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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Anchal Agarwal <anchalag@amazon.com>, mingo@redhat.com,
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Cc:     anchalag@amazon.com
Subject: Re: [RFC PATCH V2 09/11] xen: Clear IRQD_IRQ_STARTED flag during shutdown PIRQs
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References: <20200107234420.GA18738@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>
Date:   Wed, 08 Jan 2020 16:23:25 +0100
Message-ID: <877e22ezv6.fsf@nanos.tec.linutronix.de>
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Anchal Agarwal <anchalag@amazon.com> writes:

> shutdown_pirq is invoked during hibernation path and hence
> PIRQs should be restarted during resume.
> Before this commit'020db9d3c1dc0a' xen/events: Fix interrupt lost
> during irq_disable and irq_enable startup_pirq was automatically
> called during irq_enable however, after this commit pirq's did not
> get explicitly started once resumed from hibernation.
>
> chip->irq_startup is called only if IRQD_IRQ_STARTED is unset during
> irq_startup on resume. This flag gets cleared by free_irq->irq_shutdown
> during suspend. free_irq() never gets explicitly called for ioapic-edge
> and ioapic-level interrupts as respective drivers do nothing during
> suspend/resume. So we shut them down explicitly in the first place in
> syscore_suspend path to clear IRQ<>event channel mapping. shutdown_pirq
> being called explicitly during suspend does not clear this flags, hence
> .irq_enable is called in irq_startup during resume instead and pirq's
> never start up.

What? 

> +void irq_state_clr_started(struct irq_desc *desc)
>  {
>  	irqd_clear(&desc->irq_data, IRQD_IRQ_STARTED);
>  }
> +EXPORT_SYMBOL_GPL(irq_state_clr_started);

This is core internal state and not supposed to be fiddled with by
drivers.

irq_chip has irq_suspend/resume/pm_shutdown callbacks for a reason.

Thanks,

       tglx