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SubjectRe: [PATCH v6 0/7] enable CAAM's HWRNG as default
Date
On 1/8/2020 5:41 PM, Andrey Smirnov wrote:
> Everyone:
>
> This series is a continuation of original [discussion]. I don't know
> if what's in the series is enough to use CAAMs HWRNG system wide, but
> I am hoping that with enough iterations and feedback it will be.
>
Testing on DPAA2-based Layerscape platforms, for e.g. LS1088A:
[...]
[ 12.379136] caam_jr 8010000.jr: 20000256: CCB: desc idx 2: RNG: Prediction resistance
[ 12.387036] hwrng: no data available
[...]

caamrng driver fails, because RNG initialization is skipped
in ctrl.c - caam_probe():
[...]
np = of_find_compatible_node(NULL, NULL, "fsl,qoriq-mc");
ctrlpriv->mc_en = !!np;
[...]
/*
* If SEC has RNG version >= 4 and RNG state handle has not been
* already instantiated, do RNG instantiation
* In case of SoCs with Management Complex, RNG is managed by MC f/w.
*/
if (!ctrlpriv->mc_en && rng_vid >= 4) {
[...]

NXP is working at adding RNG Prediction Resistance support in MC f/w
(will be available in v10.20.1).

However, there's a backwards-compatibility requirement: kernel should work
with older MC f/w versions.
To fix this, my suggestion is to force RNG (re)initialization in case
MC f/w is present and its version is < 10.20.1, i.e.:
if ((!ctrlpriv->mc_en || (fsl_mc_get_version() < "10.20.1")) &&
rng_vid >= 4) {
[...]

fsl_mc_get_version() - I've made this up, it currently doesn't exist,
it should be added in fsl-mc bus driver (drivers/bus/fsl-mc).
We will provide this shortly, the plan being to integrate this change
as part of this series.

Thanks,
Horia

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