Re: [PATCH 2/4] DynamicTablesPkg: AcpiSsdtPcieLibArm: Allow use of segment number as UID

["Jeff Brasen" <jbrasen@nvidia.com>]

So to detail the use case we have an embedded device on a known controller (we know the segment number) by forcing the autogeneration to the segment number we could in another SSDT create the subdevice node right. With just \SB\PCI9\D0x as the scope right? If we had a callback I suppose we don't need that. I think we could handle that with the proposed change you had in [4/4] if we just chain the implementation of GeneratePciDeviceInfo to our second place we would implement this. I think we can drop this patch and do it that way. Will move additional thoughts to the other patch.

Thanks,
Jeff


> -----Original Message-----
> From: Pierre Gondois <pierre.gondois@arm.com>
> Sent: Monday, July 4, 2022 2:38 AM
> To: Jeff Brasen <jbrasen@nvidia.com>; devel@edk2.groups.io
> Cc: Sami.Mujawar@arm.com; Alexei.Fedorov@arm.com
> Subject: Re: [PATCH 2/4] DynamicTablesPkg: AcpiSsdtPcieLibArm: Allow use
> of segment number as UID
> 
> External email: Use caution opening links or attachments
> 
> 
> Hello Jeff,
> I understand that since the _UID value is generated, it is not possible for an
> external module to guess its value.
> However, the pcd (and the case you detailed) seem to be really specific.
> If you need an interface in the AmlLib to locate an AML node based on
> custom callback, we can help.
> Would this fit your need ?
> Also I don't understand how having a known _UID would ease locating the
> PCI device node.
> 
> Regards,
> Pierre
> 
> On 7/1/22 17:54, Jeff Brasen wrote:
> > I don't think there are any requirements that this should be mapped this
> way which is why I added this under a PCD to enable it. We have a use case
> where it would be helpful to know the ACPI path of the PCIe controllers
> externally and using the segment number for that would allow us to do this
> without having to have matching logic that calculates the PCIe UID from the
> CM object list again.
> >
> > Thanks,
> > Jeff
> >
> >
> >> -----Original Message-----
> >> From: Pierre Gondois <pierre.gondois@arm.com>
> >> Sent: Friday, July 1, 2022 6:42 AM
> >> To: Jeff Brasen <jbrasen@nvidia.com>; devel@edk2.groups.io
> >> Cc: Sami.Mujawar@arm.com; Alexei.Fedorov@arm.com
> >> Subject: Re: [PATCH 2/4] DynamicTablesPkg: AcpiSsdtPcieLibArm: Allow
> >> use of segment number as UID
> >>
> >> External email: Use caution opening links or attachments
> >>
> >>
> >> Hello Jeff,
> >>
> >>   From "PCI Firmware Specification Revision 3.3", s4.1.2.
> >> "MCFG Table Description", the "PCI Segment Group Number" field of the
> >> MCFG table must match the value returned by the _SEG object in the
> >> corresponding object.
> >>
> >> I didn't find any constraint about the _UID value. Would it be
> >> possible to know why this is required ?
> >>
> >> Regards,
> >> Pierre
> >>
> >> On 6/30/22 17:48, Jeff Brasen wrote:
> >>> Add support for selecting to use index or segment number as UID and
> >> name.
> >>> This allows the path of the nodes to be well known.
> >>>
> >>> Signed-off-by: Jeff Brasen <jbrasen@nvidia.com>
> >>> ---
> >>>    DynamicTablesPkg/DynamicTablesPkg.dec         |  3 +++
> >>>    .../AcpiSsdtPcieLibArm/SsdtPcieGenerator.c    | 19
> >> ++++++++++++++++++-
> >>>    .../Arm/AcpiSsdtPcieLibArm/SsdtPcieLibArm.inf |  3 +++
