Re: [PATCH 1/1] MdePkg/IoLib: Add support for big-endian MMIO

[Leif Lindholm <leif.lindholm@linaro.org>]

Mike,

In that case - do you think it should be added to MdeModulePkg?

Should it be implemented simply as a wrapper on IoLib (depending on
it)?

/
    Leif

On Fri, Dec 01, 2017 at 10:41:26PM +0000, Kinney, Michael D wrote:
> Udit,
> 
> I agree with your concern.
> 
> I am in favor of adding new APIs that perform the
> byte swap operations.
> 
> Mike
> 
> > -----Original Message-----
> > From: Udit Kumar [mailto:udit.kumar@nxp.com]
> > Sent: Friday, December 1, 2017 9:58 AM
> > To: Leif Lindholm <leif.lindholm@linaro.org>; Meenakshi
> > Aggarwal <meenakshi.aggarwal@nxp.com>; Varun Sethi
> > <V.Sethi@nxp.com>
> > Cc: Kinney, Michael D <michael.d.kinney@intel.com>; edk2-
> > devel@lists.01.org; Gao, Liming <liming.gao@intel.com>;
> > Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Subject: RE: [edk2] [PATCH 1/1] MdePkg/IoLib: Add support
> > for big-endian MMIO
> > 
> > Thanks Leif,
> > 
> > > It may require a little bit more of up-front work, but
> > the end result will be a
> > > platform port that works with the intended edk2 design
> > principles rather than
> > 
> > Yes, this will be re-design/code for us, breaking all
> > software pieces into
> > smaller blocks and exposing protocol from the same.
> > This could be managed.
> > 
> > But how do you see,  if there is such dependency oN lib.
> > Say a driver which is in BE mode, and is using DebugLib
> > (BaseDebugLibSerialPort)
> > And DebugLib uses SerialPortLib, which is in LE mode
> > 
> > Thanks
> > Udit
> > 
> > > -----Original Message-----
> > > From: edk2-devel [mailto:edk2-devel-
> > bounces@lists.01.org] On Behalf Of Leif
> > > Lindholm
> > > Sent: Friday, December 01, 2017 4:28 PM
> > > To: Meenakshi Aggarwal <meenakshi.aggarwal@nxp.com>
> > > Cc: Kinney, Michael D <michael.d.kinney@intel.com>;
> > edk2-devel@lists.01.org;
> > > Gao, Liming <liming.gao@intel.com>; Ard Biesheuvel
> > > <ard.biesheuvel@linaro.org>
> > > Subject: Re: [edk2] [PATCH 1/1] MdePkg/IoLib: Add
> > support for big-endian
> > > MMIO
> > >
> > > On Thu, Nov 30, 2017 at 04:15:38AM +0000, Meenakshi
> > Aggarwal wrote:
> > > > Hi Leif, Mike,
> > > >
> > > >
> > > > NXP boards, at present, have few controllers with big
> > endian and other
> > > > with little endian memory access.
> > >
> > > Sure, this is not a problem.
> > >
> > > > Maximum controllers depend on SocLib library for
> > clock information and
> > > > endianness for SocLib and controllers is different.
> > >
> > > OK, I see in SocLib you have something called a Gur
> > that is read once (and again
> > > does a special per-device Pcd dance for runtime
> > selection between
> > > byteswapping Mmio and plain Mmio).
> > >
> > > > So this option will not work for us,
> > > >   You would then just do (in your .dsc):
> > > >   Platform/NXP/Drivers/WatchDog/WatchDogDxe.inf {
> > > >       IoLib|<path to BeIoLib .inf>
> > > >   }
> > > >
> > > > Because all libraries included by WatchDog will then
> > access BE mode Mmio
> > > APIs.
> > >
> > > Which libraries performing Mmio accesses are you
> > intending to include in your
> > > watchdog driver? You have submitted none as part of
> > this series.
> > >
> > > > And breaking code into separate modules with
> > different access will be
> > > > very difficult.
> > >
> > > It may require a little bit more of up-front work, but
> > the end result will be a
> > > platform port that works with the intended edk2 design
> > principles rather than
> > > against them. And that will reduce the overall effort
> > (not to mention code
> > > duplication).
> > >
> > > From the patches you have sent, the only required
> > change I see (if a
> > > byteswapping IoLib was added to edk2) would be to
> > create a tiny driver for this
> > > "Gur" device that installs a protocol containing a
> > single function for reading
> > > from that device's register space. That driver can be
> > built against the swapping
> > > or non-swapping IoLib as appropriate.
