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 <[email protected]>; Kinney, Michael D
> <[email protected]>
> Cc: Gao, Liming <[email protected]>; [email protected];
> Meenakshi Aggarwal <[email protected]>
> Subject: RE: [edk2] [PATCH 1/1] MdePkg/IoLib: Add support for big-endian
> MMIO
>
> Hi Ard,
>
> > -----Original Message-----
> > From: Ard Biesheuvel [mailto:[email protected]]
> > Sent: Monday, October 17, 2016 1:12 PM
> > To: Kinney, Michael D <[email protected]>
> > Cc: Gao, Liming <[email protected]>; Bhupesh Sharma
> > <[email protected]>; [email protected]
> > Subject: Re: [edk2] [PATCH 1/1] MdePkg/IoLib: Add support for big-
> > endian MMIO
> >
> > On 17 October 2016 at 05:10, Kinney, Michael D
> > <[email protected]> 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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