> >>>    3 files changed, 24 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/DynamicTablesPkg/DynamicTablesPkg.dec
> >>> b/DynamicTablesPkg/DynamicTablesPkg.dec
> >>> index 9b74c5a671..a890a048be 100644
> >>> --- a/DynamicTablesPkg/DynamicTablesPkg.dec
> >>> +++ b/DynamicTablesPkg/DynamicTablesPkg.dec
> >>> @@ -57,5 +57,8 @@
> >>>      # Non BSA Compliant 16550 Serial HID
> >>>
> >>>
> >>
> gEdkiiDynamicTablesPkgTokenSpaceGuid.PcdNonBsaCompliant16550SerialHi
> >> d|
> >>> ""|VOID*|0x40000008
> >>>
> >>> +  # Use PCI segment numbers as UID
> >>> +
> >>> +
> >>
> gEdkiiDynamicTablesPkgTokenSpaceGuid.PcdPciUseSegmentAsUid|FALSE|B
> >> OO
> >>> + LEAN|0x40000009
> >>> +
> >>>    [Guids]
> >>>      gEdkiiDynamicTablesPkgTokenSpaceGuid = { 0xab226e66, 0x31d8,
> >>> 0x4613, { 0x87, 0x9d, 0xd2, 0xfa, 0xb6, 0x10, 0x26, 0x3c } } diff
> >>> --git
> >>>
> >>
> a/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieGenera
> >> t
> >>> or.c
> >>>
> >>
> b/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieGenera
> >> t
> >>> or.c
> >>> index f0d15f69a4..85782af380 100644
> >>> ---
> >>>
> >>
> a/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieGenera
> >> t
> >>> or.c
> >>> +++
> >> b/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieGen
> >>> +++ erator.c
> >>> @@ -996,6 +996,7 @@ BuildSsdtPciTableEx (
> >>>      UINTN                         Index;
> >>>      EFI_ACPI_DESCRIPTION_HEADER   **TableList;
> >>>      ACPI_PCI_GENERATOR            *Generator;
> >>> +  UINT32                        Uid;
> >>>
> >>>      ASSERT (This != NULL);
> >>>      ASSERT (AcpiTableInfo != NULL); @@ -1051,13 +1052,29 @@
> >>> BuildSsdtPciTableEx (
> >>>      *Table = TableList;
> >>>
> >>>      for (Index = 0; Index < PciCount; Index++) {
> >>> +    if (PcdGetBool (PcdPciUseSegmentAsUid)) {
> >>> +      Uid = PciInfo[Index].PciSegmentGroupNumber;
> >>> +      if (Uid > MAX_PCI_ROOT_COMPLEXES_SUPPORTED) {
> >>> +        DEBUG ((
> >>> +          DEBUG_ERROR,
> >>> +          "ERROR: SSDT-PCI: Pci root complexes segment number: %d."
> >>> +          " Greater than maximum number of Pci root complexes
> >>> + supported =
> >> %d.\n",
> >>> +          Uid,
> >>> +          MAX_PCI_ROOT_COMPLEXES_SUPPORTED
> >>> +          ));
> >>> +        return EFI_INVALID_PARAMETER;
> >>> +      }
> >>> +    } else {
> >>> +      Uid = Index;
> >>> +    }
> >>> +
> >>>        // Build a SSDT table describing the Pci devices.
> >>>        Status = BuildSsdtPciTable (
> >>>                   Generator,
> >>>                   CfgMgrProtocol,
> >>>                   AcpiTableInfo,
> >>>                   &PciInfo[Index],
> >>> -               Index,
> >>> +               Uid,
> >>>                   &TableList[Index]
> >>>                   );
> >>>        if (EFI_ERROR (Status)) {
> >>> diff --git
> >>>
> >>
> a/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieLibArm.
> >>> inf
> >>>
> >>
> b/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieLibArm.
> >>> inf
> >>> index 283b564801..431e32a777 100644
> >>> ---
> >>>
> >>
> a/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieLibArm.
> >>> inf
> >>> +++
> >> b/DynamicTablesPkg/Library/Acpi/Arm/AcpiSsdtPcieLibArm/SsdtPcieLib
> >>> +++ Arm.inf
> >>> @@ -30,3 +30,6 @@
> >>>      AcpiHelperLib
> >>>      AmlLib
> >>>      BaseLib
> >>> +
> >>> +[Pcd]
> >>> +  gEdkiiDynamicTablesPkgTokenSpaceGuid.PcdPciUseSegmentAsUid