> > >
> > > > Watchdog is not the only module which need BE Mmio
> > APIs, we have MMC
> > > > and other controllers also with same requirement.
> > >
> > > And the same solutions are possible everywhere.
> > >
> > > Best Regards,
> > >
> > > Leif
> > >
> > > > We need BE Mmio APIs with a different name.
> > > >
> > > > Please see the possibility.
> > > >
> > > > Thanks & Regards,
> > > > Meenakshi
> > > >
> > > > > -----Original Message-----
> > > > > From: Leif Lindholm
> > [mailto:leif.lindholm@linaro.org]
> > > > > Sent: Thursday, November 30, 2017 1:19 AM
> > > > > To: Kinney, Michael D <michael.d.kinney@intel.com>
> > > > > Cc: Meenakshi Aggarwal
> > <meenakshi.aggarwal@nxp.com>; Gao, Liming
> > > > > <liming.gao@intel.com>; edk2-devel@lists.01.org;
> > Ard Biesheuvel
> > > > > <ard.biesheuvel@linaro.org>
> > > > > Subject: Re: [edk2] [PATCH 1/1] MdePkg/IoLib: Add
> > support for
> > > > > big-endian MMIO
> > > > >
> > > > > I guess there is no strict rule about a driver only
> > directly
> > > > > accessing one piece of HW?
> > > > >
> > > > > Still, that would be one possible solution:
> > breaking accesses to a
> > > > > separate HW in need of byteswapping out into its
> > own module and
> > > > > letting it override IoLib version there.
> > > > >
> > > > > Regards,
> > > > >
> > > > > Leif
> > > > >
> > > > > On Wed, Nov 29, 2017 at 07:25:05PM +0000, Kinney,
> > Michael D wrote:
> > > > > > Leif,
> > > > > >
> > > > > > I agree that this should be described as byte
> > swapping.
> > > > > >
> > > > > > What about a module that needs to access HW with
> > and without the
> > > > > > bytes swapped?  It gets more complex if a module
> > is linked against
> > > > > > several libs and some libs access HW with bytes
> > swapped and some
> > > > > > do not.
> > > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > Mike
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: edk2-devel [mailto:edk2-devel-
> > bounces@lists.01.org] On
> > > > > > > Behalf Of Leif Lindholm
> > > > > > > Sent: Wednesday, November 29, 2017 4:51 AM
> > > > > > > To: Meenakshi Aggarwal
> > <meenakshi.aggarwal@nxp.com>; Gao, Liming
> > > > > > > <liming.gao@intel.com>
> > > > > > > Cc: Kinney, Michael D
> > <michael.d.kinney@intel.com>;
> > > > > > > edk2-devel@lists.01.org; Ard Biesheuvel
> > > > > > > <ard.biesheuvel@linaro.org>
> > > > > > > Subject: Re: [edk2] [PATCH 1/1] MdePkg/IoLib:
> > Add support for
> > > > > > > big-endian MMIO
> > > > > > >
> > > > > > > Hi Meenakshi,
> > > > > > >
> > > > > > > I finally got around to looking at the watchdog
> > code (that uses
> > > > > > > this library), and that has convinced me the
> > best solution is to
> > > > > > > do what Liming proposed.
> > > > > > >
> > > > > > > Looking at this snippet:
> > > > > > >
> > > > > > > > +STATIC
> > > > > > > > +UINT16
> > > > > > > > +EFIAPI
> > > > > > > > +WdogRead (
> > > > > > > > +  IN  UINTN     Address
> > > > > > > > +  )
> > > > > > > > +{
> > > > > > > > +  if (FixedPcdGetBool (PcdWdogBigEndian)) {
> > > > > > > > +    return BeMmioRead16 (Address);
> > > > > > > > +  } else {
> > > > > > > > +    return MmioRead16(Address);
> > > > > > > > +  }
> > > > > > >
> > > > > > > This is actually a pretty good demonstration of
> > the arguments
> > > > > > > that were made with regards to how the BeIoLib
> > could be just
> > > > > > > another implementation of IoLib.
> > > > > > >
> > > > > > > You would then just do (in your .dsc):
> > > > > > >   Platform/NXP/Drivers/WatchDog/WatchDogDxe.inf
> > {
> > > > > > >     IoLib|<path to BeIoLib .inf>
> > > > > > >   }
> > > > > > >
> > > > > > > This causes the big-endian version of the
> > library to be used for
> > > > > > > this component. This makes these Wdog<access>
> > functions and the
> > > > > > > Pcd redundant, and the rest of the code can use
> > > > > > > MmioRead16()/MmioWrite16()
> > > > > > > directly.
