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

[Daniil Egranov <daniil.egranov@arm.com>]

On 09/23/2016 11:21 AM, Ard Biesheuvel wrote:
> 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.
This implementation will be almost the same as NullDmaLib one :). If you 
think it will be better structure-wise to remap it in .dsc file, let's 
go this path and disregard this patch.

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