[PATCH v1 1/6] PcAtChipsetPkg: Add MMIO Support to SerialIo Lib

[Sami Mujawar <sami.mujawar@arm.com>]

Some virtual machine managers like kvmtool emulate the PC AT
Serial Port UART in the MMIO space so that architectures that
do not support I/O Mapped I/O can use the UART.

This patch adds MMIO support to the PC AT SerialPortLib.

PcdSerialUseMmio is used to select I/O or MMIO support.
  If PcdSerialUseMmio is
    TRUE  - The value is read/written from MMIO space.
    FALSE - The value is read/written from I/O space.
            The Default is I/O space.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
---
The changes can be seen at https://github.com/samimujawar/edk2/commit/84f908387d2031def5d374759e7ad4cf90786c91

Notes:
    v1:
    - Add support to read/write from UART registers using MMIO access [SAMI]

 PcAtChipsetPkg/Library/SerialIoLib/SerialIoLib.inf |  4 +
 PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c | 98 ++++++++++++++++----
 2 files changed, 84 insertions(+), 18 deletions(-)

diff --git a/PcAtChipsetPkg/Library/SerialIoLib/SerialIoLib.inf b/PcAtChipsetPkg/Library/SerialIoLib/SerialIoLib.inf
index 959d6e27c9812d201d44d9249070ab7758cbfe00..d0689793040fd930701b02dae51ff59ea16a10c4 100644
--- a/PcAtChipsetPkg/Library/SerialIoLib/SerialIoLib.inf
+++ b/PcAtChipsetPkg/Library/SerialIoLib/SerialIoLib.inf
@@ -2,6 +2,7 @@
 #   Library instance for SerialIo library class
 #
 #  Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.<BR>
+#  Copyright (c) 2018, ARM Limited. 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
@@ -23,6 +24,7 @@ [Defines]
 
 [Packages]
   MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
 
 [LibraryClasses]
   BaseLib
@@ -31,3 +33,5 @@ [LibraryClasses]
 [Sources]
   SerialPortLib.c
 
+[FixedPcd]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio                 ## CONSUMES
diff --git a/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c b/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
index d1a1c6a03facad09e781b5605e22a24e5f51c618..898e5f957aae998624189c6b538912da0439dfe8 100644
--- a/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
+++ b/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
@@ -2,6 +2,8 @@
   UART Serial Port library functions
 
   Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2018, ARM Limited. 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
@@ -57,6 +59,66 @@ UINT8   gParity   = 0;
 UINT8   gBreakSet = 0;
 
 /**
+  Reads an 8-bit value from the serial port.
+
+  This function checks PcdSerialUseMmio to determine if I/O
+  mapped IO or Memory Mapped IO operations must be performed on
+  the serial port. It then uses the appropriate interface to
+  read the Value from the serial port.
+
+  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.
+
+  @param  Address   The UART register to read from.
+
+  @return The value read from the serial port.
+
+**/
+STATIC
+UINT8
+SerialPortRead8 (
+  IN  UINTN   Address
+)
+{
+  if (FixedPcdGetBool (PcdSerialUseMmio)) {
+    return MmioRead8 (Address);
+  }
+
+  return IoRead8 (Address);
+}
+
+/**
+  Writes an 8-bit value to the serial port.
+
+  This function checks PcdSerialUseMmio to determine if I/O
+  mapped IO or Memory Mapped IO operations must be performed on
+  the serial port. It then uses the appropriate interface to
+  write the Value to the serial port.
+
+  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.
+
+  @param  Address   The UART register to write.
+  @param  Value     The value to write to the I/O port.
+
+  @return The value written to the serial port.
+
+**/
+STATIC
+UINT8
+SerialPortWrite8 (
+  IN  UINTN   Address,
+  IN  UINT8   Value
+)
+{
+  if (FixedPcdGetBool (PcdSerialUseMmio)) {
+    return MmioWrite8 (Address, Value);
+  }
+
+  return IoWrite8 (Address, Value);
+}
+
+/**
   Initialize the serial device hardware.
 
   If no initialization is required, then return RETURN_SUCCESS.
@@ -91,19 +153,19 @@ SerialPortInitialize (
   // Set communications format
   //
   OutputData = (UINT8) ((DLAB << 7) | (gBreakSet << 6) | (gParity << 3) | (gStop << 2) | Data);
-  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
+  SerialPortWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   //
   // Configure baud rate
   //
-  IoWrite8 (gUartBase + BAUD_HIGH_OFFSET, (UINT8) (Divisor >> 8));
-  IoWrite8 (gUartBase + BAUD_LOW_OFFSET, (UINT8) (Divisor & 0xff));
+  SerialPortWrite8 (gUartBase + BAUD_HIGH_OFFSET, (UINT8) (Divisor >> 8));
+  SerialPortWrite8 (gUartBase + BAUD_LOW_OFFSET, (UINT8) (Divisor & 0xff));
 
