Re: [RFC PATCH V2 07/19] MdePkg: Add ArchTimerLib library

[Heinrich Schuchardt <heinrich.schuchardt@canonical.com>]

On 9/7/22 13:36, Sunil V L wrote:
> This library implements the TimerLib.h functionality. This library
> is similar to CpuTimerLib but needs the library constructor.
> 
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> ---
>   MdePkg/Library/ArchTimerLib/ArchTimerLib.inf      |  40 +++
>   MdePkg/Library/ArchTimerLib/RiscV64/CpuTimerLib.c | 299 ++++++++++++++++++++
>   MdePkg/Library/ArchTimerLib/ArchTimerLib.uni      |  14 +
>   3 files changed, 353 insertions(+)
> 
> diff --git a/MdePkg/Library/ArchTimerLib/ArchTimerLib.inf b/MdePkg/Library/ArchTimerLib/ArchTimerLib.inf
> new file mode 100644
> index 000000000000..b61ae58d0142
> --- /dev/null
> +++ b/MdePkg/Library/ArchTimerLib/ArchTimerLib.inf
> @@ -0,0 +1,40 @@
> +## @file
> +# Timer Library Instance which needs a constructor for the architecture.
> +#
> +#  Copyright (c) 2016 - 2019, Hewlett Packard Enterprise Development LP. All rights reserved.<BR>
> +#  Copyright (c) 2022, Ventana Micro System Inc. All rights reserved.<BR>
> +#
> +#  SPDX-License-Identifier: BSD-2-Clause-Patent
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION          = 0x0001001b
> +  BASE_NAME            = ArchTimerLib
> +  FILE_GUID            = D3CF51A9-1CEA-4776-A8AB-CCFD14D7DAAF
> +  MODULE_TYPE          = BASE
> +  VERSION_STRING       = 1.0
> +  LIBRARY_CLASS        = TimerLib
> +  MODULE_UNI_FILE      = ArchTimerLib.uni
> +  CONSTRUCTOR          = ArchTimerLibConstructor
> +
> +[Sources.RISCV64]
> +  RiscV64/CpuTimerLib.c
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +  MdeModulePkg/MdeModulePkg.dec
> +  UefiCpuPkg/UefiCpuPkg.dec
> +  EmbeddedPkg/EmbeddedPkg.dec
> +
> +[LibraryClasses]
> +  BaseLib
> +  DebugLib
> +  FdtLib
> +  HobLib
> +
> +[Pcd]
> +  gUefiCpuPkgTokenSpaceGuid.PcdRiscVTimerFrequencyInHz  ## CONSUMES
> +
> +[Guids]
> +  gFdtHobGuid
> diff --git a/MdePkg/Library/ArchTimerLib/RiscV64/CpuTimerLib.c b/MdePkg/Library/ArchTimerLib/RiscV64/CpuTimerLib.c
> new file mode 100644
> index 000000000000..a81ac8c37cad
> --- /dev/null
> +++ b/MdePkg/Library/ArchTimerLib/RiscV64/CpuTimerLib.c
> @@ -0,0 +1,299 @@
> +/** @file
> +  RISC-V instance of Timer Library.
> +
> +  Copyright (c) 2016 - 2022, Hewlett Packard Enterprise Development LP. All rights reserved.<BR>
> +  Copyright (c) 2022, Ventana Micro Systems Inc. All rights reserved.<BR>
> +
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> +
> +**/
> +
> +#include <Uefi.h>
> +#include <PiDxe.h>
> +#include <Library/BaseLib.h>
> +#include <Library/DebugLib.h>
> +#include <Library/PcdLib.h>
> +#include <Library/UefiDriverEntryPoint.h>
> +#include <Library/UefiBootServicesTableLib.h>
> +#include <Library/HobLib.h>
> +#include <Guid/FdtHob.h>
> +#include <Register/RiscV64/RiscVAsm.h>
> +#include <Register/RiscV64/RiscVImpl.h>
> +#include <libfdt.h>
> +
> +
> +STATIC UINT32 mTimeBaseFrequency;
> +STATIC BOOLEAN mTimeBaseFreqInitialized;
> +
> +UINT32
> +InternalGetTimerFrequency(
> +  VOID
> +  )
> +{
> +  return mTimeBaseFrequency;
> +}
> +
> +
> +/**
> +  Stalls the CPU for at least the given number of ticks.
> +
> +  Stalls the CPU for at least the given number of ticks. It's invoked by
> +  MicroSecondDelay() and NanoSecondDelay().
> +
> +  @param  Delay     A period of time to delay in ticks.
> +
> +**/
> +VOID
> +InternalRiscVTimerDelay (
> +  IN UINT32  Delay
> +  )
> +{
> +  UINT32  Ticks;
> +  UINT32  Times;
> +
> +  Times  = Delay >> (RISCV_TIMER_COMPARE_BITS - 2);
> +  Delay &= ((1 << (RISCV_TIMER_COMPARE_BITS - 2)) - 1);
> +  do {
> +    //
> +    // The target timer count is calculated here
> +    //
> +    Ticks = csr_read(CSR_TIME) + Delay;
> +    Delay = 1 << (RISCV_TIMER_COMPARE_BITS - 2);
> +    while (((Ticks - csr_read(CSR_TIME)) & (1 << (RISCV_TIMER_COMPARE_BITS - 1))) == 0) {
> +      CpuPause ();

Is CpuPause() guaranteed to return before two ticks have elapsed?

