# Re: \[PATCH v3 1/2\] powerpc/PCI: move DMA \& IRQ init to device\_add() notification path

- From: Bjorn Helgaas \<bhelgaas@google.com\>
- Date: 2012-06-18 21:07:06 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2012/06/9469749
- Thread: https://ratatoskr.run/linux-pci/2012/05/9469402/t.md

```text
I'm trying to make some progress on these patches, but I'm concerned
about this bit:

> diff --git a/drivers/pcmcia/cardbus.c b/drivers/pcmcia/cardbus.c
> index 24caeaf..a980691 100644
> --- a/drivers/pcmcia/cardbus.c
> +++ b/drivers/pcmcia/cardbus.c
> @@ -85,7 +84,6 @@ int __ref cb_alloc(struct pcmcia_socket *s)
> =A0 =A0 =A0 =A0 */
> =A0 =A0 =A0 =A0pci_bus_size_bridges(bus);
> =A0 =A0 =A0 =A0pci_bus_assign_resources(bus);
> - =A0 =A0 =A0 cardbus_config_irq_and_cls(bus, s->pci_irq);
>
> =A0 =A0 =A0 =A0/* socket specific tune function */
> =A0 =A0 =A0 =A0if (s->tune_bridge)
> @@ -93,6 +91,7 @@ int __ref cb_alloc(struct pcmcia_socket *s)
>
> =A0 =A0 =A0 =A0pci_enable_bridges(bus);
> =A0 =A0 =A0 =A0pci_bus_add_devices(bus);
> + =A0 =A0 =A0 cardbus_config_irq_and_cls(bus, s->pci_irq);
>
> =A0 =A0 =A0 =A0return 0;
> =A0}

We're moving the CardBus IRQ config from before pci_bus_add_devices()
to after.  I see why you did that: we're proposing to do the powerpc
DMA & IRQ setup in pci_bus_add_devices(), so we don't want to have the
powerpc IRQ init clobber the CardBus IRQ config.

But a driver can claim the device as soon as we call
pci_bus_add_devices(), so we're potentially changing dev->irq after a
driver has already looked at it, which sounds like a bug.

There are only five possibilities for powerpc pci_irq_fixup:

      ppc47x_pci_irq_fixup
      mpc85xx_cds_pci_irq_fixup
      maple_pci_irq_fixup
      pmac_pci_irq_fixup
      rtas_msi_pci_irq_fixup

If these were normal PCI header quirks instead, they could run
earlier, and we wouldn't need to move this
cardbus_config_irq_and_cls() call.  Is it possible to make these
quirks, Ben?

Bjorn
```