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

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

Hello Jeff,

Sorry for the delayed response.

I have verified your patch with the board on my side and it is working
fine. And I saw around 3~4 milliseconds performance boost. So I think the
patch will bring performance benefit to the driver.

Some minor inline comments below:

From: Jeff Brasen [mailto:jbrasen@nvidia.com]
Sent: Saturday, February 02, 2019 1:53 AM
To: Wu, Hao A; edk2-devel@lists.01.org
Cc: Edgar Handal
Subject: Re: [edk2] [PATCH] MdeModulePkg/SdMmcPciHcDxe: Use 16/32-bit IO widths




________________________________
From: Wu, Hao A <hao.a.wu@intel.com>
Sent: Friday, February 1, 2019 12:54 AM
To: Jeff Brasen; edk2-devel@lists.01.org
Cc: Edgar Handal
Subject: RE: [edk2] [PATCH] MdeModulePkg/SdMmcPciHcDxe: Use 16/32-bit IO widths

> -----Original Message-----
> From: Jeff Brasen [mailto:jbrasen@nvidia.com]
> Sent: Friday, February 01, 2019 3:12 PM
> To: Wu, Hao A; edk2-devel@lists.01.org
> Cc: Edgar Handal
> Subject: RE: [edk2] [PATCH] MdeModulePkg/SdMmcPciHcDxe: Use 16/32-bit IO
> widths
>
>
>
> -----Original Message-----
> From: Wu, Hao A <hao.a.wu@intel.com>
> Sent: Thursday, January 31, 2019 10:56 PM
> To: Jeff Brasen <jbrasen@nvidia.com>; edk2-devel@lists.01.org
> Cc: Edgar Handal <ehandal@nvidia.com>
> Subject: RE: [edk2] [PATCH] MdeModulePkg/SdMmcPciHcDxe: Use 16/32-bit IO
> widths
>
> > -----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
> >

Could you help to file a Bugzilla tracker to state the purpose of this
patch and make a reference in the commit log message here? Thanks.

> > 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.

'accessable' -> 'accessible'.
Also, could you help to quote the detailed context from the SD HCI spec
for the above statement?

Lastly, could you help to add your performance evaluation data in the
commit log message as well?

With the above 3 minor comments handled:
Reviewed-by: Hao Wu <hao.a.wu@intel.com>

Best Regards,
Hao Wu

>
> 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
>
> [JMB] We were working with a simulation module that has some issues when
> accessing 16 or 32 bit registers by byte (This should be supported per the SDHCI
> specification.), and this patch resolves this while we work on getting the model
> fixed. This should also optimize performance as there will less read/write
> instructions (My guess is this is a marginal improvement as most of the SD
> access time would be DMA operations.)

Thanks Jeff,

Got it. May I know is it possible for you to collect some performance data
for the change?

[JMB] Sure, did a several boots on silicon platform and see an average boot time improvement of 15ms. With a range of 10-20ms and never saw the performance get worse.

Meanwhile, I will test this patch with the boards I own and try to collect
some data. Please grant me some time for this. Since the current
implementation does not violate the spec, let us evaluate whether better
performance will be brought.

Best Regards,
Hao Wu

>
> Thanks,
> Jeff
>
>
>
> >
> > 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
> >
> > _______________________________________________
> > edk2-devel mailing list
> > edk2-devel@lists.01.org
> > https://lists.01.org/mailman/listinfo/edk2-devel
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