Re: [PATCH 05/15] PCI: mvebu: Disallow mapping interrupts on emulated bridges

Bjorn Helgaas
2022-01-07T21:32:20Z

On Thu, Nov 25, 2021 at 01:45:55PM +0100, Pali Rohár wrote:
> Interrupt support on mvebu emulated bridges is not implemented yet.

Is this mvebu-specific, or is aardvar also affected?

> So properly indicate return value to callers that they cannot request
> interrupts from emulated bridge.

Pet peeve: descriptions that say "do this *properly*". As though the
previous authors were just ignorant or intentionally did something
*improperly* :)

> Signed-off-by: Pali Rohár <pali@kernel.org>
> Cc: stable@vger.kernel.org
> ---
> drivers/pci/controller/pci-mvebu.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
> index 19c6ee298442..a3df352d440e 100644
> --- a/drivers/pci/controller/pci-mvebu.c
> +++ b/drivers/pci/controller/pci-mvebu.c
> @@ -705,6 +705,15 @@ static struct pci_ops mvebu_pcie_ops = {
> .write = mvebu_pcie_wr_conf,
> };
>
> +static int mvebu_pcie_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
> +{
> + /* Interrupt support on mvebu emulated bridges is not implemented yet */
> + if (dev->bus->number == 0)
> + return 0; /* Proper return code 0 == NO_IRQ */
> +
> + return of_irq_parse_and_map_pci(dev, slot, pin);

Is this something that could be done with a .read_base() op, e.g.,
make PCI_INTERRUPT_PIN contain zero (PCI_INTERRUPT_UNKNOWN)?

> +}
> +
> static resource_size_t mvebu_pcie_align_resource(struct pci_dev *dev,
> const struct resource *res,
> resource_size_t start,
> @@ -1119,6 +1128,7 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
> bridge->sysdata = pcie;
> bridge->ops = &mvebu_pcie_ops;
> bridge->align_resource = mvebu_pcie_align_resource;
> + bridge->map_irq = mvebu_pcie_map_irq;

I assume this means INTx doesn't work for some devices? Which ones?
I guess anything on the root bus? But INTx for devices *below* these
emulated Root Ports *does* work?

> return pci_host_probe(bridge);
> }
> --
> 2.20.1
>