PcAtChipsetPkg: Add MMIO Support to RTC driver

Some virtual machine managers like Kvmtool emulate the MC146818
RTC controller in the MMIO space so that architectures that do
not support I/O Mapped I/O can use the RTC. This patch adds MMIO
support to the RTC controller driver.

The PCD PcdRtcUseMmio has been added to select I/O or MMIO support.
  If PcdRtcUseMmio is:
    TRUE  - Indicates the RTC port registers are in MMIO space.
    FALSE - Indicates the RTC port registers are in I/O space.
            Default is I/O space.

Additionally two new PCDs PcdRtcIndexRegister64 and
PcdRtcTargetRegister64 have been introduced to provide the base
address for the RTC registers in the MMIO space.

When MMIO support is selected (PcdRtcUseMmio == TRUE) the driver
converts the pointers to the RTC MMIO registers so that the
RTC registers are accessible post ExitBootServices.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>

PcAtChipsetPkg/PcAtChipsetPkg.dec

@@ -6,6 +6,7 @@
 #
 # Copyright (c) 2009 - 2019, Intel Corporation. All rights reserved.<BR>
 # Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+# Copyright (c) 2018 - 2020, ARM Limited. All rights reserved.<BR>
 #
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -41,6 +42,13 @@
   # @Prompt Configure HPET to use MSI.
   gPcAtChipsetPkgTokenSpaceGuid.PcdHpetMsiEnable|TRUE|BOOLEAN|0x00001000
 
+  ## Indicates the RTC port registers are in MMIO space, or in I/O space.
+  #  Default is I/O space.<BR><BR>
+  #   TRUE  - RTC port registers are in MMIO space.<BR>
+  #   FALSE - RTC port registers are in I/O space.<BR>
+  # @Prompt RTC port registers use MMIO.
+  gPcAtChipsetPkgTokenSpaceGuid.PcdRtcUseMmio|FALSE|BOOLEAN|0x00000021
+
 [PcdsFixedAtBuild, PcdsDynamic, PcdsDynamicEx, PcdsPatchableInModule]
   ## This PCD specifies the base address of the HPET timer.
   # @Prompt HPET base address.
@@ -68,6 +76,14 @@
   # @Expression 0x80000001 | gPcAtChipsetPkgTokenSpaceGuid.PcdMaximalValidYear < gPcAtChipsetPkgTokenSpaceGuid.PcdMinimalValidYear + 100
   gPcAtChipsetPkgTokenSpaceGuid.PcdMaximalValidYear|2097|UINT16|0x0000000E
 
+  ## Specifies RTC Index Register address in MMIO space.
+  # @Prompt RTC Index Register address
+  gPcAtChipsetPkgTokenSpaceGuid.PcdRtcIndexRegister64|0x0|UINT64|0x00000022
+
+  ## Specifies RTC Target Register address in MMIO space.
+  # @Prompt RTC Target Register address
+  gPcAtChipsetPkgTokenSpaceGuid.PcdRtcTargetRegister64|0x0|UINT64|0x00000023
+
 [PcdsFixedAtBuild, PcdsPatchableInModule]
   ## Defines the ACPI register set base address.
   #  The invalid 0xFFFF is as its default value. It must be configured to the real value.

PcAtChipsetPkg/PcatRealTimeClockRuntimeDxe/PcRtc.c

@@ -3,6 +3,7 @@
 
 Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
 Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+Copyright (c) 2018 - 2020, ARM Limited. All rights reserved.<BR>
 
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -10,6 +11,9 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 
 #include "PcRtc.h"
 
+extern UINTN  mRtcIndexRegister;
+extern UINTN  mRtcTargetRegister;
+
 //
 // Days of month.
 //
@@ -54,38 +58,132 @@ IsWithinOneDay (
   );
 
 /**
-  Read RTC content through its registers.
+  Read RTC content through its registers using IO access.
 
-  @param  Address  Address offset of RTC. It is recommended to use macros such as
-                   RTC_ADDRESS_SECONDS.
+  @param  Address   Address offset of RTC. It is recommended to use
+                    macros such as RTC_ADDRESS_SECONDS.
 
