• Krzysztof Kozlowski's avatar
    crypto: exynos - Add new Exynos RNG driver · c46ea13f
    Krzysztof Kozlowski authored
    Replace existing hw_ranndom/exynos-rng driver with a new, reworked one.
    This is a driver for pseudo random number generator block which on
    Exynos4 chipsets must be seeded with some value.  On newer Exynos5420
    chipsets it might seed itself from true random number generator block
    but this is not implemented yet.
    
    New driver is a complete rework to use the crypto ALGAPI instead of
    hw_random API.  Rationale for the change:
    1. hw_random interface is for true RNG devices.
    2. The old driver was seeding itself with jiffies which is not a
       reliable source for randomness.
    3. Device generates five random 32-bit numbers in each pass but old
       driver was returning only one 32-bit number thus its performance was
       reduced.
    
    Compatibility with DeviceTree bindings is preserved.
    
    New driver does not use runtime power management but manually enables
    and disables the clock when needed.  This is preferred approach because
    using runtime PM just to toggle clock is huge overhead.
    
    Another difference is reseeding itself with generated random data
    periodically and during resuming from system suspend (previously driver
    was re-seeding itself again with jiffies).
    Signed-off-by: 's avatarKrzysztof Kozlowski <krzk@kernel.org>
    Reviewed-by: 's avatarStephan Müller <smueller@chronox.de>
    Reviewed-by: 's avatarPrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
    Reviewed-by: 's avatarBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
    Signed-off-by: 's avatarHerbert Xu <herbert@gondor.apana.org.au>
    c46ea13f
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