[PATCH 4/5] Silicon/Broadcom/Bcm27xx: Tweak PCIe for CM4

["Jeremy Linton" <jeremy.linton@arm.com>]

The CM4 has an actual pcie slot, so we need to move the linkup
check to the configuration probe logic. Further the device
restriction logic needs to be relaxed to support downstream
PCIe switches.

Suggested-by: René Treffer <treffer+groups.io@measite.de>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
---
 .../Bcm2711PciHostBridgeLibConstructor.c           |  5 -----
 .../Library/Bcm2711PciSegmentLib/PciSegmentLib.c   | 24 +++++++++++++++-------
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciHostBridgeLib/Bcm2711PciHostBridgeLibConstructor.c b/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciHostBridgeLib/Bcm2711PciHostBridgeLibConstructor.c
index 8587d2d36d..4d4c584726 100644
--- a/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciHostBridgeLib/Bcm2711PciHostBridgeLibConstructor.c
+++ b/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciHostBridgeLib/Bcm2711PciHostBridgeLibConstructor.c
@@ -204,11 +204,6 @@ Bcm2711PciHostBridgeLibConstructor (
   } while (((Data & 0x30) != 0x030) && (Timeout));
   DEBUG ((DEBUG_VERBOSE, "PCIe link ready (status=%x) Timeout=%d\n", Data, Timeout));
 
-  if ((Data & 0x30) != 0x30) {
-    DEBUG ((DEBUG_ERROR, "PCIe link not ready (status=%x)\n", Data));
-    return EFI_DEVICE_ERROR;
-  }
-
   if ((Data & 0x80) != 0x80) {
     DEBUG ((DEBUG_ERROR, "PCIe link not in RC mode (status=%x)\n", Data));
     return EFI_UNSUPPORTED;
diff --git a/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciSegmentLib/PciSegmentLib.c b/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciSegmentLib/PciSegmentLib.c
index 44ce3b4b99..3ccc131eab 100644
--- a/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciSegmentLib/PciSegmentLib.c
+++ b/Silicon/Broadcom/Bcm27xx/Library/Bcm2711PciSegmentLib/PciSegmentLib.c
@@ -78,6 +78,8 @@ PciSegmentLibGetConfigBase (
   UINT64        Base;
   UINT64        Offset;
   UINT32        Dev;
+  UINT32        Bus;
+  UINT32        Data;
 
   Base = PCIE_REG_BASE;
   Offset = Address & 0xFFF;         /* Pick off the 4k register offset */
@@ -89,17 +91,25 @@ PciSegmentLibGetConfigBase (
     Base += PCIE_EXT_CFG_DATA;
     if (mPciSegmentLastAccess != Address) {
       Dev = EFI_PCI_ADDR_DEV (Address);
+      Bus = EFI_PCI_ADDR_BUS (Address);
+      
       /*
-       * Scan things out directly rather than translating the "bus" to a device, etc..
-       * only we need to limit each bus to a single device.
+       * There can only be a single device on bus 1 (downstream of root).
+       * Subsequent busses (behind a PCIe switch) can have more.
        */
-      if (Dev < 1) {
-          MmioWrite32 (PCIE_REG_BASE + PCIE_EXT_CFG_INDEX, Address);
-          mPciSegmentLastAccess = Address;
-      } else {
-          mPciSegmentLastAccess = 0;
+      if (Dev > 0 && (Bus < 2)) {
           return 0xFFFFFFFF;
       }
+
+      /* Don't probe slots if the link is down */
+      Data = MmioRead32 (PCIE_REG_BASE + PCIE_MISC_PCIE_STATUS);
+      if ((Data & 0x30) != 0x30) {
+          DEBUG ((DEBUG_ERROR, "PCIe link not ready (status=%x)\n", Data));
+          return 0xFFFFFFFF;
+      }
+
+      MmioWrite32 (PCIE_REG_BASE + PCIE_EXT_CFG_INDEX, Address);
+      mPciSegmentLastAccess = Address;
     }
   }
   return Base + Offset;
-- 
2.13.7