lkml.org 
[lkml]   [2013]   [Dec]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2 16/16] misc: support for I-8024 in LP-8x4x
From
Date
On Sat, 2013-12-14 at 21:59 +0100, Arnd Bergmann wrote:
> Have you checked that the nsleep definition actually does the
> right thing here? 450 nanoseconds must be close the latency
> you get from calling schedule_hrtimeout(). I'd suggest using
> either ndelay() or usleep_range() instead, depending on your
> needs.

Documentation/timers/timers-howto.txt stated there was a significant
overhead when setting up usleep_range. I studied implementation and
found that schedule_hrtimeout was certainly less than 520000 CPU cycles
that udelay(1) would consume.

It worked. I haven't checked actual delay time. However, machines with
the driver (based on 3.8) are in production since May 2013 without
issues.

> If nsleep is really useful here, we should probably add that
> as a generic API rather than having it in one driver.

I've also used this nsleep for driving RTC clock (DS1302) since May
2013.

Now I see that my code is a clone of usleep_range(x, x). I will convert
my code to use it.




\
 
 \ /
  Last update: 2013-12-15 00:21    [W:0.480 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site