On 05/05/2014 09:45 AM, Ralf Roesch wrote:
> On Sun May 04 2014 17:57:55 GMT+0200 (CEST), Gilles Chanteperdrix
> <[email protected]> wrote:
>> On 05/04/2014 12:40 PM, Ralf Roesch wrote:
>>> Hi,
>>>
>>> based on your suggestions from thread "[Xenomai] ipipe-core-3.10 patch
>>> for arm"
>>> I started testing Xenomai on an i.MX6 board [1].
>>>
>>> * checked out branch imx_3.10.17_1.0.0_ga from linux-2.6-imx.git [2]
>>> * merged vanilla v3.10.32 tag
>>> resolved 3 conflicts:
>>> drivers/net/can/flexcan.c
>>> drivers/usb/host/ehci.h
>>> sound/soc/codecs/wm8962.c
>>> * applied ipipe-v3.10.32.patch
>>> resolved 4 conflicts:
>>> arch/arm/mach-imx/clk-imx6q.c
>>> arch/arm/mach-imx/mach-imx6q.c
>>> arch/arm/mach-imx/mm-imx27.c
>>> arch/arm/mach-imx/mm-imx3.c
>>> * applied xenomai-2.6 support (prepare-kernel.sh)
>>>
>>> My box boots without errors and seems to be quiet stable at the first
>>> glance.
>>> Linux arm 3.10.32-xenomai-armv7-x1 #24 SMP Sun May 4 12:17:10 CEST 2014
>>> armv7l GNU/Linux
>>>
>>> The first thing I observed is a system time problem:
>>> the RTC and system time clocks get out of phase very quickly.
>>> I do compare the timers (end - start) on console by calling:
>>> - hwclock && date (start)
>>> - wait an hour or more
>>> - hwclock && date (end)
>>> The hwclock time is always o.k. but the system time reported by date is
>>> roughly 25% faster.
>>> Do you have an idea what could go wrong here?
>> The timer frequency. Did you not forget to disable CONFIG_CPU_FREQ? Do
>> you have the same issue without the I-pipe patch?
>>
>>
> Thanks Gilles, I had not disabled the CONFIG_CPU_FREQ.
> After disabling I had also to disable CONFIG_PM, because I got a lot of
> unresolved linker errors.
> More fixes had to be made in various modules where CONFIG_PM was not
> taken into account.
> In the end I had a bootable kernel, where the "out of phase of timer
> problem" has been resolved.
> Both timers keep in sync now.
>
> The kernel without I-pipe patch did work correctly, sorry for not
> mentioning that before.
>
> I have some more questions regarding timer frequency:
>
> * I prefer to leave CONFIG_CPU_FREQ enabled,
> because in this case I can use the CPUFreq governor (cpufrequtils
> package)
> to use the highest frequency, i.e. "performance"
> * if the governer is set to "performance" a frequency switch shoud not
> be possible
> (because the processor is fixed to the high rate)
> * without governer I can not use the highest rate of the processor:
> - the frequency (now) without CONFIG_CPU_FREQ is 792MHz
> - when CONFIG_CPU_FREQ is enabled (before) and governer set to
> performance it is 996MHz
>
> If I compare this both frequencies (792MHz vs. 996MHz) I estimate there
> is a wrong scaling factor responsible for the "out of phase" problem.
Look at the mx6 patch for 3.0.43, it solves a similar issue. We support
mainline, and freescale 3.0.35, not freescale 3.10, so, you may have a
lot of issues with this version which were solved for 3.0.43 but are not
in the patch for mainline 3.10. If I remember correctly, there were
multiple such issues such as idle thread and broadcast timer.
--
Gilles.
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