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airoha: reduce HWRNG quality

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Backport a patch that reduces the quality of HWRNG. HWRNG has lower
entropy than expected. Thanks to this patch, it has a lower priority.

Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Link: https://github.com/openwrt/openwrt/pull/21722
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
This commit is contained in:
Aleksander Jan Bajkowski 2026-01-26 23:49:55 +01:00 • committed by Hauke Mehrtens
parent b59a89bde6
commit 5cd176925e
1 changed files with 57 additions and 0 deletions
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target/linux/airoha/patches-6.12/114-v7.0-hwrng-airoha-set-rng-quality-to-900.patch Normal file
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@ -0,0 +1,57 @@
From c0008a29a006091d7f9d288620c2456afa23ff27 Mon Sep 17 00:00:00 2001
From: Aleksander Jan Bajkowski <olek2@wp.pl>
Date: Mon, 5 Jan 2026 21:41:49 +0100
Subject: [PATCH] hwrng: airoha - set rng quality to 900
Airoha uses RAW mode to collect noise from the TRNG. These appear to
be unprocessed oscillations from the tero loop. For this reason, they
do not have a perfect distribution and entropy. Simple noise compression
reduces its size by 9%, so setting the quality to 900 seems reasonable.
The same value is used by the downstream driver.
Compare the size before and after compression:
$ ls -l random_airoha*
-rw-r--r-- 1 aleksander aleksander 76546048 Jan 3 23:43 random_airoha
-rw-rw-r-- 1 aleksander aleksander 69783562 Jan 5 20:23 random_airoha.zip
FIPS test results:
$ cat random_airoha | rngtest -c 10000
rngtest 2.6
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
rngtest: starting FIPS tests...
rngtest: bits received from input: 200000032
rngtest: FIPS 140-2 successes: 0
rngtest: FIPS 140-2 failures: 10000
rngtest: FIPS 140-2(2001-10-10) Monobit: 9957
rngtest: FIPS 140-2(2001-10-10) Poker: 10000
rngtest: FIPS 140-2(2001-10-10) Runs: 10000
rngtest: FIPS 140-2(2001-10-10) Long run: 4249
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=953.674; avg=27698.935; max=19073.486)Mibits/s
rngtest: FIPS tests speed: (min=59.791; avg=298.028; max=328.853)Mibits/s
rngtest: Program run time: 647638 microseconds
In general, these data look like real noise, but with lower entropy
than expected.
Fixes: e53ca8efcc5e ("hwrng: airoha - add support for Airoha EN7581 TRNG")
Suggested-by: Benjamin Larsson <benjamin.larsson@genexis.eu>
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
drivers/char/hw_random/airoha-trng.c | 1 +
1 file changed, 1 insertion(+)
--- a/drivers/char/hw_random/airoha-trng.c
+++ b/drivers/char/hw_random/airoha-trng.c
@@ -212,6 +212,7 @@ static int airoha_trng_probe(struct plat
trng->rng.init = airoha_trng_init;
trng->rng.cleanup = airoha_trng_cleanup;
trng->rng.read = airoha_trng_read;
+ trng->rng.quality = 900;
ret = devm_hwrng_register(dev, &trng->rng);
if (ret) {