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

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Message-ID: <56EC1719.5020408@nvidia.com>
Date:	Fri, 18 Mar 2016 14:56:25 +0000
From:	Jon Hunter <jonathanh@...dia.com>
To:	Grygorii Strashko <grygorii.strashko@...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 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?

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.

>>> 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()?

Jon