[edk2-devel] [edk2-platforms][PATCH v2 1/1] Platform/RaspberryPi: Fix mini UART clock divisor calculation

[Pete Batard]

From: Mario Bălănică <mariobalanica02 at gmail.com>

The VPU clock divisor has changed in this commit: https://github.com/raspberrypi/firmware/commit/1e5456a,
thus breaking the mini UART clock divisor calculation on the Pi 4.

Fix this by reading the core clock from the mailbox instead.

Signed-off-by: Mario Bălănică <mariobalanica02 at gmail.com>
---
 Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c   | 15 +++------------
 Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S |  4 ----
 Platform/RaspberryPi/RPi4/RPi4.dsc                                   |  6 ++++--
 3 files changed, 7 insertions(+), 18 deletions(-)

diff --git a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
index 5e83bbf022eb..d2f983bf0a9f 100644
--- a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
+++ b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
@@ -34,25 +34,16 @@ SerialPortGetDivisor (
   UINT32  SerialBaudRate
 )
 {
-  UINT64              BaseClockRate;
+  UINT32              BaseClockRate;
   UINT32              Divisor;
 
-  //
-  // On the Raspberry Pi, the clock to use for the 16650-compatible UART
-  // is the base clock divided by the 12.12 fixed point VPU clock divisor.
-  //
-  BaseClockRate = (UINT64)PcdGet32 (PcdSerialClockRate);
-#if (RPI_MODEL == 4)
-  Divisor = MmioRead32(BCM2836_CM_BASE + BCM2836_CM_VPU_CLOCK_DIVISOR) & 0xFFFFFF;
-  if (Divisor != 0)
-    BaseClockRate = (BaseClockRate << 12) / Divisor;
-#endif
+  BaseClockRate = PcdGet32 (PcdSerialClockRate);
 
   //
   // As per the BCM2xxx datasheets:
   // baudrate = system_clock_freq / (8 * (divisor + 1)).
   //
-  Divisor = (UINT32)BaseClockRate / (SerialBaudRate * 8);
+  Divisor = BaseClockRate / (SerialBaudRate * 8);
   if (Divisor != 0) {
     Divisor--;
   }
diff --git a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
index 58351e4fb8cc..7008aaf8aa4c 100644
--- a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
+++ b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
@@ -85,13 +85,11 @@ ASM_FUNC (ArmPlatformPeiBootAction)
     adr     x2, mBoardRevision
     str     w0, [x2]
 
-#if (RPI_MODEL == 3)
     run     .Lclkinfo_buffer
 
     ldr     w0, .Lfrequency
     adr     x2, _gPcd_BinaryPatch_PcdSerialClockRate
     str     w0, [x2]
-#endif
 
     ret
 
@@ -135,7 +133,6 @@ ASM_FUNC (ArmPlatformPeiBootAction)
     .long   0                           // end tag
     .set    .Lrevinfo_size, . - .Lrevinfo_buffer
 
-#if (RPI_MODEL == 3)
     .align  4
 .Lclkinfo_buffer:
     .long   .Lclkinfo_size
@@ -148,7 +145,6 @@ ASM_FUNC (ArmPlatformPeiBootAction)
     .long   0                           // frequency
     .long   0                           // end tag
     .set    .Lclkinfo_size, . - .Lclkinfo_buffer
-#endif
 
 //UINTN
 //ArmPlatformGetPrimaryCoreMpId (
diff --git a/Platform/RaspberryPi/RPi4/RPi4.dsc b/Platform/RaspberryPi/RPi4/RPi4.dsc
index 2c05c31118d2..ff802d8347ea 100644
--- a/Platform/RaspberryPi/RPi4/RPi4.dsc
+++ b/Platform/RaspberryPi/RPi4/RPi4.dsc
@@ -429,7 +429,6 @@ [PcdsFixedAtBuild.common]
   gArmPlatformTokenSpaceGuid.PL011UartClkInHz|48000000
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterStride|4
-  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|1000000000
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialFifoControl|0x27
   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialExtendedTxFifoSize|8
   gEfiMdePkgTokenSpaceGuid.PcdUartDefaultBaudRate|115200
@@ -465,6 +464,9 @@ [PcdsFixedAtBuild.common]
   gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareVendor|L"EDK2"
   gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack|TRUE
 
+[PcdsPatchableInModule]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|500000000
+
 [PcdsDynamicHii.common.DEFAULT]
 
   #
@@ -621,7 +623,7 @@ [Components.common]
   MdeModulePkg/Universal/Console/TerminalDxe/TerminalDxe.inf
   MdeModulePkg/Universal/SerialDxe/SerialDxe.inf {
     <LibraryClasses>
-      SerialPortLib|Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.inf
+      SerialPortLib|Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortDxeLib.inf
   }
   Platform/RaspberryPi/Drivers/DisplayDxe/DisplayDxe.inf
   EmbeddedPkg/Drivers/ConsolePrefDxe/ConsolePrefDxe.inf
-- 2.29.2.windows.2


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