linux-kernel - Re: [Patch v2 4/4] PCI, MSI: Optionally free legacy PCI IRQ when enabling MSI/MSI-X

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Message-ID: <20150605212252.GT3631@google.com>
Date:	Fri, 5 Jun 2015 16:22:52 -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>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, "x86 @ kernel . org" <x86@...nel.org>
Subject: Re: [Patch v2 4/4] PCI, MSI: Optionally free legacy PCI IRQ when
 enabling MSI/MSI-X

>From the point of view of the generic code in this patch, freeing the IRQ
isn't optional -- there's no "if" in this this patch.

It's true that the default pcibios_free_irq() implementation does nothing,
but the changelog of this patch should describe what this patch does.

On Tue, Jun 02, 2015 at 10:49:19AM +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.
> 
> 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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