> > > > > > >
> > > > > > > But then, it is not really a big-endian or
> > litte-endian version
> > > > > > > of the library we need. We always know which
> > endianness we are
> > > > > > > building for.
> > > > > > > What we need is a byteswapping flavour of
> > IoLib.
> > > > > > >
> > > > > > > So Liming, what if we do something like adding
> > a
> > > > > > >
> > MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsicSwa
> > > > > > > p.inf
> > > > > > > ---
> > > > > > > [Defines]
> > > > > > >   INF_VERSION                    = 0x0001001A
> > > > > > >   BASE_NAME                      =
> > > > > > > BaseIoLibIntrinsicSwap
> > > > > > >   MODULE_UNI_FILE                =
> > > > > > > BaseIoLibIntrinsic.uni
> > > > > > >   FILE_GUID                      = d4a60d44-
> > 3688-4a50-
> > > > > > > b2d0-5c6fc2422523
> > > > > > >   MODULE_TYPE                    = BASE
> > > > > > >   VERSION_STRING                 = 1.0
> > > > > > >   LIBRARY_CLASS                  = IoLib
> > > > > > >
> > > > > > >
> > > > > > > #
> > > > > > > #  VALID_ARCHITECTURES           = IA32 X64 EBC
> > IPF ARM
> > > > > > > AARCH64
> > > > > > > #
> > > > > > >
> > > > > > > [Sources]
> > > > > > >   BaseIoLibIntrinsicInternal.h
> > > > > > >   IoHighLevel.c
> > > > > > >   IoLib.c
> > > > > > >   IoLibEbc.c         # Asserts on all i/o port
> > accesses
> > > > > > >   IoLibMmioBuffer.c
> > > > > > >
> > > > > > > [Packages]
> > > > > > >   MdePkg/MdePkg.dec
> > > > > > >
> > > > > > > [LibraryClasses]
> > > > > > >   DebugLib
> > > > > > >   BaseLib
> > > > > > >
> > > > > > > [BuildOptions]
> > > > > > >   GCC:*_*_*_CC_FLAGS  = -DSWAP_BYTES
> > > > > > > ---
> > > > > > >
> > > > > > > And then add
> > > > > > >
> > > > > > > #ifdef SWAP_BYTES
> > > > > > >   return SwapBytesXX (Value);
> > > > > > > #else
> > > > > > >   return Value;
> > > > > > > #fi
> > > > > > >
> > > > > > > for the read operations and
> > > > > > >
> > > > > > > #ifdef SWAP_BYTES
> > > > > > >   *(type)Address = SwapBytesXX (Value); #else
> > > > > > >   *(type)Address = Value;
> > > > > > > #fi
> > > > > > >
> > > > > > > for the write operations in IoLib.c?
> > > > > > >
> > > > > > > /
> > > > > > >     Leif
> > > > > > >
> > > > > > > On Mon, Nov 27, 2017 at 06:06:33AM +0000,
> > Meenakshi Aggarwal
> > > > > > > wrote:
> > > > > > > > Hi Leif,
> > > > > > > >
> > > > > > > > This is regarding Big-Endian Library patch
> > ([PATCH v2
> > > > > > > 1/9]
> > > > > > > > Platform/NXP: Add support for Big Endian Mmio
> > APIs)
> > > > > > > >
> > > > > > > > We have started this discussion before and
> > the
> > > > > > > suggestion was to
> > > > > > > > create a separate .inf file keeping APIs name
> > same e.g.
> > > > > > > > MmioRead/MmioWrite in MdePkg.
> > > > > > > >
> > > > > > > > But we can't go with this approach (reason
> > mentioned
> > > > > > > by Udit).
> > > > > > > >
> > > > > > > > So please suggest if we should keep this
> > library
> > > > > > > under Platform/NXP
> > > > > > > > or I send a new patch moving this library in
> > MdePkg.
> > > > > > > >
> > > > > > > > But we have to keep a different name for Big
> > Endian
> > > > > > > MMIO APIs.
