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>

1 files changed, 53 insertions, 1 deletions

diff --git a/PcAtChipsetPkg/PcatRealTimeClockRuntimeDxe/PcRtcEntry.c b/PcAtChipsetPkg/PcatRealTimeClockRuntimeDxe/PcRtcEntry.c
index ccda633137..606b88adaf 100644
--- a/PcAtChipsetPkg/PcatRealTimeClockRuntimeDxe/PcRtcEntry.c
+++ b/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.

@@ -106,6 +113,30 @@ PcRtcEfiSetWakeupTime (
 }

 

 /**

+  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.

 

   This is the entry point for PcRTC module. It installs the UEFI runtime service

@@ -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;

 }