JZ4780 RNG and entropy depletion

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Hi Everyone,

I have a MIPSEL ci20 dev board for testing. The board has a hardware
based rng, but its suffering entropy depletion. I have Debian's
rng-tools package installed.

The board lacks /dev/hwrng. /dev/random blocks indefinitely after
draining the device. "Indefinitely" may not be accurate, but I killed
a program that waited over 4 hours for 16 bytes after draining
/dev/random.

The ci20's documentation is a bit scant, but it can be found at
http://mipscreator.imgtec.com/CI20/hardware/soc/JZ4780_PM.pdf. I'm not
sure what the output rate is, but it seems to be capable of one
machine word (4 bytes) every few milliseconds. Without a delay, I can
see values being shifted into the register mapped at 0x100000DC.

I have a few questions:

  * Is there a driver for JZ4780 rng?
  * Is there a particular package for the driver that needs to be installed?
  * What causes/triggers /dev/hwrng to replenish /dev/random?

Thanks in advance.

Jeff
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