1) Add PcdSerialDetectCable to MdeModulePkg to enable/disable cable detection if hardware flow control is enabled. The default is to not perform cable detection.

2) Update BaseSerialPortLib16550 to use this new PCD.

This addresses an issue that was introduced on Feb 3, 2011 when all references to Carrier Detect(CD) were removed from the BaseSerialPortLib16550.  When that change was made, a target would block on the first Tx operation if hardware flow control was enabled and no cable or serial application was running on a host. Now the behavior when no cable is connected or no serial app is running on the host is controlled through a PCD.  The default is for the target to continue execution even if there is no cable or serial app running.  If PcdSerialDetectCable is set to TRUE, then the target will block on any transmit that does not have a cable connected or a serial app running in the host.

If hardware flow control is disabled, then this update will have no impact on behavior.


git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11301 6f19259b-4bc3-4df7-8a09-765794883524

2 files changed, 32 insertions, 5 deletions

diff --git a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c
index 04d8ca1..a6c990d 100644
--- a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c
+++ b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c
@@ -38,6 +38,7 @@
 #define   B_UART_LSR_TEMT     BIT6

 #define R_UART_MSR            6

 #define   B_UART_MSR_CTS      BIT4

+#define   B_UART_MSR_DSR      BIT5

 

 /**

   Read an 8-bit 16550 register.  If PcdSerialUseMmio is TRUE, then the value is read from 

@@ -226,10 +227,35 @@ SerialPortWrite (
     //

     for (Index = 0; Index < FifoSize && NumberOfBytes != 0; Index++, NumberOfBytes--, Buffer++) {

       if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {

-        //

-        // Wait for notification from peer to send data

-        //

-        while ((SerialPortReadRegister (R_UART_MSR) & (B_UART_MSR_CTS)) == 0);

+        if (PcdGetBool (PcdSerialDetectCable)) {

+          //

+          // Wait for both DSR and CTS to be set

+          //   DSR is set if a cable is connected.

+          //   CTS is set if it is ok to transmit data

+          //

+          //   DSR  CTS  Description                               Action

+          //   ===  ===  ========================================  ========

+          //    0    0   No cable connected.                       Wait

+          //    0    1   No cable connected.                       Wait

+          //    1    0   Cable connected, but not clear to send.   Wait

+          //    1    1   Cable connected, and clear to send.       Transmit

+          //

+          while ((SerialPortReadRegister (R_UART_MSR) & (B_UART_MSR_DSR | B_UART_MSR_CTS)) != (B_UART_MSR_DSR | B_UART_MSR_CTS));

+        } else {

+          //

+          // Wait for both DSR and CTS to be set OR for DSR to be clear.  

+          //   DSR is set if a cable is connected.

+          //   CTS is set if it is ok to transmit data

+          //

+          //   DSR  CTS  Description                               Action

+          //   ===  ===  ========================================  ========

+          //    0    0   No cable connected.                       Transmit

+          //    0    1   No cable connected.                       Transmit

+          //    1    0   Cable connected, but not clear to send.   Wait

+          //    1    1   Cable connected, and clar to send.        Transmit

+          //

+          while ((SerialPortReadRegister (R_UART_MSR) & (B_UART_MSR_DSR | B_UART_MSR_CTS)) == (B_UART_MSR_DSR));

+        }

       }

       

       //

diff --git a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf
index 251f353..3f22366 100644
--- a/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf
+++ b/MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf
@@ -1,7 +1,7 @@
 ## @file

 #   SerialPortLib instance for 16550 UART

 #

-#  Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>

+#  Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>

 #  This program and the accompanying materials

 #  are licensed and made available under the terms and conditions of the BSD License

 #  which accompanies this distribution.  The full text of the license may be found at

@@ -35,6 +35,7 @@
 [Pcd]

   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio

   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseHardwareFlowControl

+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialDetectCable

   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterBase

   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialBaudRate

   gEfiMdeModulePkgTokenSpaceGuid.PcdSerialLineControl