Re: [PATCH] MdeModulePkg/PciHostBridgeDxe: Fixed PCI DMA Map/Umap bounce buffer

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

On 9 October 2017 at 08:42, Ni, Ruiyu <ruiyu.ni@intel.com> wrote:
> The "read"/"write" is from the Bus Master's point of view.
>
>
> Thanks/Ray
>
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Daniil
>> Egranov
>> Sent: Monday, October 9, 2017 9:16 AM
>> To: edk2-devel@lists.01.org
>> Cc: leif.lindholm@linaro.org; Zeng, Star <star.zeng@intel.com>;
>> ard.biesheuvel@linaro.org
>> Subject: [edk2] [PATCH] MdeModulePkg/PciHostBridgeDxe: Fixed PCI DMA
>> Map/Umap bounce buffer
>>
>> The patch corrects the logic of transferring data between a bounce buffer and a
>> real buffer above 4GB:
>> 1. In the case of mapping a bounce buffer for the write operation, data from a
>> real buffer should be copied into a bounce buffer.
>> 2.In the case of unmapping a bounce buffer for the read operation, data should
>> be copied from a bounce buffer into a real buffer.
>>
>> The patch resolves a Juno board issue with the the grub and SATA drives.
>>

I am intrigued by this.

So as I suggested, this has to do with 64-bit DMA, but not in the way
I suspected. UEFI itself never hits this code path, because it runs
entirely < 32 GB, but as soon as GRUB starts allocating loader data
and use it for DMA, the bounce buffering kicks in because apparently,
the SATA controller is not 64-bit DMA capable.

Are you using the SataSiI3132Dxe driver on Juno? Does this help at all?

diff --git a/EmbeddedPkg/Drivers/SataSiI3132Dxe/SiI3132AtaPassThru.c
b/EmbeddedPkg/Drivers/SataSiI3132Dxe/SiI3132AtaPassThru.c
index 2fb5fd68db01..a938563ebdd6 100644
--- a/EmbeddedPkg/Drivers/SataSiI3132Dxe/SiI3132AtaPassThru.c
+++ b/EmbeddedPkg/Drivers/SataSiI3132Dxe/SiI3132AtaPassThru.c
@@ -104,7 +104,7 @@ SiI3132AtaPassThruCommand (
     }

     Status = PciIo->Map (
-               PciIo, EfiPciIoOperationBusMasterRead,
+               PciIo, EfiPciIoOperationBusMasterWrite,
                Packet->InDataBuffer, &InDataBufferLength,
&PhysInDataBuffer, &PciAllocMapping
                );
     if (EFI_ERROR (Status)) {
@@ -139,7 +139,7 @@ SiI3132AtaPassThruCommand (
     OutDataBufferLength = Packet->OutTransferLength * SataDevice->BlockSize;

     Status = PciIo->Map (
-               PciIo, EfiPciIoOperationBusMasterWrite,
+               PciIo, EfiPciIoOperationBusMasterRead,
                Packet->OutDataBuffer, &OutDataBufferLength,
&PhysOutDataBuffer, &PciAllocMapping
                );
     if (EFI_ERROR (Status)) {