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

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

On 5 June 2018 at 14:23, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> 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

I forgot: the Null suffix is inappropriate here. Please invent a name
that reflects the fixed, constant nature of the clock frequency.

>> +  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
>>