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

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

Loop Ashish in.
Some comments below.

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Cohen, Eugene
> Sent: Wednesday, February 27, 2019 6:59 PM
> To: edk2-devel@lists.01.org; Wu, Hao A
> Subject: [edk2] [PATCH] MdeModulePkg/SdMmcPciHcDxe: Fix DMA on SDHC
> v3 64-bit systems
> 
> 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.

I remember the commit b5547b9ce97e80c3127682a2a5d4b9bd14af353e from Ashish
only handles the controllers with version greater or equal to 4.00.

And the ADMA2 (96-bit Descriptor) mode for V3 controllers is selected by
setting the 'DMA Select' filed in the Host Control 1 Register to 11b. But
the currently behavior of the driver is setting the field to 10b, which I
think will not switch to the ADMA2 (96-bit Descriptor) mode for V3.

Maybe there is something I miss here. Could you help to provide some more
detail on the issue you met? Thanks.

Best Regards,
Hao Wu

> 
> Cc: Hao Wu <hao.a.wu@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Eugene Cohen <eugene@hp.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 b474f8d..5bc91c5 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;
>      }
> 
> --
> 2.7.4
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