On Wednesday, November 05, 2014 02:57:13 PM Bjorn Helgaas wrote:
> On Wed, Nov 05, 2014 at 10:44:25PM +0100, Rafael J. Wysocki wrote:
> > On Wednesday, November 05, 2014 01:22:52 PM Bjorn Helgaas wrote:
> > > ...
> > > The acpi_pci_get_bridge_handle(struct pci_bus *) interface niggles at me a
> > > little because I don't think there's any concept of an ACPI device for a
> > > PCI *bus*, so it doesn't seem like a very good fit to say "find the handle
> > > for this bus". But that's for later.
> >
> > To me it does what it says: Get me the handle of the bridge leading to
> > this bus.
>
> Yeah, I know, it's a great name because it does *exactly* what the name
> says. I'm just wondering if there's a nicer way to express what the caller
> needs.
>
> Two of the three callers start with a pci_dev, look up a pci_bus to pass
> in, and get back a handle corresponding to a pci_host_bridge or a pci_dev
> (or a NULL). It seems a little cluttered because the pci_bus is only
> incidental and the caller doesn't care about it at all except for passing
> it to acpi_pci_get_bridge_handle().
>
> It's relatively common to start with a pci_dev and look for an ACPI handle
> that corresponds to that device or the closest enclosing scope, so maybe
> there should be a way to do that directly.
Well, the bridge in question should be the parent of the device if I'm
not mistaken. At least that's the assumption made by acpi_pci_find_companion().
> For pci_get_hp_params(), I think the current code is actually slightly
> buggy because we don't look for _HPP/_HPX on the device itself; we only
> look at the bridges upstream from it.
>
> What I had in mind was something like the following (untested and not for
> application).
So perhaps pci_find_acpi_handle() below may be somewhat simpler?
> diff --git a/drivers/pci/hotplug/acpi_pcihp.c
> b/drivers/pci/hotplug/acpi_pcihp.c
> index 876ccc620440..5e95df56b8ae 100644
> --- a/drivers/pci/hotplug/acpi_pcihp.c
> +++ b/drivers/pci/hotplug/acpi_pcihp.c
> @@ -116,20 +116,11 @@ int acpi_get_hp_hw_control_from_firmware(struct pci_dev
> *pdev, u32 flags)
> string = (struct acpi_buffer){ ACPI_ALLOCATE_BUFFER, NULL };
> }
>
> - handle = ACPI_HANDLE(&pdev->dev);
> - if (!handle) {
> - /*
> - * This hotplug controller was not listed in the ACPI name
> - * space at all. Try to get acpi handle of parent pci bus.
> - */
> - struct pci_bus *pbus;
> - for (pbus = pdev->bus; pbus; pbus = pbus->parent) {
> - handle = acpi_pci_get_bridge_handle(pbus);
> - if (handle)
> - break;
> - }
> - }
> -
> + /*
> + * We did not find _OSC on the host bridge, so look for any
> + * enclosing device with an OSHP method.
> + */
> + handle = pci_find_acpi_handle(pdev);
> while (handle) {
> acpi_get_name(handle, ACPI_FULL_PATHNAME, &string);
> dbg("Trying to get hotplug control for %s \n",
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index 6ebf8edc5f3c..3b3f0720fff0 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -246,14 +246,8 @@ int pci_get_hp_params(struct pci_dev *dev, struct
> hotplug_params *hpp)
> {
> acpi_status status;
> acpi_handle handle, phandle;
> - struct pci_bus *pbus;
>
> - handle = NULL;
> - for (pbus = dev->bus; pbus; pbus = pbus->parent) {
> - handle = acpi_pci_get_bridge_handle(pbus);
> - if (handle)
> - break;
> - }
> + handle = pci_find_acpi_handle(dev);
>
> /*
> * _HPP settings apply to all child buses, until another _HPP is
> @@ -279,6 +273,33 @@ int pci_get_hp_params(struct pci_dev *dev, struct
> hotplug_params *hpp)
> }
> EXPORT_SYMBOL_GPL(pci_get_hp_params);
>
> +/*
> + * Search for an ACPI handle. The PCI device itself may have one, or an
> + * upstream device (either a PCI-to-PCI bridge or a PCI host bridge) may
> + * have one.
> + */
> +acpi_handle pci_find_acpi_handle(struct pci_dev *pdev)
> +{
> + struct device *dev;
> + acpi_handle handle;
> + struct pci_bus *bus;
> +
> + dev = &pdev->dev;
> + handle = ACPI_HANDLE(dev);
> + while (!handle) {
> + pdev = pci_physfn(pdev);
> + bus = pdev->bus;
> + if (pci_is_root_bus(bus))
> + dev = bus->bridge;
> + else {
> + pdev = bus->self;
> + dev = &pdev->dev;
> + }
> + handle = ACPI_HANDLE(dev);
> + }
> + return handle;
> +}
> +
> /**
> * pci_acpi_wake_bus - Root bus wakeup notification fork function.
> * @work: Work item to handle.
> --
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--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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