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

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

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.