> > > > > > > >
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > > Meenakshi
> > > > > > > >
> > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: Udit Kumar
> > > > > > > > > Sent: Monday, October 23, 2017 12:38 PM
> > > > > > > > > To: Gao, Liming <liming.gao@intel.com>;
> > Meenakshi
> > > > > > > Aggarwal
> > > > > > > > > <meenakshi.aggarwal@nxp.com>; Ard
> > Biesheuvel
> > > > > > > > > <ard.biesheuvel@linaro.org>; Kinney,
> > Michael D
> > > > > > > > > <michael.d.kinney@intel.com>; edk2-
> > > > > > > devel@lists.01.org
> > > > > > > > > Subject: RE: [edk2] [PATCH 1/1]
> > MdePkg/IoLib: Add
> > > > > > > support for big-endian
> > > > > > > > > MMIO
> > > > > > > > >
> > > > > > > > > Hi Meenakshi/Liming,
> > > > > > > > > My 2 cents, around this.
> > > > > > > > >
> > > > > > > > > 1)
> > > > > > > > > Having a new lib for BE read might not be
> > helpful
> > > > > > > for us, e.g. a IP which is in
> > > > > > > > > BE mode access the UART for print or system
> > > > > > > registers which are in LE, then
> > > > > > > > > with new Lib, we will get all read/write in
> > BE mode
> > > > > > > > >
> > > > > > > > > 2)
> > > > > > > > > Especially for our IPs, which are changing
> > from BE
> > > > > > > to LE depending on
> > > > > > > > > platform.
> > > > > > > > > As said before, having BE read lib with API
> > name of
> > > > > > > MmioRead32 etc, will not
> > > > > > > > > help (I guess Meenakshi already seen some
> > problems
> > > > > > > around this) Adding a
> > > > > > > > > new lib with MmioRead32BE API name could
> > help, but
> > > > > > > IP driver we need to
> > > > > > > > > take care of IP mode either by Pcd or
> > #define, to
> > > > > > > select MmioRead32 or
> > > > > > > > > MmioRead32BE.
> > > > > > > > > This conditional compile needs to be done
> > for all
> > > > > > > IPs (which works in BE/LE
> > > > > > > > > mode on different platforms).
> > > > > > > > >
> > > > > > > > > My preferred way of implementation to use
> > one
> > > > > > > function in IP driver, And
> > > > > > > > > based on IP mode, do the switch.
> > > > > > > > >
> > > > > > > > > New Lib could have function like below
> > > > > > > > > MmioRead32Generic(IN  UINTN     Address,
> > BOOL
> > > > > > > IsIPBE) {
> > > > > > > > >    UINT32                            Value;
> > > > > > > > >
> > > > > > > > >    ASSERT ((Address & 3) == 0);
> > > > > > > > >    Value = *(volatile UINT32*)Address;
> > > > > > > > >    If(IsIPBE)
> > > > > > > > >      Value = SwapBytes32(Value);  return
> > Value; }
> > > > > > > > >
> > > > > > > > > And IP driver can use it
> > > > > > > > > MmioRead32Generic(ADDR,
> > > > > > > > > FixedPcdGet(This_IP_Mode_For_This_platform)
> > > > > > > > >
> > > > > > > > > Comments are welcome.
> > > > > > > > >
> > > > > > > > > Regards
> > > > > > > > > Udit
> > > > > > > > >
> > > > > > > > > > -----Original Message-----
> > > > > > > > > > From: edk2-devel [mailto:edk2-devel-
> > > > > > > bounces@lists.01.org] On Behalf Of
> > > > > > > > > > Gao, Liming
> > > > > > > > > > Sent: Monday, October 16, 2017 8:48 AM
> > > > > > > > > > To: Meenakshi Aggarwal
> > > > > > > <meenakshi.aggarwal@nxp.com>; Ard Biesheuvel
> > > > > > > > > > <ard.biesheuvel@linaro.org>; Kinney,
> > Michael D
> > > > > > > > > > <michael.d.kinney@intel.com>; edk2-
> > > > > > > devel@lists.01.org
> > > > > > > > > > Subject: Re: [edk2] [PATCH 1/1]
> > MdePkg/IoLib: Add
> > > > > > > support for
> > > > > > > > > > big-endian MMIO
> > > > > > > > > >
> > > > > > > > > > Meenakshi:
> > > > > > > > > >   I suggest to introduce new IoLib
> > library
> > > > > > > instance, not to add new IoLib
> > > > > > > > > APIs.
> > > > > > > > > > New IoLib library instance will perform
> > IO
> > > > > > > operation as the big
> > > > > > > > > > endian. You can update
> > > > > > > MdePkg/Library/BaseIoLibIntrinsic instance, add
> > > > > > > > > > new source file and new INF for it.
