linux-kernel - Re: [RFC 2/4] PCI, MSI: Optionally free legacy PCI IRQ when enabling MSI/MSI-X

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Message-ID: <20150519213937.GR31666@google.com>
Date:	Tue, 19 May 2015 16:39:37 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Lv Zheng <lv.zheng@...el.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, "x86 @ kernel . org" <x86@...nel.org>
Subject: Re: [RFC 2/4] PCI, MSI: Optionally free legacy PCI IRQ when enabling
 MSI/MSI-X

On Thu, May 07, 2015 at 11:12:52AM +0800, Jiang Liu wrote:
> Once PCI MSI/MSI-X is enabled by the device driver, PCI device won't
> make use of legacy PCI IRQ until PCI MSI/MSI-X is disabled again.
> So optionally free legacy PCI IRQ when enabling MSI/MSI-X and reallocate
> when disabling MSI/MSI-X.

The rest of this series makes sense to me.  If you want to remove an
IOAPIC, you want to make sure all of the IRQs using that IOAPIC have been
freed.

But I'm trying to figure out this patch.  Do you want to free the IRQ when
enabling MSI because it enables you to remove the IOAPIC without removing
the device?  That wouldn't really make sense to me because then the device
has no possibility of using INTx.

Bjorn

> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
> ---
>  drivers/pci/msi.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index c3e7dfcf9ff5..47cf72c669f0 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -686,6 +686,7 @@ static int msi_capability_init(struct pci_dev *dev, int nvec)
>  	msi_set_enable(dev, 1);
>  	dev->msi_enabled = 1;
>  
> +	pcibios_free_irq(dev);
>  	dev->irq = entry->irq;
>  	return 0;
>  }
> @@ -813,9 +814,10 @@ static int msix_capability_init(struct pci_dev *dev,
>  	/* Set MSI-X enabled bits and unmask the function */
>  	pci_intx_for_msi(dev, 0);
>  	dev->msix_enabled = 1;
> -
>  	msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
>  
> +	pcibios_free_irq(dev);
> +
>  	return 0;
>  
>  out_avail:
> @@ -930,6 +932,7 @@ void pci_msi_shutdown(struct pci_dev *dev)
>  
>  	/* Restore dev->irq to its default pin-assertion irq */
>  	dev->irq = desc->msi_attrib.default_irq;
> +	pcibios_alloc_irq(dev);
>  }
>  
>  void pci_disable_msi(struct pci_dev *dev)
> @@ -1030,6 +1033,7 @@ void pci_msix_shutdown(struct pci_dev *dev)
>  	msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
>  	pci_intx_for_msi(dev, 1);
>  	dev->msix_enabled = 0;
> +	pcibios_alloc_irq(dev);
>  }
>  
>  void pci_disable_msix(struct pci_dev *dev)
> -- 
> 1.7.10.4
> 
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