'== 0' might be too strict especially when considering that interrupts 
might have to be handled in future.

You don't want this routine to hang for another 2^32 ticks.

Best regards

Heinrich

> +    }
> +  } while (Times-- > 0);
> +}
> +
> +/**
> +  Stalls the CPU for at least the given number of microseconds.
> +
> +  Stalls the CPU for the number of microseconds specified by MicroSeconds.
> +
> +  @param  MicroSeconds  The minimum number of microseconds to delay.
> +
> +  @return MicroSeconds
> +
> +**/
> +UINTN
> +EFIAPI
> +MicroSecondDelay (
> +  IN UINTN  MicroSeconds
> +  )
> +{
> +  InternalRiscVTimerDelay (
> +    (UINT32)DivU64x32 (
> +              MultU64x32 (
> +                MicroSeconds,
> +                InternalGetTimerFrequency()
> +                ),
> +              1000000u
> +              )
> +    );
> +  return MicroSeconds;
> +}
> +
> +/**
> +  Stalls the CPU for at least the given number of nanoseconds.
> +
> +  Stalls the CPU for the number of nanoseconds specified by NanoSeconds.
> +
> +  @param  NanoSeconds The minimum number of nanoseconds to delay.
> +
> +  @return NanoSeconds
> +
> +**/
> +UINTN
> +EFIAPI
> +NanoSecondDelay (
> +  IN UINTN  NanoSeconds
> +  )
> +{
> +  InternalRiscVTimerDelay (
> +    (UINT32)DivU64x32 (
> +              MultU64x32 (
> +                NanoSeconds,
> +                InternalGetTimerFrequency()
> +                ),
> +              1000000000u
> +              )
> +    );
> +  return NanoSeconds;
> +}
> +
> +/**
> +  Retrieves the current value of a 64-bit free running performance counter.
> +
> +  Retrieves the current value of a 64-bit free running performance counter. The
> +  counter can either count up by 1 or count down by 1. If the physical
> +  performance counter counts by a larger increment, then the counter values
> +  must be translated. The properties of the counter can be retrieved from
> +  GetPerformanceCounterProperties().
> +
> +  @return The current value of the free running performance counter.
> +
> +**/
> +UINT64
> +EFIAPI
> +GetPerformanceCounter (
> +  VOID
> +  )
> +{
> +  return (UINT64)csr_read (CSR_TIME);
> +}
> +
> +/**return
> +  Retrieves the 64-bit frequency in Hz and the range of performance counter
> +  values.
> +
> +  If StartValue is not NULL, then the value that the performance counter starts
> +  with immediately after is it rolls over is returned in StartValue. If
> +  EndValue is not NULL, then the value that the performance counter end with
> +  immediately before it rolls over is returned in EndValue. The 64-bit
> +  frequency of the performance counter in Hz is always returned. If StartValue
> +  is less than EndValue, then the performance counter counts up. If StartValue
> +  is greater than EndValue, then the performance counter counts down. For
> +  example, a 64-bit free running counter that counts up would have a StartValue
> +  of 0 and an EndValue of 0xFFFFFFFFFFFFFFFF. A 24-bit free running counter
> +  that counts down would have a StartValue of 0xFFFFFF and an EndValue of 0.
> +
> +  @param  StartValue  The value the performance counter starts with when it
> +                      rolls over.
> +  @param  EndValue    The value that the performance counter ends with before
> +                      it rolls over.
> +
> +  @return The frequency in Hz.
> +
> +**/
> +UINT64
> +EFIAPI
> +GetPerformanceCounterProperties (
> +  OUT      UINT64 *StartValue, OPTIONAL
> +  OUT      UINT64                    *EndValue     OPTIONAL
> +  )
> +{
> +  if (StartValue != NULL) {
> +    *StartValue = 0;
> +  }
> +
> +  if (EndValue != NULL) {
> +    *EndValue = 32 - 1;
> +  }
> +
> +  return InternalGetTimerFrequency();
> +}
> +
> +/**
