hwrng: imx-rngc - add quality to use it as kernel entropy pool
The RNGB can generate 2^20 words (1 word == 4 byte) of 'random' data
after the seed pool was initialized. The pool needs to be reseeded if
more words are required. The reseeding is done automatically since
commit 3acd9ea933
("hwrng: imx-rngc - use automatic seeding").
We can't retrieve the TRNG values directly so we need a other way to get
the quality level. We know that the PRNG uses 20.000 entropy samples
from the TRNG to generate 2^20 words (1MiB) and the quality level is
defined as (in bits of entropy per 1024 bits of input). So the quality
level can be calculated by:
20.000 * 1024
------------- = ~ 19.5
2^20
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
parent
45cb6653b0
commit
9769635423
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@ -285,6 +285,7 @@ static int imx_rngc_probe(struct platform_device *pdev)
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rngc->rng.init = imx_rngc_init;
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rngc->rng.read = imx_rngc_read;
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rngc->rng.cleanup = imx_rngc_cleanup;
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rngc->rng.quality = 19;
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rngc->dev = &pdev->dev;
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platform_set_drvdata(pdev, rngc);
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