[PATCH RFC v4 2/9] powerpc/powernv/pci: Suppress an EEH error when reading an empty slot

[Sergey Miroshnichenko <s.miroshnichenko@yadro.com>]

Reading an empty slot returns all ones, which triggers a false
EEH error event on PowerNV. This patch unfreezes the bus where
it has happened.

Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko@yadro.com>
---
 arch/powerpc/include/asm/ppc-pci.h   |  1 +
 arch/powerpc/kernel/pci_dn.c         |  2 +-
 arch/powerpc/platforms/powernv/pci.c | 34 ++++++++++++++++++++++++----
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/ppc-pci.h b/arch/powerpc/include/asm/ppc-pci.h
index f67da277d652..737393c54f58 100644
--- a/arch/powerpc/include/asm/ppc-pci.h
+++ b/arch/powerpc/include/asm/ppc-pci.h
@@ -40,6 +40,7 @@ void *traverse_pci_dn(struct pci_dn *root,
 		      void *(*fn)(struct pci_dn *, void *),
 		      void *data);
 extern void pci_devs_phb_init_dynamic(struct pci_controller *phb);
+struct pci_dn *pci_bus_to_pdn(struct pci_bus *bus);
 
 /* From rtas_pci.h */
 extern void init_pci_config_tokens (void);
diff --git a/arch/powerpc/kernel/pci_dn.c b/arch/powerpc/kernel/pci_dn.c
index ab147a1909c8..341ed71250f1 100644
--- a/arch/powerpc/kernel/pci_dn.c
+++ b/arch/powerpc/kernel/pci_dn.c
@@ -40,7 +40,7 @@
  * one of PF's bridge. For other devices, their firmware
  * data is linked to that of their bridge.
  */
-static struct pci_dn *pci_bus_to_pdn(struct pci_bus *bus)
+struct pci_dn *pci_bus_to_pdn(struct pci_bus *bus)
 {
 	struct pci_bus *pbus;
 	struct device_node *dn;
diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 3260250d2029..73c2d0aed996 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -761,6 +761,21 @@ static inline pnv_pci_cfg_check(struct pci_dn *pdn)
 }
 #endif /* CONFIG_EEH */
 
+static int get_bus_pe_number(struct pci_bus *bus)
+{
+	struct pci_dn *pdn = pci_bus_to_pdn(bus);
+	struct pci_dn *child;
+
+	if (!pdn)
+		return IODA_INVALID_PE;
+
+	list_for_each_entry(child, &pdn->child_list, list)
+		if (child->pe_number != IODA_INVALID_PE)
+			return child->pe_number;
+
+	return IODA_INVALID_PE;
+}
+
 static int pnv_pci_read_config(struct pci_bus *bus,
 			       unsigned int devfn,
 			       int where, int size, u32 *val)
@@ -769,12 +784,23 @@ static int pnv_pci_read_config(struct pci_bus *bus,
 	struct pci_controller *hose = pci_bus_to_host(bus);
 	struct pnv_phb *phb = hose->private_data;
 	int ret;
+	u32 empty_val = 0xFFFFFFFF;
 
-	*val = 0xFFFFFFFF;
+	*val = empty_val;
 	pdn = pci_get_pdn_by_devfn(bus, devfn);
-	if (!pdn)
-		return pnv_pci_cfg_read_raw(phb->opal_id, bus->number, devfn,
-					    where, size, val);
+	if (!pdn) {
+		int pe_number = get_bus_pe_number(bus);
+
+		ret = pnv_pci_cfg_read_raw(phb->opal_id, bus->number, devfn,
+					   where, size, val);
+
+		if (!ret && (*val == empty_val) && phb->unfreeze_pe)
+			phb->unfreeze_pe(phb, (pe_number == IODA_INVALID_PE) ?
+					 0xff : pe_number,
+					 OPAL_EEH_ACTION_CLEAR_FREEZE_ALL);
+
+		return ret;
+	}
 
 	if (!pnv_pci_cfg_check(pdn))
 		return PCIBIOS_DEVICE_NOT_FOUND;
-- 
2.20.1