Commit Graph

3 Commits

Author SHA1 Message Date
Lee Jones 9ad92bdff7 hwrng: st - Improve FIFO size/depth description
The original representation of FIFO size in the driver coupled with the
ambiguity in the documentation meant that it was easy to confuse readers.
This lead to a false positive BUG-find and subsequently time wastage
debugging this phantom issue.

Hopefully this patch can prevent future readers from falling into the
same trap.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-10-08 21:42:25 +08:00
Lee Jones 93d649bd94 hwrng: st - Use real-world device timings for timeout
Samples are documented to be available every 0.667us, so in theory
the 8 sample deep FIFO should take 5.336us to fill.  However, during
thorough testing, it became apparent that filling the FIFO actually
takes closer to 12us.

Also take into consideration that udelay() can behave oddly i.e. not
delay for as long as requested.

  Suggested-by: Russell King <rmk+kernel@arm.linux.org.uk>:

    "IIRC, Linus recommends a x2 factor on delays, especially
     timeouts generated by these functions.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-10-08 21:42:24 +08:00
Lee Jones 4a4da53c40 hwrng: st - Add support for ST's HW Random Number Generator
Signed-off-by: Pankaj Dev <pankaj.dev@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Kieran Bingham <kieranbingham@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-09-21 22:00:42 +08:00