> > > > > > > > > >
> > > > > > > > > > UINT32
> > > > > > > > > > EFIAPI
> > > > > > > > > > MmioRead32 (
> > > > > > > > > >   IN  UINTN     Address
> > > > > > > > > >   )
> > > > > > > > > > {
> > > > > > > > > >   UINT32
> > Value;
> > > > > > > > > >
> > > > > > > > > >   ASSERT ((Address & 3) == 0);
> > > > > > > > > >   Value = *(volatile UINT32*)Address;
> > > > > > > > > >   return SwapBytes32(Value); }
> > > > > > > > > >
> > > > > > > > > > Thanks
> > > > > > > > > > Liming
> > > > > > > > > > >-----Original Message-----
> > > > > > > > > > >From: Meenakshi Aggarwal
> > > > > > > [mailto:meenakshi.aggarwal@nxp.com]
> > > > > > > > > > >Sent: Friday, October 13, 2017 2:07 PM
> > > > > > > > > > >To: Ard Biesheuvel
> > <ard.biesheuvel@linaro.org>;
> > > > > > > Kinney, Michael D
> > > > > > > > > > ><michael.d.kinney@intel.com>; edk2-
> > > > > > > devel@lists.01.org; Gao, Liming
> > > > > > > > > > ><liming.gao@intel.com>
> > > > > > > > > > >Subject: RE: [edk2] [PATCH 1/1]
> > MdePkg/IoLib:
> > > > > > > Add support for
> > > > > > > > > > >big-endian MMIO
> > > > > > > > > > >
> > > > > > > > > > >Hi All,
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >It’s a pretty old discussion, we have
> > left the
> > > > > > > upstreaming of NXP
> > > > > > > > > > >package in between because of some other
> > work,
> > > > > > > but have started it
> > > > > > > > > > >again
> > > > > > > > > > now.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >Issue  : Few NXP modules support Big
> > Endian
> > > > > > > MMIOs as these are ported
> > > > > > > > > > >from PowerPC.
> > > > > > > > > > >
> > > > > > > > > > >Solution suggested : Create a separate
> > library
> > > > > > > for BE MMIO APIs.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >So what I have done is, I have created a
> > > > > > > separate library to support
> > > > > > > > > > >BE MMIO APIs and currently keeping it to
> > my
> > > > > > > package.
> > > > > > > > > > >This library is basically a wrapper over
> > > > > > > existing MMIO APIs.
> > > > > > > > > > >
> > > > > > > > > > >UINT32
> > > > > > > > > > >EFIAPI
> > > > > > > > > > >BeMmioRead32 (
> > > > > > > > > > >  IN  UINTN     Address
> > > > > > > > > > >  )
> > > > > > > > > > >{
> > > > > > > > > > >  UINT32  Value;
> > > > > > > > > > >
> > > > > > > > > > >  Value = MmioRead32(Address);
> > > > > > > > > > >
> > > > > > > > > > >  return SwapBytes32(Value); }
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >Need your opinion on below optinos:
> > > > > > > > > > >
> > > > > > > > > > >1. Will this be a good idea to make this
> > library
> > > > > > > a part of MdePkg? OR
> > > > > > > > > > >
> > > > > > > > > > >2. Add a new file e.g. IoBeMmio.c like
> > > > > > > IoHighLevel.c in
> > > > > > > > > > >MdePkg/Library/BaseIoLibIntrinsic/
> > > > > > > > > > > And made these APIs a part of IoLib
> > itself. OR
> > > > > > > > > > >
> > > > > > > > > > >3. Keep this library internal to NXP
> > package.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >Please provide your inputs.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >Thanks & Regards,
> > > > > > > > > > >Meenakshi
> > > > > > > > > > >
> > > > > > > > > > >> -----Original Message-----
> > > > > > > > > > >> From: Bhupesh Sharma
> > > > > > > > > > >> Sent: Monday, October 17, 2016 3:28 PM
> > > > > > > > > > >> To: Ard Biesheuvel
> > > > > > > <ard.biesheuvel@linaro.org>; Kinney, Michael D
> > > > > > > > > > >> <michael.d.kinney@intel.com>
> > > > > > > > > > >> Cc: Gao, Liming
> > <liming.gao@intel.com>; edk2-
