[Skiboot] [PATCH 1/2] core/pci: Ignore PCI slot capability on root port

Gavin Shan gwshan at linux.vnet.ibm.com
Fri Mar 10 11:25:45 AEDT 2017

We are creating PCI slot on root port, where the PCI slot isn't
supported from hardware. For this case, we shouldn't read the PCI
slot capability from hardware. When bogus data returned from the
hardware, we will attempt to the PCI slot's power state or enable
surprise hotplug functionality. All of them can't be accomplished
without hardware support.

This leaves the PCI slot's capability list 0 if PCICAP_EXP_CAP_SLOT
isn't set in hardware (pcie_cap + 0x2). Otherwise, the PCI slot's
capability list is retrieved from hardware (pcie_cap + 0x14).

Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
 core/pcie-slot.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/core/pcie-slot.c b/core/pcie-slot.c
index 64f0da6..aca59dd 100644
--- a/core/pcie-slot.c
+++ b/core/pcie-slot.c
@@ -461,8 +461,13 @@ struct pci_slot *pcie_slot_create(struct phb *phb, struct pci_device *pd)
 	pci_cfg_read32(phb, pd->bdfn, ecap + PCICAP_EXP_LCAP,
-	pci_cfg_read32(phb, pd->bdfn, ecap + PCICAP_EXP_SLOTCAP,
-		       &slot->slot_cap);
+	/* Leave PCI slot capability blank if PCI slot isn't supported */
+	if (slot->pcie_cap & PCICAP_EXP_CAP_SLOT)
+		pci_cfg_read32(phb, pd->bdfn, ecap + PCICAP_EXP_SLOTCAP,
+			       &slot->slot_cap);
+	else
+		slot->slot_cap = 0;
 	if (slot->slot_cap & PCICAP_EXP_SLOTCAP_HPLUG_CAP)
 		slot->pluggable = 1;

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