Update the Timeout used for Write() operations to consider the case where the Tx FIFO is full on entry to Write().

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11211 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 33 insertions, 1 deletions

diff --git a/IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/Serial.c b/IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/Serial.c
index c62e60b6f5..4a12eb9e04 100644
--- a/IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/Serial.c
+++ b/IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/Serial.c
@@ -1744,6 +1744,8 @@ IsaSerialWrite (
   UINTN       Elapsed;

   UINTN       ActualWrite;

   EFI_TPL     Tpl;

+  UINTN       Timeout;

+  UINTN       BitsPerCharacter;

 

   SerialDevice  = SERIAL_DEV_FROM_THIS (This);

   Elapsed       = 0;

@@ -1767,6 +1769,36 @@ IsaSerialWrite (
 

   CharBuffer  = (UINT8 *) Buffer;

 

+  //

+  // Compute the number of bits in a single character.  This is a start bit,

+  // followed by the number of data bits, followed by the number of stop bits.

+  // The number of stop bits is specified by an enumeration that includes 

+  // support for 1.5 stop bits.  Treat 1.5 stop bits as 2 stop bits.

+  //

+  BitsPerCharacter = 

+    1 + 

+    This->Mode->DataBits + 

+    ((This->Mode->StopBits == TwoStopBits) ? 2 : This->Mode->StopBits);

+

+  //

+  // Compute the timeout in microseconds to wait for a single byte to be 

+  // transmitted.  The Mode structure contans a Timeout field that is the 

+  // maximum time to transmit or receive a character.  However, many UARTs 

+  // have a FIFO for transmits, so the time required to add one new character

+  // to the transmit FIFO may be the time required to flush a full FIFO.  If 

+  // the Timeout in the Mode structure is smaller than the time required to

+  // flush a full FIFO at the current baud rate, then use a timeout value that

+  // is required to flush a full transmit FIFO.

+  //

+  Timeout = MAX (

+              This->Mode->Timeout,

+              (UINTN)DivU64x64Remainder (

+                BitsPerCharacter * (SERIAL_PORT_MAX_RECEIVE_FIFO_DEPTH + 1) * 1000000,

+                This->Mode->BaudRate,

+                NULL

+                )

+              );

+  

   for (Index = 0; Index < *BufferSize; Index++) {

     IsaSerialFifoAdd (&SerialDevice->Transmit, CharBuffer[Index]);

 

@@ -1775,7 +1807,7 @@ IsaSerialWrite (
       //  Unsuccessful write so check if timeout has expired, if not,

       //  stall for a bit, increment time elapsed, and try again

       //

-      if (Elapsed >= This->Mode->Timeout) {

+      if (Elapsed >= Timeout) {

         *BufferSize = ActualWrite;

         gBS->RestoreTPL (Tpl);

         return EFI_TIMEOUT;