linux-kernel - Re: [PATCH V5 4/9] genirq: Add runtime power management support for IRQ chips

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Date:	Mon, 6 Jun 2016 17:36:51 +0300
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>
CC:	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>,
	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>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V5 4/9] genirq: Add runtime power management support for
 IRQ chips

On 06/06/2016 05:30 PM, Jon Hunter wrote:
> 
> On 06/06/16 15:13, Grygorii Strashko wrote:
>> On 06/06/2016 02:53 PM, 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.
>>>
>>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
>>> Reviewed-by: Kevin Hilman <khilman@...libre.com>
>>> Reviewed-by: Marc Zyngier <marc.zyngier@....com>
>>> ---
>>>    include/linux/irq.h    |  4 ++++
>>>    kernel/irq/chip.c      | 35 +++++++++++++++++++++++++++++++++++
>>>    kernel/irq/internals.h |  1 +
>>>    kernel/irq/manage.c    | 31 ++++++++++++++++++++++++++++++-
>>>    4 files changed, 70 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/irq.h b/include/linux/irq.h
>>> index 4d758a7c604a..6c92a847394d 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_device:	pointer to parent device for irqchip
>>>     * @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_device;
>>>    	const char	*name;
>>>    	unsigned int	(*irq_startup)(struct irq_data *data);
>>>    	void		(*irq_shutdown)(struct irq_data *data);
>>> @@ -488,6 +490,8 @@ extern void handle_bad_irq(struct irq_desc *desc);
>>>    extern void handle_nested_irq(unsigned int irq);
>>>    
>>>    extern int irq_chip_compose_msi_msg(struct irq_data *data, struct msi_msg *msg);
>>> +extern int irq_chip_pm_get(struct irq_data *data);
>>> +extern int irq_chip_pm_put(struct irq_data *data);
>>>    #ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY
>>>    extern void irq_chip_enable_parent(struct irq_data *data);
>>>    extern void irq_chip_disable_parent(struct irq_data *data);
>>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>>> index 2f9f2b0e79f2..b09226e895c7 100644
>>> --- a/kernel/irq/chip.c
>>> +++ b/kernel/irq/chip.c
>>> @@ -1093,3 +1093,38 @@ int irq_chip_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>>>    
>>>    	return 0;
>>>    }
>>> +
>>> +/**
>>> + * irq_chip_pm_get - Enable power for an IRQ chip
>>> + * @data:	Pointer to interrupt specific data
>>> + *
>>> + * Enable the power to the IRQ chip referenced by the interrupt data
>>> + * structure.
>>> + */
>>> +int irq_chip_pm_get(struct irq_data *data)
>>> +{
>>> +	int retval = 0;
>>> +
>>> +	if (IS_ENABLED(CONFIG_PM) && data->chip->parent_device)
>>> +		retval = pm_runtime_get_sync(data->chip->parent_device);
>>
>> Sry, for the late comment - above require pm_runtime_put_noidle(data->chip->parent_device);
>> in case of failure.
> 
> No problem. Sorry, can you elaborate? I am not familiar with the
> _put_noidle().
> 

Question here in use counter - pm_runtime_get_sync() will increment usage_count
always and it will not decrement it in case of failure.
pm_runtime_put_noidle() expected to restore usage_count state (-1).


-- 
regards,
-grygorii