Hi Alexander,
Alexander Stein (alexander.stein@xxxxxxxxxxxxxxx) wrote:
> Am Dienstag, 22. August 2023, 17:25:53 CEST schrieb Martin Kaiser:
> > Use polling to wait until the imx-rngc is properly seeded.
> What is the benefit of burning CPU cycles while waiting for hardware?
it seems to me that
readl_poll_timeout
readx_poll_timeout
usleep_range
usleep_range_state
schedule_hrtimeout_range
will not wait in the foreground and burn CPU cycles.
The comment for schedule_hrtimeout_range says
* Make the current task sleep until the given expiry time has
* elapsed.
> > We do this only in the init function when the imx-rngc becomes active.
> > Polling is ok at this time, there's nothing else we could do while
> > we're waiting.
> > We can now remove the code for the interrupt and the completion.
> Please split the change to polling and IRQ removal into two patches.
Good point. Will do this in v2.
> RNGC_STATUS_SEED_DONE, 1000, RNGC_TIMEOUT * 1000);
> So you want to poll for up to 3s?
According to the manual, "The initial seed takes approximately 2,000,000
clock cycles." With a 66.5MHz clock, this is approx 30ms. So that should
be
RNGC_STATUS_SEED_DONE, 20000, 100000);
The comment for readx_poll_timeout suggests <= 20ms for the poll
interval.
Best regards,
Martin
