[PATCH v2 1/1] MdeModulePkg/SdMmcPciHcDxe: Fix DMA on SDHC v3 64-bit systems

[Hao Wu <hao.a.wu@intel.com>]

From: "Cohen, Eugene" <eugene@hp.com>

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1583

The SdMmcPciHcDriverBindingStart function was checking two different
capability bits in determining whether 64-bit DMA modes were supported,
one mode is defined in the SDHC version 3 specification (using 96-bit
descriptors) and another is defined in the SDHC version 4 specification
(using 128-bit descriptors).

Since the currently implementation of 64-bit ADMA2 only supports the SDHC
version 4 implementation, it is incorrect to check the V3 64-bit
capability bit since this will activate V4 ADMA2 on V3 controllers which
then causes buffers to be allocated that cannot be DMAed.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ashish Singhal <ashishsingha@nvidia.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Eugene Cohen <eugene@hp.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Ashish Singhal <ashishsingha@nvidia.com>
Reviewed-by: Hao Wu <hao.a.wu@intel.com>
---
 MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHcDxe.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHcDxe.c b/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHcDxe.c
index b474f8decd..5bc91c5337 100644
--- a/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHcDxe.c
+++ b/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHcDxe.c
@@ -666,8 +666,7 @@ SdMmcPciHcDriverBindingStart (
     // If any of the slots does not support 64b system bus
     // do not enable 64b DMA in the PCI layer.
     //
-    if (Private->Capability[Slot].SysBus64V3 == 0 &&
-        Private->Capability[Slot].SysBus64V4 == 0) {
+    if (Private->Capability[Slot].SysBus64V4 == 0) {
       Support64BitDma = FALSE;
     }
 
-- 
2.12.0.windows.1