Re: [PATCH] PCI: allow acpiphp to handle PCIe ports without native PCIe hotplug capability

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Thursday, May 17, 2012, Jiang Liu wrote:
> From: Jiang Liu <jiang.liu@huawei.com>
> 
> 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.
> 
> 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.

I'm not sure that the patch is sufficient, but I don't have the time to
look into the details at the moment.  I'll try to do that tomorrow.

Thanks,
Rafael


> Signed-off-by: Jiang Liu <liuj97@gmail.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;
>