On Tue, Apr 26, 2016 at 09:44:30PM -0500, Bjorn Helgaas wrote:
On Fri, Apr 15, 2016 at 07:06:41PM +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.
Can you be a little more specific about the issue here? I think you mean pci_device_add()-time, because that's where we call pcibios_add_device. Which ACPI tables are involved? _PRT? Why is that a problem? We don't cache those tables any more after 181380b702ee ("PCI/ACPI: Don't cache _PRT, and don't associate them with bus numbers").
https://lists.linaro.org/pipermail/linaro-acpi/2015-October/005944.html
I think it is a scan handler ordering issue and probably by caching _PRT this problem would not exist but I have to read the commit above in details to understand if that's the case.
x86 and ia64 both call acpi_pci_irq_enable() from pcibios_enable_device(). Could you do the same on ARM64? pcibios_enable_device() happens later than either pci_device_add() or pci_device_probe().
We could in theory. In practice we have to see if that triggers DT regressions on PCI host controllers that do not call pci_fixup_irqs(), but rely on the legacy IRQ routing to be done in arm64 pcibios_add_device().
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 c72de66..15109c11 100644 --- a/arch/arm64/kernel/pci.c +++ b/arch/arm64/kernel/pci.c @@ -50,11 +50,16 @@ 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
Not your problem, but your patch makes it obvious: it's ugly that we set dev->irq to the IRQ returned from of_irq_parse_and_map_pci(), but acpi_pci_irq_enable() sets dev->irq internally.
x86 also has the situation of calling either acpi_pci_irq_enable() or of_irq_parse_and_map_pci(), and it looks like they can even decide at run-time as you can here. If we're solving the same problem, can we use a similar mechanism? x86 sets a pcibios_enable_irq function pointer.
Yes we could, but that's orthogonal to this patch, it's basically rewriting this code in a different way and adding flexibility to the function mapping irqs.
Thanks, Lorenzo
return 0; } -- 1.9.1
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