Re: [PATCH 1/2] ArmPlatformPkg/ArmJunoPkg/Drivers/PciHostBridgeDxe: Remove calls to ArmDmaLib

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

On 23 September 2016 at 17:20, Daniil Egranov <daniil.egranov@arm.com> wrote:
> Hi Ard,
>
>
> On 09/23/2016 02:57 AM, Ard Biesheuvel wrote:
>>
>> Hi Daniil,
>>
>> On 22 September 2016 at 23:33, Daniil Egranov <daniil.egranov@arm.com>
>> wrote:
>>>
>>> The PCI on Juno is DMA coherent, which means it should not be
>>> using ArmDmaLib for PCI DMA.
>>>
>>> Contributed-under: TianoCore Contribution Agreement 1.0
>>> Signed-off-by: Daniil Egranov <daniil.egranov@arm.com>
>>> ---
>>>   ArmPlatformPkg/ArmJunoPkg/Drivers/PciHostBridgeDxe/PciHostBridgeDxe.inf
>>> | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git
>>> a/ArmPlatformPkg/ArmJunoPkg/Drivers/PciHostBridgeDxe/PciHostBridgeDxe.inf
>>> b/ArmPlatformPkg/ArmJunoPkg/Drivers/PciHostBridgeDxe/PciHostBridgeDxe.inf
>>> index de28c80..597154c 100644
>>> ---
>>> a/ArmPlatformPkg/ArmJunoPkg/Drivers/PciHostBridgeDxe/PciHostBridgeDxe.inf
>>> +++
>>> b/ArmPlatformPkg/ArmJunoPkg/Drivers/PciHostBridgeDxe/PciHostBridgeDxe.inf
>>> @@ -36,7 +36,7 @@
>>>     MemoryAllocationLib
>>>     DxeServicesTableLib
>>>     CacheMaintenanceLib
>>> -  DmaLib
>>> +  NullDmaLib
>>>
>> This is wrong. The module .inf lists library *classes* and the
>> platform .dsc decides how each class maps onto an implementation (aka
>> library resolution)
>
> Agree. However, this is platform specific module and as i understand, the
> behavior of it will not change so, I think, having NullDmaLib here will be
> appropriate as well. We can move it to .dsc file, if it fits better to the
> platform description/module dependencies structure.
>

What you could do is remove the DmaLib dependency altogether, and just
implement PciIo->Map and PciIo->Unmap directly, and always return the
host address.