Hi, On 2024-06-23 09:00, Krzysztof Kozlowski wrote: > On 23/06/2024 05:33, Daniel Golle wrote: > > + > > + rk_rng->rng.name = dev_driver_string(dev); > > +#ifndef CONFIG_PM > > + rk_rng->rng.init = rk_rng_init; > > + rk_rng->rng.cleanup = rk_rng_cleanup; > > +#endif > > + rk_rng->rng.read = rk_rng_read; > > + rk_rng->rng.priv = (unsigned long) dev; > > + rk_rng->rng.quality = 900; > > I doubt in this value. Usually SoC vendors do not provide datasheet with > any reliable and verifiable (so one which could be proven by 3rd party) > information. Can you provide a source? (and vendor downstream tree does > not really count) As the original author of the patch, I am the one who have chosen the value. I did it as explained in the commit message: | The TRNG device does not seem to have a signal conditionner and the FIPS | 140-2 test returns a lot of failures. They can be reduced by increasing | RK_RNG_SAMPLE_CNT, in a tradeoff between quality and speed. This value | has been adjusted to get ~90% of successes and the quality value has | been set accordingly. It is also explained, admittedly more briefly, above the RK_RNG_SAMPLE_CNT #define, as the commit messages are not really relevant anymore once the patches are accepted: | * TRNG collects osc ring output bit every RK_RNG_SAMPLE_CNT time. The value is | * a tradeoff between speed and quality and has been adjusted to get a quality | * of ~900 (~90% of FIPS 140-2 successes). | */ The decision to adjust RK_RNG_SAMPLE_CNT to reach ~90% of FIPS 140-2 successes was based on the quality chosen by most hw_random drivers currently in the kernel sources. The FIPS 140-2 tests were performed using rngtest from the rng-tools project. All that said, I am not an expert in that domain, so feel free to point to the documentation or provide the correct method to determine the quality. Regards Aurelien [1] https://git.kernel.org/pub/scm/utils/kernel/rng-tools/rng-tools.git/ -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@xxxxxxxxxxx http://aurel32.net
