linux-kernel - Re: [PATCH 08/15] genirq: Add runtime power management support for IRQ chips

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Message-ID: <56EC404A.9060001@ti.com>
Date:	Fri, 18 Mar 2016 19:52:10 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Jon Hunter <jonathanh@...dia.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Benoît Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>
CC:	Kevin Hilman <khilman@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	<linux-tegra@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/15] genirq: Add runtime power management support for
 IRQ chips

On 03/18/2016 04:56 PM, Jon Hunter wrote:
> 
> On 18/03/16 14:40, Jon Hunter wrote:
>> On 18/03/16 14:23, Grygorii Strashko wrote:
>>> On 03/18/2016 02:27 PM, Jon Hunter wrote:
>>>>
>>>> On 18/03/16 11:11, Grygorii Strashko wrote:
> 
> [snip]
> 
>>> oh :( That will require updating of all drivers (and if it will be taken into account that
>>> wakeup can be configured from sysfs + devm_ - it will be painful).
>>
>> Will it? I know that there are a few gpio chips that have some hacked
>> ways to get around the PM issue, but I wonder how many drivers this
>> really impacts. What sysfs entries are you referring too?

echo enabled > /sys/devices/platform/44000000.ocp/48020000.serial/tty/ttyS2/power/wakeup

> 
> Thinking about this some more, yes I guess it would impact all drivers
> that use a gpio but don't use it for a wake-up. I could see that could
> be a few drivers indeed.

yep. I've just tested it
- gpio was requested through sysfs and configured as IRQ
- do suspend

the same is if GPIO is requested as IRQ only and not configured as wakeup source 

[  319.669760] PM: late suspend of devices complete after 0.213 msecs
[  319.671195] irq 191 has no wakeup set and has not been freed!
[  319.673453] PM: noirq suspend of devices complete after 2.258 msecs

this is very minimal configuration - the regular one is at ~30-50 devices
most of them will use IRQ and only ~10% are used as wakeup sources.


> 
>>>> but it would avoid every irqchip having to
>>>> handle this themselves and having a custom handler.
>>>
>>> irqchip like TI OMAP GPIO will need custom handling any way even if it's not expected
>>> to be Powered off during Suspend or deep CPUIdle states, simply because its state
>>> in suspend is unknown - PM state managed automatically (and depends on many factors)
>>> and wakeup can be handled by special HW in case if GPIO bank was really switched off.
>>>
>>>>> I propose do not touch common/generic suspend code now. Any common code can be always
>>>>> refactored later once there will be real drivers updated to use irqchip RPM
>>>>> and which will support Suspend.
>>>>
>>>> If this is strongly opposed, I would concede to making this a pr_debug()
>>>> as I think it could be useful.
>>>
>>> Probably yes, because most of the drivers now and IRQ PM core are not ready
>>> for this approach.
>>
>> May be this calls for a new flag to not WARN if non-wakeup IRQs are not
>> freed when entering suspend.
> 
> Flag or pr_debug()?
> 

Honestly, I don't know how to proceed - minimum is pr_debug.
My personal opinion is still the same - don't touch suspend core code now, within this series.


-- 
regards,
-grygorii