford wrote:
> > > I applied this on 5.3 and it is working.  I assume the same is true in for-next.
>
> Hmm I noticed I stopped getting RNG data after several rmmod modprobe
> cycles, or several hd /dev/random reads. Anybody else seeing that?
>
> > > Do you want to submit a formal patch?  I  can mark it as 'tested-by'
> > > This really helps speed up the startup sequence on boards with sshd
> > > because it delays for nearly 80 seconds waiting for entropy without
> > > the hwrng.
> >
> > Hi! When applying a patch, could you please disable this rng for n900?
> >
> > In omap3-n900.dts for rng should be status = "disabled" (as Tony already
> > wrote), similarly like for aes.
>
> Yeah I'll post a proper patch after -rc1.

Tony,

I am just following up on this.  Without the HWRNG there are some
tools and daemons like sshd which wait a long time at startup.  The
patch you sent really helps speed up the startup time in these cases.
At least in my case, it shaves 80 seconds off by eliminating the
delays.

Do you think you'll have time to post a more formal patch?  If not, I
can do it.  I just don't know which mailing list is the more
appropriate.  I was able to verity your patch on a DM3730 and OMAP3530

Thanks,

adam


>
> Regards,
>
> Tony