On 30 Nov 2016 19:05, "Lars-Peter Clausen" <lars@xxxxxxxxxx> wrote: > > On 11/27/2016 11:51 AM, Jonathan Cameron wrote: > > On 26/11/16 03:47, Aniroop Mathur wrote: > >> msleep(1~20) may not do what the caller intends, and will often sleep longer. > >> (~20 ms actual sleep for any value given in the 1~20ms range) > >> This is not the desired behaviour for many cases like device resume time, > >> device suspend time, device enable time, data reading time, etc. > >> Thus, change msleep to usleep_range for precise wakeups. > >> > >> Signed-off-by: Aniroop Mathur <a.mathur@xxxxxxxxxxx> > > As these need individual review by the various original authors and driver maintainers to > > establish the intent of the sleep, it would have been better to have done a series of > > patches (one per driver) with the relevant maintainers cc'd on the ones that they care about. > > > > Most of these are ADI parts looked after by Lars though so perhaps wait for his comments > > before respining. > > I agree with what Jonathan said. For most of these extending the maximum > sleep time a bit further is ok. > Well, its right that sleep a bit further is okay but this patch is not trying to solve any major bug. This patch is only trying to make the wake up more precise than before. So like with msleep(1), process could sleep for 20 ms so this patch only making the making the process to sleep for 1 ms as mentioned in the parameter. So I think, changing to usleep_range is only advantageous and does not cause any harm here. We have also applied the same change in enable/disable/suspend/resume functions in accel, gyro, mag, etc drivers and found decent results like the first sesor data is generated much faster than before so response time increased. This is critical as sensor can run at a rate of 200Hz / 5ms or even more now a days in new devices. We even applied in probe as doing the same in many drivers contribute to a little saving overall in kernel boot up. Also, it is recommended and mentioned in kernel documentation to use usleep_range for 1-10 ms. Sources - https://www.kernel.org/doc/Documentation/timers/timers-howto.txt https://lkml.org/lkml/2007/8/3/250 Thanks. BR, Aniroop Mathur
