diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c
index d12ea7b9fd47..3f48f6df1cf3 100644
--- a/arch/powerpc/platforms/powernv/eeh-powernv.c
+++ b/arch/powerpc/platforms/powernv/eeh-powernv.c
@@ -48,6 +48,7 @@ static int pnv_eeh_init(void)
 {
 	struct pci_controller *hose;
 	struct pnv_phb *phb;
+	int max_diag_size = PNV_PCI_DIAG_BUF_SIZE;
 
 	if (!firmware_has_feature(FW_FEATURE_OPAL)) {
 		pr_warn("%s: OPAL is required !\n",
@@ -69,6 +70,9 @@ static int pnv_eeh_init(void)
 		if (phb->model == PNV_PHB_MODEL_P7IOC)
 			eeh_add_flag(EEH_ENABLE_IO_FOR_LOG);
 
+		if (phb->diag_data_size > max_diag_size)
+			max_diag_size = phb->diag_data_size;
+
 		/*
 		 * PE#0 should be regarded as valid by EEH core
 		 * if it's not the reserved one. Currently, we
@@ -82,6 +86,8 @@ static int pnv_eeh_init(void)
 		break;
 	}
 
+	eeh_set_pe_aux_size(max_diag_size);
+
 	return 0;
 }
 
@@ -540,7 +546,7 @@ static void pnv_eeh_get_phb_diag(struct eeh_pe *pe)
 	s64 rc;
 
 	rc = opal_pci_get_phb_diag_data2(phb->opal_id, pe->data,
-					 PNV_PCI_DIAG_BUF_SIZE);
+					 phb->diag_data_size);
 	if (rc != OPAL_SUCCESS)
 		pr_warn("%s: Failure %lld getting PHB#%x diag-data\n",
 			__func__, rc, pe->phb->global_number);
@@ -1314,7 +1320,8 @@ static void pnv_eeh_dump_hub_diag_common(struct OpalIoP7IOCErrorData *data)
 static void pnv_eeh_get_and_dump_hub_diag(struct pci_controller *hose)
 {
 	struct pnv_phb *phb = hose->private_data;
-	struct OpalIoP7IOCErrorData *data = &phb->diag.hub_diag;
+	struct OpalIoP7IOCErrorData *data =
+		(struct OpalIoP7IOCErrorData*)phb->diag_data;
 	long rc;
 
 	rc = opal_pci_get_hub_diag_data(phb->hub_id, data, sizeof(*data));
@@ -1549,10 +1556,10 @@ static int pnv_eeh_next_error(struct eeh_pe **pe)
 
 				/* Dump PHB diag-data */
 				rc = opal_pci_get_phb_diag_data2(phb->opal_id,
-					phb->diag.blob, PNV_PCI_DIAG_BUF_SIZE);
+					phb->diag_data, phb->diag_data_size);
 				if (rc == OPAL_SUCCESS)
 					pnv_pci_dump_phb_diag_data(hose,
-							phb->diag.blob);
+							phb->diag_data);
 
 				/* Try best to clear it */
 				opal_pci_eeh_freeze_clear(phb->opal_id,
@@ -1795,7 +1802,6 @@ static int __init eeh_powernv_init(void)
 {
 	int ret = -EINVAL;
 
-	eeh_set_pe_aux_size(PNV_PCI_DIAG_BUF_SIZE);
 	ret = eeh_ops_register(&pnv_eeh_ops);
 	if (!ret)
 		pr_info("EEH: PowerNV platform initialized\n");
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 283caf1070c9..96d0156f48db 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -3123,13 +3123,13 @@ static int pnv_pci_diag_data_set(void *data, u64 val)
 	phb = hose->private_data;
 
 	/* Retrieve the diag data from firmware */
-	ret = opal_pci_get_phb_diag_data2(phb->opal_id, phb->diag.blob,
-					  PNV_PCI_DIAG_BUF_SIZE);
+	ret = opal_pci_get_phb_diag_data2(phb->opal_id, phb->diag_data,
+					  phb->diag_data_size);
 	if (ret != OPAL_SUCCESS)
 		return -EIO;
 
 	/* Print the diag data to the kernel log */
-	pnv_pci_dump_phb_diag_data(phb->hose, phb->diag.blob);
+	pnv_pci_dump_phb_diag_data(phb->hose, phb->diag_data);
 	return 0;
 }
 
@@ -3725,6 +3725,15 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
 	else
 		phb->model = PNV_PHB_MODEL_UNKNOWN;
 
+	/* Initialize diagnostic data buffer */
+	prop32 = of_get_property(np, "ibm,phb-diag-data-size", NULL);
+	if (prop32)
+		phb->diag_data_size = be32_to_cpup(prop32);
+	else
+		phb->diag_data_size = PNV_PCI_DIAG_BUF_SIZE;
+
+	phb->diag_data = memblock_virt_alloc(phb->diag_data_size, 0);
+
 	/* Parse 32-bit and IO ranges (if any) */
 	pci_process_bridge_OF_ranges(hose, np, !hose->global_number);
 
diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 40071ad0bc42..209ad47a3383 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -456,8 +456,8 @@ static void pnv_pci_handle_eeh_config(struct pnv_phb *phb, u32 pe_no)
 	spin_lock_irqsave(&phb->lock, flags);
 
 	/* Fetch PHB diag-data */
-	rc = opal_pci_get_phb_diag_data2(phb->opal_id, phb->diag.blob,
-					 PNV_PCI_DIAG_BUF_SIZE);
+	rc = opal_pci_get_phb_diag_data2(phb->opal_id, phb->diag_data,
+					 phb->diag_data_size);
 	has_diag = (rc == OPAL_SUCCESS);
 
 	/* If PHB supports compound PE, to handle it */
@@ -485,7 +485,7 @@ static void pnv_pci_handle_eeh_config(struct pnv_phb *phb, u32 pe_no)
 	 * with the normal errors generated when probing empty slots
 	 */
 	if (has_diag && ret)
-		pnv_pci_dump_phb_diag_data(phb->hose, phb->diag.blob);
+		pnv_pci_dump_phb_diag_data(phb->hose, phb->diag_data);
 
 	spin_unlock_irqrestore(&phb->lock, flags);
 }
diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
index 6abc77dd9261..f16bc403ec03 100644
--- a/arch/powerpc/platforms/powernv/pci.h
+++ b/arch/powerpc/platforms/powernv/pci.h
@@ -172,13 +172,9 @@ struct pnv_phb {
 		unsigned int		pe_rmap[0x10000];
 	} ioda;
 
-	/* PHB and hub status structure */
-	union {
-		unsigned char			blob[PNV_PCI_DIAG_BUF_SIZE];
-		struct OpalIoP7IOCPhbErrorData	p7ioc;
-		struct OpalIoPhb3ErrorData	phb3;
-		struct OpalIoP7IOCErrorData 	hub_diag;
-	} diag;
+	/* PHB and hub diagnostics */
+	unsigned int		diag_data_size;
+	u8			*diag_data;
 
 	/* Nvlink2 data */
 	struct npu {