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SubjectRe: [PATCH 3/3] hwrng: ba431-rng: add support for BA431 hwrng
On Mon, May 25, 2020 at 10:07 PM Olivier Sobrie
<olivier.sobrie@silexinsight.com> 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@silexinsight.com>
> Signed-off-by: Waleed Ziad <waleed94ziad@gmail.com>

The driver looks good to me.

Acked-by: Arnd Bergmann <arnd@arndb.de>

> 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

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