| Message ID | 20221012160924.12226-2-tomas.marek@elrest.cz |
|---|---|
| State | Accepted |
| Commit | 7e11a4fc84dcc9746936c46d9a88489a365fea45 |
| Headers | show |
| Series | hwrng: stm32 - improve performance | expand |
On Wed, Oct 12, 2022 at 06:09:23PM +0200, Tomas Marek wrote: > > diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c > index bc22178f83e8..8eaacefd498b 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 This would make a lot more sense if you called it err instead of ret. But as you're fixing a real bug I'm going to apply your patch as is and you can post an incremental patch to improve it. Thanks,
On Fri, Oct 21, 2022 at 06:41:07PM +0800, Herbert Xu wrote: > On Wed, Oct 12, 2022 at 06:09:23PM +0200, Tomas Marek wrote: > > > > diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c > > index bc22178f83e8..8eaacefd498b 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 > > This would make a lot more sense if you called it err instead of ret. > > But as you're fixing a real bug I'm going to apply your patch as is > and you can post an incremental patch to improve it. OK, sounds reasonable. I'll post new patch and rename ret to err. Thanks for the hint and for the review. Tomas > > Thanks, > -- > Email: Herbert Xu <herbert@gondor.apana.org.au> > Home Page: http://gondor.apana.org.au/~herbert/ > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c index bc22178f83e8..8eaacefd498b 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); }
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 <oleg.karfich@wago.com> Signed-off-by: Tomas Marek <tomas.marek@elrest.cz> --- drivers/char/hw_random/stm32-rng.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)