netdev - Re: [PATCH 13/17] net: gianfar: remove misuse of IRQF_NO

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Date:	Thu, 24 Sep 2015 16:17:38 -0500
From:	Li Yang <leoli@...escale.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Manoil Claudiu <claudiu.manoil@...escale.com>,
	Sudeep Holla <sudeep.holla@....com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"David S. Miller" <davem@...emloft.net>,
	Kevin Hao <haokexin@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 13/17] net: gianfar: remove misuse of IRQF_NO_SUSPEND flag

On Wed, Sep 23, 2015 at 5:03 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Wed, 23 Sep 2015, Li Yang wrote:
>> On Mon, Sep 21, 2015 at 11:51 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
>> > On Mon, 21 Sep 2015, Manoil Claudiu wrote:
>> >> >The device is set as wakeup capable using proper wakeup API but the
>> >> >driver misuses IRQF_NO_SUSPEND to set the interrupt as wakeup source
>> >> >which is incorrect.
>> >> >
>> >> >This patch removes the use of IRQF_NO_SUSPEND flags replacing it with
>> >> >enable_irq_wake instead.
>> >> >
>> >>
>> >> What would be the purpose of IRQF_NO_SUSPEND flag then?  The flag is a
>> >> friendlier API compared to calling enable_irq_wake().  For older kernels,
>> >
>> > It's not an API, it's just a bandaid for lazy programmers.
>> >
>> >> on PPC architectures, the flag did the job.  When did this change? Since
>> >> when using IRQF_NO_SUSPEND is a "misuse"?
>> >
>> > It always was. Simply because IRQF_NO_SUSPEND has absolutely nothing
>> > to do with wakeup interrupt sources. It's a flag which excludes the
>> > interrupt from the suspend mechanism, but it does not flag it a wakeup
>> > source.
>>
>> It was not very clear on the intended use of IRQF_NO_SUSPEND at the
>> beginning as it was not documented anywhere.  It's good that we have
>> the Documentation/power/suspend-and-interrupts.txt to clarify that
>> now.
>
> This is complete and utter bullshit to put it blunt.
>
> The documentation of IRQF_NO_SUSPEND as non suitable for marking a
> particular device interrupt as wakeup source was added on Feb 20 2015
> with commit 737eb0301f2. Further clarification was added with commit
> 7438b633a6b on Mar 4 2015.
>
> The IRQF_NO_SUSPEND crap was introduced to gianfar with commit
> 614b42426cc3 on Jul 31 2015.

It is definitely an oversight of us to have missed the new development
on this topic.  It's a problem for us and I'm not trying to defend
that.  But the decision to use IRQF_NO_SUSPEND for wakeup interrupt
was made several years ago. (https://lkml.org/lkml/2012/7/20/174)  I
was just trying to say that it's hard to make the right decision at
the beginning.

Regards,
Leo
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