[Very RFC 27/46] powernv/pci: Clear reserved PE freezes

[Oliver O'Halloran]

When we scan an empty slot the PHB gets an Unsupported Request from the
downstream bridge when there's no device present at that BDFN.  Some older
PHBs (p7-IOC) don't allow further config space accesses while the PE is
frozen, so clear it here without bothering with the diagnostic log.

Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
 arch/powerpc/platforms/powernv/pci.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 36eea4bb514c..5b1f4677cdce 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -642,6 +642,19 @@ static void pnv_pci_config_check_eeh(struct pnv_phb *phb, u16 bdfn)
 	if (fstate == OPAL_EEH_STOPPED_MMIO_FREEZE ||
 	    fstate == OPAL_EEH_STOPPED_DMA_FREEZE  ||
 	    fstate == OPAL_EEH_STOPPED_MMIO_DMA_FREEZE) {
+
+		/*
+		 * Scanning an empty slot will result in a freeze on the reserved PE.
+		 *
+		 * Some old and bad PHBs block config space access to frozen PEs in
+		 * addition to MMIOs, so unfreeze it here.
+		 */
+		if (pe_no == phb->ioda.reserved_pe_idx) {
+			phb->unfreeze_pe(phb, phb->ioda.reserved_pe_idx,
+					 OPAL_EEH_ACTION_CLEAR_FREEZE_ALL);
+			return;
+		}
+
 		/*
 		 * If PHB supports compound PE, freeze it for
 		 * consistency.
-- 
2.21.0