Re: [PATCH 1/2] ArmPlatformPkg: PL011 Dynamic clock freq Support

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 5 June 2018 at 01:35, Udit Kumar <udit.kumar@nxp.com> wrote:
> Some platform support dynamic clocking, Which is controlled
> by some jumper setting or hardware registers.
> Result of that PCD PL011UartClkInHz needs to be updated for
> frequency change.
> This patch implements support for dynamic frequency for
> PL011 uart.
> This patch implement NULL lib for such platform where
> Pcd clock frequency to PL011 can change
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Udit Kumar <udit.kumar@nxp.com>

I'm not crazy about this. How exactly are you reading the frequency in
your case?

> ---
>  .../Include/Library/ArmPlatformClockLib.h          | 32 ++++++++++++++++++++
>  .../ArmPlatformClockLib.inf                        | 33 ++++++++++++++++++++
>  .../ArmPlatformClockLibNull.c                      | 35 ++++++++++++++++++++++
>  3 files changed, 100 insertions(+)
>  create mode 100644 ArmPlatformPkg/Include/Library/ArmPlatformClockLib.h
>  create mode 100644 ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLib.inf
>  create mode 100644 ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLibNull.c
>

ArmPlatformClockLib doesn't make sense, since this is specific to PL011, no?


> diff --git a/ArmPlatformPkg/Include/Library/ArmPlatformClockLib.h b/ArmPlatformPkg/Include/Library/ArmPlatformClockLib.h
> new file mode 100644
> index 0000000..f9d1425
> --- /dev/null
> +++ b/ArmPlatformPkg/Include/Library/ArmPlatformClockLib.h

Please add new library classes to the package .dec file

> @@ -0,0 +1,32 @@
> +/** @file
> +*
> +*  Copyright 2018 NXP
> +*
> +*  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
> +*  http://opensource.org/licenses/bsd-license.php
> +*
> +*  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
> +*  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +*
> +**/
> +
> +#ifndef _ARMPLATFORMCLOCKLIB_H_
> +#define _ARMPLATFORMCLOCKLIB_H_
> +
> +
> +/**
> +  Return frequency of PL011.
> +
> +  If this function return 0 then fixed value in Pcd will be used
> +
> +  @return Return frequency of PL011
> +
> +**/
> +UINT32
> +ArmPlatformGetPL011ClockFreq (
> +  VOID
> +  );
> +
> +#endif
> diff --git a/ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLib.inf b/ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLib.inf
> new file mode 100644
> index 0000000..b708ad3
> --- /dev/null
> +++ b/ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLib.inf
> @@ -0,0 +1,33 @@
> +#/* @file
> +#  Copyright 2018 NXP
> +#
> +#  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
> +#  http://opensource.org/licenses/bsd-license.php
> +#
> +#  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
> +#  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +#
> +#*/
> +
> +[Defines]
> +  INF_VERSION                    = 0x0001000A
> +  BASE_NAME                      = ArmPlatformClockLibNull
> +  FILE_GUID                      = af8fef24-afbb-472a-b8b7-13101a79703c
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = ArmPlatformClockLib
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +  MdeModulePkg/MdeModulePkg.dec
> +  ArmPkg/ArmPkg.dec
> +  ArmPlatformPkg/ArmPlatformPkg.dec
> +
> +[LibraryClasses]
> +  ArmLib
> +  DebugLib
> +
> +[Sources.common]
> +  ArmPlatformClockLibNull.c
> diff --git a/ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLibNull.c b/ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLibNull.c
> new file mode 100644
> index 0000000..28eaa63
> --- /dev/null
> +++ b/ArmPlatformPkg/Library/ArmPlatformClockLibNull/ArmPlatformClockLibNull.c
> @@ -0,0 +1,35 @@
> +/** @file
> +*
> +*  Copyright 2018 NXP
> +*
> +*  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
> +*  http://opensource.org/licenses/bsd-license.php
> +*
> +*  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
> +*  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +*
> +**/
> +
> +#include <Library/ArmPlatformClockLib.h>
> +
> +
> +
> +/**
> +  Return clock in for PL011 Uart IP.
> +**/
> +UINT32
> +ArmPlatformGetPL011ClockFreq (
> +  VOID
> +  )
> +{
> +  // Implement platform specific code
> +  // and return PL011 freq
> +
> +  // Some platform supports dynamic clocking,
> +  // This function needs to be implemented on platforms which supports
> +  // dynamic clocking to avoid re-building of UEFI firmware for PL011
> +  // clock change
> +  return 0;

Why not return the PCD value here? That way, you can also get rid of
the horrid conditional expression in the next patch.

> +}
> --
> 1.9.1
>