Re: [PATCH 2/6] EmbeddedPkg/CoherentDmaLib: add support for non-1:1 DMA translation

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

On Wed, Aug 30, 2017 at 11:54:05AM +0100, Ard Biesheuvel wrote:
> On 30 August 2017 at 11:51, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > On Wed, Aug 30, 2017 at 09:21:04AM +0100, Ard Biesheuvel wrote:
> >> Bring CoherentDmaLib in line with ArmDmaLib, and add support for
> >> defining a static offset between the host's and the bus master's
> >> view of memory.
> >>
> >> Contributed-under: TianoCore Contribution Agreement 1.1
> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> ---
> >>  EmbeddedPkg/EmbeddedPkg.dec                           |  7 +++++++
> >>  EmbeddedPkg/Library/CoherentDmaLib/CoherentDmaLib.c   | 10 +++++++++-
> >>  EmbeddedPkg/Library/CoherentDmaLib/CoherentDmaLib.inf |  3 +++
> >>  3 files changed, 19 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/EmbeddedPkg/EmbeddedPkg.dec b/EmbeddedPkg/EmbeddedPkg.dec
> >> index 8ad2a84c045c..ccdf38e36a8c 100644
> >> --- a/EmbeddedPkg/EmbeddedPkg.dec
> >> +++ b/EmbeddedPkg/EmbeddedPkg.dec
> >> @@ -208,3 +208,10 @@ [PcdsFixedAtBuild.X64]
> >>
> >>  [PcdsFixedAtBuild.common, PcdsDynamic.common]
> >>    gEmbeddedTokenSpaceGuid.PcdFdtDevicePaths|L""|VOID*|0x00000055
> >> +
> >> +  #
> >> +  # Value to add to a host address to obtain a device address, using
> >> +  # unsigned 64-bit integer arithmetic. This means we can rely on
> >> +  # truncation on overflow to specify negative offsets.
> >
> > Is that promotion-safe on 32-bit archs?
> 
> Yes. EFI_PHYSICAL_ADDRESS is always 64-bits, and so is this PCD, so
> whether it is a 32-bit platform or not should not make any difference.

Right.

Well, EFI_PHYSICAL_ADDRESS is. PHYSICAL_ADDRESS appears to also be
(they are not derived from each other).

+  return (PHYSICAL_ADDRESS)(UINTN)Address + PcdGet64 (PcdDmaDeviceOffset);

(I think I misparsed the above as
   return (PHYSICAL_ADDRESS)((UINTN)Address + PcdGet64 (PcdDmaDeviceOffset));
)

Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

/
    Leif