From 7e11a4fc84dcc9746936c46d9a88489a365fea45 Mon Sep 17 00:00:00 2001 From: Tomas Marek Date: Wed, 12 Oct 2022 18:09:23 +0200 Subject: [PATCH] hwrng: stm32 - fix number of returned bytes on read The stm32_rng_read() function uses `retval` variable as a counter of generated random bytes. However, the same variable is used to store a result of the polling function in case the driver is waiting until the TRNG is ready. The TRNG generates random numbers by 16B. One loop read 4B. So, the function calls the polling every 16B, i.e. every 4th loop. The `retval` counter is reset on poll call and only number of bytes read after the last poll call is returned to the caller. The remaining sampled random bytes (for example 48 out of 64 in case 64 bytes are read) are not used. Use different variable to store the polling function result and do not overwrite `retval` counter. Cc: Oleg Karfich Signed-off-by: Tomas Marek Signed-off-by: Herbert Xu --- drivers/char/hw_random/stm32-rng.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c index bc22178..8eaacef 100644 --- a/drivers/char/hw_random/stm32-rng.c +++ b/drivers/char/hw_random/stm32-rng.c @@ -49,11 +49,13 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) /* Manage timeout which is based on timer and take */ /* care of initial delay time when enabling rng */ if (!sr && wait) { - retval = readl_relaxed_poll_timeout_atomic(priv->base + int ret; + + ret = readl_relaxed_poll_timeout_atomic(priv->base + RNG_SR, sr, sr, 10, 50000); - if (retval) + if (ret) dev_err((struct device *)priv->rng.priv, "%s: timeout %x!\n", __func__, sr); } -- 2.7.4