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SubjectRe: [PATCH V4 22/23] arm64, pci, acpi: Assign legacy IRQs once device is enable.
On Thu, Feb 04, 2016 at 06:29:00PM +0100, Tomasz Nowicki wrote:
> This is the last step before enabling generic ACPI PCI host controller
> for ARM64. We need to take care of legacy IRQ mapping for non-MSI(X)
> PCI devices. pcibios_enable_device() boot order is not sensitive to
> ACPI device enumeration, so it is the best place to assign device's IRQs.

I guess you are referring to:

https://lists.linaro.org/pipermail/linaro-acpi/2015-October/005944.html

It is weird that the dependency can't be enforced, I will have a look
into this, it would be nice to have DT and ACPI legacy IRQs mapping
confined in pcibios_add_device() so that we can remove them in one go
when Matthew's series is merged.

As for the MSI check, by reading commit history its need I think
it harks back to bba6f6fc, which was supposed to be a quick hack and it
has been in the kernel for 9 years :), is it really needed ?

> NOTE: *This is going to be temporary solution*. There is ongoing work
> which aims for cleaning legacy IRQ allocation, see [1].
> We can consider this patch as the necessary evil which will be removed
> once [1] series hits mailnline in the near future.
>
> 1. http://comments.gmane.org/gmane.linux.kernel.pci/46461
>
> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
> ---
> arch/arm64/kernel/pci.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> index 023b983..d1a701f 100644
> --- a/arch/arm64/kernel/pci.c
> +++ b/arch/arm64/kernel/pci.c
> @@ -39,16 +39,26 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res,
> }
>
> /**
> - * pcibios_enable_device - Enable I/O and memory.
> + * pcibios_enable_device - Enable I/O, memory and legacy IRQs for ACPI.
> * @dev: PCI device to be enabled
> * @mask: bitmask of BARs to enable
> */
> int pcibios_enable_device(struct pci_dev *dev, int mask)
> {
> + int ret;
> +
> if (pci_has_flag(PCI_PROBE_ONLY))
> return 0;
>
> - return pci_enable_resources(dev, mask);
> + ret = pci_enable_resources(dev, mask);
> + if (ret < 0)
> + return ret;
> +
> +#ifdef CONFIG_ACPI
> + if (!pci_dev_msi_enabled(dev))
> + return acpi_pci_irq_enable(dev);

You need a guard here anyway, we do not want to probe ACPI IRQ if
it is disabled (ie acpi_pci_disabled). Same goes for DT in
pcibios_add_device(), which is not making this code any nicer.

Lorenzo

> +#endif
> + return 0;
> }
>
> /*
> --
> 1.9.1
>

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