Re: [RFC HIFN 00/02]: RNG support

[Patrick McHardy <kaber@trash.net>]

Evgeniy Polyakov wrote:
> On Sat, Nov 17, 2007 at 08:30:09PM +0100, Patrick McHardy (kaber@trash.net) wrote:
> 
>> The second patch adds hw_random support. The ugly part is finding out
>> when to allow reads from the RNG. It currently translates the public
>> key engine clock cycles to CPU cycles based on a 4GHz CPU and uses
>> get_cycles(). The problems with this are obvious, it only works on CPUs
>> that actually have some kind of cycle counter, has problems with
>> unsynchronized TSCs and the 4GHz assumption is not very nice either,
>> but I was reluctant to use ktime for this since it seems rather
>> expensive to call ktime_get once per 4 bytes of random. Suggestion
>> for improvement of this are also welcome :)
> 
> It will not work on arm, but I'm not sure this is relevant...
> Another option is to directly access xtime without all wrappers in the
> ktime_get().


I'll look into that, thanks.

>> Running rngtest on the random number generator indicates that it works
>> properly, with an average failure ratio of about 1:1000 at ~2.5mbit.
>>
>>
>>  drivers/crypto/hifn_795x.c |  158 +++++++++++++++++++++++++++++++++++++++++++-
>>  1 files changed, 156 insertions(+), 2 deletions(-)
>>
>> Patrick McHardy (2):
>>       [HIFN]: Improve PLL initialization
>>       [HIFN]: Add support for using the random number generator
> 
> Ack both patches.


Just in case, they shouldn't be applied yet, I forgot one minor bit
when splitting them (discarding the first value read from the RNG).

The PLL initialization also doesn't seem to follow the specified way
from the documentation, I want to have another look at this.