linux-kernel - Re: [Resend with Ack][PATCH v1] PCI: allow acpiphp to handle PCIe ports without native PCIe hotplug capability

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Date:	Wed, 15 Aug 2012 13:12:14 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiang Liu <jiang.liu@...wei.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Yinghai Lu <yinghai@...nel.org>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	Don Dutile <ddutile@...hat.com>,
	Yijing Wang <wangyijing@...wei.com>,
	Keping Chen <chenkeping@...wei.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jiang Liu <liuj97@...il.com>
Subject: Re: [Resend with Ack][PATCH v1] PCI: allow acpiphp to handle PCIe
 ports without native PCIe hotplug capability

On Mon, Jun 4, 2012 at 1:44 AM, Jiang Liu <jiang.liu@...wei.com> wrote:
> Commit 0d52f54e2ef64c189dedc332e680b2eb4a34590a (PCI / ACPI: Make acpiphp
> ignore root bridges using PCIe native hotplug) added code that made the
> acpiphp driver completely ignore PCIe root complexes for which the kernel
> had been granted control of the native PCIe hotplug feature by the BIOS
> through _OSC. Later commit 619a5182d1f38a3d629ee48e04fa182ef9170052
> "PCI hotplug: Always allow acpiphp to handle non-PCIe bridges" relaxed
> the constraints to allow acpiphp driver handle non-PCIe bridges under
> such a complex. The constraint needs to be relaxed further to allow
> acpiphp driver to hanlde PCIe ports without native PCIe hotplug capability.

Gerry, I assume you'll refresh and repost this after we get the PCIe
capability stuff squared away, so I'll ignore this patch for now.

> Some MR-IOV switch chipsets, such PLX8696, support multiple virtual PCIe
> switches and may migrate downstream ports among virtual switches.
> To migrate a downstream port from the source virtual switch to the target,
> the port needs to be hot-removed from the source and hot-added into the
> target. pciehp driver can't be used here because there's no slots within
> the virtual PCIe switch. So acpiphp driver is used to support downstream
> port migration. A typical configuration is as below:
> [Root w/o native PCIe HP]
>         [Upstream port of vswitch w/o native PCIe HP]
>                 [Downstream port of vswitch w/ native PCIe HP]
>                         [PCIe enpoint]
>
> Here acpiphp driver will be used to handle root ports and upstream port
> in the virtual switch, and pciehp driver will be used to handle downstream
> ports in the virtual switch.
>
> Acked-by: Rafael J. Wysocki <rjw@...k.pl>
> Signed-off-by: Jiang Liu <liuj97@...il.com>
>
> ---
>  drivers/pci/hotplug/acpiphp_glue.c |   49 ++++++++++++++++++++++++++++-------
>  1 files changed, 39 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> index 806c44f..4889448 100644
> --- a/drivers/pci/hotplug/acpiphp_glue.c
> +++ b/drivers/pci/hotplug/acpiphp_glue.c
> @@ -115,6 +115,43 @@ static const struct acpi_dock_ops acpiphp_dock_ops = {
>         .handler = handle_hotplug_event_func,
>  };
>
> +/* Check whether device is managed by native PCIe hotplug driver */
> +static bool device_is_managed_by_native_pciehp(struct pci_dev *pdev)
> +{
> +       int pos;
> +       u16 reg16;
> +       u32 reg32;
> +       acpi_handle tmp;
> +       struct acpi_pci_root *root;
> +
> +       if (!pci_is_pcie(pdev))
> +               return false;
> +
> +       /* Check whether PCIe port supports native PCIe hotplug */
> +       pos = pci_pcie_cap(pdev);
> +       pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &reg16);
> +       if (!(reg16 & PCI_EXP_FLAGS_SLOT))
> +               return false;
> +       pci_read_config_dword(pdev, pos + PCI_EXP_SLTCAP, &reg32);
> +       if (!(reg32 & PCI_EXP_SLTCAP_HPC))
> +               return false;
> +
> +       /*
> +        * Check whether native PCIe hotplug has been enabled for
> +        * this PCIe hierarchy.
> +        */
> +       tmp = acpi_find_root_bridge_handle(pdev);
> +       if (!tmp)
> +               return false;
> +       root = acpi_pci_find_root(tmp);
> +       if (!root)
> +               return false;
> +       if (!(root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
> +               return false;
> +
> +       return true;
> +}
> +
>  /* callback routine to register each ACPI PCI slot object */
>  static acpi_status
>  register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
> @@ -133,16 +170,8 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
>                 return AE_OK;
>
>         pdev = pbus->self;
> -       if (pdev && pci_is_pcie(pdev)) {
> -               tmp = acpi_find_root_bridge_handle(pdev);
> -               if (tmp) {
> -                       struct acpi_pci_root *root = acpi_pci_find_root(tmp);
> -
> -                       if (root && (root->osc_control_set &
> -                                       OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
> -                               return AE_OK;
> -               }
> -       }
> +       if (pdev && device_is_managed_by_native_pciehp(pdev))
> +               return AE_OK;
>
>         acpi_evaluate_integer(handle, "_ADR", NULL, &adr);
>         device = (adr >> 16) & 0xffff;
> --
> 1.7.1
>
>
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