> > > > > > > devel@ml01.01.org;
> > > > > > > > > > >> Meenakshi Aggarwal
> > > > > > > <meenakshi.aggarwal@nxp.com>
> > > > > > > > > > >> Subject: RE: [edk2] [PATCH 1/1]
> > MdePkg/IoLib:
> > > > > > > Add support for
> > > > > > > > > > >> big-endian MMIO
> > > > > > > > > > >>
> > > > > > > > > > >> Hi Ard,
> > > > > > > > > > >>
> > > > > > > > > > >> > -----Original Message-----
> > > > > > > > > > >> > From: Ard Biesheuvel
> > > > > > > [mailto:ard.biesheuvel@linaro.org]
> > > > > > > > > > >> > Sent: Monday, October 17, 2016 1:12
> > PM
> > > > > > > > > > >> > To: Kinney, Michael D
> > > > > > > <michael.d.kinney@intel.com>
> > > > > > > > > > >> > Cc: Gao, Liming
> > <liming.gao@intel.com>;
> > > > > > > Bhupesh Sharma
> > > > > > > > > > >> > <bhupesh.sharma@nxp.com>; edk2-
> > > > > > > devel@ml01.01.org
> > > > > > > > > > >> > Subject: Re: [edk2] [PATCH 1/1]
> > > > > > > MdePkg/IoLib: Add support for
> > > > > > > > > > >> > big- endian MMIO
> > > > > > > > > > >> >
> > > > > > > > > > >> > On 17 October 2016 at 05:10, Kinney,
> > Michael
> > > > > > > D
> > > > > > > > > > >> > <michael.d.kinney@intel.com> wrote:
> > > > > > > > > > >> > > Bhupesh,
> > > > > > > > > > >> > >
> > > > > > > > > > >> > > It is also possible to add an ARM
> > specific
> > > > > > > PCD to select
> > > > > > > > > > >> > > endianness and update
> > > > > > > > > > >> > >
> > > > > > > MdePkg/Library/BaseIoLibIntrinsic/IoLibArm.c to
> > use that PCD in
> > > > > > > > > > >> > > MmioRead/Write() APIs in that file
> > to
> > > > > > > support both endian types.
> > > > > > > > > > >> > > You can use the SwapBytesxx()
> > functions
> > > > > > > from BaseLib(as
> > > > > > > > > > >> > Laszlo
> > > > > > > > > > >> > > suggested) based on the setting of
> > this
> > > > > > > ARM specific PCD.
> > > > > > > > > > >> > >
> > > > > > > > > > >> > > Modules that link against this lib
> > can
> > > > > > > select endianness by
> > > > > > > > > > >> > > setting PCD in the scope of that
> > module.
> > > > > > > > > > >> > >
> > > > > > > > > > >> > > The IPF version of IoLib uses an
> > IPF
> > > > > > > specific PCD to translate
> > > > > > > > > > >> > > I/O port accesses to MMIO
> > accesses.  So
> > > > > > > there is already an
> > > > > > > > > > >> > > example of an arch specific PCD in
> > this
> > > > > > > lib instance.
> > > > > > > > > > >> > >
> > > > > > > > > > >> >
> > > > > > > > > > >> > This is not a platform wide thing,
> > it is a
> > > > > > > per-device property
> > > > > > > > > > >> > whether the MMIO occurs in big
> > endian or
> > > > > > > little endian manner.
> > > > > > > > > > >> >
> > > > > > > > > > >> > So I think Liming's suggestion makes
> > sense:
> > > > > > > create an IoLib
> > > > > > > > > > >> > implementation that performs the
> > byte
> > > > > > > swapping, and selectively
> > > > > > > > > > >> > incorporate it into drivers that
> > require it
> > > > > > > using
> > > > > > > > > > >> >
> > > > > > > > > > >> > BeMmioDeviceDxe.inf {
> > > > > > > > > > >> >   <LibraryClasses>
> > > > > > > > > > >> >
> > IoLib|SomePkg/Library/BigEndianIoLib.inf
> > > > > > > > > > >> > }
> > > > > > > > > > >>
> > > > > > > > > > >> That's correct. I think creating a
> > separate
> > > > > > > IoLib for byte-swapping
> > > > > > > > > > >> makes sense.
> > > > > > > > > > >>
> > > > > > > > > > >> We will rework the patch accordingly.
> > > > > > > > > > >>
> > > > > > > > > > >> Regards,
> > > > > > > > > > >> Bhupesh
> > > > > > > > > >
> > _______________________________________________
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