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

[Adam Ford]

On Mon, Sep 9, 2019 at 7:13 AM Adam Ford <aford173@xxxxxxxxx> wrote:
>
> On Thu, Sep 5, 2019 at 6:04 PM Tony Lindgren <tony@xxxxxxxxxxx> wrote:
> >
> > Hi,
> >
> > * Adam Ford <aford173@xxxxxxxxx> [190828 15:01]:
> > > The datasheet for the AM3517 shows the RNG is connected to L4.
> > > It shows the module address for the RNG is 0x480A0000, and it
> > > matches the omap2.dtsi description.  Since the driver can support
> > > omap2 and omap4, it seems reasonable to assume the omap3 would
> > > use the same core for the RNG.
> > >
> > > This RFC, mimics much of the omap2 hwmods on the OMAP3. It
> > > also adds the necessary clock for driving the RNG.  Unfortunately,
> > > it appears non-functional.  If anyone has any suggestions on how
> > > to finish the hwmod (or port it to the newer l4 device tree
> > > format), feedback is requested.
> >
> > Yup I'll take the bait :) The patch below seems to do the trick
> > for me on dm3730 based on translating your patch to probe with
> > ti-sysc.
> >
> > Not sure about 34xx, it seems we're missing rng_clk? Care
> > to give it a try and attempt simlar patches for 34xx and
> > 3517?
> >
> > At least I'm not needing the "ti,no-reset-on-init" property
> > that your patch has a comment for. Maybe that's needed on
> > some other omap3.
> >
> > Oh and this needs to default to status = "disabled" for
> > HS devices like n900 as it needs to use the omap3-rom-rng.
> >
> > Regards,
> >
> > Tony
> >
> > 8< -----------------------
> > diff --git a/arch/arm/boot/dts/omap36xx.dtsi b/arch/arm/boot/dts/omap36xx.dtsi
> > --- a/arch/arm/boot/dts/omap36xx.dtsi
> > +++ b/arch/arm/boot/dts/omap36xx.dtsi
> > @@ -140,6 +140,29 @@
> >                         };
> >                 };
> >
> > +               rng_target: target-module@480a0000 {
> > +                       compatible = "ti,sysc-omap2", "ti,sysc";
> > +                       reg = <0x480a003c 0x4>,
> > +                             <0x480a0040 0x4>,
> > +                             <0x480a0044 0x4>;
> > +                       reg-names = "rev", "sysc", "syss";
> > +                       ti,sysc-mask = <(SYSC_OMAP2_AUTOIDLE)>;
> > +                       ti,sysc-sidle = <SYSC_IDLE_FORCE>,
> > +                                       <SYSC_IDLE_NO>;
> > +                       ti,syss-mask = <1>;
> > +                       clocks = <&rng_ick>;
> > +                       clock-names = "ick";
> > +                       #address-cells = <1>;
> > +                       #size-cells = <1>;
> > +                       ranges = <0 0x480a0000 0x2000>;
> > +
> > +                       rng: rng@0 {
> > +                               compatible = "ti,omap2-rng";
> > +                               reg = <0x0 0x2000>;
> > +                               interrupts = <52>;
> > +                       };
> > +               };
> > +

I applied this on 5.3 and it is working.  I assume the same is true in for-next.

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.

adam
>
> Tony,
>
> Can you tell me what branch you're using?  I am not seeing the note
> below, so I am not exactly sure what version to base my testing.
>
> ada,
> >                 /*
> >                  * Note that the sysconfig register layout is a subset of the
> >                  * "ti,sysc-omap4" type register with just sidle and midle bits