powerpc/powernv/pci: Add PHB register dump debugfs handle

On EEH events the kernel will print a dump of relevant registers.
If EEH is unavailable (i.e. CONFIG_EEH is disabled, a new platform
doesn't have EEH support, etc) this information isn't readily available.

Add a new debugfs handler to trigger a PHB register dump, so that this
information can be made available on demand.
Signed-off-by: Russell Currey <ruscur@russell.cc>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/pci-ioda.c

@@ -3025,6 +3025,38 @@ static void pnv_ioda_setup_pe_seg(struct pnv_ioda_pe *pe)
 	}
 }
 
+#ifdef CONFIG_DEBUG_FS
+static int pnv_pci_diag_data_set(void *data, u64 val)
+{
+	struct pci_controller *hose;
+	struct pnv_phb *phb;
+	s64 ret;
+
+	if (val != 1ULL)
+		return -EINVAL;
+
+	hose = (struct pci_controller *)data;
+	if (!hose || !hose->private_data)
+		return -ENODEV;
+
+	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);
+	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);
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(pnv_pci_diag_data_fops, NULL,
+			pnv_pci_diag_data_set, "%llu\n");
+
+#endif /* CONFIG_DEBUG_FS */
+
 static void pnv_pci_ioda_create_dbgfs(void)
 {
 #ifdef CONFIG_DEBUG_FS
@@ -3040,9 +3072,14 @@ static void pnv_pci_ioda_create_dbgfs(void)
 
 		sprintf(name, "PCI%04x", hose->global_number);
 		phb->dbgfs = debugfs_create_dir(name, powerpc_debugfs_root);
-		if (!phb->dbgfs)
+		if (!phb->dbgfs) {
 			pr_warning("%s: Error on creating debugfs on PHB#%x\n",
 				__func__, hose->global_number);
+			continue;
+		}
+
+		debugfs_create_file("dump_diag_regs", 0200, phb->dbgfs, hose,
+				    &pnv_pci_diag_data_fops);
 	}
 #endif /* CONFIG_DEBUG_FS */
 }