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| author | Vadim Sukhomlinov <sukhomlinov@google.com> | 2020-06-18 09:09:04 -0700 |
|---|---|---|
| committer | Commit Bot <commit-bot@chromium.org> | 2020-06-18 22:23:45 +0000 |
| commit | 0c649ba01ab555e84ab030b7f1a38c48b294bbe2 (patch) | |
| tree | 3015e0a1340a540d7e001feb3e373c8d91e0924d | |
| parent | 08b1e22d83bd1d6c07619065fded9d0496f90e58 (diff) | |
| download | chrome-ec-0c649ba01ab555e84ab030b7f1a38c48b294bbe2.tar.gz | |
trng: adjust TRNG timeout to reduce TRNG resets
Time it takes for TRNG to come-up with 32-bit of randomness
varies, and once TRNG started to use 1-bit alphabet, it's average
increased. We handle this timeout by resetting TRNG and
writing record in the flash log. With current setting of EMPTY_COUNT
set to 400 it's almost never happens under normal use, and is harmless,
but adds unnecessary records in the log under heavy use like TRNG
health tests. Adjusting EMPTY_COUNT to higher value reduce probability
of TRNG reset when value is just delayed, but TRNG is not stalled yet.
BUG=b:138578157
TEST=tpmtest -t0
Signed-off-by: Vadim Sukhomlinov <sukhomlinov@google.com>
Change-Id: Ic0152da05934a70dd16b3e4178361bfcefbdda26
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2252481
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>
Reviewed-by: William Wesson <wesson@google.com>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Auto-Submit: Vadim Sukhomlinov <sukhomlinov@chromium.org>
Commit-Queue: Vadim Sukhomlinov <sukhomlinov@chromium.org>
Commit-Queue: Vadim Bendebury <vbendeb@chromium.org>
Tested-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>
| -rw-r--r-- | chip/g/trng.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/chip/g/trng.c b/chip/g/trng.c index b64c3c7dbe..e817034937 100644 --- a/chip/g/trng.c +++ b/chip/g/trng.c @@ -33,10 +33,10 @@ /** * Attempts to read TRNG_EMPTY before reporting a stall. - * Practically data should be available in less than 400 + * Practically data should be available in less than 777 * cycles under normal conditions. */ -#define TRNG_EMPTY_COUNT 400 +#define TRNG_EMPTY_COUNT 777 void init_trng(void) { |