linux-kernel - Re: [PATCH v3 1/2] kernel: time: Add udelay

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Date:	Fri, 13 Jun 2014 09:22:21 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	David Riley <davidriley@...gle.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Doug Anderson <dianders@...omium.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] kernel: time: Add udelay_test module to validate udelay

On Fri, Jun 13, 2014 at 9:13 AM, David Riley <davidriley@...gle.com> wrote:
> On Fri, Jun 13, 2014 at 9:06 AM, John Stultz <john.stultz@...aro.org> wrote:
>> On Thu, Jun 12, 2014 at 1:13 PM, David Riley <davidriley@...omium.org> wrote:
>>> Create a module that allows udelay() to be executed to ensure that
>>> it is delaying at least as long as requested (with a little bit of
>>> error allowed).
>>>
>>> There are some configurations which don't have reliably udelay
>>> due to using a loop delay with cpufreq changes which should use
>>> a counter time based delay instead.  This test aims to identify
>>> those configurations where timing is unreliable.
>>>
>>> Signed-off-by: David Riley <davidriley@...omium.org>
>>> ---
>>>  kernel/time/Kconfig       |   7 ++
>>>  kernel/time/Makefile      |   1 +
>>>  kernel/time/udelay_test.c | 170 ++++++++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 178 insertions(+)
>>>  create mode 100644 kernel/time/udelay_test.c
>>>
>>> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
>>> index f448513..c6af048 100644
>>> --- a/kernel/time/Kconfig
>>> +++ b/kernel/time/Kconfig
>>> @@ -202,3 +202,10 @@ config HIGH_RES_TIMERS
>>>
>>>  endmenu
>>>  endif
>>> +
>>> +config UDELAY_TEST
>>> +       tristate "udelay test driver"
>>> +       default n
>>> +       help
>>> +         This builds the "udelay_test" module that helps to make sure
>>> +         that udelay() is working properly.
>>
>>
>> Thanks for resubmitting! So I've queued this for my testing.
>>
>> My only thoughts playing with it now, is that the Kconfig entry is
>> just in an awkward spot. There isn't really a udelay, or really
>> general timekeeping specific area in the menus, so it just shows up in
>> "General Setup" between the "Timer Subsystem" and "Cpu/task time.."
>> submenus.
>>
>> I suspect this would be better added in lib/Kconfig.debug near
>> TEST_MODULE.  Any objections to me changing that?
>>
>> Also I'd probably rename the config option to TEST_UDELAY, as well as
>> tweak the option string to be more consistent with those similar test
>> driver options.
>
> Hi John,
>
> I'm okay with those changes.  Do you want me to resubmit or will you
> just make the changes locally?

Don't bother, already made them locally..

thanks
-john
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