   //
   // Switch back to bank 0
   //
   OutputData = (UINT8) ( (gBreakSet << 6) | (gParity << 3) | (gStop << 2) | Data);
-  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
+  SerialPortWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   return RETURN_SUCCESS;
 }
@@ -148,9 +210,9 @@ SerialPortWrite (
     // Wait for the serail port to be ready.
     //
     do {
-      Data = IoRead8 ((UINT16) gUartBase + LSR_OFFSET);
+      Data = SerialPortRead8 ((UINT16) gUartBase + LSR_OFFSET);
     } while ((Data & LSR_TXRDY) == 0);
-    IoWrite8 ((UINT16) gUartBase, *Buffer++);
+    SerialPortWrite8 ((UINT16) gUartBase, *Buffer++);
   }
 
   return Result;
@@ -189,10 +251,10 @@ SerialPortRead (
     // Wait for the serail port to be ready.
     //
     do {
-      Data = IoRead8 ((UINT16) gUartBase + LSR_OFFSET);
+      Data = SerialPortRead8 ((UINT16) gUartBase + LSR_OFFSET);
     } while ((Data & LSR_RXDA) == 0);
 
-    *Buffer++ = IoRead8 ((UINT16) gUartBase);
+    *Buffer++ = SerialPortRead8 ((UINT16) gUartBase);
   }
 
   return Result;
@@ -220,7 +282,7 @@ SerialPortPoll (
   //
   // Read the serial port status.
   //
-  Data = IoRead8 ((UINT16) gUartBase + LSR_OFFSET);
+  Data = SerialPortRead8 ((UINT16) gUartBase + LSR_OFFSET);
 
   return (BOOLEAN) ((Data & LSR_RXDA) != 0);
 }
@@ -253,7 +315,7 @@ SerialPortSetControl (
   //
   // Read the Modem Control Register.
   //
-  Mcr = IoRead8 ((UINT16) gUartBase + MCR_OFFSET);
+  Mcr = SerialPortRead8 ((UINT16) gUartBase + MCR_OFFSET);
   Mcr &= (~(MCR_DTRC | MCR_RTS));
 
   if ((Control & EFI_SERIAL_DATA_TERMINAL_READY) == EFI_SERIAL_DATA_TERMINAL_READY) {
@@ -267,7 +329,7 @@ SerialPortSetControl (
   //
   // Write the Modem Control Register.
   //
-  IoWrite8 ((UINT16) gUartBase + MCR_OFFSET, Mcr);
+  SerialPortWrite8 ((UINT16) gUartBase + MCR_OFFSET, Mcr);
 
   return RETURN_SUCCESS;
 }
@@ -297,7 +359,7 @@ SerialPortGetControl (
   //
   // Read the Modem Status Register.
   //
-  Msr = IoRead8 ((UINT16) gUartBase + MSR_OFFSET);
+  Msr = SerialPortRead8 ((UINT16) gUartBase + MSR_OFFSET);
 
   if ((Msr & MSR_CTS) == MSR_CTS) {
     *Control |= EFI_SERIAL_CLEAR_TO_SEND;
@@ -318,7 +380,7 @@ SerialPortGetControl (
   //
   // Read the Modem Control Register.
   //
-  Mcr = IoRead8 ((UINT16) gUartBase + MCR_OFFSET);
+  Mcr = SerialPortRead8 ((UINT16) gUartBase + MCR_OFFSET);
 
   if ((Mcr & MCR_DTRC) == MCR_DTRC) {
     *Control |= EFI_SERIAL_DATA_TERMINAL_READY;
@@ -331,7 +393,7 @@ SerialPortGetControl (
   //
   // Read the Line Status Register.
   //
-  Lsr = IoRead8 ((UINT16) gUartBase + LSR_OFFSET);
+  Lsr = SerialPortRead8 ((UINT16) gUartBase + LSR_OFFSET);
 
   if ((Lsr & LSR_TXRDY) == LSR_TXRDY) {
     *Control |= EFI_SERIAL_OUTPUT_BUFFER_EMPTY;
@@ -470,19 +532,19 @@ SerialPortSetAttributes (
   // Set communications format
   //
   OutputData = (UINT8) ((DLAB << 7) | (gBreakSet << 6) | (LcrParity << 3) | (LcrStop << 2) | LcrData);
-  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
+  SerialPortWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   //
   // Configure baud rate
   //
-  IoWrite8 (gUartBase + BAUD_HIGH_OFFSET, (UINT8) (Divisor >> 8));
-  IoWrite8 (gUartBase + BAUD_LOW_OFFSET, (UINT8) (Divisor & 0xff));
+  SerialPortWrite8 (gUartBase + BAUD_HIGH_OFFSET, (UINT8) (Divisor >> 8));
+  SerialPortWrite8 (gUartBase + BAUD_LOW_OFFSET, (UINT8) (Divisor & 0xff));
 
   //
   // Switch back to bank 0
   //
   OutputData = (UINT8) ((gBreakSet << 6) | (LcrParity << 3) | (LcrStop << 2) | LcrData);
-  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
+  SerialPortWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   return RETURN_SUCCESS;
 }
-- 
'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'