From edf289685b9244d27602addd9ea5d933fade839f Mon Sep 17 00:00:00 2001
From: Ruiyu Ni <ruiyu.ni@intel.com>
Date: Wed, 27 May 2015 01:22:13 +0000
Subject: [PATCH] MdeModulePkg: Fix PciBus hang issue

LocatePciExpressCapabilityRegBlock () doesn't check the return status of Pci.Read().
Certain platform's PciRootBridge.Pci.Read() doesn't support PCIE access causing the CapabilityEntry not updated.
If the uninitialized CapabilityEntry equals to a big enough initial value, the while-loop will never end.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Maurice Ma <maurice.ma@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17513 6f19259b-4bc3-4df7-8a09-765794883524
---
 MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c | 26 ++++++++++++---------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c b/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c
index 9f3fcce6f7..8a8b4b8fac 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c
@@ -1,7 +1,7 @@
 /** @file
   PCI command register operations supporting functions implementation for PCI Bus module.
 
-Copyright (c) 2006 - 2009, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2015, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -200,9 +200,10 @@ LocatePciExpressCapabilityRegBlock (
      OUT UINT32        *NextRegBlock OPTIONAL
   )
 {
-  UINT32  CapabilityPtr;
-  UINT32  CapabilityEntry;
-  UINT16  CapabilityID;
+  EFI_STATUS           Status;
+  UINT32               CapabilityPtr;
+  UINT32               CapabilityEntry;
+  UINT16               CapabilityID;
 
   //
   // To check the capability of this device supports
@@ -222,13 +223,16 @@ LocatePciExpressCapabilityRegBlock (
     // Mask it to DWORD alignment per PCI spec
     //
     CapabilityPtr &= 0xFFC;
-    PciIoDevice->PciIo.Pci.Read (
-                             &PciIoDevice->PciIo,
-                             EfiPciIoWidthUint32,
-                             CapabilityPtr,
-                             1,
-                             &CapabilityEntry
-                             );
+    Status = PciIoDevice->PciIo.Pci.Read (
+                                      &PciIoDevice->PciIo,
+                                      EfiPciIoWidthUint32,
+                                      CapabilityPtr,
+                                      1,
+                                      &CapabilityEntry
+                                      );
+    if (EFI_ERROR (Status)) {
+      break;
+    }
 
     CapabilityID = (UINT16) CapabilityEntry;
 
-- 
2.39.2