linux-kernel - Re: [PATCH v2 1/3] genirq: Allow the irqchip state of an IRQ to be save/restored

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Date:	Wed, 07 Jan 2015 16:09:54 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Jason Cooper <jason@...edaemon.net>
CC:	Bjorn Andersson <bjorn@...o.se>,
	Abhijeet Dharmapurikar <adharmap@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>, Phong Vo <pvo@....com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Tin Huynh <tnhuynh@....com>, Y Vo <yvo@....com>,
	Thomas Gleixner <tglx@...utronix.de>, Toan Le <toanle@....com>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/3] genirq: Allow the irqchip state of an IRQ to be
 save/restored

On 07/01/15 16:05, Jason Cooper wrote:
> Marc,
> 
> On Tue, Dec 09, 2014 at 09:37:26AM +0000, Marc Zyngier wrote:
>> On 08/12/14 22:42, Bjorn Andersson wrote:
>>> On Wed, Dec 3, 2014 at 8:18 AM, Marc Zyngier <marc.zyngier@....com> wrote:
>>>> There is a number of cases where a kernel subsystem may want to
>>>> introspect the state of an interrupt at the irqchip level:
>>>>
>>>> - When a peripheral is shared between virtual machines,
>>>>   its interrupt state becomes part of the guest's state,
>>>>   and must be switched accordingly. KVM on arm/arm64 requires
>>>>   this for its guest-visible timer
>>>> - Some GPIO controllers seem to require peeking into the
>>>>   interrupt controller they are connected to to report
>>>>   their internal state
>>>>
>>>> This seem to be a pattern that is common enough for the core code
>>>> to try and support this without too many horrible hacks. Introduce
>>>> a pair of accessors (irq_get_irqchip_state/irq_set_irqchip_state)
>>>> to retrieve the bits that can be of interest to another subsystem:
>>>> pending, active, and masked.
>>>>
>>>> - irq_get_irqchip_state returns the state of the interrupt according
>>>>   to a parameter set to IRQCHIP_STATE_PENDING, IRQCHIP_STATE_ACTIVE,
>>>>   IRQCHIP_STATE_MASKED or IRQCHIP_STATE_LINE_LEVEL.
>>>> - irq_set_irqchip_state similarly sets the state of the interrupt.
>>>>
>>>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>>>
>>> With the addition of actually assigning err to something useful in the
>>> setter below:
>>>
>>> Reviewed-by: Bjorn Andersson <bjorn.andersson@...ymobile.com>
>>> Tested-by: Bjorn Andersson <bjorn.andersson@...ymobile.com>
>>>
>>>> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
>>>
>>> [..]
>>>
>>>> +/**
>>>> + *     irq_set_irqchip_state - set the state of a forwarded interrupt.
>>>> + *     @irq: Interrupt line that is forwarded to a VM
>>>> + *     @which: State to be restored (one of IRQCHIP_STATE_*)
>>>> + *     @val: Value corresponding to @which
>>>> + *
>>>> + *     This call sets the internal irqchip state of an interrupt,
>>>> + *     depending on the value of @which.
>>>> + *
>>>> + *     This function should be called with preemption disabled if the
>>>> + *     interrupt controller has per-cpu registers.
>>>> + */
>>>> +int irq_set_irqchip_state(unsigned int irq, enum irqchip_irq_state which,
>>>> +                         bool val)
>>>> +{
>>>> +       struct irq_desc *desc;
>>>> +       struct irq_data *data;
>>>> +       struct irq_chip *chip;
>>>> +       unsigned long flags;
>>>> +       int err = -EINVAL;
>>>> +
>>>> +       desc = irq_get_desc_buslock(irq, &flags, 0);
>>>> +       if (!desc)
>>>> +               return err;
>>>> +
>>>> +       data = irq_desc_get_irq_data(desc);
>>>> +
>>>> +       do {
>>>> +               chip = irq_data_get_irq_chip(data);
>>>> +               if (chip->irq_set_irqchip_state)
>>>> +                       break;
>>>> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
>>>> +               data = data->parent_data;
>>>> +#else
>>>> +               data = NULL;
>>>> +#endif
>>>> +       } while (data);
>>>> +
>>>> +       if (data)
>>>> +               chip->irq_set_irqchip_state(data, which, val);
>>>
>>> err =
>>
>> Ah, that will teach me to write test code that actually checks the
>> return value! :-)
>>
>> Thanks for the fix and the tags.
> 
> Did I miss the new version of this?

I'm rebasing all my stuff at the moment. Expect something later today
(or tomorrow morning worse case).

Thanks,

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