Re: [PATCH V9 09/11] ARM64/PCI: ACPI support for legacy IRQs parsing and consolidation with DT code

[Duc Dang]

On Mon, Jun 13, 2016 at 3:40 AM, Lorenzo Pieralisi
<lorenzo.pieralisi@xxxxxxx> 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.

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.

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@xxxxxxxxxxxx>
> > > Suggested-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > > ---
> > >  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
> > >
> >