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    SubjectRe: [PATCH V9 09/11] ARM64/PCI: ACPI support for legacy IRQs parsing and consolidation with DT code
    On Mon, Jun 13, 2016 at 01:01:35PM -0700, Duc Dang wrote:
    > On Mon, Jun 13, 2016 at 3:40 AM, Lorenzo Pieralisi
    > <lorenzo.pieralisi@arm.com> wrote:
    > >
    > > On Fri, Jun 10, 2016 at 06:36:12PM -0500, Bjorn Helgaas wrote:
    > > > On Fri, Jun 10, 2016 at 09:55:17PM +0200, Tomasz Nowicki wrote:
    > > > > To enable PCI legacy IRQs on platforms booting with ACPI, arch code
    > > > > should include ACPI specific callbacks that parse and set-up the
    > > > > device IRQ number, equivalent to the DT boot path. Owing to the current
    > > > > ACPI core scan handlers implementation, ACPI PCI legacy IRQs bindings
    > > > > cannot be parsed at device add time, since that would trigger ACPI scan
    > > > > handlers ordering issues depending on how the ACPI tables are defined.
    > > >
    > > > Uh, OK :) I can't figure out exactly what the problem is here -- I
    > > > don't know where to look if I wanted to fix the scan handler ordering
    > > > issues, and I don't know how I could tell if it would ever be safe to
    > > > move this from driver probe-time back to device add-time.
    > >
    > > Right, the commit log could have been more informative.
    > >
    > > pcibios_add_device() was added in:
    > >
    > > commit d1e6dc91b532 ("arm64: Add architectural support for PCI")
    > >
    > > whose commit log does not specify why legacy IRQ parsing should
    > > be done at pcibios_add_device() either, so honestly we had to
    > > do with the information we have at hand.
    > >
    > > > I also notice that x86 and ia64 call acpi_pci_irq_enable() even later,
    > > > when the driver *enables* the device. Is there a reason you didn't do
    > > > it at the same time as x86 and ia64? This is another of those pcibios
    > > > hooks that really don't do anything arch-specific, so I can imagine
    > > > refactoring this somehow, someday.
    > >
    > > Yes, with [1], that was the goal, that stopped because [1] does not
    > > work on x86.
    > >
    > > Only DT platform(s) affected by this change are all platforms relying on
    > > drivers/pci/host/pci-xgene.c (others rely on pci_fixup_irqs() that
    > > should be removed too), if on those platforms probing IRQs at device
    > > enable time works ok I can update this patch (it can be done through [1]
    > > once we figure out what to do with it on x86) and move the IRQ set-up at
    > > pcibios_enable_device() time.
    > >
    > > @Duc: any feedback on this ?
    >
    > Hi Lorenzo,
    >
    > The changes to add pcibios_alloc_irq works fine on X-Gene PCIe
    >
    > I also tried to remove pcibios_alloc_irq and move its code into
    > pcibios_enable_device
    > after pci_enable_resource call and legacy IRQ also works.

    Thank you, that was important to check.

    > Can you also point me to the discussion thread or some info. about the
    > issue on x86 with [1]?
    > I want to check if there is any more test case I need to verify.

    http://marc.info/?l=linux-pci&m=145091187918297&w=2

    I do not think there is much we can do, unless we convert pci_fixup_irqs
    as per [1] but keep x86 code as-is (for now), there is a way to do it
    it is just a matter of taking Matt's series and refactor it, there are
    potential problems (not on xgene, but on other ARM platforms
    where the IRQ legacy routing is done through pci_fixup_irqs()).

    Lorenzo

    > Regards,
    > Duc Dang.
    >
    > >
    > > Thanks,
    > > Lorenzo
    > >
    > > [1] http://www.spinics.net/lists/linux-pci/msg45950.html
    > >
    > > > Did we have this conversation before? It seems vaguely familiar, so I
    > > > apologize if you already explained this once.
    > > >
    > > > > To solve this problem and consolidate FW PCI legacy IRQs parsing in
    > > > > one single pcibios callback (pending final removal), this patch moves
    > > > > DT PCI IRQ parsing to the pcibios_alloc_irq() callback (called by
    > > > > PCI core code at device probe time) and adds ACPI PCI legacy IRQs
    > > > > parsing to the same callback too, so that FW PCI legacy IRQs parsing
    > > > > is confined in one single arch callback that can be easily removed
    > > > > when code parsing PCI legacy IRQs is consolidated and moved to core
    > > > > PCI code.
    > > > >
    > > > > Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
    > > > > Suggested-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    > > > > ---
    > > > > arch/arm64/kernel/pci.c | 11 ++++++++---
    > > > > 1 file changed, 8 insertions(+), 3 deletions(-)
    > > > >
    > > > > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
    > > > > index d5d3d26..b3b8a2c 100644
    > > > > --- a/arch/arm64/kernel/pci.c
    > > > > +++ b/arch/arm64/kernel/pci.c
    > > > > @@ -51,11 +51,16 @@ int pcibios_enable_device(struct pci_dev *dev, int mask)
    > > > > }
    > > > >
    > > > > /*
    > > > > - * Try to assign the IRQ number from DT when adding a new device
    > > > > + * Try to assign the IRQ number when probing a new device
    > > > > */
    > > > > -int pcibios_add_device(struct pci_dev *dev)
    > > > > +int pcibios_alloc_irq(struct pci_dev *dev)
    > > > > {
    > > > > - dev->irq = of_irq_parse_and_map_pci(dev, 0, 0);
    > > > > + if (acpi_disabled)
    > > > > + dev->irq = of_irq_parse_and_map_pci(dev, 0, 0);
    > > > > +#ifdef CONFIG_ACPI
    > > > > + else
    > > > > + return acpi_pci_irq_enable(dev);
    > > > > +#endif
    > > > >
    > > > > return 0;
    > > > > }
    > > > > --
    > > > > 1.9.1
    > > > >
    > > >
    >

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