Re: [Patch v2 20/22] x86/PCI: Refine the way to release PCI IRQ resources

[Bjorn Helgaas]

On Wed, Jan 28, 2015 at 06:57:38PM +0800, Jiang Liu wrote:
> Some PCI device drivers assume that pci_dev->irq won't change after
> calling pci_disable_device() and pci_enable_device() during suspend and
> resume.
> 
> Commit c03b3b0738a56cf283b0d05256988d5e3c8bd719 ("x86, irq, mpparse:

Cosmetic: please use the conventional 12-char SHA1 as you did below.

> Release IOAPIC pin when PCI device is disabled") frees PCI IRQ
> resources when pci_disable_device() is called and reallocate IRQ
> resources when pci_enable_device() is called again. This breaks
> above assumption. So commit 3eec595235c1 ("x86, irq, PCI: Keep IRQ
> assignment for PCI devices during suspend/hibernation") and
> 9eabc99a635a ("x86, irq, PCI: Keep IRQ assignment for runtime power
> management") fix the issue by avoiding freeing/reallocating IRQ
> resources during PCI device suspend/resume. They achieve this by
> checking dev.power.is_prepared and dev.power.runtime_status.
> PM maintainer, Rafael, then pointed out that it's really an ugly fix
> which leaking PM internal state information to IRQ subsystem.
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