linux-kernel - Re: [linux-pm] [PATCH] acpi: intel_idle : break dependency between modules

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Date:	Thu, 28 Jun 2012 16:53:34 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Thomas Renninger <trenn@...e.de>
CC:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linaro-dev@...ts.linaro.org, linux-pm@...r.kernel.org,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: Re: [linux-pm] [PATCH] acpi: intel_idle : break dependency between
 modules

On 06/28/2012 01:04 PM, Thomas Renninger wrote:
> On Wednesday, June 27, 2012 06:16:33 PM Srivatsa S. Bhat wrote:
>> On 06/27/2012 02:37 PM, Daniel Lezcano wrote:
>>> When the system is booted with some cpus offline, the idle
>>> driver is not initialized. When a cpu is set online, the
>>> acpi code call the intel idle init function. Unfortunately
>>> this code introduce a dependency between intel_idle and acpi.
>>>
>>> This patch is intended to remove this dependency by using the
>>> notifier of intel_idle. In order to make it work, the notifier
>>> must be initialized in the right order, acpi then intel_idle.
>>> This is done in the Makefile.
>>
>> There is a much better way of doing this. See below.
>>
>>> This patch has the benefit of
>>> encapsulating the intel_idle driver and remove some exported
>>> functions.
>>>
>>
>> Nice :)
>>
>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>>> ---
>>>  drivers/Makefile                |    3 ++-
>>>  drivers/acpi/processor_driver.c |    7 -------
>>>  drivers/idle/intel_idle.c       |   22 ++++++++++++++--------
>>>  include/linux/cpuidle.h         |    7 -------
>>>  4 files changed, 16 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/drivers/Makefile b/drivers/Makefile
>>> index 2ba29ff..a2454b8 100644
>>> --- a/drivers/Makefile
>>> +++ b/drivers/Makefile
>>> @@ -12,8 +12,9 @@ obj-$(CONFIG_PCI)		+= pci/
>>>  obj-$(CONFIG_PARISC)		+= parisc/
>>>  obj-$(CONFIG_RAPIDIO)		+= rapidio/
>>>  obj-y				+= video/
>>> -obj-y				+= idle/
>>> +# acpi must come before idle for initialization
>>>  obj-$(CONFIG_ACPI)		+= acpi/
>>> +obj-y				+= idle/
>>>  obj-$(CONFIG_SFI)		+= sfi/
>>>  # PnP must come after ACPI since it will eventually need to check if acpi
>>>  # was used and do nothing if so
>>
>> OK, so all you are trying to do here is ensure that the intel idle related
>> notifier runs _after_ the acpi related one.
> I might oversee something, if you have concerns, please point me to it.
> If it's all about keeping the order of excuting these functions:
>    acpi_processor_start(pr)
> and
>    intel_idle_cpu_init()
> There should be no need for it. Intel idle is pretty separated.
> 

I digged through the code a bit, and even I couldn't find any reason why there
should be a dependency between the two events.

Regards,
Srivatsa S. Bhat

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