[OpenWrt-Devel] [RFC/RFT PATCH] ath9k: implement kthread entropy collection for AR5008 and AR9002 PHYs.

[Felix Fietkau]

On 2020-01-30 21:03, Rui Salvaterra wrote:
> The mainline ath9k driver is able to provide a hardware random number
> generator by collecting radio noise from the PHY ADC (using a kthread
> to fill up the entropy pool as needed). Nevertheless, this feature has
> only been implemented for the more recent AR9003 PHYs.
> 
> Meanwhile, OpenWrt has been carrying a patch to provide entropy from the
> ADC for the three supported PHYs for a long time, but this patch only
> collects entropy once per existing PHY, at the driver initialisation
> time.
> 
> This patch enables kconfig support for this feature and updates the
> OpenWrt patch, in order to add ADC entropy collection support to both
> AR5008 and AR9002 PHYs.
> 
> Signed-off-by: Rui Salvaterra <rsalvaterra at gmail.com>
For at least AR5008 and AR9002, but probably also for AR9003 I would
like to keep the behavior of collecting entropy only once at driver
initialization.
Last time I worked on this I noticed that on several chips, sampling
entropy during normal operation caused stability issues that were hard
to pin down but quite noticeable.
I think the benefit of continuous entropy collection is simply not worth
the extra cost of potential stability issues and debugging time.

- Felix

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