From c8edb70945099fd35a0997d3f3db105efc144e13 Mon Sep 17 00:00:00 2001
From: Irene Park <ipark@nvidia.com>
Date: Tue, 9 Jun 2020 13:56:31 -0400
Subject: ArmPlatformPkg/PL011UartLib: Check PID2 if FiFoDepth is zero

PL011UartLib determines its FIFO depth based on the PID2 value but
the register PID2 is not mandatory as per the SBSA spec.
This change won't check PID2 if PcdUartDefaultReceiveFifoDepth is set
to a value > 0.

Signed-off-by: Irene Park <ipark@nvidia.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
---
 ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c   | 10 +++++++---
 ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.inf |  1 +
 2 files changed, 8 insertions(+), 3 deletions(-)

(limited to 'ArmPlatformPkg')

diff --git a/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c b/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c
index 801990d955..f1015b1fce 100644
--- a/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c
+++ b/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.c
@@ -78,10 +78,14 @@ PL011UartInitializePort (
   UINT32      Integer;
   UINT32      Fractional;
   UINT32      HardwareFifoDepth;
+  UINT32      UartPid2;
+
+  HardwareFifoDepth = FixedPcdGet16 (PcdUartDefaultReceiveFifoDepth);
+  if (HardwareFifoDepth == 0) {
+    UartPid2 = MmioRead32 (UartBase + UARTPID2);
+    HardwareFifoDepth = (PL011_UARTPID2_VER (UartPid2) > PL011_VER_R1P4) ? 32 : 16;
+  }
 
-  HardwareFifoDepth = (PL011_UARTPID2_VER (MmioRead32 (UartBase + UARTPID2)) \
-                       > PL011_VER_R1P4) \
-                      ? 32 : 16 ;
   // The PL011 supports a buffer of 1, 16 or 32 chars. Therefore we can accept
   // 1 char buffer as the minimum FIFO size. Because everything can be rounded
   // down, there is no maximum FIFO size.
diff --git a/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.inf b/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.inf
index d99e89fe00..e3da507988 100644
--- a/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.inf
+++ b/ArmPlatformPkg/Library/PL011UartLib/PL011UartLib.inf
@@ -30,6 +30,7 @@
   ArmPlatformPkg/ArmPlatformPkg.dec
 
 [FixedPcd]
+  gEfiMdePkgTokenSpaceGuid.PcdUartDefaultReceiveFifoDepth
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialBaudRate
 
   gArmPlatformTokenSpaceGuid.PL011UartInteger
-- 
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