[PATCH v6 2/5] 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.

Reviewed-by: Oliver O'Halloran <oohall@gmail.com>
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 | 31 +++++++++++++++++++++++++---
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/ppc-pci.h b/arch/powerpc/include/asm/ppc-pci.h
index cec2d6409515..8b51c8577b94 100644
--- a/arch/powerpc/include/asm/ppc-pci.h
+++ b/arch/powerpc/include/asm/ppc-pci.h
@@ -36,6 +36,7 @@ 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 c4c8c237a106..e1a0ab2caafe 100644
--- a/arch/powerpc/kernel/pci_dn.c
+++ b/arch/powerpc/kernel/pci_dn.c
@@ -27,7 +27,7 @@
  * 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 8d6c094f074e..a5b04410c8b4 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -756,6 +756,21 @@ 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)
@@ -767,9 +782,19 @@ static int pnv_pci_read_config(struct pci_bus *bus,
 
 	*val = 0xFFFFFFFF;
 	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 == EEH_IO_ERROR_VALUE(size)) && phb->unfreeze_pe)
+			phb->unfreeze_pe(phb, (pe_number == IODA_INVALID_PE) ?
+					 phb->ioda.reserved_pe_idx : pe_number,
+					 OPAL_EEH_ACTION_CLEAR_FREEZE_ALL);
+
+		return ret;
+	}
 
 	if (!pnv_pci_cfg_check(pdn))
 		return PCIBIOS_DEVICE_NOT_FOUND;
-- 
2.21.0