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

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

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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