Commit c238252f authored by Sinan Kaya's avatar Sinan Kaya Committed by Bjorn Helgaas
Browse files

PCI/ACPI: Allow _OSC presence to be optional for PCI 



The PCI Firmware Spec, r3.2, sec 4.5.1, says:

  For a host bridge device that originates a PCI Express hierarchy, the
  _OSC interface defined in this section is required.  For a host bridge
  device that originates a PCI/PCI-X bus hierarchy, inclusion of an _OSC
  object is optional.

Allow PCI host bridges to bail out silently if _OSC is not found.

Reported-by: default avatarMichael Kelley <mikelley@microsoft.com>
Signed-off-by: default avatarSinan Kaya <okaya@kernel.org>
[bhelgaas: cite PCI Firmware spec, the authoritative source]
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent 1ad61b61

drivers/acpi/pci_root.c

+11 −3
Original line number Diff line number Diff line
@@ -421,7 +421,8 @@ out: 
}

EXPORT_SYMBOL(acpi_pci_osc_control_set);



static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)

static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,

				 bool is_pcie)

{

	u32 support, control, requested;

	acpi_status status;
@@ -455,10 +456,15 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm) 
	decode_osc_support(root, "OS supports", support);

	status = acpi_pci_osc_support(root, support);

	if (ACPI_FAILURE(status)) {

		*no_aspm = 1;



		/* _OSC is optional for PCI host bridges */

		if ((status == AE_NOT_FOUND) && !is_pcie)

			return;



		dev_info(&device->dev, "_OSC failed (%s)%s\n",

			 acpi_format_exception(status),

			 pcie_aspm_support_enabled() ? "; disabling ASPM" : "");

		*no_aspm = 1;

		return;

	}
@@ -534,6 +540,7 @@ static int acpi_pci_root_add(struct acpi_device *device, 
	acpi_handle handle = device->handle;

	int no_aspm = 0;

	bool hotadd = system_state == SYSTEM_RUNNING;

	bool is_pcie;



	root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);

	if (!root)
@@ -591,7 +598,8 @@ static int acpi_pci_root_add(struct acpi_device *device, 


	root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);



	negotiate_os_control(root, &no_aspm);

	is_pcie = strcmp(acpi_device_hid(device), "PNP0A08") == 0;

	negotiate_os_control(root, &no_aspm, is_pcie);



	/*

	 * TBD: Need PCI interface for enumeration/configuration of roots.

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