linux-kernel - Re: [PATCH] OMAP GPIO - don't wake from suspend unless requested.

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Message-ID: <CAMQu2gzY5V19sBvCx1zcYe+KMQEX9g2c5KvHQ4UgdeuEWB_gcQ@mail.gmail.com>
Date:	Thu, 6 Sep 2012 14:13:24 +0530
From:	"Shilimkar, Santosh" <santosh.shilimkar@...com>
To:	NeilBrown <neilb@...e.de>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Tarun Kanti DebBarma <tarun.kanti@...com>,
	Kevin Hilman <khilman@...com>,
	Tony Lindgren <tony@...mide.com>, Benoit <b-cousson@...com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Felipe Balbi <balbi@...com>, linux-omap@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>,
	Jon Hunter <jon-hunter@...com>
Subject: Re: [PATCH] OMAP GPIO - don't wake from suspend unless requested.

On Thu, Sep 6, 2012 at 1:21 PM, NeilBrown <neilb@...e.de> wrote:
> On Thu, 6 Sep 2012 12:57:46 +0530 "Shilimkar, Santosh"
> <santosh.shilimkar@...com> wrote:
>
>> On Thu, Sep 6, 2012 at 12:32 PM, NeilBrown <neilb@...e.de> wrote:
>> > On Thu, 6 Sep 2012 11:18:09 +0530 "Shilimkar, Santosh"
>> > <santosh.shilimkar@...com> wrote:
>> >
>> >> On Thu, Sep 6, 2012 at 8:35 AM, NeilBrown <neilb@...e.de> wrote:
>> >> > On Mon, 3 Sep 2012 22:59:06 -0700 "Shilimkar, Santosh"
>> >> > <santosh.shilimkar@...com> wrote:
>> >
>> >> >> After thinking bit more on this, the problem seems to be coming
>> >> >> mainly because the gpio device is runtime suspended bit early than
>> >> >> it should be. Similar issue seen with i2c driver as well. The i2c issue
>> >> >> was discussed with Rafael at LPC last week. The idea is to move
>> >> >> the pm_runtime_enable/disable() calls entirely up to the
>> >> >> _late/_early stage of device suspend/resume.
>> >> >> Will update this thread once I have further update.
>> >> >
>> >> > This won't be late enough.  IRQCHIP_MASK_ON_SUSPEND takes effect after all
>> >> > the _late callbacks have been called.
>> >> > I, too, spoke to Rafael about this in San Diego.  He seemed to agree with me
>> >> > that the interrupt needs to be masked in the ->suspend callback.  any later
>> >> > is too late.
>> >> >
>> >> Thanks for information about your discussion. Will wait for the patch then.
>> >>
>> >> Regards
>> >> santosh
>> >
>> > I already sent a patch - that is what started this thread :-)
>> >
>> > I include it below.
>> > You said "The patch doesn't seems to be correct" but didn't expand on why.
>> > Do you still think it is not correct?  I wouldn't be surprised if there is
>> > some case that it doesn't handle quite right, but it seems right to me.
>> >
>> Sorry I though you were talking about moving the "Checking wakeup interrupts"
>> bit early as discussed on the follow up of alternate suggested patch to make
>> use of  IRQCHIP_MASK_ON_SUSPEND.
>>
>> I think we need to fix the issue seen with ' IRQCHIP_MASK_ON_SUSPEND'
>> patch. That is at least the expected way to manage suspend and wakeup
>> irq masks for a IRQCHIP.
>
> That is what I thought at first too.  But when talking to Rafael he said that
> IRQCHIP_MASK_ON_SUSPEND was intended mainly for clock interrupts.  For other
> less fundamental interrupts, doing the mask/unmask in suspend/resume
> callbacks is sufficient and simpler... and actually works.
>
That is not the how I undetand IRQCHIP_MASK_ON_SUSPEND use.
I thought it can be used for any IRQ chip for masking or setting wakeup on
interrupts lines managed by that chip for suspend. May be I am wrong.

> IRQCHIP_MASK_ON_SUSPEND is currently used by precisely two drivers:
>
>    arch/arm/mach-omap2/omap-wakeupgen.c
> and
>    drivers/mfd/pm8xxx-irq.c
>
> which suggests that it isn't widely used and quite possibly doesn't actually
> work in general.
I have seen lot more platforms use in downstream kernels. Also seen recently
patches on the linux-arm list for couple of platforms.

>
> Maybe we need to start a new thread and pester Rafael or Thomas Gleixner
> to either explain what is intended for this case, or to fix
> IRQCHIP_MASK_ON_SUSPEND so that it can be used in general.
>
Sounds a good idea. Since you already had discussion with Rafael,
probably you can describe the issue better.

Regards
Santosh
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