> +  Converts elapsed ticks of performance counter to time in nanoseconds.
> +
> +  This function converts the elapsed ticks of running performance counter to
> +  time value in unit of nanoseconds.
> +
> +  @param  Ticks     The number of elapsed ticks of running performance counter.
> +
> +  @return The elapsed time in nanoseconds.
> +
> +**/
> +UINT64
> +EFIAPI
> +GetTimeInNanoSecond (
> +  IN      UINT64  Ticks
> +  )
> +{
> +  UINT64  NanoSeconds;
> +  UINT32  Remainder;
> +
> +  //
> +  //          Ticks
> +  // Time = --------- x 1,000,000,000
> +  //        Frequency
> +  //
> +  NanoSeconds = MultU64x32 (DivU64x32Remainder (Ticks, InternalGetTimerFrequency(), &Remainder), 1000000000u);
> +
> +  //
> +  // Frequency < 0x100000000, so Remainder < 0x100000000, then (Remainder * 1,000,000,000)
> +  // will not overflow 64-bit.
> +  //
> +  NanoSeconds += DivU64x32 (MultU64x32 ((UINT64)Remainder, 1000000000u), InternalGetTimerFrequency());
> +
> +  return NanoSeconds;
> +}
> +
> +STATIC
> +RETURN_STATUS
> +EFIAPI
> +FdtInitializeTimerFrequency (
> +  VOID
> +  )
> +{
> +  VOID            *Hob;
> +  VOID            *Fdt;
> +  INT32           CpusNode, Len;
> +  const fdt32_t   *Prop;
> +
> +  Hob = GetFirstGuidHob (&gFdtHobGuid);
> +  if ((Hob == NULL) || (GET_GUID_HOB_DATA_SIZE (Hob) != sizeof (UINT64))) {
> +    DEBUG ((DEBUG_ERROR, "%a: No FDT Hob found\n", __FUNCTION__));
> +    return EFI_NOT_FOUND;
> +  }
> +
> +  Fdt = (VOID *)(UINTN)*(UINT64 *)GET_GUID_HOB_DATA (Hob);
> +
> +  if (fdt_check_header (Fdt) != 0) {
> +    DEBUG ((
> +      DEBUG_ERROR,
> +      "%a: No DTB found @ 0x%p\n",
> +      __FUNCTION__,
> +      Fdt
> +      ));
> +    return EFI_NOT_FOUND;
> +  }
> +
> +  // The "cpus" node resides at the the root of the DT. Fetch it.
> +  CpusNode = fdt_path_offset (Fdt, "/cpus");
> +  if (CpusNode < 0) {
> +    DEBUG ((DEBUG_ERROR, "%a: Invalid /cpus node\n", __FUNCTION__));
> +    return EFI_NOT_FOUND;
> +  }
> +
> +  Prop = fdt_getprop((void *)Fdt, CpusNode, "timebase-frequency", &Len);
> +  if (!Prop) {
> +    DEBUG ((DEBUG_ERROR, "%a: timebase-frequency propertynot found\n", __FUNCTION__));
> +    return EFI_NOT_FOUND;
> +  }
> +
> +  mTimeBaseFrequency = fdt32_to_cpu(*Prop);
> +  DEBUG((DEBUG_INFO, "%a: Timer Frequency (DT) is set to 0x%x\n", __FUNCTION__, mTimeBaseFrequency));
> +
> +  return EFI_SUCCESS;
> +}
> +/**
> +  Initializes the Timer Frequency by reading it from the DTB
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +ArchTimerLibConstructor (
> +  VOID
> +  )
> +{
> +  EFI_STATUS      Status;
> +
> +  /*
> +   * Initialize only once
> +   */
> +  if (mTimeBaseFreqInitialized) {
> +    return EFI_SUCCESS;
> +  }
> +
> +  mTimeBaseFreqInitialized = 1;
> +
> +  Status = FdtInitializeTimerFrequency();
> +
> +  if (EFI_ERROR(Status)) {
> +    mTimeBaseFrequency = PcdGet32 (PcdRiscVTimerFrequencyInHz);
> +    DEBUG((DEBUG_INFO, "%a: Timer Frequency (PCD) is set to 0x%x\n", __FUNCTION__, mTimeBaseFrequency));
> +  }
> +
> +  return EFI_SUCCESS;
> +}
> diff --git a/MdePkg/Library/ArchTimerLib/ArchTimerLib.uni b/MdePkg/Library/ArchTimerLib/ArchTimerLib.uni
> new file mode 100644
> index 000000000000..1c900bea42bf
> --- /dev/null
> +++ b/MdePkg/Library/ArchTimerLib/ArchTimerLib.uni
> @@ -0,0 +1,14 @@
> +// /** @file
> +// Base CPU Timer Library
> +//
> +// Provides basic timer support using architecture specific methods.
> +//
> +// Copyright (c) 2022, Ventana Micro Systems Inc. All rights reserved.<BR>
> +//
> +// SPDX-License-Identifier: BSD-2-Clause-Patent
> +//
> +// **/
> +
> +#string STR_MODULE_ABSTRACT             #language en-US "CPU Timer Library"
> +
> +#string STR_MODULE_DESCRIPTION          #language en-US "Provides basic timer support using architecture specific methods"