lkml.org 
[lkml]   [2014]   [May]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH] ARM: Don't ever downscale loops_per_jiffy in SMP systems
    From
    Russel,

    On Thu, May 8, 2014 at 1:55 PM, Russell King - ARM Linux
    <linux@arm.linux.org.uk> wrote:
    > On Thu, May 08, 2014 at 11:06:24AM -0700, Doug Anderson wrote:
    >> I guess I would say that my patch is unhacking the this code. The
    >> code after my patch is simpler. I would perhaps argue that (ec971ea
    >> ARM: add cpufreq transiton notifier to adjust loops_per_jiffy for smp)
    >> should never have landed to begin with.
    >
    > That depends on your point of view. As I've already pointed out through
    > the examples of why udelay() is inaccurate, for driver authors, they
    > should assume that udelay() just gives you an "approximate" delay and
    > it has no accuracy.

    That disagrees with what Thomas Gleixner says at
    <http://lkml.iu.edu//hypermail/linux/kernel/1203.1/01034.html>. It
    also seems like perhaps the regulator core is broken, then... If a
    udelay(30) can end up as a udelay(20) then we may return from a
    regulator code 10us earlier than we should and we'll assume that a
    regulator is ramped before it really is...

    I'm out tomorrow but I can confirm on Monday that I was really seeing
    udelay(30) be a udelay(20) without this patch.


    \
     
     \ /
      Last update: 2014-05-09 02:41    [W:3.991 / U:0.068 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site