[PATCH v2 2/2] hwrng: iproc-rng200 - Add Broadcom IPROC RNG driver
From: sbranden@broadcom.com (Scott Branden)
Date: 2015-02-26 19:37:38
Also in:
linux-devicetree, lkml
Response inline. On 15-02-25 11:17 AM, Arnd Bergmann wrote:
On Wednesday 25 February 2015 10:16:24 Scott Branden wrote:quoted
This adds a driver for random number generator present on Broadcom IPROC devices. Reviewed-by: Ray Jui <rjui@broadcom.com> Signed-off-by: Scott Branden <sbranden@broadcom.com>The driver looks reasonable overall, I have just one question about something that sticks out:quoted
+ while ((num_remaining > 0) && time_before(jiffies, idle_endtime)) {...quoted
+ + /* Are there any random numbers available? */ + if ((ioread32(rng_base + RNG_FIFO_COUNT_OFFSET) & + RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK) > 0) {...quoted
+ } 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.
This code was following examples of other open source drivers - bcm2835 and exynos both use cpu_relax. I'll have to look into this more to understand.
Arnd