diff options
Diffstat (limited to 'IntelFrameworkModulePkg')
| -rw-r--r-- | IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/Serial.c | 34 |
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;
|