Per Downstream Port Containment Related Enhancements ECN[1]
Table 4-6, Interpretation of _OSC Control Field Returned Value,
for bit 7 of _OSC control return value:
"Firmware sets this bit to 1 to grant the OS control over PCI Express
Downstream Port Containment configuration."
"If control of this feature was requested and denied,
or was not requested, the firmware returns this bit set to 0."
We store bit 7 of _OSC control return value in host->native_dpc,
check it before enable the dpc service as the firmware may not
grant the control.
[1] Downstream Port Containment Related Enhancements ECN,
Jan 28, 2019, affecting PCI Firmware Specification, Rev. 3.2
https://members.pcisig.com/wg/PCI-SIG/document/12888
Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
---
Change since v1:
- use correct reference for _OSC control return value
drivers/pci/pcie/portdrv_core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index e1fed664..7445d03 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -253,7 +253,8 @@ static int get_port_device_capability(struct pci_dev *dev)
*/
if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC) &&
pci_aer_available() &&
- (pcie_ports_dpc_native || (services & PCIE_PORT_SERVICE_AER)))
+ (pcie_ports_dpc_native ||
+ ((services & PCIE_PORT_SERVICE_AER) && host->native_dpc)))
services |= PCIE_PORT_SERVICE_DPC;
if (pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
--
2.8.1
