[edk2-devel] [PATCH edk2-platforms v2 12/16] Silicon/NXP: PciSegmentLib: LsGen4Ctrl: Add Workaround for A-011264

[Wasim Khan]

From: Wasim Khan <wasim.khan at nxp.com>

With PCIe LsGen4 controller, clearing the Bus Master Enable bit in
Command register blocks all outbound transactions to be sent out
in RC mode.

According to PCI Express base specification, the Command register’s
Bus Master Enable bit of a PCI Express RC controller can only
control the forwarding of memory requests received at its root port
in the upstream direction. In other words, clearing the Bus Master
Enable bit must not block all outbound transactions to be sent out
toward RC’s downstream devices. Due to this erratum, when the
Command register’s Bus Master Enable bit is cleared, all the outbound
transactions from the device’s internal bus masters, including but
not limited to configuration read and write transactions, are
terminated with the slave error (SLVERR) response status on the PCI
Express RC controller’s internal AXI bus interface.

Signed-off-by: Wasim Khan <wasim.khan at nxp.com>
---

Notes:
    V2:
    - Addressed review comments to:
      - Drop outer () while calculating Target
      - Use (Bus > 0) instead of (Bus)

 Silicon/NXP/Library/PciSegmentLib/PciSegmentLib.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Silicon/NXP/Library/PciSegmentLib/PciSegmentLib.c b/Silicon/NXP/Library/PciSegmentLib/PciSegmentLib.c
index 09ce620ef988..572fbb195c19 100755
--- a/Silicon/NXP/Library/PciSegmentLib/PciSegmentLib.c
+++ b/Silicon/NXP/Library/PciSegmentLib/PciSegmentLib.c
@@ -39,6 +39,21 @@ static BOOLEAN PciLsGen4Ctrl;
 
 STATIC
 VOID
+PciLsGen4SetBusMaster (
+  IN EFI_PHYSICAL_ADDRESS Dbi
+  )
+{
+  UINT32 Val;
+
+  //Make sure the Master Enable bit not cleared
+  Val = PciLsGen4Read32 ((UINTN)Dbi, PCI_COMMAND_OFFSET);
+  if (!(Val & EFI_PCI_COMMAND_BUS_MASTER)) {
+    PciLsGen4Write32 ((UINTN)Dbi, PCI_COMMAND_OFFSET, Val | EFI_PCI_COMMAND_BUS_MASTER);
+  }
+}
+
+STATIC
+VOID
 PcieCfgSetTarget (
   IN EFI_PHYSICAL_ADDRESS Dbi,
   IN UINT32 Target)
@@ -71,6 +86,8 @@ PciLsGen4GetConfigBase (
   UINT32 Target;
 
   if (Bus > 0) {
+    PciLsGen4SetBusMaster (PCI_SEG0_DBI_BASE + PCI_DBI_SIZE_DIFF* Segment);
+
     Target = (((Address >> 20) & 0xFF) << 24) |
              (((Address >> 15) & 0x1F) << 19) |
              (((Address >> 12) & 0x7) << 16);
-- 
2.7.4


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