https://lists.01.org/pipermail/edk2-devel/2017-July/012385.html reported the timeout processing in SerialRead is not consistent.
Since SerialPortPoll only checks the status of serial port and returns immediately, and SerialPortRead does not really implement a time out mechanism and will always wait for enough input, it will cause below results: 1. If there is no serial input at all, this interface will return timeout immediately without any waiting; 2. If there is A characters in serial port FIFO, and caller requires A+1 characters, it will wait until a new input is coming and timeout will not really occur. This patch is to update SerialRead() to check SerialPortPoll() and read data through SerialPortRead() one byte by one byte, and check timeout against mSerialIoMode.Timeout if no input. Cc: Heyi Guo <[email protected]> Cc: Ruiyu Ni <[email protected]> Cc: Laszlo Ersek <[email protected]> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Star Zeng <[email protected]> --- MdeModulePkg/Universal/SerialDxe/SerialIo.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/MdeModulePkg/Universal/SerialDxe/SerialIo.c b/MdeModulePkg/Universal/SerialDxe/SerialIo.c index d2383e56dd8f..43d33dba0c2a 100644 --- a/MdeModulePkg/Universal/SerialDxe/SerialIo.c +++ b/MdeModulePkg/Universal/SerialDxe/SerialIo.c @@ -465,11 +465,25 @@ SerialRead ( ) { UINTN Count; + UINTN TimeOut; Count = 0; - if (SerialPortPoll ()) { - Count = SerialPortRead (Buffer, *BufferSize); + while (Count < *BufferSize) { + TimeOut = 0; + while (TimeOut < mSerialIoMode.Timeout) { + if (SerialPortPoll ()) { + break; + } + gBS->Stall (10); + TimeOut += 10; + } + if (TimeOut >= mSerialIoMode.Timeout) { + break; + } + SerialPortRead (Buffer, 1); + Count++; + Buffer = (VOID *) ((UINT8 *) Buffer + 1); } if (Count != *BufferSize) { -- 2.7.0.windows.1 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