   @return The data of UINT8 type read from RTC.
 **/
+STATIC
 UINT8
-RtcRead (
-  IN  UINT8 Address
+IoRtcRead (
+  IN  UINTN Address
   )
 {
-  IoWrite8 (PcdGet8 (PcdRtcIndexRegister), (UINT8) (Address | (UINT8) (IoRead8 (PcdGet8 (PcdRtcIndexRegister)) & 0x80)));
+  IoWrite8 (
+    PcdGet8 (PcdRtcIndexRegister),
+    (UINT8)(Address | (UINT8)(IoRead8 (PcdGet8 (PcdRtcIndexRegister)) & 0x80))
+    );
   return IoRead8 (PcdGet8 (PcdRtcTargetRegister));
 }
 
+/**
+  Write RTC through its registers  using IO access.
+
+  @param  Address   Address offset of RTC. It is recommended to use
+                    macros such as RTC_ADDRESS_SECONDS.
+  @param  Data      The content you want to write into RTC.
+
+**/
+STATIC
+VOID
+IoRtcWrite (
+  IN  UINTN   Address,
+  IN  UINT8   Data
+  )
+{
+  IoWrite8 (
+    PcdGet8 (PcdRtcIndexRegister),
+    (UINT8)(Address | (UINT8)(IoRead8 (PcdGet8 (PcdRtcIndexRegister)) & 0x80))
+    );
+  IoWrite8 (PcdGet8 (PcdRtcTargetRegister), Data);
+}
+
+/**
+  Read RTC content through its registers using MMIO access.
+
+  @param  Address   Address offset of RTC. It is recommended to use
+                    macros such as RTC_ADDRESS_SECONDS.
+
+  @return The data of UINT8 type read from RTC.
+**/
+STATIC
+UINT8
+MmioRtcRead (
+  IN  UINTN Address
+  )
+{
+  MmioWrite8 (
+    mRtcIndexRegister,
+    (UINT8)(Address | (UINT8)(MmioRead8 (mRtcIndexRegister) & 0x80))
+    );
+  return MmioRead8 (mRtcTargetRegister);
+}
+
+/**
+  Write RTC through its registers using MMIO access.
+
+  @param  Address   Address offset of RTC. It is recommended to use
+                    macros such as RTC_ADDRESS_SECONDS.
+  @param  Data      The content you want to write into RTC.
+
+**/
+STATIC
+VOID
+MmioRtcWrite (
+  IN  UINTN   Address,
+  IN  UINT8   Data
+  )
+{
+  MmioWrite8 (
+    mRtcIndexRegister,
+    (UINT8)(Address | (UINT8)(MmioRead8 (mRtcIndexRegister) & 0x80))
+    );
+  MmioWrite8 (mRtcTargetRegister, Data);
+}
+
+/**
+  Read RTC content through its registers.
+
+  @param  Address   Address offset of RTC. It is recommended to use
+                    macros such as RTC_ADDRESS_SECONDS.
+
+  @return The data of UINT8 type read from RTC.
+**/
+STATIC
+UINT8
+RtcRead (
+  IN  UINTN Address
+  )
+{
+  if (FeaturePcdGet (PcdRtcUseMmio)) {
+    return MmioRtcRead (Address);
+  }
+
+  return IoRtcRead (Address);
+}
+
 /**
   Write RTC through its registers.
 
-  @param  Address  Address offset of RTC. It is recommended to use macros such as
-                   RTC_ADDRESS_SECONDS.
-  @param  Data     The content you want to write into RTC.
+  @param  Address   Address offset of RTC. It is recommended to use
+                    macros such as RTC_ADDRESS_SECONDS.
+  @param  Data      The content you want to write into RTC.
 
 **/
+STATIC
 VOID
 RtcWrite (
-  IN  UINT8   Address,
+  IN  UINTN   Address,
   IN  UINT8   Data
   )
 {
-  IoWrite8 (PcdGet8 (PcdRtcIndexRegister), (UINT8) (Address | (UINT8) (IoRead8 (PcdGet8 (PcdRtcIndexRegister)) & 0x80)));
-  IoWrite8 (PcdGet8 (PcdRtcTargetRegister), Data);
+  if (FeaturePcdGet (PcdRtcUseMmio)) {
+    MmioRtcWrite (Address, Data);
+  } else {
+    IoRtcWrite (Address, Data);
+  }
 }
 
 /**

PcAtChipsetPkg/PcatRealTimeClockRuntimeDxe/PcRtcEntry.c

@@ -2,16 +2,23 @@
   Provides Set/Get time operations.
 
 Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2018 - 2020, ARM Limited. All rights reserved.<BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
 
+#include <Library/DxeServicesTableLib.h>
 #include "PcRtc.h"
 
 PC_RTC_MODULE_GLOBALS  mModuleGlobal;
 
 EFI_HANDLE             mHandle = NULL;
 
+STATIC EFI_EVENT       mVirtualAddrChangeEvent;
+
+UINTN                  mRtcIndexRegister;
+UINTN                  mRtcTargetRegister;
+
 /**
   Returns the current time and date information, and the time-keeping capabilities
   of the hardware platform.
@@ -105,6 +112,30 @@ PcRtcEfiSetWakeupTime (
   return PcRtcSetWakeupTime (Enabled, Time, &mModuleGlobal);
 }
 
+/**
+  Fixup internal data so that EFI can be called in virtual mode.
+  Call the passed in Child Notify event and convert any pointers in
+  lib to virtual mode.
+
+  @param[in]    Event   The Event that is being processed
+  @param[in]    Context Event Context
+**/
+VOID
+EFIAPI
+LibRtcVirtualNotifyEvent (
+  IN EFI_EVENT        Event,
+  IN VOID             *Context
+  )
+{
+  // Only needed if you are going to support the OS calling RTC functions in
+  // virtual mode. You will need to call EfiConvertPointer (). To convert any
+  // stored physical addresses to virtual address. After the OS transitions to
+  // calling in virtual mode, all future runtime calls will be made in virtual
+  // mode.
+  EfiConvertPointer (0x0, (VOID**)&mRtcIndexRegister);
+  EfiConvertPointer (0x0, (VOID**)&mRtcTargetRegister);
+}
+
 /**
   The user Entry Point for PcRTC module.
 
@@ -131,6 +162,11 @@ InitializePcRtc (
   EfiInitializeLock (&mModuleGlobal.RtcLock, TPL_CALLBACK);
   mModuleGlobal.CenturyRtcAddress = GetCenturyRtcAddress ();
 
+  if (FeaturePcdGet (PcdRtcUseMmio)) {
+    mRtcIndexRegister = (UINTN)PcdGet64 (PcdRtcIndexRegister64);
+    mRtcTargetRegister = (UINTN)PcdGet64 (PcdRtcTargetRegister64);
+  }
+
   Status = PcRtcInit (&mModuleGlobal);
   ASSERT_EFI_ERROR (Status);
 
@@ -165,7 +201,23 @@ InitializePcRtc (
                   NULL,
                   NULL
                   );
-  ASSERT_EFI_ERROR (Status);
+  if (EFI_ERROR (Status)) {
+    ASSERT_EFI_ERROR (Status);
+    return Status;
+  }
+
+  if (FeaturePcdGet (PcdRtcUseMmio)) {
+    // Register for the virtual address change event
+    Status = gBS->CreateEventEx (
+                    EVT_NOTIFY_SIGNAL,
+                    TPL_NOTIFY,
+                    LibRtcVirtualNotifyEvent,
+                    NULL,
+                    &gEfiEventVirtualAddressChangeGuid,
+                    &mVirtualAddrChangeEvent
+                    );
+    ASSERT_EFI_ERROR (Status);
+  }
 
   return Status;
 }

PcAtChipsetPkg/PcatRealTimeClockRuntimeDxe/PcatRealTimeClockRuntimeDxe.inf

@@ -6,6 +6,7 @@
 #
 # Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
 # Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+# Copyright (c) 2018 - 2020, ARM Limited. All rights reserved.<BR>
 #
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -61,6 +62,11 @@
   ## SOMETIMES_CONSUMES ## SystemTable
   gEfiAcpiTableGuid
 
+  gEfiEventVirtualAddressChangeGuid
+
+[FeaturePcd]
+  gPcAtChipsetPkgTokenSpaceGuid.PcdRtcUseMmio                   ## CONSUMES
+
 [FixedPcd]
   gPcAtChipsetPkgTokenSpaceGuid.PcdInitialValueRtcRegisterA     ## CONSUMES
   gPcAtChipsetPkgTokenSpaceGuid.PcdInitialValueRtcRegisterB     ## CONSUMES
@@ -72,6 +78,8 @@
   gPcAtChipsetPkgTokenSpaceGuid.PcdMaximalValidYear             ## CONSUMES
   gPcAtChipsetPkgTokenSpaceGuid.PcdRtcIndexRegister             ## CONSUMES
   gPcAtChipsetPkgTokenSpaceGuid.PcdRtcTargetRegister            ## CONSUMES
+  gPcAtChipsetPkgTokenSpaceGuid.PcdRtcIndexRegister64           ## CONSUMES
+  gPcAtChipsetPkgTokenSpaceGuid.PcdRtcTargetRegister64          ## CONSUMES
 
 [Depex]
   gEfiVariableArchProtocolGuid AND gEfiVariableWriteArchProtocolGuid