diff --git a/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/Pcie.c b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/Pcie.c
new file mode 100644
index 000000000000..b069b42d0a42
--- /dev/null
+++ b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/Pcie.c
@@ -0,0 +1,140 @@
+ /** @file
+  SynQuacer DXE platform driver - PCIe support
+
+  Copyright (c) 2017, Linaro, Ltd. 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
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+**/
+
+#include "PlatformDxe.h"
+
+#define ASMEDIA_VID                         0x1b21
+#define ASM1182E_PID                        0x1182
+#define ASM1184E_PID                        0x1184
+
+#define ASM118x_PCIE_CAPABILITY_OFFSET      0x80
+#define ASM118x_PCIE_LINK_CONTROL_OFFSET    (ASM118x_PCIE_CAPABILITY_OFFSET + \
+                                             OFFSET_OF (PCI_CAPABILITY_PCIEXP, \
+                                                        LinkControl))
+
+STATIC VOID         *mPciProtocolNotifyRegistration;
+STATIC EFI_EVENT    mPciProtocolNotifyEvent;
+
+#pragma pack(1)
+typedef struct {
+  EFI_PCI_CAPABILITY_HDR    CapHdr;
+  PCI_REG_PCIE_CAPABILITY   Pcie;
+} PCIE_CAP;
+#pragma pack()
+
+STATIC
+VOID
+RetrainAsm1184eDownstreamPort (
+  IN  EFI_PCI_IO_PROTOCOL   *PciIo
+  )
+{
+  UINT16                    PciVidPid[2];
+  EFI_STATUS                Status;
+  PCIE_CAP                  Cap;
+  PCI_REG_PCIE_LINK_CONTROL LinkControl;
+
+  Status = PciIo->Pci.Read (PciIo, EfiPciIoWidthUint16, PCI_VENDOR_ID_OFFSET,
+                        ARRAY_SIZE (PciVidPid), &PciVidPid);
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_WARN, "%a: failed to read PCI vendor/product ID - %r\n",
+      __FUNCTION__, Status));
+    return;
+  }
+
+  if (PciVidPid[0] != ASMEDIA_VID ||
+      (PciVidPid[1] != ASM1182E_PID && PciVidPid[1] != ASM1184E_PID)) {
+    return;
+  }
+
+  //
+  // The upstream and downstream ports share the same PID/VID, so check
+  // the port type. This assumes the PCIe Express capability block lives
+  // at offset 0x80 in the port's config space, which is known to be the
+  // case for these particular chips.
+  //
+  ASSERT (sizeof (Cap) == sizeof (UINT32));
+  ASSERT (sizeof (LinkControl) == sizeof (UINT16));
+
+  Status = PciIo->Pci.Read (PciIo, EfiPciIoWidthUint32,
+                        ASM118x_PCIE_CAPABILITY_OFFSET, 1, &Cap);
+  ASSERT_EFI_ERROR (Status);
+  ASSERT (Cap.CapHdr.CapabilityID == EFI_PCI_CAPABILITY_ID_PCIEXP);
+
+  if (Cap.Pcie.Bits.DevicePortType != PCIE_DEVICE_PORT_TYPE_DOWNSTREAM_PORT) {
+    return;
+  }
+
+  DEBUG ((DEBUG_INFO, "%a: retraining ASM1184x downstream PCIe port\n",
+    __FUNCTION__));
+
+  Status = PciIo->Pci.Read (PciIo, EfiPciIoWidthUint16,
+                        ASM118x_PCIE_LINK_CONTROL_OFFSET, 1, &LinkControl);
+  ASSERT_EFI_ERROR (Status);
+
+  LinkControl.Bits.RetrainLink = 1;
+
+  Status = PciIo->Pci.Write (PciIo, EfiPciIoWidthUint16,
+                        ASM118x_PCIE_LINK_CONTROL_OFFSET, 1, &LinkControl);
+  ASSERT_EFI_ERROR (Status);
+}
+
+STATIC
+VOID
+EFIAPI
+OnPciIoProtocolNotify (
+  IN EFI_EVENT      Event,
+  IN VOID           *Context
+  )
+{
+  EFI_PCI_IO_PROTOCOL       *PciIo;
+  EFI_STATUS                Status;
+  EFI_HANDLE                HandleBuffer;
+  UINTN                     BufferSize;
+
+  while (TRUE) {
+    BufferSize = sizeof (EFI_HANDLE);
+    Status = gBS->LocateHandle (ByRegisterNotify, NULL,
+                    mPciProtocolNotifyRegistration, &BufferSize, &HandleBuffer);
+    if (EFI_ERROR (Status)) {
+      break;
+    }
+
+    Status = gBS->HandleProtocol (HandleBuffer, &gEfiPciIoProtocolGuid,
+                    (VOID **)&PciIo);
+    ASSERT_EFI_ERROR (Status);
+
+    //
+    // The ASM1184E 4-port PCIe switch on the DeveloperBox board (and its
+    // 2-port sibling of which samples were used in development) needs a
+    // little nudge to get it to train the downstream links at Gen2 speed.
+    //
+    RetrainAsm1184eDownstreamPort (PciIo);
+  }
+}
+
+EFI_STATUS
+EFIAPI
+RegisterPcieNotifier (
+  VOID
+  )
+{
+  mPciProtocolNotifyEvent = EfiCreateProtocolNotifyEvent (
+                              &gEfiPciIoProtocolGuid,
+                              TPL_CALLBACK,
+                              OnPciIoProtocolNotify,
+                              NULL,
+                              &mPciProtocolNotifyRegistration);
+
+  return EFI_SUCCESS;
+}
diff --git a/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.c b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.c
index e58a2093eb49..098a4dbd324e 100644
--- a/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.c
+++ b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.c
@@ -12,15 +12,7 @@
   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 **/
 
