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Subject[PATCH 2/2] PCI/ACPI: allow _OSC presence to be optional for PCI
Date
ACPI Spec 6.0 Section 6.2.11.3 OSC Implementation Example for PCI
Host Bridge Devices:

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.

Signed-off-by: Sinan Kaya <okaya@kernel.org>
Reported-by: Michael Kelley <mikelley@microsoft.com>
---
drivers/acpi/pci_root.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 9d738e2..c94ed01 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -421,7 +421,8 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 req)
}
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;
@@ -460,9 +461,14 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
if (pcie_aspm_support_enabled())
aspm_msg = "; disabling ASPM";

- dev_info(&device->dev, "_OSC failed (%s) %s\n",
- acpi_format_exception(status), aspm_msg);
*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), aspm_msg);
return;
}

@@ -538,6 +544,7 @@ 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)
@@ -595,7 +602,8 @@ 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.
--
2.7.4
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