Messages in this thread | | | Date | Thu, 26 Feb 2015 11:37:20 -0800 | From | Scott Branden <> | Subject | Re: [PATCH v2 2/2] hwrng: iproc-rng200 - Add Broadcom IPROC RNG driver |
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Response inline.
On 15-02-25 11:17 AM, Arnd Bergmann wrote: > 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@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: > >> + 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.
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 >
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