Re: [edk2-devel] [PATCH 2/4] DynamicTablesPkg: AcpiSsdtPcieLibArm: Allow use of segment number as UID

[PierreGondois]

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.gond...@arm.com>
Sent: Friday, July 1, 2022 6:42 AM
To: Jeff Brasen <jbra...@nvidia.com>; devel@edk2.groups.io
Cc: sami.muja...@arm.com; alexei.fedo...@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 <jbra...@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

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