-#include <PiDxe.h>
-#include <Library/BaseMemoryLib.h>
-#include <Library/DebugLib.h>
-#include <Library/DtPlatformDtbLoaderLib.h>
-#include <Library/IoLib.h>
-#include <Library/MemoryAllocationLib.h>
-#include <Library/UefiBootServicesTableLib.h>
-#include <Platform/MemoryMap.h>
-#include <Protocol/NonDiscoverableDevice.h>
+#include "PlatformDxe.h"
 
 STATIC EFI_ACPI_ADDRESS_SPACE_DESCRIPTOR mNetsecDesc[] = {
   {
@@ -202,5 +194,8 @@ PlatformDxeEntryPoint (
 
   SmmuEnableCoherentDma ();
 
+  Status = RegisterPcieNotifier ();
+  ASSERT_EFI_ERROR (Status);
+
   return EFI_SUCCESS;
 }
diff --git a/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.h b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.h
new file mode 100644
index 000000000000..d1dad2a3eace
--- /dev/null
+++ b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.h
@@ -0,0 +1,37 @@
+/** @file
+  SynQuacer DXE platform driver.
+
+  Copyright (c) 2017, Linaro, Ltd. 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
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+**/
+
+#ifndef __PLATFORM_DXE_H__
+#define __PLATFORM_DXE_H__
+
+#include <PiDxe.h>
+#include <IndustryStandard/Pci.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/DebugLib.h>
+#include <Library/DtPlatformDtbLoaderLib.h>
+#include <Library/IoLib.h>
+#include <Library/MemoryAllocationLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/UefiLib.h>
+#include <Platform/MemoryMap.h>
+#include <Protocol/NonDiscoverableDevice.h>
+#include <Protocol/PciIo.h>
+
+EFI_STATUS
+EFIAPI
+RegisterPcieNotifier (
+  VOID
+  );
+
+#endif
diff --git a/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.inf b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.inf
index 00c1130906c4..84498eaddcef 100644
--- a/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.inf
+++ b/Silicon/Socionext/SynQuacer/Drivers/PlatformDxe/PlatformDxe.inf
@@ -23,6 +23,7 @@ [Defines]
   ENTRY_POINT                    = PlatformDxeEntryPoint
 
 [Sources]
+  Pcie.c
   PlatformDxe.c
 
 [Packages]
@@ -41,6 +42,7 @@ [LibraryClasses]
   MemoryAllocationLib
   UefiBootServicesTableLib
   UefiDriverEntryPoint
+  UefiLib
 
 [Guids]
   gFdtTableGuid
@@ -50,6 +52,7 @@ [Guids]
 
 [Protocols]
   gEdkiiNonDiscoverableDeviceProtocolGuid         ## PRODUCES
+  gEfiPciIoProtocolGuid                           ## CONSUMES
   gPcf8563RealTimeClockLibI2cMasterProtolGuid     ## PRODUCES
 
 [FixedPcd]
