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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
This commit is contained in:
mdkinney 2010-12-30 22:30:57 +00:00
parent abef1c7a09
commit 9969fde78d
1 changed files with 33 additions and 1 deletions
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34
IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/Serial.c
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@ -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;