Re: [PATCH] MdeModulePkg/SdMmcPciHcDxe: Use 16/32-bit IO widths

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

> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: Sunday, February 03, 2019 8:39 PM
> To: Wu, Hao A
> Cc: Jeff Brasen; edk2-devel@lists.01.org; Edgar Handal; Marcin Wojtas
> Subject: Re: [edk2] [PATCH] MdeModulePkg/SdMmcPciHcDxe: Use 16/32-bit
> IO widths
> 
> On Fri, 1 Feb 2019 at 06:55, Wu, Hao A <hao.a.wu@intel.com> wrote:
> >
> > > -----Original Message-----
> > > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Jeff
> > > Brasen
> > > Sent: Thursday, January 31, 2019 7:59 AM
> > > To: edk2-devel@lists.01.org
> > > Cc: Edgar Handal; Jeff Brasen
> > > Subject: [edk2] [PATCH] MdeModulePkg/SdMmcPciHcDxe: Use 16/32-bit
> IO
> > > widths
> > >
> > > From: Edgar Handal <ehandal@nvidia.com>
> > >
> > > Use 16-bit and 32-bit IO widths for SDMMC MMIO to prevent all register
> > > accesses from being split up into 8-bit accesses.
> > >
> > > The SDHCI specification states that the registers shall be accessable in
> > > byte, word, and double word accesses.
> >
> 
> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Ard,

Really sorry for missing your 'Acked-by' tag.
It came to me after I pushed the commit.

Sorry again for this.

Best Regards,
Hao Wu

> 
> I think we should always prefer accessing MMIO registers using their
> native size, unless there are pressing reasons not to.
> 
> 
> > Hi,
> >
> > Thanks for the contribution. The change seems good to me.
> >
> > Just curious, if the accesses are always slit into byte(8-bit), is there any
> > issue or performance impact is encountered during your usage?
> >
> > It will be helpful to get more information on the purpose of the patch.
> > Thanks.
> >
> > Best Regards,
> > Hao Wu
> >
> > >
> > > Contributed-under: TianoCore Contribution Agreement 1.1
> > > Signed-off-by: Jeff Brasen <jbrasen@nvidia.com>
> > > ---
> > >  MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHci.c | 25
> > > ++++++++++++++++++++----
> > >  1 file changed, 21 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHci.c
> > > b/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHci.c
> > > index 5aec8c6..82f4493 100644
> > > --- a/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHci.c
> > > +++ b/MdeModulePkg/Bus/Pci/SdMmcPciHcDxe/SdMmcPciHci.c
> > > @@ -152,19 +152,36 @@ SdMmcHcRwMmio (
> > >    )
> > >  {
> > >    EFI_STATUS                   Status;
> > > +  EFI_PCI_IO_PROTOCOL_WIDTH    Width;
> > >
> > >    if ((PciIo == NULL) || (Data == NULL))  {
> > >      return EFI_INVALID_PARAMETER;
> > >    }
> > >
> > > -  if ((Count != 1) && (Count != 2) && (Count != 4) && (Count != 8)) {
> > > -    return EFI_INVALID_PARAMETER;
> > > +  switch (Count) {
> > > +    case 1:
> > > +      Width = EfiPciIoWidthUint8;
> > > +      break;
> > > +    case 2:
> > > +      Width = EfiPciIoWidthUint16;
> > > +      Count = 1;
> > > +      break;
> > > +    case 4:
> > > +      Width = EfiPciIoWidthUint32;
> > > +      Count = 1;
> > > +      break;
> > > +    case 8:
> > > +      Width = EfiPciIoWidthUint32;
> > > +      Count = 2;
> > > +      break;
> > > +    default:
> > > +      return EFI_INVALID_PARAMETER;
> > >    }
> > >
> > >    if (Read) {
> > >      Status = PciIo->Mem.Read (
> > >                            PciIo,
> > > -                          EfiPciIoWidthUint8,
> > > +                          Width,
> > >                            BarIndex,
> > >                            (UINT64) Offset,
> > >                            Count,
> > > @@ -173,7 +190,7 @@ SdMmcHcRwMmio (
> > >    } else {
> > >      Status = PciIo->Mem.Write (
> > >                            PciIo,
> > > -                          EfiPciIoWidthUint8,
> > > +                          Width,
> > >                            BarIndex,
> > >                            (UINT64) Offset,
> > >                            Count,
> > > --
> > > 2.7.4
> > >
> > > _______________________________________________
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