Re: [PATCH 3/3] hwrng: ba431-rng: add support for BA431 hwrng

[Arnd Bergmann]

On Mon, May 25, 2020 at 10:07 PM Olivier Sobrie
<olivier.sobrie@xxxxxxxxxxxxxxxx> wrote:
>
> Silex insight BA431 is an IP designed to generate random numbers that
> can be integrated in various FPGA.
> This driver adds support for it through the hwrng interface.
>
> This driver is used in Silex Insight Viper OEM boards.
>
> Signed-off-by: Olivier Sobrie <olivier.sobrie@xxxxxxxxxxxxxxxx>
> Signed-off-by: Waleed Ziad <waleed94ziad@xxxxxxxxx>

The driver looks good to me.

Acked-by: Arnd Bergmann  <arnd@xxxxxxxx>

>  drivers/char/hw_random/Kconfig     |  10 ++
>  drivers/char/hw_random/Makefile    |   1 +
>  drivers/char/hw_random/ba431-rng.c | 240 +++++++++++++++++++++++++++++

I wonder if we should move drivers/char/hw_random to its own top-level drivers
subsystem outside of drivers/char. It seems to be growing steadily and is larger
than a lot of other subsystems with currently 34 drivers in there.

Not your problem though.

> +       /* Wait until the state changed */
> +       for (i = 0; i < BA431_RESET_READ_STATUS_RETRIES; ++i) {
> +               state = ba431_trng_get_state(ba431);
> +               if (state >= BA431_STATE_STARTUP)
> +                       break;
> +
> +               udelay(BA431_RESET_READ_STATUS_INTERVAL);
> +       }

Looking for something to improve, I noticed that this loop can take over
a millisecond to time out, and it always runs in non-atomic context.
It may be better to use usleep_range() than udelay().

      Arnd