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

From: Sebastian Reichel
Date: Tue Sep 10 2019 - 10:37:37 EST


On Tue, Sep 10, 2019 at 08:56:49AM -0500, Adam Ford wrote:
> On Thu, Sep 5, 2019 at 6:04 PM Tony Lindgren <tony@xxxxxxxxxxx> wrote:
> > Oh and this needs to default to status = "disabled" for
> > HS devices like n900 as it needs to use the omap3-rom-rng.
> I don't know enough about the HS version of the OMAP3, but what's the
> main difference between omap3-rom-rng and this one?

The OMAP HS chips have the bus firewall configured to block direct
access to some cryptography related devices. The kernel will crash
with a bus error, if you try to read/write the registers for
protected devices. The omap3-rom-rng avoids this by communicating
with the security middleware component instead of directly accessing
the RNG hardware.

-- Sebastian

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