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

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Message-ID: <56EACD21.20309@arm.com>
Date:	Thu, 17 Mar 2016 15:28:33 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Jon Hunter <jonathanh@...dia.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	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>,
	Linus Walleij <linus.walleij@...aro.org>
Cc:	Kevin Hilman <khilman@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	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 17/03/16 15:13, Jon Hunter wrote:
> Hi Marc,
> 
> On 17/03/16 15:02, Marc Zyngier wrote:
>> Hi Jon,
>>
>> On 17/03/16 14:19, Jon Hunter wrote:
>>> Some IRQ chips may be located in a power domain outside of the CPU
>>> subsystem and hence will require device specific runtime power
>>> management. In order to support such IRQ chips, add a pointer for a
>>> device structure to the irq_chip structure, and if this pointer is
>>> populated by the IRQ chip driver and CONFIG_PM is selected in the kernel
>>> configuration, then the pm_runtime_get/put APIs for this chip will be
>>> called when an IRQ is requested/freed, respectively.
>>>
>>> When entering system suspend and each interrupt is disabled if there is
>>> no wake-up set for that interrupt. For an IRQ chip that utilises runtime
>>> power management, print a warning message for each active interrupt that
>>> has no wake-up set because these interrupts may be unnecessarily keeping
>>> the IRQ chip enabled during system suspend.
>>>
>>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
>>> ---
>>>  include/linux/irq.h    |  5 +++++
>>>  kernel/irq/chip.c      | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  kernel/irq/internals.h |  1 +
>>>  kernel/irq/manage.c    | 14 +++++++++++---
>>>  kernel/irq/pm.c        |  3 +++
>>>  5 files changed, 72 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/include/linux/irq.h b/include/linux/irq.h
>>> index c4de62348ff2..82f36390048d 100644
>>> --- a/include/linux/irq.h
>>> +++ b/include/linux/irq.h
>>> @@ -315,6 +315,7 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
>>>  /**
>>>   * struct irq_chip - hardware interrupt chip descriptor
>>>   *
>>> + * @parent:		pointer to associated device
>>>   * @name:		name for /proc/interrupts
>>>   * @irq_startup:	start up the interrupt (defaults to ->enable if NULL)
>>>   * @irq_shutdown:	shut down the interrupt (defaults to ->disable if NULL)
>>> @@ -354,6 +355,7 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
>>>   * @flags:		chip specific flags
>>>   */
>>>  struct irq_chip {
>>> +	struct device	*parent;
>>
>> Nit: Please don't call this just "parent". We have parent fields in
>> irq_data and irq_domain structures, and they always are a pointer to the
>> same type, indicating some form of stacking. Here, we're pointing to a
>> different type altogether...
>>
>> How about calling it "dev", or "device" instead? It would make it much
>> clearer that when crossing that pointer, we're in another subsystem
>> altogether.
> 
> I will defer to Linus W here, as it was his request we make this
> 'parent' and not 'dev'. See ...
> 
> http://marc.info/?l=linux-kernel&m=145035839623442&w=2

Well, that contradicts the way use use the word "parent" in the IRQ
subsystem, I guess. I'd settle for parent_device or something along
those lines (but keep in mind I'm really bad at naming things).

Anyway, enough bikeshedding... ;-)

	M.
-- 
Jazz is not dead. It just smells funny...