At least the D1 variant requires a separate clock for the TRNG.
Without this clock enabled, reading from /dev/hwrng reports:

   sun8i-ce 3040000.crypto: DMA timeout for TRNG (tm=96) on flow 3

Experimentation shows that the necessary clock is the SoC's internal
RC oscillator. This makes sense, as noise from the oscillator can be
used as a source of entropy.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Acked-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>