ArmPlatformPkg: Add support to configure PL011 UART clock

On some platforms the UART clock is not the same for all the serial
ports. The PL011 driver must be capable of handling serial ports with
different clock rates, so must not rely on a PCD for the clock rate.

This patch allows the UART clock rate to be passed as a parameter
to PL011UartInitializePort(), which is called from the serial port
library. This patch also contains the corresponding changes in the
serial port library.

The PCD in Drivers/PL011Uart is replaced by an extra parameter for
PL011UartInitializePort.  The PCD is moved to Library/PL011SerialPortLib
to supply the value to pass.

A corresponding patch to ArmVirtPkg is included in the same bundle to
align that with these changes.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>

2 files changed, 19 insertions, 7 deletions

diff --git a/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c b/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c
index db15a8b322..3c283fdf33 100644
--- a/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c
+++ b/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.c
@@ -35,6 +35,8 @@ STATIC CONST UINT32 mInvalidControlBits = EFI_SERIAL_SOFTWARE_LOOPBACK_ENABLE;
   All unspecified settings will be set to the default values.

 

   @param  UartBase                The base address of the serial device.

+  @param  UartClkInHz             The clock in Hz for the serial device.

+                                  Ignored if the PCD PL011UartInteger is not 0

   @param  BaudRate                The baud rate of the serial device. If the

                                   baud rate is not supported, the speed will be

                                   reduced to the nearest supported one and the

@@ -63,6 +65,7 @@ RETURN_STATUS
 EFIAPI

 PL011UartInitializePort (

   IN     UINTN               UartBase,

+  IN     UINT32              UartClkInHz,

   IN OUT UINT64              *BaudRate,

   IN OUT UINT32              *ReceiveFifoDepth,

   IN OUT EFI_PARITY_TYPE     *Parity,

@@ -72,6 +75,8 @@ PL011UartInitializePort (
 {

   UINT32      LineControl;

   UINT32      Divisor;

+  UINT32      Integer;

+  UINT32      Fractional;

 

   // 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

@@ -168,19 +173,27 @@ PL011UartInitializePort (
 

   // If PL011 Integer value has been defined then always ignore the BAUD rate

   if (FixedPcdGet32 (PL011UartInteger) != 0) {

-      MmioWrite32 (UartBase + UARTIBRD, FixedPcdGet32 (PL011UartInteger));

-      MmioWrite32 (UartBase + UARTFBRD, FixedPcdGet32 (PL011UartFractional));

+    Integer = FixedPcdGet32 (PL011UartInteger);

+    Fractional = FixedPcdGet32 (PL011UartFractional);

   } else {

     // If BAUD rate is zero then replace it with the system default value

     if (*BaudRate == 0) {

       *BaudRate = FixedPcdGet32 (PcdSerialBaudRate);

-      ASSERT (*BaudRate != 0);

+      if (*BaudRate == 0) {

+        return RETURN_INVALID_PARAMETER;

+      }

+    }

+    if (0 == UartClkInHz) {

+      return RETURN_INVALID_PARAMETER;

     }

 

-    Divisor = (FixedPcdGet32 (PL011UartClkInHz) * 4) / *BaudRate;

-    MmioWrite32 (UartBase + UARTIBRD, Divisor >> FRACTION_PART_SIZE_IN_BITS);

-    MmioWrite32 (UartBase + UARTFBRD, Divisor & FRACTION_PART_MASK);

+    Divisor = (UartClkInHz * 4) / *BaudRate;

+    Integer = Divisor >> FRACTION_PART_SIZE_IN_BITS;

+    Fractional = Divisor & FRACTION_PART_MASK;

   }

+  // Set Baud Rate Registers

+  MmioWrite32 (UartBase + UARTIBRD, Integer);

+  MmioWrite32 (UartBase + UARTFBRD, Fractional);

 

   // No parity, 1 stop, no fifo, 8 data bits

   MmioWrite32 (UartBase + UARTLCR_H, LineControl);

diff --git a/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.inf b/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.inf
index 5afce36d39..0154f3bd2e 100644
--- a/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.inf
+++ b/ArmPlatformPkg/Drivers/PL011Uart/PL011Uart.inf
@@ -37,6 +37,5 @@
 [FixedPcd]

   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialBaudRate

 

-  gArmPlatformTokenSpaceGuid.PL011UartClkInHz

   gArmPlatformTokenSpaceGuid.PL011UartInteger

   gArmPlatformTokenSpaceGuid.PL011UartFractional