Re: [PATCH v2 1/2] MdeModulePkg: introduce SD/MMC override protocol

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

> -----Original Message-----
> From: Ni, Ruiyu
> Sent: Tuesday, December 05, 2017 6:35 PM
> To: Ard Biesheuvel; Wu, Hao A
> Cc: edk2-devel@lists.01.org; Leif Lindholm; Tian, Feng; Zeng, Star
> Subject: Re: [edk2] [PATCH v2 1/2] MdeModulePkg: introduce SD/MMC override
> protocol
> 
> On 12/5/2017 6:24 PM, Ard Biesheuvel wrote:
> > On 5 December 2017 at 10:12, Ni, Ruiyu <ruiyu.ni@intel.com> wrote:
> >> Some comments re the detailed interfaces embedded in below.
> >>
> >> On 11/30/2017 6:11 PM, Ard Biesheuvel wrote:
> >>>
> >>> Many ARM based SoCs have integrated SDHCI controllers, and often,
> >>> these implementations deviate in subtle ways from the pertinent
> >>> specifications. On the one hand, these deviations are quite easy
> >>> to work around, but on the other hand, having a collection of SoC
> >>> specific workarounds in the generic driver stack is undesirable.
> >>>
> >>> So let's introduce an optional SD/MMC override protocol that we
> >>> can invoke at the appropriate moments in the device initialization.
> >>> That way, the workaround itself remains platform specific, but we
> >>> can still use the generic driver stack on such platforms.
> >>>
> >>> Contributed-under: TianoCore Contribution Agreement 1.1
> >>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>> ---
> >>>    MdeModulePkg/Include/Protocol/SdMmcOverride.h | 103
> ++++++++++++++++++++
> >>>    MdeModulePkg/MdeModulePkg.dec                 |   3 +
> >>>    2 files changed, 106 insertions(+)
> >>>
> >>> diff --git a/MdeModulePkg/Include/Protocol/SdMmcOverride.h
> >>> b/MdeModulePkg/Include/Protocol/SdMmcOverride.h
> >>> new file mode 100644
> >>> index 000000000000..5a5c393896f4
> >>> --- /dev/null
> >>> +++ b/MdeModulePkg/Include/Protocol/SdMmcOverride.h
> >>> @@ -0,0 +1,103 @@
> >>> +/** @file
> >>> +  Protocol to describe overrides required to support non-standard SDHCI
> >>> +  implementations
>  >>> ...
> >>> +  IN      EFI_SD_MMC_PASS_THRU_PROTOCOL   *PassThru,
> >>> +  IN      EFI_HANDLE                      ControllerHandle,
> >>> +  IN      UINT8                           Slot,
> >>> +  IN  OUT UINT64                          *SdMmcHcSlotCapability
> >>> +  );
> >>
> >>
> >> Is this API too specific?
> >> Besides SlotCapability, is there any other attributes that may need
> >> override as well?
> >>
> >
> > The capability structure is the root data structure that describes the
> > SD/MMC host controller. Which other data structures did you have in
> > mind?
> >
> 
> I do not know either.
> Hao, any comments?

The service is overriding the 'Capability' field of the private data
structure within the HC driver. It's the value read from the 'CAP'
register of the SD/MMC HC.

After a glance of the other fields in 'SD_MMC_HC_PRIVATE_DATA', maybe the
'MaxCurrent' field is another candidate can be overriden. However, I am
not sure about this.

Best Regards,
Hao Wu

> 
> --
> Thanks,
> Ray