Re: [PATCH v2] crypto: atmel-sha204a - drop hwrng quality reduction for ATSHA204A

Herbert Xu
2026-05-05T09:30:32Z

On Tue, Apr 28, 2026 at 12:14:32PM +0200, Thorsten Blum wrote:
> Commit 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to
> lowest possible") reduced the hwrng quality to 1 based on a review by
> Bill Cox [1]. However, despite its title, the review only tested the
> ATSHA204, not the ATSHA204A.
>
> In the same thread, Atmel engineer Landon Cox wrote "this behavior has
> been eliminated entirely"[2] in the ATSHA204A and "this problem does not
> affect the ATECC108 or the ATECC108A (or the ATSHA204A)"[3].
>
> According to the official ATSHA204A datasheet [4], the device contains a
> high-quality hardware RNG that combines its output with an internal seed
> value stored in EEPROM or SRAM to generate random numbers. The device
> also implements all security functions using SHA-256, and the driver
> uses the chip's Random command in seed-update mode.
>
> Keep 'quality = 1' for ATSHA204, but drop the explicit hwrng quality
> reduction for ATSHA204A and fall back to the hwrng core default.
>
> [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html
> [2] https://www.metzdowd.com/pipermail/cryptography/2014-December/023852.html
> [3] https://www.metzdowd.com/pipermail/cryptography/2014-December/023886.html
> [4] https://ww1.microchip.com/downloads/en/DeviceDoc/ATSHA204A-Data-Sheet-40002025A.pdf
>
> Fixes: 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to lowest possible")
> Cc: stable@vger.kernel.org
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
> Changes in v2:
> - Drop the enum and dereference match data if needed as suggested by Ard
> - Keep the review comment
> - v1: https://lore.kernel.org/lkml/20260427124030.315590-3-thorsten.blum@linux.dev/
> ---
> drivers/crypto/atmel-sha204a.c | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)

Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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