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Subject: Re: [RFC PATCH v0.2] PCI: Add support for tango PCIe host bridge
To: Mason <slash.tmp@free.fr>, Thomas Gleixner <tglx@linutronix.de>
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Cc: Bjorn Helgaas <helgaas@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Liviu Dudau <liviu.dudau@arm.com>,
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From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
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Date: Thu, 20 Apr 2017 10:43:11 +0100
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On 20/04/17 09:20, Mason wrote:
> On 19/04/2017 13:19, Mason wrote:
> 
>> My biggest problem is that tango_unmask() is never called.
> 
> FTR, the missing incantation was:
> Explicitly calling tango_{mask/unmask/ack} from the corresponding msi_{mask/unmask/ack}

Using irq_chip_mask_parent and co, you mean?

> Marc, I have one nagging doubt, wrt splitting MSI line selection
> and MSI enable.
> 
> tango_irq_domain_alloc : finds an available MSI 'j' to allocate
> tango_irq_domain_free : release MSI 'j'
> tango_unmask : enable MSI 'j'
> tango_mask : disable MSI 'j'
> 
> Is the following scenario guaranteed to never happen?
> 
> tango_irq_domain_alloc // alloc 0
> tango_irq_domain_free  // free 0
> tango_irq_domain_alloc // alloc 0
> tango_unmask // enable 0
> tango_unmask // enable 0 = NOP
> tango_mask   // disable 0
> 
> In this theoretical scenario, we would be left with a non-functional
> MSI 0.

I'm not sure I get the example above, and what the various alloc/free
calls have to do with anything. If you have unbalanced
enable/disable_irq, you loose. Don't do that.

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