https://lists.01.org/pipermail/edk2-devel/2017-October/016479.html
reported "Xen Console input very slow in recent UEFI" that appears
after 4cf3f37c87 "MdeModulePkg
SerialDxe: Process timeout consistently in SerialRead".
Julien did more debugging and find out the following is happening in
TerminalConInTimerHandler (MdeModulePkg/Universal/Console/TerminalDxe)
when a character is received:
1) GetControl will return EFI_SERIAL_INPUT_BUFFER_EMPTY unset
=> Entering in the loop to fetch character from the serial
2) GetOneKeyFromSerial()
=> Return directly with the character read
3) Looping as the fifo is not full and no error
4) GetOneKeyFromSerial() -> SerialRead()
=> No more character so SerialPortPoll() will return FALSE and loop
until timeout
=> Return EFI_TIMEOUT
5) Exiting the loop from TerminalConInTimerHandler
6) Characters are printed
After some investigation, I found it is related to the Timeout value.
The Timeout is 1000000 (1s) by default to follow UEFI spec.
And the Terminal driver will recalculate and set the Timeout value
based on the properties of UART in TerminalDriverBindingStart()/
TerminalConInTimerHandler().
SerialInTimeOut = 0;
if (Mode->BaudRate != 0) {
//
// According to BAUD rate to calculate the timeout value.
//
SerialInTimeOut = (1 + Mode->DataBits + Mode->StopBits) *
2 * 1000000 / (UINTN) Mode->BaudRate;
}
For example, based on the PCD values of PcdUartDefaultBaudRate,
PcdUartDefaultDataBits and PcdUartDefaultStopBits, SerialInTimeOut =
(1 + 8 + 1) * 2 * 1000000 / (UINTN) 115200 = 173 (us).
When SerialDxe is used,
TerminalDriverBindingStart()/TerminalConInTimerHandler() ->
SerialIo->SetAttributes() ->
SerialSetAttributes() ->
SerialPortSetAttributes()
Some implementations of SerialPortSetAttributes() could handle the
input parameters and return RETURN_SUCCESS, for example
BaseSerialPortLib16550, then Timeout value will be changed to 173 (us),
no "slow down" will be observed.
But some implementations of SerialPortSetAttributes() just return
RETURN_UNSUPPORTED, for example XenConsoleSerialPortLib, then Timeout
value will be not changed and kept 1000000 (1s), "slow down" will be
observed.
SerialPortLib instance can be enhanced to
1. Handle the input parameters and return status accordingly instead of
just returning RETURN_UNSUPPORTED in SerialPortSetAttributes().
2. Just return RETURN_SUCCESS instead of RETURN_UNSUPPORTED in
SerialPortSetAttributes() if the instance does not care the input
parameters at all.
And SerialDxe can also be enhanced like this patch to be more robust
to handle Timeout change.
Cc: Julien Grall <julien.grall@linaro.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Compare against the original parameters
Suggested-by: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Julien Grall <julien.grall@linaro.org>
Issue : When try to change serial attributes using sermode
command, the default values are set with the execute flow
as below.
The sermode command calls SerialSetAttributes, which sets H/W
attributes of Serial device. After that the SerialIo protocol is
reinstalled, which causes MdeModulePkg/Universal/Console/TerminalDxe
and MdeModulePkg/Universal/Console/ConPlatformDxe drivers' bindings
to stop and then start. This in turn calls SerialReset, which undoes
changes of SerialSetAttributes.
Cause : The SerialReset command resets the attributes' values
to default.
Fix : Serial Reset command should set the attributes which have
been changed by user after calling SerialSetAttributes.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Pankaj Bansal <pankaj.bansal@nxp.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
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 <heyi.guo@linaro.org>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Set UART receive FIFO depth with PCD instead of fixed number "1".
The default value of PCD is also 1, so it makes no difference for
platforms which do not explicitly set this PCD.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
In "11.8 Serial I/O Protocol", UEFI 2.5 requires:
The default attributes for all UART-style serial device interfaces are:
(a) 115,200 baud,
(b) a 1 byte receive FIFO,
(c) a 1,000,000 microsecond timeout per character,
(d) no parity,
(e) 8 data bits,
(f) and 1 stop bit.
It also says, about the EFI_SERIAL_IO_MODE.ControlMask member:
(g) A mask of the Control bits that the device supports. The device must
always support the Input Buffer Empty control bit.
SerialDxe complies with requirement (b) via hard-coded constants. It
complies with requirements (a), (d), (e) and (f) through PCD defaults (see
MdePkg/MdePkg.dec):
(a) 115,200 baud:
gEfiMdePkgTokenSpaceGuid.PcdUartDefaultBaudRate|115200|UINT64|0x00000020
(d) no parity:
# 1 - No Parity.<BR>
gEfiMdePkgTokenSpaceGuid.PcdUartDefaultParity|1|UINT8|0x00000022
(e) 8 data bits:
gEfiMdePkgTokenSpaceGuid.PcdUartDefaultDataBits|8|UINT8|0x00000021
(f) 1 stop bit:
# 1 - One Stop Bit.<BR>
gEfiMdePkgTokenSpaceGuid.PcdUartDefaultStopBits|1|UINT8|0x00000023
SerialDxe does not comply with requirements (c) and (g). In this patch, we
fix (c), and leave (g) for later.
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ryan Harkin <ryan.harkin@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>
Reviewed-by: Star Zeng <star.zeng@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19700 6f19259b-4bc3-4df7-8a09-765794883524
This Serial driver layers on top of a Serial Port Library instance
to produce serial IO protocol.
There is also another SerialDxe implementation in CorebootPayloadPkg,
but SerialDxe from EmbeddedPkg should be better that also consumes
the extended interfaces GetControl/SetControl/SetAttributes in
EmbeddedPkg/Include/Library/SerialPortExtLib.h for serial IO protocol.
And the extended interfaces GetControl/SetControl/SetAttributes in
EmbeddedPkg/Include/Library/SerialPortExtLib.h has been upstream to
MdePkg/Include/Library/SerialPortLib.h.
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18966 6f19259b-4bc3-4df7-8a09-765794883524
Star Zeng
Pankaj Bansal
Heyi Guo
Laszlo Ersek
Liming Gao
Jordan Justen