Re: [PATCH][upstream] PCI: Add PCI_DEV_FLAGS_USE_NON_MSI_INTX_IRQ to enable non MSI/INTx interrupt

[Scott Wood <scottwood@freescale.com>]

On 07/12/2012 05:02 AM, Shengzhou Liu wrote:
> On some platforms, in RC mode, root port has neither MSI/MSI-X nor INTx
> interrupt generated, which are available only in EP mode on those platform.
> In this case, we try to use other interrupt for port service driver to have
> AER, Hot-plug, etc, services to work. (i.e. there is the shared error interrupt
> on platform P1010/P3041/P4080 etc)
> 
> Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
> ---
>  drivers/pci/pcie/portdrv_core.c |   10 ++++++++--
>  drivers/pci/quirks.c            |   12 ++++++++++++
>  include/linux/pci.h             |    5 +++++
>  3 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 75915b3..837ad15 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -212,8 +212,14 @@ static int init_service_irqs(struct pci_dev *dev, int *irqs, int mask)
>  	if (!pcie_port_enable_msix(dev, irqs, mask))
>  		return 0;
>  
> -	/* We're not going to use MSI-X, so try MSI and fall back to INTx */
> -	if (!pci_enable_msi(dev) || dev->pin)
> +	/*
> +	 * We're not going to use MSI-X, so try MSI and fall back to INTx.
> +	 * Eventually, if neither MSI/MSI-X nor INTx available, try other
> +	 * interrupt. (On some platforms, root port doesn't support generating
> +	 * MSI/MSI-X/INTx in RC mode)
> +	 */
> +	if (!pci_enable_msi(dev) || dev->pin || ((dev->dev_flags &
> +			PCI_DEV_FLAGS_USE_NON_MSI_INTX_IRQ) && dev->irq))
>  		irq = dev->irq;

I'd still like to hear someone say what specifically would go wrong if
we just did s/dev->pin/dev->irq/ (and even that much seems to be only
because the code is using a non-standard indicator of an invalid IRQ).
When would dev->irq contain a non-zero value that is not usable?

-Scott