Re: [PATCH V2 3/5] PCI: xilinx: Modifying AXI PCIe Host Bridge driver to work on both Zynq and Microblaze

From: Arnd Bergmann
Date: Thu Jan 28 2016 - 09:24:43 EST

On Thursday 28 January 2016 14:18:15 Bharat Kumar Gogada wrote:
> >
> > I see. In the upstream code you seem to do it in
> > pcibios_setup_bus_devices(), while arm64 and powerpc do it in
> > pcibios_add_device().
> >
> No that function is not getting called with generic API's, its getting called with pcibios_init flow which is tightly bound with struct pci_controller microblaze specific structure. So I added pcibios_add_device in pci-common.c.


> > > May be we can add similar on arm and test out, but we might need some
> > > cleanup in arch/arm/kernel/bios32.c
> >
> > I think that would still just be a half-baked solution. This should really be fully
> > automatic. We could do it in the __weak
> > pcibios_add_device() for all architectures that don't override it when the bus
> > was probed from DT, or we could do it in pci_read_irq().
> When will pci_read_irq() call get invoked ?

This is called early on when a device gets created in pci_setup_device(),
so platforms can still override the value later.

The idea here is that normally a BIOS stores the interrupt number in
the PCI_INTERRUPT_LINE config space byte, and we just read it from
there. Generally speaking though, for non-PC systems we tend to not
have a BIOS that writes these values to start with, and any values
stored in here have no meaning in combination with SPARSE_IRQ
and/or IRQ_DOMAINS because the bootloader or BIOS doesn't know
what IRQ number will refer to hardware IRQ line in Linux.