[PATCH v5 1/1] MdeModulePkg: BaseSerialPortLib16550: Add Mmio32 support

["Loh, Tien Hock" <tien.hock.loh@intel.com>]

From: "Tien Hock, Loh" <tien.hock.loh@intel.com>

Some busses doesn't allow 8 bit MMIO read/write, this adds support for
32 bits read/write

Signed-off-by: "Tien Hock, Loh" <tien.hock.loh@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>

---
v5
- Updates function header comments
- Change the implementation to eliminate unnecessary else clause
v4
- Updates Pcd name to a better name: PcdSerialRegisterAccessWidth
v3
- Updates the Pcd to be UINT8 to allow more options such as 16 bits access
in the future
- Updated copyright date
v2
- Updates the Pcd name to PcdSerialMmio32BitAccess and access 32 bits
register if PcdSerialUseMmio and PcdSerialMmio32BitAccess is set
---
 .../BaseSerialPortLib16550/BaseSerialPortLib16550.c        | 14 +++++++++++---
 .../BaseSerialPortLib16550/BaseSerialPortLib16550.inf      |  3 ++-
 MdeModulePkg/MdeModulePkg.dec                              |  7 +++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c
index 34df34d..bbae379 100644
--- a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c
+++ b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c
@@ -2,7 +2,7 @@
   16550 UART Serial Port library functions
 
   (C) Copyright 2014 Hewlett-Packard Development Company, L.P.<BR>
-  Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
   Copyright (c) 2018, AMD Incorporated. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
@@ -62,7 +62,8 @@ typedef struct {
   Read an 8-bit 16550 register.  If PcdSerialUseMmio is TRUE, then the value is read from
   MMIO space.  If PcdSerialUseMmio is FALSE, then the value is read from I/O space.  The
   parameter Offset is added to the base address of the 16550 registers that is specified
-  by PcdSerialRegisterBase.
+  by PcdSerialRegisterBase. PcdSerialRegisterAccessWidth specifies the MMIO space access
+  width and defaults to 8 bit access, and supports 8 or 32 bit access.
 
   @param  Base    The base address register of UART device.
   @param  Offset  The offset of the 16550 register to read.
@@ -77,6 +78,9 @@ SerialPortReadRegister (
   )
 {
   if (PcdGetBool (PcdSerialUseMmio)) {
+    if (PcdGet8 (PcdSerialRegisterAccessWidth) == 32) {
+      return (UINT8) MmioRead32 (Base + Offset * PcdGet32 (PcdSerialRegisterStride));
+    }
     return MmioRead8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride));
   } else {
     return IoRead8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride));
@@ -87,7 +91,8 @@ SerialPortReadRegister (
   Write an 8-bit 16550 register.  If PcdSerialUseMmio is TRUE, then the value is written to
   MMIO space.  If PcdSerialUseMmio is FALSE, then the value is written to I/O space.  The
   parameter Offset is added to the base address of the 16550 registers that is specified
-  by PcdSerialRegisterBase.
+  by PcdSerialRegisterBase. PcdSerialRegisterAccessWidth specifies the MMIO space access
+  width and defaults to 8 bit access, and supports 8 or 32 bit access.
 
   @param  Base    The base address register of UART device.
   @param  Offset  The offset of the 16550 register to write.
@@ -104,6 +109,9 @@ SerialPortWriteRegister (
   )
 {
   if (PcdGetBool (PcdSerialUseMmio)) {
+    if (PcdGet8 (PcdSerialRegisterAccessWidth) == 32) {
+      return (UINT8) MmioWrite32 (Base + Offset * PcdGet32 (PcdSerialRegisterStride), (UINT8)Value);
+    }
     return MmioWrite8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride), Value);
   } else {
     return IoWrite8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride), Value);
diff --git a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf
index b60779c..8b4ae3f 100644
--- a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf
+++ b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf
@@ -1,7 +1,7 @@
 ## @file
 #  SerialPortLib instance for 16550 UART.
 #
-#  Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+#  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
 ##
@@ -29,6 +29,7 @@
   BaseSerialPortLib16550.c
 
 [Pcd]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterAccessWidth     ## SOMETIMES_CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio                 ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseHardwareFlowControl  ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialDetectCable             ## SOMETIMES_CONSUMES
diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index be84916..2ef48f2 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -1170,6 +1170,13 @@
   # @Prompt Serial port registers use MMIO.
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio|FALSE|BOOLEAN|0x00020000
 
+  ## Indicates the access width for 16550 serial port registers.
+  # Default is 8-bit access mode.<BR><BR>
+  #    8  - 16550 serial port registers are accessed in 8-bit width.<BR>
+  #   32 - 16550 serial port registers are accessed in 32-bit width.<BR>
+  # @Prompt Serial port register access width.
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterAccessWidth|8|UINT8|0x00020007
+
   ## Indicates if the 16550 serial port hardware flow control will be enabled. Default is FALSE.<BR><BR>
   #   TRUE  - 16550 serial port hardware flow control will be enabled.<BR>
   #   FALSE - 16550 serial port hardware flow control will be disabled.<BR>
-- 
2.2.2