lkml.org 
[lkml]   [2015]   [Feb]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 2/2] hwrng: iproc-rng200 - Add Broadcom IPROC RNG driver
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
>



\
 
 \ /
  Last update: 2015-02-26 20:41    [W:0.049 / U:0.744 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site