Re: [PATCH v2 2/2] hwrng: iproc-rng200 - Add Broadcom IPROC RNG driver
From: Arnd Bergmann <hidden>
Date: 2015-02-25 19:18:53
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linux-arm-kernel, lkml
On Wednesday 25 February 2015 10:16:24 Scott Branden wrote:
This adds a driver for random number generator present on Broadcom IPROC devices. Reviewed-by: Ray Jui <rjui-dY08KVG/lbpWk0Htik3J/w@public.gmane.org> Signed-off-by: Scott Branden <sbranden-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
The driver looks reasonable overall, I have just one question about something that sticks out:
+ while ((num_remaining > 0) && time_before(jiffies, idle_endtime)) {...
+
+ /* Are there any random numbers available? */
+ if ((ioread32(rng_base + RNG_FIFO_COUNT_OFFSET) &
+ RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK) > 0) {...
+ } else {
+ if (!wait)
+ /* Cannot wait, return immediately */
+ return max - num_remaining;
+
+ /* Can wait, give others chance to run */
+ cpu_relax();
+ }
+ }
+It looks like you do a busy-loop around cpu_relax here if asked to wait. Is this intentional? I would normally expect either cond_resched() or some msleep() instead. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html